MDC1

Gene Summary

Gene:MDC1; mediator of DNA damage checkpoint 1
Aliases: NFBD1
Location:6p21.33
Summary:The protein encoded by this gene contains an N-terminal forkhead domain, two BRCA1 C-terminal (BRCT) motifs and a central domain with 13 repetitions of an approximately 41-amino acid sequence. The encoded protein is required to activate the intra-S phase and G2/M phase cell cycle checkpoints in response to DNA damage. This nuclear protein interacts with phosphorylated histone H2AX near sites of DNA double-strand breaks through its BRCT motifs, and facilitates recruitment of the ATM kinase and meiotic recombination 11 protein complex to DNA damage foci. [provided by RefSeq, Jul 2008]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:mediator of DNA damage checkpoint protein 1
Source:NCBIAccessed: 16 March, 2017

Ontology:

What does this gene/protein do?
Show (13)

Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 16 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • siRNA
  • DNA Repair
  • Radiotherapy
  • Neoplasm Proteins
  • Prostate Cancer
  • Chromatin
  • p53 Protein
  • Tumor Suppressor Proteins
  • p300-CBP Transcription Factors
  • Single Nucleotide Polymorphism
  • Apoptosis
  • Histones
  • Radiation Tolerance
  • Nuclear Proteins
  • Cancer Gene Expression Regulation
  • Tumor Suppressor p53-Binding Protein 1
  • Trans-Activators
  • Phosphorylation
  • Immunohistochemistry
  • Vimentin
  • cdc25 Phosphatases
  • Chromosome 6
  • Cell Cycle Proteins
  • Survival Rate
  • Non-Small Cell Lung Cancer
  • Signal Transduction
  • Breast Cancer
  • DNA Damage
  • Protein-Serine-Threonine Kinases
  • Gene Expression
  • Transfection
  • DNA-Binding Proteins
  • Biomarkers, Tumor
  • Lung Cancer
  • BRCA1 Protein
  • Tumor Stem Cell Assay
  • Intracellular Signaling Peptides and Proteins
  • Ataxia Telangiectasia Mutated Proteins
  • Nerve Tissue Proteins
  • Neoplastic Cell Transformation
  • Double-Stranded DNA Breaks
Tag cloud generated 16 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: MDC1 (cancer-related)

Wang Z, Liao K, Zuo W, et al.
Depletion of NFBD1/MDC1 Induces Apoptosis in Nasopharyngeal Carcinoma Cells Through the p53-ROS-Mitochondrial Pathway.
Oncol Res. 2017; 25(1):123-136 [PubMed] Related Publications
NFBD1, a signal amplifier of the p53 pathway, is vital for protecting cells from p53-mediated apoptosis and the early phase of DNA damage response under normal culture conditions. Here we investigated its expression in patients with nasopharyngeal carcinoma (NPC), and we describe the biological functions of the NFBD1 gene. We found that NFBD1 mRNA and protein were more highly expressed in NPC tissues than in nontumorous tissues. To investigate the function of NFBD1, we created NFBD1-depleted NPC cell lines that exhibited decreased cellular proliferation and colony formation, an increase in their rate of apoptosis, and an enhanced sensitivity to chemotherapeutic agents compared with in vitro controls. However, N-acetyl cysteine (NAC) and downregulation of p53 expression could partially reverse the apoptosis caused by the loss of NFBD1. Further analysis showed that loss of NFBD1 resulted in increased production of intracellular reactive oxygen species (ROS) depending on p53, which subsequently triggered the mitochondrial apoptotic pathway. Using a xenograft model in nude mice, we showed that silencing NFBD1 also significantly inhibited tumor growth and led to apoptosis. Taken together, our data suggest that inhibition of NFBD1 in NPC could be therapeutically useful.

Cirauqui B, Margelí M, Quiroga V, et al.
DNA repair pathways to regulate response to chemoradiotherapy in patients with locally advanced head and neck cancer.
Tumour Biol. 2016; 37(10):13435-13443 [PubMed] Related Publications
Platinum-based chemoradiotherapy (CRT) is a preferred standard of care for locally advanced head and neck cancer (HNC). However, survival benefit is small, with substantial toxicity and biomarkers of CRT resistance that could guide treatment selection and spare morbidity. Increased DNA repair in solid tumors may contribute to cancer cells' ability to survive in genotoxic stress environments afforded by therapy. We assessed mRNA expression levels of DNA repair-related genes BRCA1, RAP80, 53 binding protein 1 (53BP1), mediator of DNA damage checkpoint 1 (MDC1), and RNF8. We correlated our findings with response and overall survival in 72 head and neck patients treated with weekly carboplatin AUC 2 and radiotherapy. Complete response (CR) to CRT was 50 % in patients with low levels of 53BP1 compared to 6.3 % in patients with high levels (p = 0.0059). Of high BRCA1 mRNA expressors, 41.2 % had CR compared to 29.4 % of low expressors (p = 0.72). For a small group of patients with low 53BP1 and either high BRCA1 or RAP80, CRs were 66.7 and 71.4 %, respectively. A trend for better overall survival (OS) was found for patients with low 53BP1 (15 vs 8 m; p = 0.056). Our findings highlight the potential usefulness of 53BP1 mRNA as a predictive biomarker of response and overall survival in HNC patients treated with chemoradiotherapy. Those with high 53BP1 expression could derive only a meager benefit from treatment. Analysis of BRCA1 and RAP80 could further reinforce the predictive value of 53BP1. Although this was a retrospective study with small sample size, it could inform larger translational studies in HNC.

Zeng Q, Wang Z, Liu C, et al.
Knockdown of NFBD1/MDC1 enhances chemosensitivity to cisplatin or 5-fluorouracil in nasopharyngeal carcinoma CNE1 cells.
Mol Cell Biochem. 2016; 418(1-2):137-46 [PubMed] Related Publications
Nasopharyngeal carcinoma (NPC) is a rare but highly invasive cancer that is prevalent among people of southern Chinese ancestry in southern China and Southeast Asia. Radiotherapy and cisplatin (CDDP)-based chemotherapy are the main treatment options. Unfortunately, disease response to concurrent chemoradiotherapy varies among patients with NPC, and many cases are resistant to CDDP and radiotherapy. NFBD1 functions in cell cycle checkpoint activation and DNA repair following DNA damage. In this study, we identified the NFBD1 as a tractable molecular target to chemosensitize NPC cells. NFBD1 expression in NPC CNE1 cell lines was depleted using lentivirus-mediated short hairpin RNA, and the elevated sensitivity of these NFBD1-inhibited NPC cells to therapeutic reagent CDDP and 5-fluorouracil (5-FU) was evaluated using MTS assays. Flow cytometry analysis also showed that NFBD1 knockdown led to an obvious induction of apoptosis in CDDP- or 5-FU-treated CNE1 cells. Furthermore, we implicated the involvement of NFBD1 in Rad51 and DNA-PKcs foci formation following CDDP or 5-FU chemotherapy. In conclusion, NFBD1 knockdown improves the chemosensitivity of NPC cells by inhibiting cell growth and promoting apoptosis through the impairment of DNA damage repair, suggesting NFBD1 as a novel therapeutic target for NPC.

Yue H, Zhu J, Xie S, et al.
MDC1-AS, an antisense long noncoding RNA, regulates cell proliferation of glioma.
Biomed Pharmacother. 2016; 81:203-9 [PubMed] Related Publications
BACKGROUND: Growing number of long noncoding RNAs (lncRNAs) are emerging as new modulators in cancer origination and progression. A lncRNA, mediator of DNA damage checkpoint protein 1antisense RNA (MDC1-AS), with unknown function, is the antisense transcript of tumor suppressor MDC1.
METHOD: In this study, we investigated the expression pattern and functional role of lncRNA MDC1-AS in glioma by using real time PCR and gain-/loss-of-function studies.
RESULT: The results showed that the expression levels of lncRNA MDC1-AS and MDC1 were significantly downregulated in glioma tissues compared with normal brain tissues, and in glioma cell lines U87MG, U251 and HEB. Overexpression of MDC1-AS resulted in significant inhibition of cell proliferation and cell cycle in U87MG and U251. We also found that MDC1-AS expression was positively correlated with MDC1 expression. In addition, the inhibitory role of MDC1-AS was remarkably diminished when MDC1 was knockdown.
CONCLUSION: Together, the results suggest that MDC1-AS is a novel tumor suppressor through up-regulation of its antisense tumor-suppressing gene MDC1 in glioma and leads us to propose that MDC1-AS may serve as a potential biomarker and therapeutic target for glioma.

Kanojia D, Nagata Y, Garg M, et al.
Genomic landscape of liposarcoma.
Oncotarget. 2015; 6(40):42429-44 [PubMed] Free Access to Full Article Related Publications
Liposarcoma (LPS) is the most common type of soft tissue sarcoma accounting for 20% of all adult sarcomas. Due to absence of clinically effective treatment options in inoperable situations and resistance to chemotherapeutics, a critical need exists to identify novel therapeutic targets. We analyzed LPS genomic landscape using SNP arrays, whole exome sequencing and targeted exome sequencing to uncover the genomic information for development of specific anti-cancer targets. SNP array analysis indicated known amplified genes (MDM2, CDK4, HMGA2) and important novel genes (UAP1, MIR557, LAMA4, CPM, IGF2, ERBB3, IGF1R). Carboxypeptidase M (CPM), recurrently amplified gene in well-differentiated/de-differentiated LPS was noted as a putative oncogene involved in the EGFR pathway. Notable deletions were found at chromosome 1p (RUNX3, ARID1A), chromosome 11q (ATM, CHEK1) and chromosome 13q14.2 (MIR15A, MIR16-1). Significantly and recurrently mutated genes (false discovery rate < 0.05) included PLEC (27%), MXRA5 (21%), FAT3 (24%), NF1 (20%), MDC1 (10%), TP53 (7%) and CHEK2 (6%). Further, in vitro and in vivo functional studies provided evidence for the tumor suppressor role for Neurofibromin 1 (NF1) gene in different subtypes of LPS. Pathway analysis of recurrent mutations demonstrated signaling through MAPK, JAK-STAT, Wnt, ErbB, axon guidance, apoptosis, DNA damage repair and cell cycle pathways were involved in liposarcomagenesis. Interestingly, we also found mutational and copy number heterogeneity within a primary LPS tumor signifying the importance of multi-region sequencing for cancer-genome guided therapy. In summary, these findings provide insight into the genomic complexity of LPS and highlight potential druggable pathways for targeted therapeutic approach.

Nomura H, Kataoka F, Aoki D, et al.
Expression of potential biomarkers associated with homologous recombination repair in patients with ovarian or triple-negative breast cancer.
Cancer Biomark. 2016; 16(1):145-52 [PubMed] Related Publications
BACKGROUND: Poly(ADP)-ribose polymerase (PARP) inhibitors such as olaparib can induce cell death in cancer cells with homologous recombination (HR) DNA repair deficiencies, such as BRCA1/2 mutations.
AIM: To identify prognostic biomarkers of long-term outcomes in cancer patients.
METHODS: Immunohistochemistry was used to analyse expression of key HR pathway proteins (ATM, ATR, BRCA1, MDC1, MRE11) and PARP-1 in 100 serous ovarian cancer (SOC) and 100 triple-negative breast cancer (TNBC) tumour samples from Japanese patients. RECIST assessment was used.
RESULTS: Patient demographic data and BRCA1/2 mutation status were unavailable. Most proteins listed previously were detected in > 80% of tissue samples, with BRCA1 expression detected in 60-65%. A potential link between BRCA1 expression and overall survival (M stage adjusted) in SOC patients was observed, but was not statistically significant after multiple testing adjustment. Correlations between other biomarker expression and survival were not observed. In TNBC patients, MDC1 staining was associated with progressive disease, but this was not statistically significant; the analysis did not identify significant correlations between biomarker expression and disease control. Limited event numbers prevented assessment of the prognostic value of BRCA1 in TNBC.
CONCLUSION: BRCA1 expression may be a candidate for a prognostic biomarker in SOC. Further studies are warranted.

Liao XH, Zheng L, He HP, et al.
STAT3 regulated ATR via microRNA-383 to control DNA damage to affect apoptosis in A431 cells.
Cell Signal. 2015; 27(11):2285-95 [PubMed] Related Publications
Skin cancer is a major cause of morbidity and mortality worldwide. Mounting evidence shows that exposure of the skin to solar UV radiation results in inflammation, oxidative stress, DNA damage, dysregulation of cellular signaling pathways and immunosuppression thereby resulting in skin cancer. Signal transducer and activator of transcription 3 (STAT3) is well known to function as an anti-apoptotic factor, especially in numerous malignancies, but the relationship between STAT3 activation and DNA damage response in skin cancer is still not fully understood. We now report that STAT3 inhibited DNA damage induced by UV and STAT3 mediated upregulation of GADD45γ and MDC-1 and the phosphorylation of H2AX in UV induced DNA damage. Notably, STAT3 can increase the expression of ATR in A431 cells. Luciferase assay shows that STAT3 activates the transcription of ATR promoter. More importantly, microRNA-383 suppressed ATR expression by targeting 3' (untranslated regions)UTR of ATR in A431 cells, and STAT3 down-regulates the transcription of miR-383 promoter. Thus, these results reveal the new insight that ATR is down-regulated by STAT3-regulated microRNA-383 in A431 cells. Moreover, overexpression of STAT3 enhanced expression of antiapoptosis genes BCL-1 and MCL-1, and depletion of STAT3 sensitized A431 cells to apoptotic cell death following UV. Collectively, these studies suggest that STAT3 may be a potential target for both the prevention and treatment of human skin cancer.

Wang Z, Zeng Q, Chen T, et al.
Silencing NFBD1/MDC1 enhances the radiosensitivity of human nasopharyngeal cancer CNE1 cells and results in tumor growth inhibition.
Cell Death Dis. 2015; 6:e1849 [PubMed] Free Access to Full Article Related Publications
NFBD1 functions in cell cycle checkpoint activation and DNA repair following ionizing radiation (IR). In this study, we defined the NFBD1 as a tractable molecular target to radiosensitize nasopharyngeal carcinoma (NPC) cells. Silencing NFBD1 using lentivirus-mediated shRNA-sensitized NPC cells to radiation in a dose-dependent manner, increasing apoptotic cell death, decreasing clonogenic survival and delaying DNA damage repair. Furthermore, downregulation of NFBD1 inhibited the amplification of the IR-induced DNA damage signal, and failed to accumulate and retain DNA damage-response proteins at the DNA damage sites, which leaded to defective checkpoint activation following DNA damage. We also implicated the involvement of NFBD1 in IR-induced Rad51 and DNA-dependent protein kinase catalytic subunit foci formation. Xenografts models in nude mice showed that silencing NFBD1 significantly enhanced the antitumor activity of IR, leading to tumor growth inhibition of the combination therapy. Our studies suggested that a combination of gene therapy and radiation therapy may be an effective strategy for human NPC treatment.

Zou R, Zhong X, Wang C, et al.
MDC1 Enhances Estrogen Receptor-mediated Transactivation and Contributes to Breast Cancer Suppression.
Int J Biol Sci. 2015; 11(9):992-1005 [PubMed] Free Access to Full Article Related Publications
Estrogen receptor α (ERα) is a key transcriptional factor in the proliferation and differentiation in mammary epithelia and has been determined to be an important predictor of breast cancer prognosis and therapeutic target. Meanwhile, diverse transcriptional co-regulators of ERα play crucial and complicated roles in breast cancer progression. Mediator of DNA damage checkpoint 1 (MDC1) has been identified as a critical upstream mediator in the cellular response to DNA damage, however, some non-DNA damage responsive functions of MDC1 haven't been fully defined. In this study, we have identified MDC1 as a co-activator of ERα in breast cancer cells and demonstrated that MDC1 associates with ERα. MDC1 was also recruited to estrogen response element (ERE) of ERα target gene. Knockdown of MDC1 reduced the transcription of the endogenous ERα target genes, including p21. MDC1 depletion led to the promotion of breast cancer progression, and the expression of MDC1 is lower in breast cancer. Taken together, these results suggested that MDC1 was involved in the enhancement of ERα-mediated transactivation in breast cancer cells. This positive regulation by MDC1 might contribute to the suppression of breast cancer progression by acting as a barrier of positive to negative ERα function transformation.

Ting CY, Wang HE, Yu CC, et al.
Curcumin Triggers DNA Damage and Inhibits Expression of DNA Repair Proteins in Human Lung Cancer Cells.
Anticancer Res. 2015; 35(7):3867-73 [PubMed] Related Publications
The study goal was to evaluate the effects of curcumin on DNA damage and expression of DNA-repair proteins in human lung cancer. Thus, NCI-H460 cells were used to study the effects of curcumin on DNA damage and repair in vitro. We investigated curcumin induces DNA damage by comet the assay and 4',6-diamidino-2-phenylindole (DAPI) staining. The DNA damage/repair-related protein levels were examined and monitored by western blotting and confocal microscopy. Curcumin significantly increased the length of comet tails and DNA condensation in NCI-H460 cells. Curcumin reduced expression of DNA-repair proteins such as 14-3-3 protein sigma (14-3-3σ), O6-methylguanine-DNA methyltransferase (MGMT), breast cancer susceptibility gene 1 (BRCA1), and mediator of DNA damage checkpoint 1 (MDC1). Curcumin also increased phosphorylation of p53 and Histone H2A.X (S140) in the nuclei of NCI-H460 cells. Taken together, our findings indicated that curcumin triggered DNA damage and inhibited expression of DNA-repair-associated proteins in NCI-H460 cells.

Chatterjee P, Choudhary GS, Alswillah T, et al.
The TMPRSS2-ERG Gene Fusion Blocks XRCC4-Mediated Nonhomologous End-Joining Repair and Radiosensitizes Prostate Cancer Cells to PARP Inhibition.
Mol Cancer Ther. 2015; 14(8):1896-906 [PubMed] Free Access to Full Article Related Publications
Exposure to genotoxic agents, such as ionizing radiation (IR), produces DNA damage, leading to DNA double-strand breaks (DSB); IR toxicity is augmented when the DNA repair is impaired. We reported that radiosensitization by a PARP inhibitor (PARPi) was highly prominent in prostate cancer cells expressing the TMPRSS2-ERG gene fusion protein. Here, we show that TMPRSS2-ERG blocks nonhomologous end-joining (NHEJ) DNA repair by inhibiting DNA-PKcs. VCaP cells, which harbor TMPRSS2-ERG and PC3 cells that stably express it, displayed γH2AX and 53BP1 foci constitutively, indicating persistent DNA damage that was absent if TMPRSS2-ERG was depleted by siRNA in VCaP cells. The extent of DNA damage was enhanced and associated with TMPRSS2-ERG's ability to inhibit DNA-PKcs function, as indicated by its own phosphorylation (Thr2609, Ser2056) and that of its substrate, Ser1778-53BP1. DNA-PKcs deficiency caused by TMPRSS2-ERG destabilized critical NHEJ components on chromatin. Thus, XRCC4 was not recruited to chromatin, with retention of other NHEJ core factors being reduced. DNA-PKcs autophosphorylation was restored to the level of parental cells when TMPRSS2-ERG was depleted by siRNA. Following IR, TMPRSS2-ERG-expressing PC3 cells had elevated Rad51 foci and homologous recombination (HR) activity, indicating that HR compensated for defective NHEJ in these cells, hence addressing why TMPRSS2-ERG alone did not lead to radiosensitization. However, the presence of TMPRSS2-ERG, by inhibiting NHEJ DNA repair, enhanced PARPi-mediated radiosensitization. IR in combination with PARPi resulted in enhanced DNA damage in TMPRSS2-ERG-expressing cells. Therefore, by inhibiting NHEJ, TMPRSS2-ERG provides a synthetic lethal interaction with PARPi in prostate cancer patients expressing TMPRSS2-ERG.

Gou Q, Xie Y, Liu L, et al.
Downregulation of MDC1 and 53BP1 by short hairpin RNA enhances radiosensitivity in laryngeal carcinoma cells.
Oncol Rep. 2015; 34(1):251-7 [PubMed] Related Publications
DNA double-strand breaks (DSBs) induced by ionizing radiation (IR) are among the most cytotoxic types of DNA damage. The DNA damage response (DDR) may be a reason for the cancer cell resistance to radiotherapy using IR. Identified as critical upstream mediators of the phosphorylation of ataxia telangiectasia-mutated (ATM) pathway, mediator of DNA damage checkpoint 1 (MDC1) and p53-binding proteins 1 (53BP1) may affect the radiosensitivity of tumor cells. In the present study, we generated two HEP-2 cell lines with a stable knockdown of MDC1 or 53BP1 with short hairpin RNA (shRNA), respectively, and investigated the effect of MDC1 and 53BP1 on cell radiosensitivity, cell cycle distribution and the formation of cell foci. Downregulation of the two proteins reduced the number of clonogenic cells that treated with IR. Accumulation of G2/M phase cells was detected after the MDC1 and 53BP1 downregulation. These results indicated that the expression of MDC1 or 53BP1 limited tumor cell sensitivity to radiotherapy and may play an important role in the DNA repair progression. Furthermore, the MDC1 foci was identified and presented in the 53BP1-inhibited cells. By contrast, the 53BP1 foci was absent from the MDC1-inhibited cells. The results confirmed that the recruitment of 53BP1 into the foci occurred in an MDC1-dependent manner.

Ko YC, Lien JC, Liu HC, et al.
Demethoxycurcumin-induced DNA Damage Decreases DNA Repair-associated Protein Expression Levels in NCI-H460 Human Lung Cancer Cells.
Anticancer Res. 2015; 35(5):2691-8 [PubMed] Related Publications
Demethoxycurcumin (DMC) is a key component of Chinese medicine (Turmeric) and has been proven effective in killing various cancer cells. Its role in inducing cytotoxic effects in many cancer cells has been reported, but its role regarding DNA damage on lung cancer cells has not been studied in detail. In the present study, we demonstrated DMC-induced DNA damage and condensation in NCI-H460 cells by using the Comet assay and DAPI staining examinations, respectively. Western blotting indicated that DMC suppressed the protein levels associated with DNA damage and repair, such as 14-3-3σ (an important checkpoint keeper of DNA damage response), DNA repair proteins breast cancer 1, early onset (BRCA1), O6-methylguanine-DNA methyltransferase (MGMT), mediator of DNA damage checkpoint 1 (MDC1), and p53 (tumor suppressor protein). DMC activated phosphorylated p53 and p-H2A.X (phospho Ser140) in NCI-H460 cells. Furthermore, we used confocal laser systems microscopy to examine the protein translocation. The results showed that DMC promotes the translocation of p-p53 and p-H2A.X from the cytosol to the nuclei in NCI-H460 cells. Taken together, DMC induced DNA damage and affected DNA repair proteins in NCI-H460 cells in vitro.

Wang C, Sun H, Zou R, et al.
MDC1 functionally identified as an androgen receptor co-activator participates in suppression of prostate cancer.
Nucleic Acids Res. 2015; 43(10):4893-908 [PubMed] Free Access to Full Article Related Publications
Mediator of DNA damage checkpoint protein 1 (MDC1) is essential for DNA damage response. However, the role of MDC1 in modulating gene transcription independently of DNA damage and the underlying mechanisms have not been fully defined. Androgen receptor (AR) is the central signaling pathway in prostate cancer (PCa) and its target genes are involved in both promotion and suppression of PCa. Here, we functionally identified MDC1 as a co-activator of AR. We demonstrate that MDC1 facilitates the association between AR and histone acetyltransferase GCN5, thereby increasing histone H3 acetylation level on cis-regulatory elements of AR target genes. MDC1 knockdown promotes PCa cells growth and migration. Moreover, depletion of MDC1 results in decreased expression of a subset of the endogenous androgen-induced target genes, including cell cycle negative regulator p21 and PCa metastasis inhibitor Vinculin, in AR positive PCa cell lines. Finally, the expression of MDC1 and p21 correlates negatively with aggressive phenotype of clinical PCa. These studies suggest that MDC1 as an epigenetic modifier regulates AR transcriptional activity and MDC1 may function as a tumor suppressor of PCa, and provide new insight into co-factor-AR-signaling pathway mechanism and a better understanding of the function of MDC1 on PCa.

Weng SW, Hsu SC, Liu HC, et al.
Gallic acid induces DNA damage and inhibits DNA repair-associated protein expression in human oral cancer SCC-4 cells.
Anticancer Res. 2015; 35(4):2077-84 [PubMed] Related Publications
Gallic acid (GA), a phenolic compound naturally present in plants, used as an antioxidant additive in food and in the pharmaceutical industry, may have cancer chemopreventive properties. In the present study, we investigated whether GA induced DNA damage and affected DNA repair-associated protein expression in human oral cancer SCC-4 cells. Flow cytometry assays were used to measure total viable cells and results indicated that GA decreased viable cells dose-dependently. The comet assay and 4',6-Diamidino-2-phenylindole dihydrochloride (DAPI) staining were used to measure DNA damage, as well as condensation and it was shown that GA induced DNA damage (comet tail) and DNA condensation in a dose-dependent manner. DNA gel electrophoresis was used to examine DNA fragmentation and we found that GA induced DNA ladder (fragmentation). Using western blotting it was shown that GA inhibited the protein expressions of MDC1, O(6)-methylguanine-DNA methyltransferase (MGMT), p-H2A.X, p53, DNA-dependent serine/threonine protein kinase (DNA-PK) and 14-3-3 proteins sigma (14-3-3σ) but increased p-p53, phosphate-ataxia-telangiectasia (p-H2A.X) and ataxia telangiectasia mutated and Rad3-related (p-ATR), phosphate-ataxia telangiectasia mutated (p-ATM) and breast cancer susceptibility protein 1 (BRCA1) in a 24-h treatment. The protein translocation was examined by confocal laser microscopy and results indicated that GA increased the levels of p-H2A.X, MDC1 and p-p53 in SCC-4 cells. In conclusion, we found that GA-induced cell death may proceed through the induced DNA damage and suppressed DNA repair-associated protein expression in SCC-4 cells.

Wu LY, Lu HF, Chou YC, et al.
Kaempferol induces DNA damage and inhibits DNA repair associated protein expressions in human promyelocytic leukemia HL-60 cells.
Am J Chin Med. 2015; 43(2):365-82 [PubMed] Related Publications
Numerous evidences have shown that plant flavonoids (naturally occurring substances) have been reported to have chemopreventive activities and protect against experimental carcinogenesis. Kaempferol, one of the flavonoids, is widely distributed in fruits and vegetables, and may have cancer chemopreventive properties. However, the precise underlying mechanism regarding induced DNA damage and suppressed DNA repair system are poorly understood. In this study, we investigated whether kaempferol induced DNA damage and affected DNA repair associated protein expression in human leukemia HL-60 cells in vitro. Percentages of viable cells were measured via a flow cytometry assay. DNA damage was examined by Comet assay and DAPI staining. DNA fragmentation (ladder) was examined by DNA gel electrophoresis. The changes of protein levels associated with DNA repair were examined by Western blotting. Results showed that kaempferol dose-dependently decreased the viable cells. Comet assay indicated that kaempferol induced DNA damage (Comet tail) in a dose-dependent manner and DAPI staining also showed increased doses of kaempferol which led to increased DNA condensation, these effects are all of dose-dependent manners. Western blotting indicated that kaempferol-decreased protein expression associated with DNA repair system, such as phosphate-ataxia-telangiectasia mutated (p-ATM), phosphate-ataxia-telangiectasia and Rad3-related (p-ATR), 14-3-3 proteins sigma (14-3-3σ), DNA-dependent serine/threonine protein kinase (DNA-PK), O(6)-methylguanine-DNA methyltransferase (MGMT), p53 and MDC1 protein expressions, but increased the protein expression of p-p53 and p-H2AX. Protein translocation was examined by confocal laser microscopy, and we found that kaempferol increased the levels of p-H2AX and p-p53 in HL-60 cells. Taken together, in the present study, we found that kaempferol induced DNA damage and suppressed DNA repair and inhibited DNA repair associated protein expression in HL-60 cells, which may be the factors for kaempferol induced cell death in vitro.

Liu X, Dong R, Jiang Z, et al.
MDC1 promotes ovarian cancer metastasis by inducing epithelial-mesenchymal transition.
Tumour Biol. 2015; 36(6):4261-9 [PubMed] Related Publications
Ovarian cancer is a highly invasive cancer with poor prognosis. Previous studies have revealed lots of connections between the invasiveness and epithelial-mesenchymal transition (EMT), which is common during the progression of ovarian cancer. MDC1, a mediator of DNA damage checkpoint, has recently been implicated as a potential oncogene. Here, in this article, we studied the role of MDC1 in ovarian cancer metastasis. First, in tissue samples, we found that high expression level of MDC1 was correlated with poor prognosis. Furthermore, MDC1 overexpression in ovarian cancer cells significantly increased migration and invasion. In contrast, silencing MDC1 reversed these processes. Consistently, nude mice xenograft confirmed that silencing MDC1 suppressed tumor metastasis in vivo. We further demonstrated that MDC1 induced EMT through modulation EMT markers such as E-cadherin, N-cadherin, and vimentin. Taken together, our findings suggest that MDC1 promotes ovarian cancer metastasis through the induction of EMT.

Xue Y, Ma G, Zhang Z, et al.
A novel antisense long noncoding RNA regulates the expression of MDC1 in bladder cancer.
Oncotarget. 2015; 6(1):484-93 [PubMed] Free Access to Full Article Related Publications
Antisense long noncoding RNAs (lncRNAs) play important roles in regulating the expression of coding genes in post-transcriptional level. However, detailed expression profile of lncRNAs and functions of antisense lncRNAs in bladder cancer remains unclear. To investigate regulation of lncRNAs in bladder cancer and demonstrate their functions, we performed lncRNAs microarray analysis in 3 paired bladder cancer tissues. Further molecular assays were conducted to determine the potential role of identified antisense lncRNA MDC1-AS. As a result, a series of lncRNAs were differentially expressed in bladder cancer tissues in microarray screen. In a larger size of samples validation, we found that the expression levels of MDC1-AS and MDC1 was down-regulated in bladder cancer. After over-expression of MDC1-AS, increased levels of MDC1 were observed in bladder cancer cells. We also found a remarkably inhibitory role of antisense lncRNA MDC1-AS on malignant cell behaviors in bladder cancer cells EJ and T24. Subsequently, knockdown of MDC1 revealed that suppressing role of MDC1-AS was attributed to up-regulation of MDC1. In summary, we have identified a novel antisense lncRNA MDC1-AS, which may participate in bladder cancer through up-regulation of its antisense tumor-suppressing gene MDC1. Further studies should be conducted to demonstrate detailed mechanism of our findings.

Wang B, Zhang L, Qiu F, et al.
A Newfound association between MDC1 functional polymorphism and lung cancer risk in Chinese.
PLoS One. 2014; 9(9):e106794 [PubMed] Free Access to Full Article Related Publications
Mediator of DNA damage checkpoint protein 1 (MDC1) plays an early and core role in Double-Strand Break Repair (DDR) and ataxia telangiectasia-mutated (ATM) mediated response to DNA double-strand breaks (DSBs), and thus involves the pathogenesis of several DNA damage-related diseases such as cancer. We hypothesized that the single nucleotide polymorphisms (SNPs) of MDC1 which have potencies on affecting MDC1 expression or function were associated with risk of lung cancer. In a two-stage case-control study, we tested the association between 5 putatively functional SNPs of MDC1 and lung cancer risk in a southern Chinese population, and validated the promising association in an eastern Chinese population. We found the SNP rs4713354A>C that is located in the 5′-untranslated region of MDC1 was significantly associated with lung cancer risk in both populations (P = 0.001), with an odds ratio as 1.33(95% confidence interval = 1.14–1.55) for the rs4713354C (CA+CC) genotypes compared to the rs4713354AA genotype. The correct sixth sentence is: The gene-based analysis rested with these SNPs suggested the MDC1 as a susceptible gene for lung cancer (P = 0.057) [corrected]. Moreover, by querying the gene expression database, we further found that the rs4713354C genotypes confer a significantly lower mRNA expression of MDC1 than the rs4713354AA genotype in 260 cases of lymphoblastoid cells (P = 0.002). Our data suggested that the SNP rs4713354A>C of MDC1 may be a functional genetic biomarker for susceptibility to lung cancer in Chinese.

Schröder-Heurich B, Bogdanova N, Wieland B, et al.
Functional deficiency of NBN, the Nijmegen breakage syndrome protein, in a p.R215W mutant breast cancer cell line.
BMC Cancer. 2014; 14:434 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Mutations in NBN, the gene for Nijmegen Breakage Syndrome (NBS), are thought to predispose women to developing breast cancer, but a breast cancer cell line containing mutations in NBN has not yet been described. The p.R215W missense mutation occurs at sub-polymorphic frequencies in several populations. We aimed to investigate its functional impact in breast cancer cells from a carrier of this NBN mutation.
METHODS: Breast cancer cell lines were screened by immunoblotting for NBN protein levels, and the NBN coding region was sequenced for mutation analysis. Radiosensitivity assays and functional studies were performed through immunocytochemistry and immunoblotting, and flow cytometry was employed to assess cell cycle progression. Impedance measurements were used to study the consequences of PARP1 inhibition. Statistical comparisons between cell lines were performed using t-tests.
RESULTS: HCC1395 breast cancer cells exhibited reduced NBN protein levels. Direct sequencing identified the NBN p.R215W mutation in the hemizygous state, in addition to a truncation in BRCA1. Mutations in both genes were already present in the heterozygous state in the patient's germline. HCC1395 cells were highly radiosensitive, susceptible to apoptosis and were deficient in the formation of NBN foci. There was also evidence for some impairment in the formation of γH2AX, MDC1, and 53BP1 foci after irradiation; these foci appeared smaller and irregular compared with repair foci in wild-type cells, although ATM signalling was largely unaffected. In line with their deficiency in NBN and BRCA1, HCC1395 cells were particularly sensitive to PARP1 inhibition.
CONCLUSION: Our results indicate that the p.R215W mutation in the HCC1395 breast cancer cell line impairs NBN function, making this cell line a potentially useful cellular model for studying defective NBN protein within a mutant BRCA1 background.

Wu SH, Wu TY, Hsiao YT, et al.
Bufalin induces cell death in human lung cancer cells through disruption of DNA damage response pathways.
Am J Chin Med. 2014; 42(3):729-42 [PubMed] Related Publications
Bufalin is a key component of a Chinese medicine (Chan Su) and has been proved effective in killing various cancer cells. Its role in inducing DNA damage and the inhibition of the DNA damage response (DDR) has been reported, but none have studied such action in lung cancer in detail. In this study, we demonstrated bufalin-induced DNA damage and condensation in NCI-H460 cells through a comet assay and DAPI staining, respectively. Western blotting indicated that bufalin suppressed the protein levels associated with DNA damage and repair, such as a DNA dependent serine/threonine protein kinase (DNA-PK), DNA repair proteins breast cancer 1, early onset (BRCA1), 14-3-3 σ (an important checkpoint keeper of DDR), mediator of DNA damage checkpoint 1 (MDC1), O6-methylguanine-DNA methyltransferase (MGMT) and p53 (tumor suppressor protein). Bufalin could activate phosphorylated p53 in NCI-H460 cells. DNA damage in NCI-H460 cells after treatment with bufalin up-regulated its ATM and ATR genes, which encode proteins functioning as sensors in DDR, and also up-regulated the gene expression (mRNA) of BRCA1 and DNA-PK. But bufalin suppressed the gene expression (mRNA) of p53 and 14-3-3 σ, however, bufalin did not significantly affect the mRNA of MGMT. In conclusion, bufalin induced DNA damage in NCI-H460 cells and also inhibited its DNA repair and checkpoint function.

Wu SH, Hsiao YT, Chen JC, et al.
Bufalin alters gene expressions associated DNA damage, cell cycle, and apoptosis in human lung cancer NCI-H460 cells in vitro.
Molecules. 2014; 19(5):6047-57 [PubMed] Related Publications
Lung cancer is the leading cause of cancer related death and there is no effective treatment to date. Bufalin has been shown effective in inducing apoptosis and DNA damage in lung cancer cells. However, the genetic mechanisms underlying these actions have not been elucidated yet. Cultured NCI-H460 cells were treated with or without 2 μM of bufalin for 24 h. The total RNA was extracted from each treatment for cDNA synthesis and labeling, microarray hybridization, and then followed by flour-labeled cDNA hybridized on chip. The localized concentrations of fluorescent molecules were detected and quantitated and analyzed by Expression Console software (Affymetrix) with default RMA parameters. The key genes involved and their possible interaction pathways were mapped by GeneGo software. About 165 apoptosis-related genes were affected. CASP9 was up-regulated by 5.51 fold and THAP1 by 2.75-fold while CCAR1 was down-regulated by 2.24 fold. 107 genes related to DNA damage/repair were affected. MDC1 was down-regulated by 2.22-fold, DDIT4 by 2.52 fold while GADD45B up-regulated by 3.72 fold. 201 genes related to cell cycles were affected. CCPG1 was down-regulated by 2.11 fold and CDCA7L by 2.71 fold. Many genes about apoptosis, cell cycle regulation and DNA repair are changed significantly following bufalin treatment in NCI-H460 cells. These changes provide an in depth understanding of cytotoxic mechanism of bufalin in genetic level and also offer many potentially useful biomarkers for diagnosis and treatment of lung cancer in future.

