Abstract
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 = 0.024), with an odds ratio as 1.23(95% confidence interval = 1.35–1.26) for the rs4713354C (CA+CC) genotypes compared to the rs4713354AA genotype. However, no significant association was observed between other SNPs and lung cancer risk. The gene-based analysis rested with these SNPs suggested the MDC1 as a susceptible gene for lung cancer (P = 0.009). 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.
Introduction
DNA damage response (DDR) is a sophisticated cellular procedure involving multiple molecules to repair DNA damage and maintain the genome integrity and fidelity. Usually, DNA damage can be caused by tobacco carcinogens or ionizing radiation, or other sources, it triggers DDR including activation of cell cycle checkpoint, commencement of transcriptional programs, and execution of DNA repair, or initiation of apoptosis when the damage is severe [1]–[3]. Failure to repair DNA lesions would result in genomic instability and a variety of genetically inherited disorders, such as cancer. DDR can protect the cellular DNA from damage by recruiting a series of DDR proteins that act as sensors, transducers, mediators and effectors in DDR. The DDR cascade starts with the sensors that detect the damage and transport the initial signal to the transducers. The transducers, aided by the mediators, amplify the signal and transmit it to the effectors, which carry out diverse roles such as repair, checkpoint activation and if necessary-apoptosis [4].
Mediator of DNA damage checkpoint protein 1 (MDC1), also known as Nuclear Factor with BRCT Domains 1 (NFBD1), is an important player in the DDR that regulates the activation of the intra-S phase and G2/M phase cell cycle checkpoints in response to DNA damage [5], [6]. MDC1 majorly functions as a mediator in the DDR, which mediates the recruitment of other DDR proteins, such as ataxia telangiectasia-mutated (ATM), Breast Cancer 1, Early Onset (BRCA1), Mre11/Rad50/NBS1 (MRN) complex, to the site of damage [7]–[10]. Recent evidences also showed that MDC1 has a direct role in repairing DNA double-strand breaks (DSBs) by participating in the two major DNA repair pathways, the homologous recombination and non-homologous end-joining response [11]–[13], and in the activation of the decatenation checkpoint21 and mitosis [14], [15]. Dysfunction of MDC1 has been reported to cause multiple disorders [16], [17], such as defective spermatogenesis [18]. Nowadays, more and more evidences supported MDC1 to be a potential tumor suppressor with roles in repairing DNA damage and inhibiting tumor growth [19]–[24]. MDC1 was found to be expressed lowly in various cancers including lung cancer, breast carcinomas [25] and gastric carcinoma [26].
Human MDC gene is located at the Chromosome 6p21.3, a region that has been reported to be a susceptible region of lung cancer in Asians by a genome-wide association study (GWAS) [27]. Previous studies have found that genetic variants of MDC1 were associated with Epstein-Barr virus (EBV) antibody titers in Chinese and radiosensitivity in American [28], [29]. EBV and radiosensitivity are two high risk factors of human cancer, therefore, these genetic variants of MDC1 may also affect the susceptibility of cancer. However, study on this aspect is still lacking. Single nucleotide polymorphisms (SNPs) that are located in the promoter or exons of genes have potencies on affecting gene expression or function, and thus influence the susceptibility of human diseases [30]–[32]. In the current study, we tested the hypothesis that these putatively functional SNPs of MDC1 were associated with risk of lung cancer based on a two-stage case-control study, and assessed the function of promising SNPs by bioinformatics analysis.
Materials and Methods
Ethics Statement
This study was approved by the institutional review boards of Guangzhou Medical University (Ethics Committee of Guangzhou Medical University: GZMC2007–07–0676) and Soochow University (Ethics Committee of Soochow University: SZUM2008031233). All participants were scheduled for a face to face interview after written informed consents were obtained.
Study subject
After got the approbation of the institutional review boards of Guangzhou Medical University and Soochow University, we conducted two independent case-control studies in southern Chinese and eastern Chinese, respectively. As described in previously published studies [33]–[35], 1056 histopathologically confirmed lung cancer cases and 1056 healthy controls that were frequency-matched with cases on age (±5) and sex, were collected in Guangzhou city and surrounding area; and 503 lung cancer cases and 623 frequency-matched controls were recruited in Suzhou city. The southern Chinese population was used as a discovery set, while the eastern Chinese was used as a validation set. All participants were scheduled for a face to face interview after written informed consents were obtained. They were asked to provide data on age, sex, smoking status, pack-years smoked, drinking status and family history of cancer with a structured questionnaire, as well as a 5-ml peripheral blood sample. The definitions of smoking status, pack-years smoked, drinking status and family history of cancer have been described in previously published studies [33]–[35].
SNP selection and genotyping
We used the FuncPred block of the SNPinfo Web Server (http://snpinfo.niehs.nih.gov/) to select putatively functional SNPs of MDC1 with a common frequency (i.e., minor allele frequency, MAF >5%) in Chinese. We found and chose five SNPs meeting the aforementioned criterion. They were rs4713354A>C (+39A>C: locating in the 39 position of the cDNA sequences), rs9262152G>A (Arg268Lys: causing an amino acid change from Arginine to Lysine at codon 268), rs2075015G>A (Glu371Lys: causing an amino acid change from Glutamic acid to Lysine at codon 371), rs28986465C>T (Pro386Leu: causing an amino acid change from Proline to Leucine at codon 386), rs9461623T>C (Ser1180Pro: causing an amino acid change from Serine to Proline at codon 1180). We genotyped above five SNPs using the Taqman allelic discrimination Assay on the ABI7900HT system (Applied Biosystems by Life Technologies, Foster City, CA) with primers and probes designed by the Primer Express 3.0 software (Applied Biosystems by Life Technologies). The primers and probes for each SNP were presented in Table S1 in File S1.
Statistical analysis
The frequency distribution of each SNP genotypes and Hardy-Weinberg equilibrium (HWE) of SNPs in controls, were tested by the chi-square test. The odds ratio (OR) and 95% confidence interval (95%CI) implicating association between each SNP of MDC1 and risk of lung cancer were calculated using the unconditional logistic regression model with or without adjustment for age, sex, smoking status, drinking status and family history of cancer. The gene-based association was tested using the VEGAS software [36]. Interaction between promising SNPs and selected factors was assessed by the multiplicative interaction analysis [37]. The homogeneity of the results in two sets and in sub-groups was tested by the Breslow-Day test. Furthermore, the statistical power was calculated by using the PS Software [38]. All tests were two-sided by using the SAS software (version 9.2; SAS Institute, Cary, NC). P<0.05 was considered to be statistically significant.
Results
Association between MDC1 SNPs and lung cancer risk
Table 1 shows the frequency distribution of the five SNPs in cases and controls. The genotype distributions of all SNPs in the controls of southern Chinese were all in agreement with the Hardy-Weinberg equilibrium (P>0.05 for all). Of the five SNPs, only the genotypes of rs4713354A>C exerted a significant difference in frequency distribution between the cases and controls in the discovery set (P = 0.006). As shown, compared with individuals carrying the common rs4713354AA genotype, those carrying the rs4713354CA genotype and rs4713354CC genotype existed 1.32-folds (odds ratio [OR] = 1.32, 95% confidence interval [95%CI] = 1.08–1.61) and 1.96-folds (OR = 1.96, 95%CI = 1.03–3.61) in risk of lung cancer, respectively. After combined the two risk genotypes, the rs4713354C variant genotypes (i.e., CA+CC) conferred a significant increase in risk of lung cancer (OR = 1.36, 95%CI = 1.12–1.65). The above associations were further verified in the eastern Chinese and the results were consistent (Berslow-Day test: P = 0.768) as shown in Table 1. The frequency distribution of rs4713354C genotypes was higher in cases than controls in the validation set (33.2% vs. 27.3%). The genotype frequency difference was approaching significant (P = 0.098). