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Molecular contribution of BRCA1 and BRCA2 to genome instability in breast cancer patients: review of radiosensitivity assays



DNA repair pathways, cell cycle arrest checkpoints, and cell death induction are present in cells to process DNA damage and prevent genomic instability caused by various extrinsic and intrinsic ionizing factors. Mutations in the genes involved in these pathways enhances the ionizing radiation sensitivity, reduces the individual’s capacity to repair DNA damages, and subsequently increases susceptibility to tumorigenesis.


BRCA1 and BRCA2 are two highly penetrant genes involved in the inherited breast cancer and contribute to different DNA damage pathways and cell cycle and apoptosis cascades. Mutations in these genes have been associated with hypersensitivity and genetic instability as well as manifesting severe radiotherapy complications in breast cancer patients. The genomic instability and DNA repair capacity of breast cancer patients with BRCA1/2 mutations have been analyzed in different studies using a variety of assays, including micronucleus assay, comet assay, chromosomal assay, colony-forming assay, γ -H2AX and 53BP1 biomarkers, and fluorescence in situ hybridization. The majority of studies confirmed the enhanced spontaneous & radiation-induced radiosensitivity of breast cancer patients compared to healthy controls. Using G2 micronucleus assay and G2 chromosomal assay, most studies have reported the lymphocyte of healthy carriers with BRCA1 mutation are hypersensitive to invitro ionizing radiation compared to non-carriers without a history of breast cancer. However, it seems this approach is not likely to be useful to distinguish the BRCA carriers from non-carrier with familial history of breast cancer.


In overall, breast cancer patients are more radiosensitive compared to healthy control; however, inconsistent results exist about the ability of current radiosensitive techniques in screening BRCA1/2 carriers or those susceptible to radiotherapy complications. Therefore, developing further radiosensitivity assay is still warranted to evaluate the DNA repair capacity of individuals with BRCA1/2 mutations and serve as a predictive factor for increased risk of cancer mainly in the relatives of breast cancer patients. Moreover, it can provide more evidence about who is susceptible to manifest severe complication after radiotherapy.


The genomic content of cells is constantly exposed to extrinsic and intrinsic factors leading to DNA damage and genomic instability. These damages can affect the integrity of one or both strands of a DNA molecule. In this case, they are called single-strand and double-strand DNA breaks, respectively [1]. Double-strand breaks (DSBs) are considered as much severe and harmful damages, which can generate extreme and disruptive mutations [2]. Several cascades of cellular events comprising DNA repair pathways, cell cycle arrest, and apoptosis are important to rectify DNA damage, prevent uncontrolled cell dividing and passing unrepair DNA damages to the daughter cells. People with mutations in the genes involved in these pathways are more sensitive to radiation (radiosensitive) and have an impaired proliferative capacity after exposure to DNA damaging agents; therefore, they are at higher risk of cancer development compared to a normal population.

Breast cancer is the most common cancer and the first leading cause of cancer-related death in women worldwide [3]. While majority of breast cancers occur sporadically, approximately 5-10 % of them follow a hereditary pattern, meaning that certain mutated genes that are passed from parents to children contribute to the development of breast cancer [4]. Several studies demonstrated an increased level of radiosensitivity among breast cancer patients. They are more radiosensitive comparing to other cancer types, like oesophageal cancer as well [5]. In this malignancy, BRCA1 and BRCA2 are among the high penetrant susceptibility genes and mutations in these genes have been associated with hypersensitivity and genetic instability [6]. Studies have reported that BRCA1−/− mouse embryonic fibroblasts (MEFs) and human breast cancer line, HCC1937 [7, 8], are highly sensitive to ionizing radiation and retrovirally transfecting these cells with wild-type BRCA1 diminished the ionizing radiation sensitivity and improved the efficiency of DSBs repair [9]. Likewise, the clinical studies stated BRCA1/2 mutation carriers are more radiosensitive than healthy control [5, 10, 11] and manifest more severe radiotherapy complications [12, 13] due to having defective DNA damage repair system.

Currently, the most reliable test for pre-screening the BRCA1/2 carriers is limited to the full sequencing of the genes. However, this technique is time-consuming, difficult, and costly and, up to 30% of mutations cannot be detected properly. Moreover, one-third of all breast cancer occurs within the families are not related to either BRCA1 or BRCA2, indicating that other low penetrate genes are involved in the development of familial breast cancer. Evaluating the DNA repair capacity may serve as a biomarker to identify individuals at increased risk of breast cancer and act as a pre-screening test in women with a family history of breast cancer. To date, several studies have utilized different types of assays to evaluate the radiosensitivity in BRCA1/BRCA2-associated breast cancer patients compared to sporadic one and healthy individuals. Here, we first give an overview of the contribution of BRCA1/2 to radiosensitivity through regulating the DNA repair pathways, and cell cycle checkpoint and apoptosis cascades. We then discuss the clinical and functional assays for determining the radiosensitivity capacity of sporadic and familial breast cancer patients.

DNA repair pathways and cell cycle mechanisms

DSBs are regarded as severe and harmful damages and can generate extreme and disruptive mutations if remain unrepaired [2]. Cells have developed two main repair pathways, homologous recombinant (HR) and non-homologous end-joining (NHEJ) repair pathway, to deal with this type of DNA damage.

HR repair pathway exclusively takes place in the late S and G2 phases of the cell cycle. This pathway requires an unharmed homologous DNA sequence located in the sister chromatin as a template for the synthesis of the damaged region. The overall process starts with the recognition of the DSB region by the Mre11-RAD50-Nbs1 (MRN) complex (Fig. 1). Next, ATM is recruited to the DNA damage location, which in turn facilitates the recruitment of other crucial proteins, including ATR, CHEK2, BARD1, BRCA1, BRCA2, and RAD51 [14]. Mutations in genes encoding these proteins have been associated with the increased risk of breast cancer.

Fig. 1
figure 1

Homologues recombinant DNA repair system. The overall process starts with the recognition of the DSB region by the Mre11-RAD50-Nbs1 (MRN) complex. Next, ATM phosphorylates γH2AX, MDC1, and RNF8, which subsequently initiate the formation of BRCA1–abraxas–RAP80 complex. Later, BRCA1 via cooperating with MRN forms a complex with CtIP, to promote 5′-end resection in the early steps of the synthesis-dependent strand annealing (SDSA) pathway of HR. BRCA1 interacts with PALB2 and BRCA2 to recruit RAD51, an essential mediator in the HR repairing pathway. The formation of BRCA1- PALB2- BRCA2 complex is relying on CHK2-mediated phosphorylation of S988 on BRCA1

While HR repair is considered as the most accurate and error-free pathway, NHEJ is a less precise repair pathway and is mainly activated in phases G0 and G1, where HR is not available. NHEJ also functions as a backup repair pathway in case of defects in components of the HR pathway [15]. The general mechanism involves the recruitment of DNA dependent protein kinases (DNA-PK) [16], following the attachment of Ku proteins on the broken ends of DNA [17] (Fig. 2). Afterward, a DNA polymerase fills the gaps that have been produced as a result of the endonuclease activity of Artemis protein. Finally, a DNA ligase IV joins the DNA ends with the help of its cofactors, XRCC4 and XLF [15].

Fig. 2
figure 2

Non-homologous end-joining DNA repair system. The general mechanism involves the recruitment of DNA dependent protein kinases (DNA-PK), following the attachment of Ku proteins on the broken ends of DNA. Afterward, a DNA polymerase fills the gaps that have been produced as a result of the endonuclease activity of Artemis protein. Finally, a DNA ligase IV joins the DNA ends with the help of its cofactors, XRCC4, and XLF

Every event that has been described above happens during the cell cycle (Fig. 3). While a normal cell cycle is vital for the development and survival of organisms, a defective one inflicts irreparable losses. To prevent such unwanted destiny, cells have developed cell cycle checkpoints to allow the progression of the cycle when the events of each phase are completed properly or arrest the cycle once there is DNA damage. The main regulators of cell cycle checkpoints are cyclin-dependent kinases (CDK), which are activated in the presence of cyclin proteins [18].

Fig. 3
figure 3

An overview of the cell cycle regulation. Cyclin D with the cooperation of CDK4/6 regulates the events is the early G1 phase. Cyclin E-CDK2 are responsible to initiate S phase, Cyclin A with CDK2 and then CDK1 involve in the completion of S phase for entry into mitosis, and Cyclin B-CDK1 fascinate this entry

In the G1 phase, two complexes of CDK4/6-Cyclin D and CDK2-Cyclin E, permit the cells to enter the S phase by phosphorylating the transcriptional repressors Retinoblastoma (Rb) and p107/p130 proteins, a process which eventually leads to initiation of DNA replication (Fig. 3). In the case of DSB, the cycle is halted by activation of ATM and phosphorylation of CHK2, which in turn phosphorylate cdc25A and p53 in order to inhibit the cell from entering the S phase [19]. Cells that have successfully passed the G1 checkpoint, start their DNA duplication in phase S. A DNA damage in this stage leads to activation of the ataxia-telangiectasia mutated and Rad3 related kinase (ATR) and chk1 kinase to stabilize p53 and degrade cdc25A [18, 20].

Prior to the mitosis, cells go through the G2 phase to grow and produce the proteins necessary for the division process (Fig. 3). In this phase, CDK1-cyclin B is the main regulator and the interruption of the cell cycle in the presence of DNA damage particularly relies on ATR and chk1 rather than ATM and CHK2 proteins [18].

The activity of each component in DNA repair pathways and cell cycle checkpoints results in the progression of cells into division or apoptosis. However, in cancerous cells, these mechanisms do not function properly and lead to harmful consequences.



Mutation in BRCA1 gene is considered as the main cause of hereditary breast cancer, and it is responsible for 40–45% of total hereditary breast cancer development [21]. Over 858 BRCA1 mutations have been confirmed to have a significant clinical impact on cancer susceptibility. Women with an inherited BRCA1 mutation have a lifetime risk of 70–80% of developing breast cancer and 37–62% of developing ovarian cancer [22]. Moreover, there are other types of cancers related to the BRCA1 mutations, such as fallopian tube and peritoneal cancer in women and prostate and breast cancer in men [23, 24].

BRCA1 mutated breast cancer is known to be triple-negative breast cancers (TNBC), characterized by negative estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). However, they manifest the same immunohistochemical profiles for the positive expression of cytokeratin (CK) 5/6 and CK14 with sporadic basal carcinoma [25].

Gene structure

BRCA1 is located on chromosome 17 and consists of 22 coding exons, which exon 11 is considered as the largest one, encoding over 60% of total 1863 amino acids encoded by the BRCA1 gene (Fig. 4a). BRCA1 gene is responsible for the translation of full-length BRCA1 protein [26] and over 4000 genetic variants of this gene have been functionally identified [27]. The mature and full-length of BRCA1 protein is located in the nucleus and consists of several functional domains, including N-terminal zinc-binding RING finger domain (amino acids #10-109), BRCA1 C-terminal (BRCT) domain (amino acids #1640-1729, #1760-1821), two nuclear localization signals (NLS), a coiled-coiled domain (amino acids #1367-1437), and Serine– Glutamine (SQ) cluster (amino acids #1280-1524) [28] (Fig. 4a).

Fig. 4
figure 4

The gene structure of BRCA1 (a) and the overall contribution of this protein (b), mainly in the cell cycle (c) and apoptosis pathways (d)

The zinc-binding RING finger motif is the main functional part of BRCA1 and it is important for E3-ubiquitin ligase activity of this protein. This motif heterodimerizes with BRCA1-Associated RING Domain 1 (BARD1) and the tandem BRCT domain, resulting in various protein-protein interactions through binding to phosphorylated serine [29].

BRCT domain appears as a tandem repeat in BRCA1 gene and it is responsible for the phosphoprotein interactions between BRCA1 and other phosphorylated proteins involved in DNA damage response, such as CtIP, BRIP1, and Abraxas [30, 31]. Shakya demonstrated that the BRCT domain is critical for the genome stability function of BRCA1, and S1598F point mutation in this domain disrupts the genomic stability function of BRCA1 and causes tumors development like when BRCA1 is completely deactivated [32]. Moreover, a recent study revealed that the interaction between this domain and mTORC2 impairs Akt activation, which is necessary for the proliferation of cancer cells [33]. Several BRCT-associated mutations have been recognized, which are able to disturb different functions of this protein, including damage foci localization, protein stability, and resection-dependent Homology directed repair (HDR) and Single Strand Annealing (SSA) [34,35,36,37].

The region between the RING and BRCT domains is called the central region of BRCA1. The central region was not studied properly as two previous domains [38]. Recently Lin reported this region contains nine highly-conserved motifs, which are necessary for DNA repair activity of BRCA1 and the deletion of these motifs could decrease cell viability following cisplatin treatment [39].

The transportation of BCRA1 from the cytosol to the nucleus is controlled by two NLS domains, which are recognized by the importin-α machinery. Mutation in the NLSs domain causes accumulation of BRCA1 in the cytosol and reduce the tumor suppressor activity of this protein [40].

The coiled-coil domain of BRCA1 is located in exons 11-13 of BRCA1 and interacts with the coiled-coil domain of PALB2 during the HR DNA repair system [41, 42]. The SQ cluster also contributes to HR and contains several serine and threonine residues that can be phosphorylated by ATM and ATR [43, 44].


Several functions have been attributed to BRCA1 protein, including transcription-coupled repair, regulation of transcription, remodeling of chromatin, apoptosis, and ligation of ubiquitin [44] (Fig. 4b). However, the well-known function of BRCA1, acting as a tumor suppressor, is related to the role of BRCA1 in promoting genomic stability [45, 46]. In order to regulate genomic stability, BRCA1 contributes to DNA repairing pathways, participates in DNA damage-induced cell cycle checkpoint mechanisms (Fig. 4c), and induce apoptosis cascade activation (Fig. 4d) [45]. Moreover, recent evidence demonstrated BRCA1 contribution to genomic stability maintenance is associated with the prevention of tandem duplication [47] and RNA-DNA hybrid (R loop) processing [48].

DNA repair

Several studies have reported that cells with defective BRCA1 gene are hypersensitive to DNA damaging agents, such as IR, UV, and alkylating agents. These defective BRCA1-cells fail to repair DNA damages properly, indicating the essential role of BRCA1 in the DNA repair system [9]. As discussed earlier, NHEJ and HR are two main DSB repairing pathways in every organism. BRCA1 influences the cellular choice to proceed toward NHEJ or HR pathways to repair the damages in DNA.

Role of BRCA1 in HR

Many studies demonstrated the direct role of BRCA1 in the HR pathway, as BRCA1 deficient cells showed severe impaired HR-mediated DSB repairing (Fig. 1) [14, 49]. Following DSB in DNA, BRCA1 binds to DSB through abraxas–RAP80 macro-complex, which induces ubiquitination of histones at DNA DSBs [14]. The formation of BRCA1–abraxas–RAP80 complex is dependent on the phosphorylation of histone H2AX (γH2AX), the mediator of DNA damage checkpoint protein 1 (MDC1) and RING finger protein 8 (RNF8) by ATM [50]. Afterward, BRCA1 via cooperating with Mre11, Rad50, and Nbs1 (MRN) forms a complex with CtIP, to promote 5′-end resection in the early steps of the synthesis-dependent strand annealing (SDSA) pathway of HR [51, 52]. Although the BRCA1–CtIP complex has been shown to be critical for the HR pathway in chicken DT40 cells, another research reported this interaction is not necessary for resection-mediated DNA repair or tumor suppression in mammalian cells [53]. In the following, BRCA1 interacts with PALB2 and BRCA2 to recruit RAD51, an essential mediator in the HR repairing pathway. The formation of BRCA1- PALB2- BRCA2 complex is relying on CHK2-mediated phosphorylation of S988 on BRCA1 [54]. Lack of BRCA1 or mutation in S971, which corresponds to human S988, breaks apart the PALB2-BRCA2 complex, which leads to the abrogated HR repair process and development of mammary and endometrial tumors in exposure to DNA damaging agents [55]. The function of BRCA1 in HR is distinct from its other functions in the DDR. Cells expressing BRCA1 mutant S988A have defective HR repair pathway, although the checkpoint regulation or resistance to ionizing radiation remains intact [56].

Furthermore, a recent study found that T1394 phosphorylation residues are influential for BRCA1-PALB2 interaction and any mutation in this site can partially impair HR pathway activity [57].

The BRCA1–BACH1 complex also contributes to the HR pathway. This complex is not HR restricted and involves many DNA repair pathways, such as cell cycle checkpoint, and DNA interstrand crosslink (ICL) repair [58]. BACH1 is one of the Fanconi anemia (FA) proteins that interact with the BRCT domain of BRCA1 through phosphoserine [59]. Mutation in BACH1 or in BRCT domain that could disrupt the interaction between BRCA1 and BACH1, affect the HR pathway, delay DNA repair, and finally increase the risk of breast cancer [60, 61].

Role of BRCA1 in NHEJ

BRCA1 contribution to the NHEJ repair pathway has been reported in different studies; however, there are contradictory results regarding this function. The role of BRCA1 in NHEJ has been initially determined in MEFs, indicating a significantly reduced end-joining activity in BRCA1 depleted MEFs comparing to the wild-type cells [62]. Later, other studies have reported the same decreased activity of the NHEJ pathway in BRCA1-deficient HCC1937 [63], and lymphoblastoid cell lines derived from breast cancer patients [64, 65]. Further studies demonstrated BRCA1 is required for precise end-joining, as knockdown of this gene significantly reduced the ability of cells in precise DNA repair mechanisms [66]. A similar result has been obtained, when other C-NHEJ components, including Ku70, XRCC4, and Ligase IV were knocked down [66]. Moreover, a reduced level of end-joining efficiency has been reported in BRCA1Δ14– 15 and BRCA1Δ17–19 splicing variants, suggesting that these splicing variants may have a prevailing negative effect on the efficiency of C-NHEJ [67].

In contrast, some evaluations concluded that BRCA1 is not part of NHEJ pathway in BRCA-deficient HCC1973 cell lines using pulsed-field gel electrophoresis [68, 69] and further showed sporadic breast cancer cells has intact NHEJ activity in DSB repairing [70].

Cell cycle checkpoints

Cell cycle checkpoints have a critical role in cell survival. During DNA damage, BRCA1 contributes to cell survival through activating DNA damage checkpoints occurring in G1/S, intra-S, and G2/M phases (Fig. 4c). Eventually, the activated checkpoints block the cell cycle progression in the presence of DNA damage and prohibit the cell cycle process until the damage is fully repaired.

Role of BRCA1 in G1/S checkpoint

In 2004 Fabbro et al. reported cells with knockdown BRCA1 failed to undergo cell cycling progression through G1/S checkpoint, indicating the important role of BRCA in this cell cycle phase [71]. The authors reported that BRCA1 mediates the phosphorylation of p53 by ATM during DNA damage and thereby, induce the expression of cyclin inhibitor p21. In their study, BRCA1 induced phosphorylation of p53 in response to both IR and UV DNA damage; however, the role of BRCA1 in G1/S arrest was merely found following IR damage. Additionally, a recent study reported that UV exposure also disrupts the G1/S cell cycle checkpoint in primary fibroblasts from individuals with a BRCA1 +/- genotype [72].

Role of BRCA1 in S-phase checkpoint

S-phase checkpoint is another cell cycle checkpoint, which inhibits the cell cycle progression following DNA damage. The impaired activity of S-phase checkpoints in BRCA1 deficient HCC1937 cells during DNA damage and its restoration to normal activity by functional complementation of the BRCA1 gene indicates that BRCA1 has a critical role in S-phase checkpoint activity [73].

In response to DNA damage, ATM and ATR are activated and promote the kinase activity of Chk1 and Chk2. These two checkpoint kinases regulate the Cdc25 phosphatase family and this family (A/B/C) controls cyclins and cyclin-dependent kinases’ activity during S-phase progression [19]. It seems that BRCA1 involvement in S-phase checkpoint is mediated through regulation of Chk1 kinase activity.

Moreover, activation of S-phase checkpoint is dependent on the phosphorylation of ser1387 of BRCA1 via ATM, indicating the possible role of phosphorylated BRCA1 in recruiting the other regulating components in the signal cascade [73]. Furthermore, BRCA1 might regulate the activation of ATM following DNA damage during S-phase. Studies have demonstrated that BRCA1 interacts with the MRN complex, which monitors cells for DSBs and activates ATM directly [74, 75].

Besides, a recent study suggested that in response to DNA damage, pCAF and GCN5 acylate the lysine 830 of BRCA1 to activate this protein. SIRT1, on the other hand, inhibits the activity of BRCA1 through the deacetylation of lysine 830. BRCA1 and SIRT1 form a reciprocal loop to regulate the intra-S-phase checkpoint, maintaining genome stability and, thereby preventing tumorigenesis [76].

The BRCA1–BACH1 is another complex that is involved in the S phase. This interaction can be immediately detected during S checkpoint and it is necessary for stalling replication forks due to DSBs or DNA lesions [77, 78]. Mutation in the BRCT domain disturbs the proper connection between BRCA1 and BACH1, which results in delayed entry into the S phase of the cell cycle, defective DNA repair, and breast cancer development [60].

Role of BRCA1 in G2/M checkpoint

Similar to G1/S and S-phase checkpoints, G2/M checkpoint is also activated in case of DNA damage, arresting the cell cycle process, and cell division.

It has been reported that intact BRCA1 is essential for both initial and the maintenance of the G2/M checkpoint function, while BRCA2 and PALB2 are only responsible for maintaining the cell arrest [79]. Following DNA damage, abraxas–RAP80 macro-complex controls the recruitment of DNA repair proteins like BRCA1 to the sites of DNA damage and BRCA1–abraxas–RAP80 complex activates the G2/M phase cell-cycle checkpoints and cause CHK1 phosphorylation later [80]. In addition, CtIP/BRCA1 only exists in the G2 phase and has been shown to be critically involved in the G2/M transition phase checkpoint activation and CHK1 phosphorylation in response to the DNA damage [81, 82]. However, damage-induced G2 accumulation checkpoint is controlled by BRCA1–BACH1 complex, not CtIP/BRCA 1[82]


Various studies revealed the consequential role of BRCA1 in inducing apoptosis through different mechanisms (Fig. 4d). 1) BRCA1 is known to be a nuclear-cytoplasmic shuttling protein and BARD1 is responsible for transporting BRCA1 to nuclear. The BRCA1-depended apoptosis occurs when the BRCA1-BARD1 complex is disrupted and BRCA1 accumulate in the cytoplasm [83, 84]. 2) BRCA1 also mediates apoptosis through regulating the p53 inducible gene 3 (PIG3) expression [85]. PIG3 is a downstream protein of p53 and it is involved in the p53-dependent apoptosis pathway. Zhang et al. demonstrated the significant association between PIG3/BRCA1 expression and better survival of breast cancer patients [85]. 3) A correlation between BRCA1 and impaired tumor necrosis factor (TNF)-α production have been reported, which is an apoptotic inducer factor [86]. Moreover, Natriuretic peptide receptor 3 suppresses cytoplasmic BRCA1 and TNF-α and protects the cardiomyocytes from cell death [87]. 4) X-linked inhibitor of apoptosis (XIAP)-associated factor 1 (XAF1) is a tumor suppressor protein that interacts with BRCA1 and makes BRCA1 bind ERα and BRCA1-mediated K48 polyubiquitination of ERα, and finally induce BRCA1-mediated apoptosis [88]. 5) BRCA1 stimulates apoptosis through binding to the inositol 1,4,5-trisphosphate receptors (IP3R), resulting in excessive calcium release and cell death [89]. IP3R acts as a calcium channel and is activated by inositol trisphosphate. BRCA1 binds to IP3R, increase the sensitivity of this receptor to its ligand, IP3, and subsequently increases IP3R-mediated apoptotic calcium release [89]. 6) BRAC1 expression could induce apoptosis in breast cancer cell lines, in response to some stress stimuli, such as serum deprivation. This apoptotic pathway is independent of p53 function and proceeds through -Ras/MEKK4/JNK and Fas-dependent signaling pathway and activation of caspase 8 [90]. 7) Cytoplasmic BRCA1 activates Growth Arrest and DNA Damage 45 (GADD45) sequences in a p53-independent manner leading to cell death. GADD45 is a DNA damage-responsive gene and function in DNA repair, cell cycle checkpoint, and apoptosis pathways. BRCA1 could either activate GADD45 through interaction with Oct-1 and CAAT motifs of this gene [91] or suppress GADD45 through its interaction with a novel zinc finger protein, ZBRK1 [92]. In response to the DNA damage, BRCA1 induces the p53- independent expression of GADD45 and subsequently activates the JNK/SAPK (c-Jun N-terminal kinase/stress-activated protein kinase) pathway of cellular apoptosis [93].



BRCA2 is another highly penetrant genes involved in hereditary breast cancer susceptibility. BRCA2 mutation increases the risk of breast cancer by 45-85% and ovarian cancer by 11-23% in the women population [94]. In addition, BRCA2 mutation has been found in 10% of pancreatic cancers studied, associated with 10-fold raised risk [95].

Unlike BRCA1 mutation carriers, the pathological feature of breast cancer patients with a BRCA2 mutation is usually similar to sporadic breast cancer. Although BRCA1 is known to be TNBC, no significant correlation between BRCA2 mutation and TNBC has been reported [96].

Gene structure

BRCA2 was discovered in 1995 [97]. This large gene contains 27 exons, which the most predominant mutations occur in the exon 10 and exon 11 in the form of insertion and deletion, resulting in several premature stop codon ending and missense mutations [98].

BRCA2 gene encodes 3418 amino acids for different functional domains (Fig. 5a). The N terminal region of BRCA2 contains eight BRC repeats (amino acids #1009-2082) with approximately 1000 amino acids. Although the function of the N-terminal region is not clear yet, it has been reported that BRC repeats in this region are responsible for protein-protein interaction, especially between BRCA2 and RAD51. The c-terminal region of BRCA2 contains BRCA2 DNA-binding domain (amino acids #2478-3185), which comprises a helical domain (HD), three oligonucleotide/oligosaccharide-binding (OB) folds and a Tower domain (T). The helical domain encodes 190 amino acids and the three OB domains named as OB1, OB2, and OB3 contain approximately 110 amino acids. The OB domains are responsible for the high affinity of BRCA2 to ssDNA and dsDNA damage, and poly (ADP-Ribose) [98, 99]. Moreover, there is a phenylalanine-proline-proline (PhePP) motif in the C-terminal region (amino acids #2386–2411), beside the DNA-binding domain. PhePP interacts with DMC1 and FANCD2 thorough meiosis [100]. There are two NLS motifs in the c–terminal of BRCA2 (amino acids #3263-3269, #3381-3385), which are required for transferring BRCA2 to the nucleus.

Fig. 5
figure 5

The gene structure of BRCA2 (a) and the overall contribution of this protein (b), mainly in the cell cycle (c) and apoptosis pathways (d)


BRCA2 participates in many biological activities. This protein mainly acts as a tumor suppressor gene and prevents cells from uncontrolled dividing and growth via regulation of DNA repair, cell cycle, and cell death pathways (Fig. 5b).

DNA repair

Similar to BRCA1, BRCA2 plays a critical role in the DNA repair system. The BRCA2 deficient cells demonstrated genomic instability and caused mouse embryonic lethality. Moreover, these cells are hypersensitive to DNA damaging agents and fail to repair DNA damages properly.

Role of BRCA2 in HR

BRCA2 contribution in the DNA repair system is mainly through regulating the HR pathway [101] (Fig. 1). Yeast two-hybrid methodology provided the first evidence that BRCA2 is one of the crucial constituents of HR-mediated DSB repair [102]. Bradley et al. demonstrated the BRCA2-associated HR repair pathway is mediated by the interaction of BRCA2 and RAD51 [102]. RAD51 interacts with 300 residues of C-terminal region of BRCA2 and TR2 domain in C-terminal region stabilized the RAD51 nucleofilaments, especially in response to nucleotide depletion after treatment with a potent ribonucleotide reductase inhibitor [103]. Deletion of C-terminal region of BRCA2 or mutants like BRCA2 6174delT and 6158insT impair the RAD51- binding activity of this domain, diminish the RAD51 recruitment to the damage site, and thereby increase the risk of tumor incidence in mice and early onset of breast and ovarian cancers in human [104, 105]. Furthermore, BRCA2 deficient cells are more sensitive to DNA damages agents, such as poly (ADP-ribose) polymerase (PARP) inhibitors or radiation due to defective HR repair pathway [106].

RAD51 also interacts with BRC motifs of BRCA2 [107]. Point mutations in BRC motifs, especially those associated with familial early-onset cancer, significantly disturb the interaction between BRCA2 and RAD51. Overexpression of BRC motifs interrupts the formation of subnuclear foci during DNA damage and increases the sensitivity of cells to the ionizing radiation [107, 108]. The affinities of BRC motifs to RAD51 protein are varied. BRC1 is critical for the interaction between BRAC2 to RAD5; however, BRC4 has a threefold stronger ability to RAD51 compered to BRC1. G1529R mutation, which belongs to the BRC4 region, is significantly associated with the risk of familial breast cancer. BRC5 and BRC6 are not required for this interaction [109].

Normally, Cyclin A-CDK2 (or cyclin B-CDK1) phosphorylate Se3291 in the C-terminal region of BRCA2 and inhibit the RAD51 binding activity of this domain and consequently, suppress HR pathway [110]. Nevertheless, following DNA damage, the phosphorylation is halted and RAD51 is recruited to the BRCA2-containing DNA repair foci. Cyclin D1 interferes with the phosphorylation of Ser3291 by A-CDK2 and fascinated the recruitment of RAD51 to BRCA2 [111]. Overexpression of cyclin D1 has been reported in several cancer types, mainly familial breast cancer [112, 113]. Moreover, polo-like kinase 1 (Plk) improves the RAD51 recruitment and accumulation at the DNA damage site. Plk is a proto-oncogene that phosphorylates RAD51 at Serin 14 and BRCA2 facilitates this process. The Plk1 phosphorylates Rad51 at T14 by CK2, which facilitates Rad51 binding to Nbs1, and finally, increase the recruitment and accumulation of RAD51 and promote HR [114]. Furthermore, Ubiquitin-specific protease 21 (USP21) enhances the efficiency of interaction between BRCA2 and RAD51at the DNA damage site through deubiquitylating and stabilization of BRCA2. Deactivation of USP21 reduces the HR activity and increases the DNA damage frequency [115].

Although BRCA2 involvement in HR pathways is principally dedicated to RAD51 binding, additional protein-protein interactions are also involved. The BRC repeat in the N-terminal region of BRCA2 interacts with PALB2/FANCN, which physically links BRCA1 to BRCA2 in a cell cycle-dependent manner. Mutation in either BRCA2 or PALB2 is associated with reducing the ability of cells in HR repairing and accordingly, increasing the risk of breast cancer [116].

Role of BRCA2 in NHEJ

Although BRCA1 is involved in both HR and NHEJ repair systems, there is no strong evidence for the contribution of BRCA2 in NEHJ. Several studies reported that BRCA2 has no effect on NHEJ.

Cell cycle checkpoints

The function of BRCA2 in controlling the cell cycle checkpoints is less studied compared to the BRCA1 (Fig. 5c). Few researchers demonstrated that truncated BRCA2 cells fail to block cell-cycle transitions during DNA damage and induce enhanced susceptibility to breast cancer, although its direct effect on cell cycle arrest is controversial and it seems the protein might cause cell cycle arrest as part of its main function in DNA repair mechanism.

Role of BRCA2 in G1/S checkpoint

It is not clear whether BRCA2 directly patriciates in the G1/S checkpoint. However, a recent study reported that defective BRCA2 stimulates replication stress, which causes DNA damage and G1 arrest in a p53-dependent manner. The author showed that the p53 level was increased in BRCA2 deficient cells and the G1 cell population was reduced when p53 was abrogated [106].

Role of BRCA2 in S-phase checkpoint

For the first time, Zwet et al demonstrated that transfecting the Chinese hamster cell V-C8 with human chromosome 13, which contains BRCA2 gene, or mouse BRCA2 cDNA, could rescue the RDS phenotype of V-C8 cells [117]. This finding showed that BRCA2 involved in S-phase, although the molecular mechanism behind was not well determined. It was speculated that BRCA2 works with BRCA1 to control this cell cycle checkpoint [118]. A recent observation found the specific expression of BRCA2 in S-phase and its important role for genome maintenance of S cells population, which directly mediates the replication stress, a hallmark of pre-cancerous lesions. BRCA2 expression in the S phase is stabilized by USP21, as USP21 loss reduces the expression of BRCA2 in this cell cycle stage [115].

Role of BRCA2 in G2/M checkpoint

Early studies reported that BRCA2 deficient mice have intact G2/M in response to DNA damage, seems that BRCA2 doesn’t control this cell cycle checkpoint. However, further studies demonstrated that BRCA2 deficient mice had defective spindle assembly checkpoint, acquired mutations in the components of the mitotic checkpoint, such as p53, Bubl, and Mad3L, and had defective mitotic checkpoints, all providing evidence for the role of BRCA2 in G2/M regulation [119, 120]. In contrary to BRCA1 which is involved in both initial and the maintenance of G2/M checkpoint, BRCA2 appears to be more important for the maintenance of this cell cycle [79, 121]. Following ionizing radiation, the BRCA2 knockdown cells showed G2 checkpoint arrest; however, over time, the cells overcame this checkpoint and entered mitosis, suggesting that BRCA2 is required for the G2 maintenance [79, 121]. BRCA2 mediates its function by interacting with BRCA2-associated factor 35 (BRAF35), which is a novel protein that binds to cruciform DNA. The nuclear staining revealed the colocalization of both BRAF35 and BRCA2 on mitotic chromosomes, which was concurrent with the phosphorylation of serine 28 (Ser-28) of histone H3 [122]. Furthermore, the antagonistic antibodies against either BRCA2 or BRAF35 delayed metaphase progression [122]. Moreover, Futamura et al. showed the interaction between BRCA2 and hBUBR1. hBUBR1 is a homolog of S. cerevisiae mitotic checkpoint protein BUB1 and phosphorylate BRCA2 [123].


There is sparse evidence about the direct role of BRCA2 in the induction of apoptosis (Fig. 5d). BRCA2 deficient mice showed defective cellular proliferation and died in utero [124] Moreover, transfecting Capan-1 cells, which expresses only a COOH-terminal truncated BRCA2 inhibited tumor growth in animal models and negatively regulated cell proliferation [125]. Further studies nominated TNF and TRAIL-R signaling pathways as potential pathways behind this phenomenon. Anne M. Heijink and his college performed a genome-wide functional genetic screen and identified the gene mutations that prevented cell death in BRCA2 siRNA silenced cells. They further validated their data in multiple BRCA2 deactivated breast- and leukemic cell lines and reported that deactivation of BRCA2 induces apoptosis through TNFα signaling pathway in these cell lines via downregulation of TNF receptor 1 (TNF-R1) or its downstream signaling component Sam68 [126]. In addition, another new study revealed that BRCA2 induces cell apoptosis through the TRAIL/TRAIL receptor signaling pathway and caspase 8 recruitment, apart from other functions of BRCA2 in cell cycle arrest and DNA repair [127]. However, inconsistent result was reported from a clinical study, reporting no significant difference between cellular proliferation and apoptosis between hereditary (with germline BRCA mutations) and sporadic (without BRCA mutation) ovarian tumors [128].

Radiosensitivity assays in Breast Cancer

Micronucleus assay

Micronuclei (MNi) acts as a biomarker for chromosome damage or entire chromosome loss. Therefore, in vitro micronucleus (MN) assay was designed to detect the genotoxic damage in the cells by scoring the presence of MNi. This test is faster than the chromosome aberration test as the population cells are in the interphase and the scoring system could be done in automation rather than manually [129].

The radiosensitivity capacity of the cells in different cell cycles is not similar. In the G0 MN assay, blood is irradiated, then cultured in the presence of phytohemagglutinin (PHA), resulting in the irradiation of T lymphocytes in the G0 phase. G0-based assays have the precondition that all lymphocytes are in the same cell cycle with G0-radiosensitivity. In contrast, in G2 MN assay cells are treated with mitogen PHA before irradiation. PHA stimulates T lymphocyte division and provides a population of cycling lymphocytes (G1, S1, G2, and M phase) after 3 days of incubation when the blood culture is irradiated [130]. In general, MNi is detectable in dividing eukaryote cells only. This technique has been further modified by Fenech and Morely, called cytokinesis-block MN (CBMN), in order to score DNA damaged in a once-divided binucleated cell, which are the cells that can express MNi. In the CBMN technique, cells are treated with cytochalasin B, which is an inhibitor of cytokinesis in cell division and the visualized binucleated cell are an indicator of cell that completed one nuclear division [131].

Nine studies compared the RS of breast cancer patients with control individuals (Table 1). The majority of studies (77.8%) reported that radiation-induced frequency of micronucleus was significantly higher in breast cancer group in comparison to control [5, 10, 11, 133, 135, 136, 145]. In contrast, Djuzenova et al. determined no significant difference between the level of MNi in breast cancer patients and healthy participants using G2 micronucleus test [12] and Francies et al. reported breast cancer patients with luminal are more radiosensitive compared to healthy control, while no difference between those with triple-negative breast cancer and healthy control has been detected [132].

Table 1 The radiosensitivity level of breast cancer patients, BRCA1/2 mutation carriers and breast cancer patients with radiotherapy complication, using micronucleus assay

Almost half of the studies which compared DNA repair capacity of healthy BRCA1 mutation carrier with non-carrier controls have reported no significant results [13, 138] while others reported monoallelic BRCA1 or BRCA2 mutations are associated with an enhanced radiosensitivity [11, 130, 137, 138, 140, 141].

Although Rothfus et al. have suggested the MN test as a screening test for carriers of a BRCA1 mutation in breast cancer families, others failed to get this result [142]. It seems this approach is not likely to be useful for identification of BRCA carriers from non-carrier with familial history of breast cancer [130, 137, 140,141,142].

To determine whether MN assay is capable to predict breast cancer patients with advanced radiotherapy complications, two studies reported that the level of MNi in cancer patients with an early adverse skin reaction was significantly higher than the unselected breast cancer group [12] and late reaction [144]. However, Finnon et al. found no evidence of a differential response between breast cancer patients with marked or mild late adverse responses to adjuvant breast radiotherapy [143]. Barber et al. also concluded no trends towards increased chromosomal RS between acute and late reactions following radiotherapy [134].

G2/0 chromosomal assay

After the MN assay, the chromosomal radiosensitivity assay is a cell-cycle-based technique that has been used extensively to investigate the association between human chromosomal RS and susceptibility to cancer or radiotherapy outcome. G2 assay most often applied on PHA-stimulated peripheral blood T-lymphocytes although it can measure the chromatid aberrations in any dividing population of cells, such as skin fibroblasts. In this technique, cells are exposed to invitro-radiation during the G2 phase of the cell cycle. The chromatid gaps and breaks can be observed in cells that progressed to metaphase. Briefly, cells are cultured for 71–72 h before irradiation. After 30 minutes of recovery, cells are treated with colcemid for 1 h. The cells observed at metaphase are those that were radiated in the G2 phase of the cell cycle [146].

In all reported results, G2 assay able to detect the RS differences in healthy donor and breast cancer patients [135, 147,148,149,150,151,152] (Table 2). About BRCA1/2 carriers, Ernestos et al. [153] and Baeyens et al. [139] have reported that breast cancer patients with BRCA1 or BRCA2 mutations were not radiosensitive than healthy women carrying no mutation.

Table 2 The radiosensitivity level of breast cancer patients, BRCA1/2 mutation carriers and breast cancer patients with radiotherapy complication, using G0/G2 chromosomal assay

Regarding the radiotherapy complications, no trends towards increased chromosomal RS between acute and late adverse reactions [134] or between marked and mild late adverse reactions [143] following radiotherapy were reported.

Comet assay

Comet Assay also called single cell gel electrophoresis (SCGE), is a sensitive and rapid technique for detecting chromosome aberration in eukaryotic cells. This technique was first introduced by Swedish researchers Östling & Johansson in 1984 [154] and modified four years later as Alkaline Comet Assay by Singh, et al. [155]. The alkaline comet assay detects a wide range of DNA damage including SSB, DSB, and alkaline- labile sites. Another most common types of comet assay is the neutral comet assay, which is more specific for detecting DSB [156].

Three Studies evaluated the RS level in breast cancer patients in comparison to healthy donors (Table 3). Two studies found no significant difference in radiation-induced DNA damage in cancer cases and healthy donors [12, 157] while LOU et al. found a significantly higher level of DNA damage in breast cancer patients [133]. Similarly, in another study, Zhang et al. found malignant breast cancer patients showed a significant upper rank of residual DNA double-strand than patients with benign breast disease in neutral comet assay [156].

Table 3 The radiosensitivity level of breast cancer patients, BRCA1/2 mutation carriers and breast cancer patients with radiotherapy complication, using comet assay

Healthy BRCA1 mutation carriers (heterozygous genotype) and non-carrier control had a similar mean tail moment at baseline, and following g-irradiation. It seems that the use of comet assay for the detection of DNA repair capacity in healthy BRCA1 mutation carriers would be limited [13].

For the predicative purpose of radiotherapy complication by comet assay, [12, 158], Oppitz et al. measured the radiosensitivity in lymphocytes, PBMC, and fibroblast of breast cancer patients and compared with the clinical acute reaction to radiotherapy. A significant association between RS level and adverse early skin reaction was found in lymphocytes cell, but not in PBMC and Fibroblast [158].

Bio markers

In response to DSB, the histone H2 variant H2AX is phosphorylated at its carboxyl-terminus on the conserved serine 139 residues and named γ-H2AX [159]. γ -H2AX is recognized as the biomarker of DSB, which can be visualized within minutes of exposure [50]. Apart from H2AX, P53 binding protein (53BP1) is another damage sensor of DSBs [160] that is localized in damage site and mediates the recruitment of BRCA1 by methylated H3 Lys 79 and signals chromatin/DNA damage [161]. Following DNA damage, 53BP1 is rapidly phosphorylated by ATM on multiple residues such as serine 25 (Ser25) and serine 1778 (Ser1778) [162,163,164]. The phosphorylated 53BP1 localizes in the damage site and mediates the recruitment of BRCA 1[165,166,167].

Djuzenova et al. reported γ-H2AX assay may be useful for screening the radiosensitivity in breast cancer patients (Table 4). In their study the number of γ-H2AX foci was significantly higher in unselected breast cancer patients compared to healthy volunteers in both initial (0.5 Gy, 30 min) and residual (2 Gy, 24 h post-radiation) DNA damage. For 53bp1, a higher level of foci was detected in the residual DNA damage only [169]. Similarly, another study reported the correlation between immunofluorescence of γ- H2AX/53BP1 residual in breast cancer patients with healthy volunteers [168].

Table 4 The radiosensitivity level of breast cancer patients, BRCA1/2 mutation carriers and breast cancer patients with radiotherapy complication, using H2AX, P53bp biomarkers

Healthy BRCA1 mutation carriers and non-carriers showed a similar level of γ-H2AX nuclear foci after exposure to radiation, indicating γ-H2AX nuclear foci assay is not likely able to distinguish women at a high risk of hereditary breast cancer [13].

Increased chromosomal radiosensitivity, quantified by γ-H2AX/53BP [168, 170] and γ-H2AX [169] immunofluorescence microscopy were observed in breast cancer patients with an adverse acute skin reaction compared to those with normal skin reaction after radiotherapy. The controversial result appeared from Finnon et al study, reported no significant association between γ -H2AX foci number in breast cancer patients with a marked adverse reaction to adjuvant breast radiotherapy with those manifesting mild late adverse reactions [143].

Colony forming assay

Colony formation is another technique to measure the intrinsic cellular radiosensitivity of tumors. It is based on the capability of a single cell to undergo multiple divisions and grow into a colony form. In the presence of DNA damage, cells fail to proliferate and lose their colony formation capacity, whereas those with intact DNA are able to survive during radiation, retain their reproductive ability and form visible colonies under a microscope [171].

Breast cancer patients with severe reactions to radiotherapy were more sensitive to invitro iodine radiation than healthy donors [172], but no evidence of a differential response was reported between breast cancer patients without radiotherapy complications and healthy donors [172] (Table 5). Moreover, colony-forming assay failed to detect the ionizing radiation sensitivity between breast cancer patients with elevated acute reactions and with average acute reactions [158].

Table 5 The radiosensitivity level of breast cancer patients, BRCA1/2 mutation carriers and breast cancer patients with radiotherapy complication, using other assays

Other assays

Telomere length assay

A telomere is a repetitive sequence structure at the end of the chromosome [175]. This specialized structure is considered as a natural DSB and acts as an inhibitor of the DSB repair pathways and DNA damage checkpoints [176].

During the division of somatic cells, the length of telomeres gradually gets shorter and this process is fascinated by various endogenous and exogenous pathogenic factors such as radiation, aging, smoking, mental stress and, etc. [177,178,179,180,181,182,183,184]. Studies showed late generation (G5–G6) mTR−/− mice were more sensitive to radiation compared with G2 mTR−/− mice, which were also deficient in telomerase activity but had longer telomere [185, 186].

Multiple methods have been developed to estimate the study of telomere including; Terminal Restriction Fragmentation (TRF), Polymerase Chain Reaction-based Technique (PCR), Single Telomere Length Analysis (STELA), Quantitative Fluorescence in situ Hybridization (Q-FISH).

TRF is often considered as the gold standard method to study telomere [187]; however, this technique failed to distinguish the level of chromosomal radiosensitivity between newly diagnosed breast cancer patients and healthy controls [174] (Table 5).

Fluorescence in situ hybridization

Fluorescence in situ hybridization (FISH), is a very highly sensitive technique that individual chromosomes are printed using a specific probe [188]. The painted chromosomes are easily visualized and the DNA damage could be scored accurately in metaphase spreads. Moreover, different types of stable DNA damage including, translocations, insertions and deletions, and unstable damage such as di centric chromosomes, rings, and acentric fragments could be differentiated [188]. Using FISH assay, Auer et al. demonstrated that breast cancer patients were significantly more sensitive compared to healthy controls [173] but not in Barwell et al.’s study [174] (Table 5).

In summary, the majority of studies confirmed the enhanced spontaneous & radiation-induced radiosensitivity of breast cancer patients compared to healthy controls (Table 6). Patients with sporadic breast cancer also had lower DNA damage capacity compared to cancer-free population, suggesting other low penetrance genes involved in DNA repair pathways, and cell cycle and apoptosis cascades, such as p53bp, ATM, BARD1, and PALb2 are involved in increased radiation susceptibility and could be a risk factor for both inherited and some sporadic breast cancer development. Therefore, evaluating the overall individual capacity of repairing DNA damages through different experimental approaches could identify the hypersensitive patients and become a marker of cancer proneness. Here we have found that MN test, G0/2 chromosomal assay, and biomarkers provided more reproducible data compared to the other assays (Table 6).

Table 6 Glance over the ability of different assays in distinguishing the radiosensitivity level among breast cancer patients, BRCA1/2 mutation carriers and breast cancer patients with radiotherapy complication

BRCA1 and BRCA2 are highly penetrated genes involved in the familial breast cancer development and about 15 % of all familial breast cancer can be attributed to a mutation in these genes. Using G2 MN and G2 chromosomal assays, some studies have reported the lymphocyte of healthy BRCA1/2 mutation carriers (heterozygous genotype) are hypersensitive to invitro ionizing radiation compared to non-carriers without a history of breast cancer. BRCA1/2 mainly function in the HR pathway. Since the HR repair pathway exclusively takes place in the late S and G2 phases of the cell cycle, increased radiosensitivity in patients harbouring BRCA1/2 mutations is mostly detected when the radiation takes place in the G2 phase. However, inconsistent evidence also exists and other studies using comment assay, and H2AX biomarker failed to detect the significant differences between these two groups as well.

Limited studies compared the radiosensitivity of healthy BRCA1/2 mutation carriers and non-carriers in the BRCA families (Table 6). Although Rothfus et al. have suggested the MN test has a potential to be a screening test for carriers of a BRCA1 mutation in breast cancer families, others failed to achieve this result. It seems this approach is not likely to be useful for the identification of BRCA carriers from non-carrier with familial history of breast cancer. Developing novel radiosensitivity assays could be a promising approach in evaluating the DNA repair capacity of individuals with BRCA1/2 mutation and consider as a predictive factor for overall increased risk mainly in the relatives of breast cancer patients.

In addition, breast cancer patients with acute early reactions to radiotherapies are more radiosensitive than those with mild/no late reactions; however, inconsistent results appear among different assays (Table 6). G2 chromosomal assay failed to differentiate these differences, while most of H2AX/p53bp biomarkers seem to be able to predict those susceptible to radiotherapy complications.

Some studies have demonstrated that the presence of BRCA1/2 mutations may increase the radiotherapy complication but others not. In the reviewed population, the genetic background of breast cancer patients has not been defined; therefore, it is not possible to figure out whether radiosensitivity assays are able to screen the BRCA1-2 mutation carrier for radiotherapy complications.


BRCA1 and BRCA2 are two highly penetrant genes involved in inherited breast cancer and contribute to different DNA damage pathways and cell cycle and apoptosis cascades. Breast cancer patients are more radiosensitive compared to healthy control; however, inconsistent results exist about the ability of current radiosensitive techniques in screening BRCA1/2 carriers or those susceptible to radiotherapy complications. Therefore, developing novel radiosensitivity assays could be a promising approach for pre-screening the BRCA1/2 mutation carriers and predict the overall increased risk mainly in the relatives of breast cancer patients. Moreover, it can provide more evidence about who is susceptible to manifest severe complication.

Availability of data and materials

All the data supporting the results are included in the article



Double-Strand Breaks


Homologous Recombinant


Non-Homologous End Joining




DNA dependent Protein Kinases


Cyclin-Dependent Kinases




Ataxia Telangiectasia mutated and Rad3 related kinase


Triple-Negative Breast Cancers


Estrogen Receptor


Progesterone Receptor


Human Epidermal Growth Factor Receptor 2 (HER2)




BRCA1 C-terminal


Nuclear Localization Signals


Serine– Glutamine


BRCA1-Associated RING Domain 1


Homology Directed Repair


Single Strand Annealing


Partner and Localizer of BRCA2


histone H2AX


Mediator of DNA Damage Checkpoint Protein 1


RING Finger Protein 8


Synthesis-Dependent Strand Annealing


Interstrand CrossLink


Fanconi Anemia


Mouse Embryonic Fibroblasts


P53 Inducible Gene 3


Tumor Necrosis Factor


X-Linked Inhibitor of Apoptosis


X-Linked Inhibitor of Apoptosis-associated factor 1


Inositol 1,4,5-trisphosphate Receptors


Growth Arrest and DNA Damage45


c-Jun N-terminal Kinase/Stress-Activated Protein Kinase


Helical Domain






Poly (ADP-Ribose) Polymerase


Polo-like kinase 1


Ubiquitin-Specific Protease 21


BRCA2-associated Factor 35


Serine 28


TNF Receptor 1








Cytokinesis-Block MN


Single Cell Gel Electrophoresis


Peripheral Blood Mononuclear cell


Histone Family member X


P53 Binding Protein


Serine 25


Serine 1778


Terminal Restriction Fragmentation


Polymerase Chain Reaction-based Technique


Single Telomere Length Analysis


Quantitative Fluorescence in situ Hybridization


Fluorescence in situ Hybridization


  1. Fuss JO, Cooper PK. DNA repair: dynamic defenders against cancer and aging. PLoS Biol. 2006;4:e203.

  2. Stark JM, Pierce AJ, Oh J, Pastink A, Jasin M. Genetic steps of mammalian homologous repair with distinct mutagenic consequences. J Mol Cell Biol. 2004;24:9305–16.

    CAS  Google Scholar 

  3. Bray F, Ferlay J, Soerjomataram I, Siegel RL, Torre LA, Jemal A. Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin. 2018;68:394–424.

    PubMed  Google Scholar 

  4. Larsen MJ, Thomassen M, Gerdes A-M, Kruse TA. Hereditary breast cancer: clinical, pathological and molecular characteristics. Breast Cancer. 2014;8:BCBCR. S18715.

  5. Mozdarani H, Mansouri Z, Haeri SA. Cytogenetic radiosensitivity of g0-lymphocytes of breast and esophageal cancer patients as determined by micronucleus assay. J Radiat Res. 2005;46:111–6.

    PubMed  Google Scholar 

  6. Kan C, Zhang J. BRCA1 mutation: a predictive marker for radiation therapy? Int J Radiat Oncol Biol Phys. 2015;93:281–93.

    CAS  PubMed  PubMed Central  Google Scholar 

  7. Shen S-X, Weaver Z, Xu X, Li C, Weinstein M, Chen L, et al. A targeted disruption of the murine Brca1 gene causes γ-irradiation hypersensitivity and genetic instability. Oncogene. 1998;17:3115–24.

    CAS  PubMed  Google Scholar 

  8. Foray N, Randrianarison V, Marot D, Perricaudet M, Lenoir G, Feunteun J. Gamma-rays-induced death of human cells carrying mutations of BRCA1 or BRCA2. Oncogene. 1999;18:7334–42.

    CAS  PubMed  Google Scholar 

  9. Scully R, Ganesan S, Vlasakova K, Chen J, Socolovsky M, Livingston DM. Genetic analysis of BRCA1 function in a defined tumor cell line. Mol Cell. 1999;4:1093–9.

    CAS  PubMed  Google Scholar 

  10. Ban S, Konomi C, Iwakawa M, Yamada S, Ohno T, Tsuji H, et al. Radiosensitivity of peripheral blood lymphocytes obtained from patients with cancers of the breast, head and neck or cervix as determined with a micronucleus assay. J Radiat Res. 2004;45:535–41.

    PubMed  Google Scholar 

  11. Varga D, Vogel W, Bender A, Surowy H, Maier C, Kreienberg R, et al. Increased radiosensitivity as an indicator of genes conferring breast cancer susceptibility. Strahlenther Onkol. 2007;183:655–60.

    PubMed  Google Scholar 

  12. Djuzenova C, Mühl B, Fehn M, Oppitz U, Müller B, Flentje M. Radiosensitivity in breast cancer assessed by the Comet and micronucleus assays. Br J Cancer. 2006;94:1194–203.

    CAS  PubMed  PubMed Central  Google Scholar 

  13. Kotsopoulos J, Chen Z, Vallis K, Poll A, Ainsworth P, Narod S. DNA repair capacity as a possible biomarker of breast cancer risk in female BRCA1 mutation carriers. Br J Cancer. 2007;96:118–25.

    CAS  PubMed  PubMed Central  Google Scholar 

  14. Wang B, Matsuoka S, Ballif BA, Zhang D, Smogorzewska A, Gygi SP, et al. Abraxas and RAP80 form a BRCA1 protein complex required for the DNA damage response. Science. 2007;316:1194–8.

    CAS  PubMed  PubMed Central  Google Scholar 

  15. Lieber MR. The mechanism of double-strand DNA break repair by the nonhomologous DNA end-joining pathway. Annu Rev Biochem. 2010;79:181–211.

    CAS  PubMed  PubMed Central  Google Scholar 

  16. Anderson CW, Carter TH. The DNA-activated protein kinase—DNA-PK. Molecular Analysis of DNA Rearrangements in the Immune System. Springer; 1996. 91-111.

  17. Falzon M, Fewell JW, Kuff EL. EBP-80, a transcription factor closely resembling the human autoantigen Ku, recognizes single-to double-strand transitions in DNA. J Biol Chem. 1993;268:10546–52.

    CAS  PubMed  Google Scholar 

  18. Nigg EA. Mitotic kinases as regulators of cell division and its checkpoints. Nat Rev Mol Cell Biol. 2001;2:21–32.

    CAS  PubMed  Google Scholar 

  19. Zhao H, Watkins JL, Piwnica-Worms H. Disruption of the checkpoint kinase 1/cell division cycle 25A pathway abrogates ionizing radiation-induced S and G2 checkpoints. Proc Natl Acad Sci U S A. 2002;99:14795–800.

    CAS  PubMed  PubMed Central  Google Scholar 

  20. Kastan MB, Bartek J. Cell-cycle checkpoints and cancer. Nature. 2004;432:316–23.

    CAS  PubMed  Google Scholar 

  21. Rosen EM, Fan S, Pestell RG, Goldberg ID. BRCA1 gene in breast cancer. J Cell Physiol. 2003;196:19–41.

    CAS  PubMed  Google Scholar 

  22. Janavičius R. Founder BRCA1/2 mutations in the Europe: implications for hereditary breast-ovarian cancer prevention and control. EPMA J. 2010;1:397–412.

    PubMed  PubMed Central  Google Scholar 

  23. Coupier I, Baldeyron C, Rousseau A, Mosseri V, Pages-Berhouet S, Caux-Moncoutier V, et al. Fidelity of DNA double-strand break repair in heterozygous cell lines harbouring BRCA1 missense mutations. Oncogene. 2004;23:914.

    CAS  PubMed  Google Scholar 

  24. Leongamornlert D, Mahmud N, Tymrakiewicz M, Saunders E, Dadaev T, Castro E, et al. Germline BRCA1 mutations increase prostate cancer risk. Br J Cancer. 2012;106:1697.

    CAS  PubMed  PubMed Central  Google Scholar 

  25. Huszno J, Kolosza Z. Molecular characteristics of breast cancer according to clinicopathological factors. Mol Clin Oncol. 2019;11:192–200.

    CAS  PubMed  PubMed Central  Google Scholar 

  26. Miki Y, Swensen J, Shattuck-Eidens D, Futreal PA, Harshman K, Tavtigian S, et al. A strong candidate for the breast and ovarian cancer susceptibility gene BRCA1. Science. 1994:66–71.

  27. Findlay GM, Daza RM, Martin B, Zhang MD, Leith AP, Gasperini M, et al. Accurate classification of BRCA1 variants with saturation genome editing. Nature. 2018;562:217.

    CAS  PubMed  PubMed Central  Google Scholar 

  28. Saha J, Davis AJ. Unsolved mystery: the role of BRCA1 in DNA end-joining. J Radiat Res. 2016;57:i18–24.

    PubMed  PubMed Central  Google Scholar 

  29. Rebbeck TR, Mitra N, Wan F, Sinilnikova OM, Healey S, McGuffog L, et al. Association of type and location of BRCA1 and BRCA2 mutations with risk of breast and ovarian cancer. JAMA. 2015;313:1347–61.

    CAS  PubMed  PubMed Central  Google Scholar 

  30. Manke IA, Lowery DM, Nguyen A, Yaffe MB. BRCT repeats as phosphopeptide-binding modules involved in protein targeting. Science. 2003;302:636–9.

    CAS  PubMed  Google Scholar 

  31. Rodriguez M, Yu X, Chen J, Songyang Z. Phosphopeptide binding specificities of BRCA1 COOH-terminal (BRCT) domains. J Biol Chem. 2003;278:52914–8.

    CAS  PubMed  Google Scholar 

  32. Shakya R, Reid LJ, Reczek CR, Cole F, Egli D, Lin C-S, et al. BRCA1 tumor suppression depends on BRCT phosphoprotein binding, but not its E3 ligase activity. Science. 2011;334:525–8.

    CAS  PubMed  PubMed Central  Google Scholar 

  33. Krieger KL. BRCA1 & CTDP1 BRCT Domainomics in the DNA Damage Response. 2019. Theses & Dissertations. 408.

  34. Anantha RW, Simhadri S, Foo TK, Miao S, Liu J, Shen Z, et al. Functional and mutational landscapes of BRCA1 for homology-directed repair and therapy resistance. Elife. 2017;6:e21350.

    PubMed  PubMed Central  Google Scholar 

  35. Lee MS, Green R, Marsillac SM, Coquelle N, Williams RS, Yeung T, et al. Comprehensive analysis of missense variations in the BRCT domain of BRCA1 by structural and functional assays. Cancer Res. 2010;70:4880–90.

    CAS  PubMed  PubMed Central  Google Scholar 

  36. Li M, Yu X. Function of BRCA1 in the DNA damage response is mediated by ADP-ribosylation. Cancer Cell. 2013;23:693–704.

    CAS  PubMed  PubMed Central  Google Scholar 

  37. Nelson AC, Holt JT. Impact of RING and BRCT domain mutations on BRCA1 protein stability, localization and recruitment to DNA damage. Radiat Res. 2010;174:1–13.

    CAS  PubMed  PubMed Central  Google Scholar 

  38. Mark W-Y, Liao JC, Lu Y, Ayed A, Laister R, Szymczyna B, et al. Characterization of segments from the central region of BRCA1: an intrinsically disordered scaffold for multiple protein–protein and protein–DNA interactions? J Mol Biol. 2005;345:275–87.

    CAS  PubMed  Google Scholar 

  39. Lin D, Izadpanah R, Braun SE, Alt E. A novel model to characterize structure and function of BRCA1. Cell Biol Int. 2018;42:34–44.

    CAS  PubMed  Google Scholar 

  40. Chen C-F, Li S, Chen Y, Chen P-L, Sharp ZD, Lee W-H. The nuclear localization sequences of the BRCA1 protein interact with the importin-α subunit of the nuclear transport signal receptor. J Biol Chem. 1996;271:32863–8.

    CAS  PubMed  Google Scholar 

  41. Zhang F, Ma J, Wu J, Ye L, Cai H, Xia B, et al. PALB2 links BRCA1 and BRCA2 in the DNA-damage response. Curr Biol. 2009;19:524–9.

    CAS  PubMed  PubMed Central  Google Scholar 

  42. Sy SM, Huen MS, Chen J. PALB2 is an integral component of the BRCA complex required for homologous recombination repair. Proc Natl Acad Sci USA. 2009;106:7155–60.

    CAS  PubMed  Google Scholar 

  43. Chen C-C, Feng W, Lim PX, Kass EM, Jasin M. Homology-directed repair and the role of BRCA1, BRCA2, and related proteins in genome integrity and cancer. Annu Rev Cancer Biol. 2018;2:313–36.

    PubMed  Google Scholar 

  44. Huen MS, Sy SM, Chen J. BRCA1 and its toolbox for the maintenance of genome integrity. Nat Rev Mol Cell Biol. 2010;11:138.

    CAS  PubMed  Google Scholar 

  45. Tirkkonen M, Johannsson O, Agnarsson BA, Olsson H, Ingvarsson S, Karhu R, et al. Distinct somatic genetic changes associated with tumor progression in carriers of BRCA1 and BRCA2 germ-line mutations. Cancer Res. 1997;57:1222–7.

    CAS  PubMed  Google Scholar 

  46. Weaver Z, Montagna C, Xu X, Howard T, Gadina M, Brodie SG, et al. Mammary tumors in mice conditionally mutant for Brca1 exhibit gross genomic instability and centrosome amplification yet display a recurring distribution of genomic imbalances that is similar to human breast cancer. Oncogene. 2002;21:5097.

    CAS  PubMed  Google Scholar 

  47. Willis NA, Frock RL, Menghi F, Duffey EE, Panday A, Camacho V, et al. Mechanism of tandem duplication formation in BRCA1-mutant cells. Nature. 2017;551:590–5.

    CAS  PubMed  PubMed Central  Google Scholar 

  48. Hatchi E, Skourti-Stathaki K, Ventz S, Pinello L, Yen A, Kamienirz-Gdula K, et al. BRCA1 recruitment to transcriptional pause sites is required for R-loop-driven DNA damage repair. Mol Cell. 2015;4:636–47.

    Google Scholar 

  49. Kim H, Huang J, Chen J. CCDC98 is a BRCA1-BRCT domain–binding protein involved in the DNA damage response. Nat Struct Mol Biol. 2007;14:710.

    CAS  PubMed  Google Scholar 

  50. Paull TT, Rogakou EP, Yamazaki V, Kirchgessner CU, Gellert M, Bonner WM. A critical role for histone H2AX in recruitment of repair factors to nuclear foci after DNA damage. Curr Biol. 2000;10:886–95.

    CAS  PubMed  Google Scholar 

  51. Li Y, Luo K, Yin Y, Wu C, Deng M, Li L, et al. USP13 regulates the RAP80-BRCA1 complex dependent DNA damage response. Nat Commun. 2017;8:15752.

    CAS  PubMed  PubMed Central  Google Scholar 

  52. Cruz-García A, López-Saavedra A, Huertas P. BRCA1 accelerates CtIP-mediated DNA-end resection. Cell Rep. 2014;9:451–9.

    PubMed  Google Scholar 

  53. Reczek CR, Szabolcs M, Stark JM, Ludwig T, Baer R. The interaction between CtIP and BRCA1 is not essential for resection-mediated DNA repair or tumor suppression. J Cell Biol. 2013;201:693–707.

    CAS  PubMed  PubMed Central  Google Scholar 

  54. Roy R, Chun J, Powell SN. BRCA1 and BRCA2: different roles in a common pathway of genome protection. Nat Rev Cancer. 2012;12:68.

    CAS  Google Scholar 

  55. Kim SS, Cao L, Li C, Xu X, Huber LJ, Chodosh LA, et al. Uterus hyperplasia and increased carcinogen-induced tumorigenesis in mice carrying a targeted mutation of the Chk2 phosphorylation site in Brca1. Mol Cell Biol. 2004;24:9498–507.

    CAS  PubMed  PubMed Central  Google Scholar 

  56. Zhang J, Willers H, Feng Z, Ghosh JC, Kim S, Weaver DT, et al. Chk2 phosphorylation of BRCA1 regulates DNA double-strand break repair. Mol Cell Biol. 2004;24:708–18.

    CAS  PubMed  PubMed Central  Google Scholar 

  57. Foo TK. BRCA1-PALB2 interaction and its roles in maintenance of genome stability and suppression of cancer development: Rutgers University-School of Graduate Studies; 2019. Theses & Dissertations. .

  58. Litman R, Peng M, Jin Z, Zhang F, Zhang J, Powell S, et al. BACH1 is critical for homologous recombination and appears to be the Fanconi anemia gene product FANCJ. Cancer Cell. 2005;8:255–65.

    CAS  PubMed  Google Scholar 

  59. Andreassen PR, Ren K. Fanconi anemia proteins, DNA interstrand crosslink repair pathways, and cancer therapy. Curr Cancer Drug Targets. 2009;9:101–17.

    CAS  PubMed  PubMed Central  Google Scholar 

  60. Peng M, Litman R, Jin Z, Fong G, Cantor SB. BACH1 is a DNA repair protein supporting BRCA1 damage response. Oncogene. 2006;25:2245.

    CAS  PubMed  Google Scholar 

  61. Takaoka M, Miki Y. BRCA1 gene: function and deficiency. Int J Clin Oncol. 2018;23:36–44.

    CAS  PubMed  Google Scholar 

  62. Redon CE, Nakamura AJ, Gouliaeva K, Rahman A, Blakely WF, Bonner WM. The use of gamma-H2AX as a biodosimeter for total-body radiation exposure in non-human primates. PLoS ONE. 2010;5:e15544.

    PubMed  PubMed Central  Google Scholar 

  63. Ernst Schmid T, Zlobinskaya O, Multhoff G. Differences in phosphorylated histone H2AX foci formation and removal of cells exposed to low and high linear energy transfer radiation. Curr Genomics. 2012;13:418–25.

    Google Scholar 

  64. Plowman P, Bridges B, Arlett C, Hinney A, Kingston J. An instance of clinical radiation morbidity and cellular radiosensitivity, not associated with ataxia-telangiectasia. Br J Radiol. 1990;63:624–8.

    CAS  PubMed  Google Scholar 

  65. Rothkamm K, Löbrich M. Evidence for a lack of DNA double-strand break repair in human cells exposed to very low x-ray doses. Proc Natl Acad Sci USA. 2003;100:5057–62.

    CAS  PubMed  Google Scholar 

  66. Zhong Q, Chen C-F, Chen P-L, Lee W-H. BRCA1 facilitates microhomology-mediated end joining of DNA double strand breaks. J Biol Chem. 2002;277:28641–7.

    CAS  PubMed  Google Scholar 

  67. Dikomey J, Dahm-daphi I, Brammer R, Martensen B, Kaina E. Correlation between cellular radiosensitivity and non-repaired double-strand breaks studied in nine mammalian cell lines. Int J Radiat Biol. 1998;73:269–78.

    CAS  PubMed  Google Scholar 

  68. Ciccia A, Elledge SJ. The DNA damage response: making it safe to play with knives. Mol Cell. 2010;40:179–204.

    CAS  PubMed  PubMed Central  Google Scholar 

  69. Roch-Lefèvre S, Mandina T, Voisin P, Gaëtan G, Mesa JEG, Valente M, et al. Quantification of γ-H2AX foci in human lymphocytes: a method for biological dosimetry after ionizing radiation exposure. Radiat Res. 2010;174:185–94.

    PubMed  Google Scholar 

  70. Merel P, Prieur A, Pfeiffer P, Delattre O. Absence of major defects in non-homologous DNA end joining in human breast cancer cell lines. Oncogene. 2002;21:5654.

    CAS  PubMed  Google Scholar 

  71. Fabbro M, Savage K, Hobson K, Deans AJ, Powell SN, McArthur GA, et al. BRCA1-BARD1 complexes are required for p53Ser-15 phosphorylation and a G1/S arrest following ionizing radiation-induced DNA damage. J Biol Chem. 2004;279:31251–8.

    CAS  PubMed  Google Scholar 

  72. Shorrocks J, Tobi SE, Latham H, Peacock JH, Eeles R, Eccles D, et al. Primary fibroblasts from BRCA1 heterozygotes display an abnormal G1/S cell cycle checkpoint following UVA irradiation but show normal levels of micronuclei following oxidative stress or mitomycin C treatment. Int J Radiat Oncol Biol Phys. 2004;58:470–8.

    CAS  PubMed  Google Scholar 

  73. Xu B, Kim S-T, Kastan MB. Involvement of Brca1 in S-phase and G2-phase checkpoints after ionizing irradiation. Mol Cell Biol. 2001;21:3445–50.

    CAS  PubMed  PubMed Central  Google Scholar 

  74. Lee J-H, Paull TT. Direct activation of the ATM protein kinase by the Mre11/Rad50/Nbs1 complex. Science. 2004;304:93–6.

    CAS  PubMed  Google Scholar 

  75. Lee J-H, Paull TT. ATM activation by DNA double-strand breaks through the Mre11-Rad50-Nbs1 complex. Science. 2005;308:551–4.

    CAS  PubMed  Google Scholar 

  76. Lahusen TJ, Kim S-J, Miao K, Huang Z, Xu X, Deng C-X. BRCA1 function in the intra-S checkpoint is activated by acetylation via a pCAF/SIRT1 axis. Oncogene. 2018;37:2343.

    CAS  PubMed  Google Scholar 

  77. Yu X, Chini CCS, He M, Mer G, Chen J. The BRCT domain is a phospho-protein binding domain. Science. 2003;302:639–42.

    CAS  PubMed  Google Scholar 

  78. Gong Z, Kim J-E, Leung CCY, Glover JM, Chen J. BACH1/FANCJ acts with TopBP1 and participates early in DNA replication checkpoint control. Mol Cell. 2010;37:438–46.

    CAS  PubMed  PubMed Central  Google Scholar 

  79. Simhadri S, Vincelli G, Huo Y, Misenko S, Foo TK, Ahlskog J, et al. PALB2 connects BRCA1 and BRCA2 in the G2/M checkpoint response. Oncogene. 2019;38:1585–96.

    CAS  PubMed  Google Scholar 

  80. Kim H, Chen J, Yu X. Ubiquitin-binding protein RAP80 mediates BRCA1-dependent DNA damage response. Science. 2007;316:1202–5.

    CAS  PubMed  Google Scholar 

  81. Escribano-Díaz C, Orthwein A, Fradet-Turcotte A, Xing M, Young JT, Tkáč J, et al. A cell cycle-dependent regulatory circuit composed of 53BP1-RIF1 and BRCA1-CtIP controls DNA repair pathway choice. Mol Cell. 2013;49:872–83.

    PubMed  Google Scholar 

  82. Yu X, Chen J. DNA damage-induced cell cycle checkpoint control requires CtIP, a phosphorylation-dependent binding partner of BRCA1 C-terminal domains. Mol Cell Biol. 2004;24:9478–86.

    CAS  PubMed  PubMed Central  Google Scholar 

  83. Fabbro M, Schuechner S, Au WW, Henderson BR. BARD1 regulates BRCA1 apoptotic function by a mechanism involving nuclear retention. Exp Cell Res. 2004;298:661–73.

    CAS  PubMed  Google Scholar 

  84. Shao N, Chai YL, Shyam E, Reddy P, Rao VN. Induction of apoptosis by the tumor suppressor protein BRCA1. Oncogene. 1996;13:1–7.

    CAS  PubMed  Google Scholar 

  85. Zhang W, Luo J, Chen F, Yang F, Song W, Zhu A, et al. BRCA1 regulates PIG3-mediated apoptosis in a p53-dependent manner. Oncotarget. 2015;6:7608.

    PubMed  PubMed Central  Google Scholar 

  86. Zielinski CC, Budinsky AC, Wagner TM, Wolfram RM, Köstler WJ, Kubista M, et al. Defect of tumour necrosis factor-α (TNF-α) production and TNF-α-induced ICAM-1–expression in BRCA1 mutations carriers. Breast Cancer Res Treat. 2003;81:99–105.

    CAS  PubMed  Google Scholar 

  87. Lin D, Chai Y, Izadpanah R, Braun SE, Alt E. NPR3 protects cardiomyocytes from apoptosis through inhibition of cytosolic BRCA1 and TNF-α. Cell Cycle. 2016;15:2414–9.

    CAS  PubMed  PubMed Central  Google Scholar 

  88. Jang S, Lim J, Jang S, Lee M, Chi S. 23P XAF1 assembles a destructive complex to induce BRCA1-mediated apoptosis via suppressing ERa and switching estrogen function. Ann Oncol. 2019;30:mdz238. 022.

  89. Hedgepeth SC, Garcia MI, Wagner LE, Rodriguez AM, Chintapalli SV, Snyder RR, et al. The BRCA1 tumor suppressor binds to inositol 1, 4, 5-trisphosphate receptors to stimulate apoptotic calcium release. J Biol Chem. 2015;290:7304–13.

    CAS  PubMed  PubMed Central  Google Scholar 

  90. Thangaraju M, Kaufmann SH, Couch FJ. BRCA1 facilitates stress-induced apoptosis in breast and ovarian cancer cell lines. J Biol Chem. 2000;275:33487–96.

    CAS  PubMed  Google Scholar 

  91. Fan W, Jin S, Tong T, Zhao H, Fan F, Antinore MJ, et al. BRCA1 regulates GADD45 through its interactions with the OCT-1 and CAAT motifs. J Biol Chem. 2002;277:8061–7.

    CAS  PubMed  Google Scholar 

  92. Zheng L, Pan H, Li S, Flesken-Nikitin A, Chen P-L, Boyer TG, et al. Sequence-specific transcriptional corepressor function for BRCA1 through a novel zinc finger protein, ZBRK1. Mol Cell. 2000;6:757–68.

    CAS  PubMed  Google Scholar 

  93. Harkin DP, Bean JM, Miklos D, Song Y-H, Truong VB, Englert C, et al. Induction of GADD45 and JNK/SAPK-dependent apoptosis following inducible expression of BRCA1. Cell. 1999;97:575–86.

    CAS  PubMed  Google Scholar 

  94. Balmana J, Diez O, Castiglione M, Group EGW. BRCA in breast cancer: ESMO clinical recommendations. Ann Oncol. 2009;20:iv19–20.

    Google Scholar 

  95. Foulkes WD. Inherited susceptibility to common cancers. N Engl J Med. 2008;359:2143–53.

    CAS  PubMed  Google Scholar 

  96. Hosey AM, Gorski JJ, Murray MM, Quinn JE, Chung WY, Stewart GE, et al. Molecular basis for estrogen receptor α deficiency in BRCA1-linked breast cancer. J Natl Cancer Inst. 2007;99:1683–94.

    CAS  PubMed  PubMed Central  Google Scholar 

  97. Wooster R, Bignell G, Lancaster J, Swift S, Seal S, Mangion J, et al. Identification of the breast cancer susceptibility gene BRCA2. Nature. 1995;378:789–92.

    CAS  PubMed  Google Scholar 

  98. Shahid T, Soroka J, Kong EH, Malivert L, McIlwraith MJ, Pape T, et al. Structure and mechanism of action of the BRCA2 breast cancer tumor suppressor. Nat Struct Mol Biol. 2014;21:962–8.

    CAS  PubMed  PubMed Central  Google Scholar 

  99. Spugnesi L, Balia C, Collavoli A, Falaschi E, Quercioli V, Caligo MA, et al. Effect of the expression of BRCA2 on spontaneous homologous recombination and DNA damage-induced nuclear foci in Saccharomyces cerevisiae. Mutagenesis. 2013;28:187–95.

    CAS  PubMed  Google Scholar 

  100. Fradet-Turcotte A, Sitz J, Grapton D, Orthwein A. BRCA2 functions: from DNA repair to replication fork stabilization. Endocr Relat Cancer. 2016;23:1–17.

    Google Scholar 

  101. Holloman WK. Unraveling the mechanism of BRCA2 in homologous recombination. Nat Struct Mol Biol. 2011;18:748.

    CAS  PubMed  PubMed Central  Google Scholar 

  102. Sharan SK, Morimatsu M, Albrecht U, Lim D-S, Regel E, Dinh C, et al. Embryonic lethality and radiation hypersensitivity mediated by Rad51 in mice lacking Brca2. Nature. 1997;386:804–10.

    CAS  PubMed  Google Scholar 

  103. Schlacher K, Christ N, Siaud N, Egashira A, Wu H, Jasin M. Double-strand break repair-independent role for BRCA2 in blocking stalled replication fork degradation by MRE11. Cell. 2011;145:529–42.

    CAS  PubMed  PubMed Central  Google Scholar 

  104. Berman DB, Costalas J, Schultz DC, Grana G, Daly M, Godwin AK. A common mutation in BRCA2 that predisposes to a variety of cancers is found in both Jewish Ashkenazi and non-Jewish individuals. Cancer Res. 1996;56:3409–14.

    CAS  PubMed  Google Scholar 

  105. Lancaster JM, Wooster R, Mangion J, Phelan CM, Cochran C, Gumbs C, et al. BRCA2 mutations in primary breast and ovarian cancers. Nat Genet. 1996;13:238–40.

    CAS  PubMed  Google Scholar 

  106. Feng W, Jasin M. BRCA2 suppresses replication stress-induced mitotic and G1 abnormalities through homologous recombination. Nat Commun. 2017;8:1–15.

    Google Scholar 

  107. Chen P-L, Chen C-F, Chen Y, Xiao J, Sharp ZD, Lee W-H. The BRC repeats in BRCA2 are critical for RAD51 binding and resistance to methyl methanesulfonate treatment. Proc Natl Acad Sci USA. 1998;95:5287–92.

    CAS  PubMed  Google Scholar 

  108. Wong AK, Pero R, Ormonde PA, Tavtigian SV, Bartel PL. RAD51 interacts with the evolutionarily conserved BRC motifs in the human breast cancer susceptibility gene brca2. J Biol Chem. 1997;272:31941–4.

    CAS  PubMed  Google Scholar 

  109. Davies AA, Masson J-Y, McIlwraith MJ, Stasiak AZ, Stasiak A, Venkitaraman AR, et al. Role of BRCA2 in control of the RAD51 recombination and DNA repair protein. Mol Cell. 2001;7:273–82.

    CAS  PubMed  Google Scholar 

  110. Esashi F, Christ N, Gannon J, Liu Y, Hunt T, Jasin M, et al. CDK-dependent phosphorylation of BRCA2 as a regulatory mechanism for recombinational repair. Nature. 2005;434:598–604.

    CAS  PubMed  Google Scholar 

  111. Chalermrujinanant C, Michowski W, Sittithumcharee G, Esashi F, Jirawatnotai S. Cyclin D1 promotes BRCA2-Rad51 interaction by restricting cyclin A/B-dependent BRCA2 phosphorylation. Oncogene. 2016;35:2815–23.

    CAS  PubMed  Google Scholar 

  112. Buckley MF, Sweeney K, Hamilton J, Sini R, Manning D, Nicholson R, et al. Expression and amplification of cyclin genes in human breast cancer. Oncogene. 1993;8:2127–33.

    CAS  PubMed  Google Scholar 

  113. Gillett C, Fantl V, Smith R, Fisher C, Bartek J, Dickson C, et al. Amplification and overexpression of cyclin D1 in breast cancer detected by immunohistochemical staining. Cancer Res. 1994;54:1812–7.

    CAS  PubMed  Google Scholar 

  114. Yata K, Bleuyard J-Y, Nakato R, Ralf C, Katou Y, Schwab RA, et al. BRCA2 coordinates the activities of cell-cycle kinases to promote genome stability. Cell Rep. 2014;7:1547–59.

    CAS  PubMed  PubMed Central  Google Scholar 

  115. Liu J, Kruswick A, Dang H, Tran AD, Kwon SM, Wang XW, et al. Ubiquitin-specific protease 21 stabilizes BRCA2 to control DNA repair and tumor growth. Nature Commun. 2017;8:1–12.

    Google Scholar 

  116. Tischkowitz M, Xia B, Sabbaghian N, Reis-Filho JS, Hamel N, Li G, et al. Analysis of PALB2/FANCN-associated breast cancer families. Proc Natl Acad Sci USA. 2007;104:6788–93.

    CAS  PubMed  Google Scholar 

  117. Kraakman-Van Der Zwet M, Overkamp WJ, van Lange RE, Essers J, van Duijn-Goedhart A, Wiggers I, et al. Brca2 (XRCC11) deficiency results in radioresistant DNA synthesis and a higher frequency of spontaneous deletions. Mol Cell Biol. 2002;22:669–79.

    CAS  PubMed  PubMed Central  Google Scholar 

  118. Chen J, Silver DP, Walpita D, Cantor SB, Gazdar AF, Tomlinson G, et al. Stable interaction between the products of the BRCA1 and BRCA2 tumor suppressor genes in mitotic and meiotic cells. Mol Cell. 1998;2:317–28.

    CAS  PubMed  Google Scholar 

  119. Lee H, Trainer AH, Friedman LS, Thistlethwaite FC, Evans MJ, Ponder BA, et al. Mitotic checkpoint inactivation fosters transformation in cells lacking the breast cancer susceptibility gene, Brca2. Mol Cell. 1999;4:1–10.

    CAS  PubMed  Google Scholar 

  120. Cahill DP, Lengauer C, Yu J, Riggins GJ, Willson JK, Markowitz SD, et al. Mutations of mitotic checkpoint genes in human cancers. Nature. 1998;392:300–3.

    CAS  PubMed  Google Scholar 

  121. Menzel T, Nähse-Kumpf V, Kousholt AN, Klein DK, Lund-Andersen C, Lees M, et al. A genetic screen identifies BRCA2 and PALB2 as key regulators of G2 checkpoint maintenance. EMBO Rep. 2011;12:705–12.

    CAS  PubMed  PubMed Central  Google Scholar 

  122. Marmorstein LY, Kinev AV, Chan GK, Bochar DA, Beniya H, Epstein JA, et al. A human BRCA2 complex containing a structural DNA binding component influences cell cycle progression. Cell. 2001;104:247–57.

    CAS  PubMed  Google Scholar 

  123. Futamura M, Arakawa H, Matsuda K, Katagiri T, Saji S, Miki Y, et al. Potential role of BRCA2 in a mitotic checkpoint after phosphorylation by hBUBR1. Cancer Res. 2000;60:1531–5.

    CAS  PubMed  Google Scholar 

  124. Cheung AM, Hande MP, Jalali F, Tsao M-S, Skinnider B, Hirao A, et al. Loss of Brca2 and p53 synergistically promotes genomic instability and deregulation of T-cell apoptosis. Cancer Res. 2002;62:6194–204.

    CAS  PubMed  Google Scholar 

  125. Wang S-C, Shao R, Pao AY, Zhang S, Hung M-C, Su L-K. Inhibition of cancer cell growth by BRCA2. Cancer Res. 2002;62:1311–4.

    CAS  PubMed  Google Scholar 

  126. Heijink AM, Talens F, Jae LT, van Gijn SE, Fehrmann RS, Brummelkamp TR, et al. BRCA2 deficiency instigates cGAS-mediated inflammatory signaling and confers sensitivity to tumor necrosis factor-alpha-mediated cytotoxicity. Nature commun. 2019;10:1–14.

    CAS  Google Scholar 

  127. De Toni EN, Ziesch A, Rizzani A, Török H-P, Hocke S, Lü S, et al. Inactivation of BRCA2 in human cancer cells identifies a subset of tumors with enhanced sensitivity towards death receptormediated apoptosis. Oncotarget. 2016;7:9477.

    PubMed  PubMed Central  Google Scholar 

  128. Levine DA, Federici MG, Reuter VE, Boyd J. Cell proliferation and apoptosis in BRCA-associated hereditary ovarian cancer. Gynecol Oncol. 2002;85:431–4.

    CAS  PubMed  Google Scholar 

  129. Doherty AT, Bryce SM, Bemis JC, The in vitro micronucleus assay. Genetic Toxicology: Principles and Methods. Elsevier; 2012. p. 121-141.

  130. Baert A, Depuydt J, Van Maerken T, Poppe B, Malfait F, Storm K, et al. Increased chromosomal radiosensitivity in asymptomatic carriers of a heterozygous BRCA1 mutation. Breast Cancer Res. 2016;18:52.

    PubMed  PubMed Central  Google Scholar 

  131. Fenech M, Morley AA. Measurement of micronuclei in lymphocytes. Mutat. Res. Environ. Mutagen. Relat. Subj. 1985 1985/02/01/;147:29-36.

  132. Francies FZ, Herd O, Cairns A, Nietz S, Murdoch M, Slabbert J, et al. Chromosomal radiosensitivity of triple negative breast cancer patients. Int J Radiat Biol. 2019;95:1507–16.

    CAS  PubMed  Google Scholar 

  133. Lou JL, Chen ZJ, Wei J, He JL, Jin LF, Chen SJ, et al. Response of lymphocytes to radiation in untreated breast cancer patients as detected with three different genetic assays. Biomed Environ Sci. 2008;21:499–508.

    PubMed  Google Scholar 

  134. Barber JB, Burrill W, Spreadborough AR, Levine E, Warren C, Kiltie AE, et al. Relationship between in vitro chromosomal radiosensitivity of peripheral blood lymphocytes and the expression of normal tissue damage following radiotherapy for breast cancer. Radiother Oncol. 2000;55:179–86.

    CAS  PubMed  Google Scholar 

  135. Scott D. Increased chromosomal radiosensitivity in breast cancer patients: a comparison of two assays. Int J Radiat Biol. 1999;75:1–10.

    CAS  PubMed  Google Scholar 

  136. Scott D, Barber JB, Levine EL, Burrill W, Roberts SA. Radiation-induced micronucleus induction in lymphocytes identifies a high frequency of radiosensitive cases among breast cancer patients: a test for predisposition? Br J Cancer. 1998;77:614–20.

    CAS  PubMed  PubMed Central  Google Scholar 

  137. Baert A, Depuydt J, Van Maerken T, Poppe B, Malfait F, Van Damme T, et al. Analysis of chromosomal radiosensitivity of healthy BRCA2 mutation carriers and non-carriers in BRCA families with the G2 micronucleus assay. Oncol Rep. 2017;37:1379–86.

    CAS  PubMed  PubMed Central  Google Scholar 

  138. Gutiérrez-Enríquez S, y Cajal TR, Alonso C, Corral A, Carrasco P, Cornet M, et al. Ionizing radiation or mitomycin-induced micronuclei in lymphocytes of BRCA1 or BRCA2 mutation carriers. Breast Cancer Res Treat. 2011;127:611-622.

  139. Baeyens A, Thierens H, Claes K, Poppe B, Messiaen L, De Ridder L, et al. Chromosomal radiosensitivity in breast cancer patients with a known or putative genetic predisposition. Br J Cancer. 2002;87:1379–85.

    CAS  PubMed  PubMed Central  Google Scholar 

  140. Trenz K, Lugowski S, Jahrsdörfer U, Jainta S, Vogel W, Speit G. Enhanced sensitivity of peripheral blood lymphocytes from women carrying a BRCA1 mutation towards the mutagenic effects of various cytostatics. Mutat Res Rev Mutat Res. 2003;544:279–88.

    CAS  Google Scholar 

  141. Trenz K, Rothfuss A, Schütz P, Speit G. Mutagen sensitivity of peripheral blood from women carrying a BRCA1 or BRCA2 mutation. Mutat Res-Fund Mol M. 2002;500:89–96.

    CAS  Google Scholar 

  142. Rothfuss A, Schütz P, Bochum S, Volm T, Eberhardt E, Kreienberg R, et al. Induced micronucleus frequencies in peripheral lymphocytes as a screening test for carriers of a BRCA1 mutation in breast cancer families. Cancer Res. 2000;60:390–4.

    CAS  PubMed  Google Scholar 

  143. Finnon P, Kabacik S, Mackay A, Raffy C, A'Hern R, Owen R, et al. Correlation of in vitro lymphocyte radiosensitivity and gene expression with late normal tissue reactions following curative radiotherapy for breast cancer. Radiother Oncol. 2012;105:329–36.

    CAS  PubMed  Google Scholar 

  144. Taghavi-Dehaghani M, Mohammadi S, Ziafazeli T, Sardari-Kermani M. A study on differences between radiation-induced micronuclei and apoptosis of lymphocytes in breast cancer patients after radiotherapy. Zeitschrift für Naturforschung C. 2005;60:938–42.

    CAS  Google Scholar 

  145. Burrill JB, SA Roberts, B. Bulman, D. Scott, W. Heritability of chromosomal radiosensitivity in breast cancer patients: a pilot study with the lymphocyte micronucleus assay. Int J Radiat Biol. 2000;76:1617-1619.

  146. Bryant P, Gray L, Riches A, Steel C, Finnon P, Howe O, et al. Technical report. The G2 chromosomal radiosensitivity assay. Int J Radiat Biol. 2002;78:863–6.

    CAS  PubMed  Google Scholar 

  147. Riches AC, Bryant PE, Steel CM, Gleig A, Robertson AJ, Preece PE, et al. Chromosomal radiosensitivity in G(2)-phase lymphocytes identifies breast cancer patients with distinctive tumour characteristics. Br J Cancer. 2001; doi: 05/14/received08/21/accepted;85:1157-61. 10.1054/bjoc.2001.2086.

  148. Ryabchenko N, Glavin O, Shtefura V, Anikusko M. Chromosomal radiosensitivity in Ukrainian breast cancer patients and healthy individuals. Exp Oncol. 2012;34:1–4.

    Google Scholar 

  149. Howe OL, Daly PA, Seymour C, Ormiston W, Nolan C, Mothersill C. Elevated G2 chromosomal radiosensitivity in Irish breast cancer patients: a comparison with other studies. Int J Radiat Biol. 2005;91:373–8.

    Google Scholar 

  150. Poggioli T, Sterpone S, Palma S, Cozzi R, Testa A. G0 and G2 chromosomal assays in the evaluation of radiosensitivity in a cohort of Italian breast cancer patients. J Radiat Res. 2010;51:615–9.

    PubMed  Google Scholar 

  151. Bryant PE, Riches AC, Shovman O, Dewar JA, Adamson DJ. Topoisomerase IIalpha levels and G2 radiosensitivity in T-lymphocytes of women presenting with breast cancer. Mutagenesis. 2012;27:737–41.

    CAS  PubMed  Google Scholar 

  152. Wang L-E, Han CH, Xiong P, Bondy ML, Yu T-K, Brewster AM, et al. Gamma-ray-induced mutagen sensitivity and risk of sporadic breast cancer in young women: a case–control study. Breast Cancer Res Treat. 2012;132:1147–55.

    CAS  PubMed  PubMed Central  Google Scholar 

  153. Ernestos B, Nikolaos P, Koulis G, Eleni R, Konstantinos B, Alexandra G, et al. Increased chromosomal radiosensitivity in women carrying BRCA1/BRCA2 mutations assessed with the G2 assay. Int J Radiat Oncol Biol Phys. 2010;76:1199–205.

    CAS  PubMed  Google Scholar 

  154. Ostling O, Johanson KJ. Microelectrophoretic study of radiation-induced DNA damages in individual mammalian cells. Biochem Biophys Res Commun. 1984;123:291–8.

    CAS  PubMed  Google Scholar 

  155. Singh NP, McCoy MT, Tice RR, Schneider EL. A simple technique for quantitation of low levels of DNA damage in individual cells. Exp Cell Res. 1988;175:184–91.

    CAS  PubMed  Google Scholar 

  156. Zhang C, Naftalis E, Euhus D. Carcinogen-induced DNA double strand break repair in sporadic breast cancer. J Surg Res. 2006;135:120–8.

    CAS  PubMed  Google Scholar 

  157. Shahidi M, Mozdarani H, Bryant PE. Radiation sensitivity of leukocytes from healthy individuals and breast cancer patients as measured by the alkaline and neutral comet assay. Cancer Lett. 2007;257:263–73.

    CAS  PubMed  Google Scholar 

  158. Oppitz U, Schulte S, Stopper H, Baier K, Müller M, Wulf J, et al. In vitro radiosensitivity measured in lymphocytes and fibroblasts by colony formation and comet assay: comparison with clinical acute reactions to radiotherapy in breast cancer patients. Int J Radiat Biol. 2002;78:611–6.

    CAS  PubMed  Google Scholar 

  159. Rogakou EP, Pilch DR, Orr AH, Ivanova VS, Bonner WM. DNA double-stranded breaks induce histone H2AX phosphorylation on serine 139. J Biol Chem. 1998;273:5858–68.

    CAS  PubMed  Google Scholar 

  160. Djuzenova CS, Zimmermann M, Katzer A, Fiedler V, Distel LV, Gasser M, et al. A prospective study on histone γ-H2AX and 53BP1 foci expression in rectal carcinoma patients: correlation with radiation therapy-induced outcome. BMC cancer. 2015;15:856.

    PubMed  PubMed Central  Google Scholar 

  161. Huyen Y, Zgheib O, DiTullio RA Jr, Gorgoulis VG, Zacharatos P, Petty TJ, et al. Methylated lysine 79 of histone H3 targets 53BP1 to DNA double-strand breaks. Nature. 2004;432:406.

    CAS  PubMed  Google Scholar 

  162. Matsuoka S, Ballif BA, Smogorzewska A, McDonald ER, Hurov KE, Luo J, et al. ATM and ATR substrate analysis reveals extensive protein networks responsive to DNA damage. Science. 2007;316:1160–6.

    CAS  PubMed  Google Scholar 

  163. Jowsey P, Morrice NA, Hastie CJ, McLauchlan H, Toth R, Rouse J. Characterisation of the sites of DNA damage-induced 53BP1 phosphorylation catalysed by ATM and ATR. DNA repair. 2007;6:1536–44.

    CAS  PubMed  Google Scholar 

  164. Ward IM, Minn K, Jorda KG, Chen J. Accumulation of checkpoint protein 53BP1 at DNA breaks involves its binding to phosphorylated histone H2AX. J Biol Chem. 2003;278:19579–82.

    CAS  PubMed  Google Scholar 

  165. Schultz LB, Chehab NH, Malikzay A, Halazonetis TD. p53 binding protein 1 (53BP1) is an early participant in the cellular response to DNA double-strand breaks. J Cell Biol. 2000;151:1381–90.

    CAS  PubMed  PubMed Central  Google Scholar 

  166. Rappold I, Iwabuchi K, Date T, Chen J. Tumor suppressor p53 binding protein 1 (53BP1) is involved in DNA damage–signaling pathways. J Cell Biol. 2001;153:613–20.

    CAS  PubMed  PubMed Central  Google Scholar 

  167. Wang B, Matsuoka S, Carpenter PB, Elledge SJ. 53BP1, a mediator of the DNA damage checkpoint. Science. 2002;298:1435–8.

    CAS  PubMed  Google Scholar 

  168. Chua MLK, Horn S, Somaiah N, Davies S, Gothard L, A’Hern R, et al. DNA double-strand break repair and induction of apoptosis in ex vivo irradiated blood lymphocytes in relation to late normal tissue reactions following breast radiotherapy. Radiat Environ Biophys. 2014;53:355–64.

    CAS  PubMed  Google Scholar 

  169. Djuzenova CS, Elsner I, Katzer A, Worschech E, Distel LV, Flentje M, et al. Radiosensitivity in breast cancer assessed by the histone γ-H2AX and 53BP1 foci. Radiat Oncol. 2013;8:98.

    CAS  PubMed  PubMed Central  Google Scholar 

  170. Chua MLK, Somaiah N, A’Hern R, Davies S, Gothard L, Yarnold J, et al. Residual DNA and chromosomal damage in ex vivo irradiated blood lymphocytes correlated with late normal tissue response to breast radiotherapy. Radiother Oncol. 2011;99:362–6.

    CAS  PubMed  Google Scholar 

  171. Vandersickel VGE, Slabbert J, Thierens H, Vral AGE. Comparison of the colony formation and crystal violet cell proliferation assays to determine cellular radiosensitivity in a repair-deficient MCF10A cell line. Radiat Meas. 2011;46:72–5.

    CAS  Google Scholar 

  172. West CM, Elyan S, Berry P, Cowan R, Scott D. A comparison of the radiosensitivity of lymphocytes from normal donors, cancer patients, individuals with ataxia-telangiectasia (AT) and AT heterozygotes. Int J Radiat Biol. 1995;68:197–203.

    CAS  PubMed  Google Scholar 

  173. Auer J, Keller U, Schmidt M, Ott O, Fietkau R, Distel LV. Individual radiosensitivity in a breast cancer collective is changed with the patients’ age. Radiother Oncol. 2014;48:80–6.

    Google Scholar 

  174. Barwell J, Pangon L, Georgiou A, Docherty Z, Kesterton I, Ball J, et al. Is telomere length in peripheral blood lymphocytes correlated with cancer susceptibility or radiosensitivity? Br J Cancer. 2007;97:1696–700.

    CAS  PubMed  PubMed Central  Google Scholar 

  175. McEachern MJ, Krauskopf A, Blackburn EH. Telomeres and their control. Annu Rev Genet. 2000;34:331–58.

    CAS  PubMed  Google Scholar 

  176. Blasco MA. Telomeres and cancer: a tale with many endings. Curr Opin Genet Dev. 2003;13:70–6.

    CAS  PubMed  Google Scholar 

  177. Brouilette S, Singh RK, Thompson JR, Goodall AH, Samani NJ. White cell telomere length and risk of premature myocardial infarction. Arterioscler Thromb Vasc Biol. 2003;23:842–6.

    CAS  PubMed  Google Scholar 

  178. Panossian L, Porter V, Valenzuela H, Zhu X, Reback E, Masterman D, et al. Telomere shortening in T cells correlates with Alzheimer’s disease status. Neurobiol Aging. 2003;24:77–84.

    CAS  PubMed  Google Scholar 

  179. Epel ES, Blackburn EH, Lin J, Dhabhar FS, Adler NE, Morrow JD, et al. Accelerated telomere shortening in response to life stress. Proc Natl Acad Sci USA. 2004;101:17312–5.

    CAS  PubMed  Google Scholar 

  180. Ogami M, Ikura Y, Ohsawa M, Matsuo T, Kayo S, Yoshimi N, et al. Telomere shortening in human coronary artery diseases. Arterioscler Thromb Vasc Biol. 2004;24:546–50.

    CAS  PubMed  Google Scholar 

  181. Valdes AM, Andrew T, Gardner JP, Kimura M, Oelsner E, Cherkas LF, et al. Obesity, cigarette smoking, and telomere length in women. Lancet. 2005;366:662–4.

    CAS  PubMed  Google Scholar 

  182. Uziel O, Singer JA, Danicek V, Sahar G, Berkov E, Luchansky M, et al. Telomere dynamics in arteries and mononuclear cells of diabetic patients: effect of diabetes and of glycemic control. Exp Gerontol. 2007;42:971–8.

    CAS  PubMed  Google Scholar 

  183. Sgura A, Antoccia A, Berardinelli F, Cherubini R, Gerardi S, Zilio C, et al. Telomere length in mammalian cells exposed to low-and high-LET radiations. Radiat Prot Dosimetry. 2006;122:176–9.

    CAS  PubMed  Google Scholar 

  184. Belloni P, Latini P, Palitti F. Radiation-induced bystander effect in healthy G 0 human lymphocytes: biological and clinical significance. Mutat Res-Fund Mol M. 2011;713:32–8.

    CAS  Google Scholar 

  185. Goytisolo FA, Samper E, Martín-Caballero J, Finnon P, Herrera E, Flores JM, et al. Short telomeres result in organismal hypersensitivity to ionizing radiation in mammals. JJ. Exp. Med. 2000;192:1625–36.

    CAS  Google Scholar 

  186. Wong K-K, Chang S, Weiler SR, Ganesan S, Chaudhuri J, Zhu C, et al. Telomere dysfunction impairs DNA repair and enhances sensitivity to ionizing radiation. Nat Genet. 2000;26:85.

    CAS  PubMed  Google Scholar 

  187. Montpetit AJ, Alhareeri AA, Montpetit M, Starkweather AR, Elmore LW, Filler K, et al. Telomere length: a review of methods for measurement. Nurs Res. 2014;63:289–99.

    PubMed  PubMed Central  Google Scholar 

  188. Beaton LA, Marro L, Samiee S, Malone S, Grimes S, Malone K, et al. Investigating chromosome damage using fluorescent in situ hybridization to identify biomarkers of radiosensitivity in prostate cancer patients. Int J Radiat Biol. 2013;89:1087–93.

    CAS  PubMed  Google Scholar 

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Concept: FS, MZ. Design: FS, MZ. Data-acquisition: FS, MA, MM, MR, NKY, TA. Supervision: FS, MZ. Drafting paper: FS, MA, MM, MR. Revising paper: FS, MA, MM, MR, NKY, TA, MZ. Approval to submit: FS, MA, MM, MR, NKY, TA, MZ.

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Correspondence to Majid Zaki-Dizaji.

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Sadeghi, F., Asgari, M., Matloubi, M. et al. Molecular contribution of BRCA1 and BRCA2 to genome instability in breast cancer patients: review of radiosensitivity assays. Biol Proced Online 22, 23 (2020).

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