Wei J, Costa C, Shen J, et al.
Differential effect of MMSET mRNA levels on survival to first-line FOLFOX and second-line docetaxel in gastric cancer.
Br J Cancer. 2014; 110(11):2662-8 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Breast cancer susceptibility gene 1 (BRCA1) expression differentially affects outcome to platinum- and taxane-based chemotherapy. Mediator of DNA damage checkpoint protein 1 (MDC1), p53-binding protein 1 (53BP1), multiple myeloma SET domain (MMSET) and ubiquitin-conjugating enzyme 9 (UBC9) are involved in DNA repair and could modify the BRCA1 predictive model.
METHODS: Mediator of DNA damage checkpoint protein 1, 53BP1, MMSET and UBC9 mRNA were assessed in gastric tumours from patients in whom BRCA1 levels had previously been determined.
RESULTS: In vitro chemosensitivity assay, MMSET levels were higher in docetaxel-sensitive samples. In a separate cohort, survival was longer in those with low MMSET (12.3 vs 8.8 months; P=0.04) or UBC9 (12.4 vs 8.8 months; P=0.01) in patients receiving only folinic acid, fluorouracil (5-FU) and oxaliplatin (FOLFOX). Conversely, among patients receiving second-line docetaxel, longer survival was associated with high MMSET (19.1 vs 13.9 months; P=0.003). Patients with high MMSET and BRCA1 attained a median survival of 36.6 months, compared with 13.9 months for those with high BRCA1 and low MMSET (P=0.003). In the multivariate analyses, low MMSET (hazard ratio (HR), 0.59; P=0.04) and low UBC9 (HR, 0.52; P=0.01) levels were markers of longer survival to first-line FOLFOX, whereas palliative surgery (HR, 2.47; P=0.005), low BRCA1 (HR, 3.17; P=0.001) and low MMSET (HR, 2.52; P=0.004) levels were markers of shorter survival to second-line docetaxel.
CONCLUSIONS: Breast cancer susceptibility gene 1, MMSET and UBC9 can be useful for customising chemotherapy in gastric cancer patients.

Watanabe Y, Maeda I, Oikawa R, et al.
Aberrant DNA methylation status of DNA repair genes in breast cancer treated with neoadjuvant chemotherapy.
Genes Cells. 2013; 18(12):1120-30 [PubMed] Related Publications
Dysregulation of homologous recombination (HR) DNA repair has been implicated in breast carcinogenesis and chemosensitivity. Here, we investigated the methylation status of sixteen HR genes and analyzed their association with tumor subtypes and responses to neoadjuvant chemotherapy. Core specimens were obtained before neoadjuvant chemotherapy from sixty cases of primary breast cancer of the following four subgroups: luminal breast cancer (LBC) with pathological complete response (pCR), LBC with stable disease, triple-negative breast cancer (TNBC) with pCR and TNBC with poor response. The aberrant DNA methylation status of the following HR related-genes was analyzed using bisulfite-pyrosequencing: BRCA1, BRCA2, BARD1, MDC1, RNF8, RNF168, UBC13, ABRA1, PALB2, RAD50, RAD51, RAD51C, MRE11, NBS1, CtIP and ATM. Among the genes analyzed, only the incidence of BRCA1 and RNF8 methylation was significantly higher in TNBC than that in LBC. Whereas the incidence of BRCA1 methylation was tended to be higher in pCR cases than in poor-response cases in TNBC, that of RNF8 was significantly lower in pCR cases than in poor-response cases. Our results indicate that the methylation status of HR genes was not generally associated with TNBC subtype or chemosensitivity although hypermethylation of BRCA1 is associated with TNBC subtype and may impact chemosensitivity.

Bonanno L, Costa C, Majem M, et al.
The predictive value of 53BP1 and BRCA1 mRNA expression in advanced non-small-cell lung cancer patients treated with first-line platinum-based chemotherapy.
Oncotarget. 2013; 4(10):1572-81 [PubMed] Free Access to Full Article Related Publications
Platinum-based chemotherapy is the standard first-line treatment for non-oncogene- addicted non-small cell lung cancers (NSCLCs) and the analysis of multiple DNA repair genes could improve current models for predicting chemosensitivity. We investigated the potential predictive role of components of the 53BP1 pathway in conjunction with BRCA1. The mRNA expression of BRCA1, MDC1, CASPASE3, UBC13, RNF8, 53BP1, PIAS4, UBC9 and MMSET was analyzed by real-time PCR in 115 advanced NSCLC patients treated with first-line platinum-based chemotherapy. Patients expressing low levels of both BRCA1 and 53BP1 obtained a median progression-free survival of 10.3 months and overall survival of 19.3 months, while among those with low BRCA1 and high 53BP1 progression-free survival was 5.9 months (P less than 0.0001) and overall survival was 8.2 months (P=0.001). The expression of 53BP1 refines BRCA1-based predictive modeling to identify patients most likely to benefit from platinum-based chemotherapy.

Wu KC, Yang ST, Hsu SC, et al.
Propofol induces DNA damage in mouse leukemic monocyte macrophage RAW264.7 cells.
Oncol Rep. 2013; 30(5):2304-10 [PubMed] Related Publications
Propofol is one of the most widely clinically used intravenous anesthetic, and it induces apoptosis in human and murine leukemia cell lines. Yet, whether propofol causes DNA damage and affects the mRNA expression of repair-associated genes in cancer cells remains undetermined. In the present study, we investigated the effects of propofol on DNA damage and associated mRNA gene expression in RAW264.7 cells. Comet assay and DNA gel electrophoresis were used to evaluate DNA damage in RAW264.7 cells and propofol-inhibited cell growth in vitro. The results revealed a longer DNA tail and DNA fragmentation. Real-time PCR assay was used to examine mRNA gene expression of DNA damage and DNA repair-associated genes. Following exposure to propofol for 48 h, a decrease in the mRNA expression of DNA-PK, BRCA1, MGMT and p53 was noted in the RAW264.7 cells. Results from the western blotting indicated that p53, MGMT, 14-3-3-σ, BRCA1 and MDC1 proteins were decreased while p-p53 and p-H2A.X(S140) were increased in the RAW264.7 cells following exposure to propofol. In conclusion, exposure to propofol caused DNA damage and inhibited mRNA expression and protein levels of repair-associated genes in RAW264.7 cells.

Xu J, Zhu W, Xu W, et al.
Silencing of MBD1 reverses pancreatic cancer therapy resistance through inhibition of DNA damage repair.
Int J Oncol. 2013; 42(6):2046-52 [PubMed] Related Publications
High resistance to traditional chemo- and radiotherapies contributes to the poor prognosis of pancreatic cancer (PC). Methyl-CpG binding domain protein 1 (MBD1), which plays an important role in disease progression, contributes to the drug resistance of PC cells; however, the mechanism underlying the drug resistance endowed by MBD1 remains unknown. In this study, we found that MBD1 was recruited to DNA damage sites under DNA damage conditions. Silencing of MBD1 significantly impaired activation of the DNA damage checkpoint response and inhibited DNA repair capacity. MBD1 binds mediator of DNA damage checkpoint protein 1 (MDC1), which is induced by radiation and regulates NBS1 activation in the presence of DNA damage repair. Knockdown of MBD1 significantly increased the sensitivity of cells to radiation and cisplatin (diamindichloridoplatin, DDP) in vitro. Importantly, the function of MBD1 in regulating chemoradioresistance is also partially dependent on DNA damage repair. Thus, we hypothesize that MBD1 may promote PC chemoradioresistance by regulating PC cell fate in the presence of DNA damage. Collectively, these findings reveal an important function of MBD1 in DNA repair and mediation of chemoradioresistance of cancer cells. Moreover, this study suggests that MBD1 is a promising molecular target for sensitizing resistant PC tumor cells to chemoradiotherapy.

Zhang ZZ, Liu YJ, Yin XL, et al.
Loss of BRCA1 expression leads to worse survival in patients with gastric carcinoma.
World J Gastroenterol. 2013; 19(12):1968-74 [PubMed] Free Access to Full Article Related Publications
AIM: To investigate the expression deficiency of key molecular markers in the homologous recombination pathway.
METHODS: Expression loss of breast cancer type 1 susceptibility protein (BRCA1), ataxia telangiectasia mutated (ATM), ATM-Rad3-related (ATR), mediator of DNA damage checkpoint protein 1 (MDC1) and meiotic recombination 11 (Mre11) were correlated with their clinicopathological parameters in gastric cancer (GC). One hundred and twenty treatment-naive GC samples were formalin-fixed and paraffin-embedded into tissue blocks. Two representative cores from each block were extracted and constructed into tissue microarrays. Expression levels of BRCA1, ATM, ATR, MDC1 and Mre11 were determined using immunohistochemical analysis, and correlated with clinical parameters, including age, gender, Lauren subtype, tumor grades, clinical stage and overall survival.
RESULTS: Expression loss of BRCA1, ATM, ATR, MDC1, and Mre11 was found in 21.4%, 20.2%, 21.0%, 11.1% and 4.6%, respectively, of interpretable cases. BRCA1 loss was significantly associated with patients of diffused subtype (intestinal vs diffused, 8.2% vs 31.7%, P = 0.001), higher tumor grade (I/II vs III, 10.7% vs 20.5; I/II vs IV, 10.7% vs 54.5%, P = 0.047) and advanced clinical stage (I/II vs III, 12.9% vs 16.9%; I/II vs IV, 12.9% vs 45.5%, P = 0.006). MDC1 loss was significantly associated with patients of diffused subtype (intestinal vs diffused, 0% vs 19.7%, P = 0.001) and higher tumor grade (I/II vs III, 0% vs 12%; I/II vs IV, 0% vs 30.8%, P = 0.012). In addition, the survival time of the patients with expression loss of BRCA1 was significantly shorter than those with positive expression of BRCA1 (2-year survival rate, 32.4% vs 62.8%, P = 0.015). No correlations were found between clinicopathological parameters and expression loss of ATM, ATR and Mre11.
CONCLUSION: Our results support the hypothesis that homologous recombination deficiency plays an important role in the progression of gastric carcinoma. Loss of expression of BRCA1 and MDC1 may serve as predictive factors in tumor development or progression in GC patients.

Agyeman A, Mazumdar T, Houghton JA
Regulation of DNA damage following termination of Hedgehog (HH) survival signaling at the level of the GLI genes in human colon cancer.
Oncotarget. 2012; 3(8):854-68 [PubMed] Free Access to Full Article Related Publications
Transcriptional regulation of the Hedgehog (HH) signaling response is mediated by GLI genes (GLI1, GLI2) downstream of SMO, that are also activated by oncogenic signaling pathways. We have demonstrated the importance of targeting GLI downstream of SMO in the induction of cell death in human colon carcinoma cells. In HT29 cells inhibition of GLI1/GLI2 by the small molecule inhibitor GANT61 induced DNA double strand breaks (DSBs) and activation of ATM, MDC1 and NBS1; γH2AX and MDC1, NBS1 and MDC1 co-localized in nuclear foci. Early activation of ATM was decreased by 24 hr, when p-NBS1(Ser343), activated by ATM, was significantly reduced in cell extracts. Bound γH2AX was detected in isolated chromatin fractions or nuclei during DNA damage but not during DNA repair. MDC1 was tightly bound to chromatin at 32 hr as cells accumulated in early S-phase prior to becoming subG1, and during DNA repair. Limited binding of NBS1 was detected at all times during DNA damage but was strongly bound during DNA repair. Transient overexpression of NBS1 protected HT29 cells from GANT61-induced cell death, while knockdown of H2AX by H2AXshRNA delayed DNA damage signaling. Data demonstrate following GLI1/GLI2 inhibition: 1) induction of DNA damage in cells that are also resistant to SMO inhibitors, 2) dynamic interactions between γH2AX, MDC1 and NBS1 in single cell nuclei and in isolated chromatin fractions, 3) expression and chromatin binding properties of key mediator proteins that mark DNA damage or DNA repair, and 4) the importance of NBS1 in the DNA damage response mechanism.

Brooks JD, Teraoka SN, Reiner AS, et al.
Variants in activators and downstream targets of ATM, radiation exposure, and contralateral breast cancer risk in the WECARE study.
Hum Mutat. 2012; 33(1):158-64 [PubMed] Free Access to Full Article Related Publications
Ionizing radiation (IR) is a breast carcinogen that induces DNA double-strand breaks (DSBs), and variation in genes involved in the DNA DSB response has been implicated in radiation-induced breast cancer. The Women's Environmental, Cancer, and Radiation Epidemiology (WECARE) study is a population-based study of cases with contralateral breast cancer (CBC) and matched controls with unilateral breast cancer. The location-specific radiation dose received by the contralateral breast was estimated from radiotherapy records and mathematical models. One hundred fifty-two SNPs in six genes (CHEK2, MRE11A, MDC1, NBN, RAD50, TP53BP1) involved in the DNA DSBs response were genotyped. No variants or haplotypes were associated with CBC risk (649 cases and 1,284 controls) and no variants were found to interact with radiation dose. Carriers of a RAD50 haplotype exposed to ≥1 gray (Gy) had an increased risk of CBC compared with unexposed carriers (Rate ratios [RR] = 4.31 [95% confidence intervals [CI] 1.93-9.62]); with an excess relative risk (ERR) per Gy = 2.13 [95% CI 0.61-5.33]). Although the results of this study were largely null, carriers of a haplotype in RAD50 treated with radiation had a greater CBC risk than unexposed carriers. This suggests that carriers of this haplotype may be susceptible to the DNA-damaging effects of radiation therapy associated with radiation-induced breast cancer.

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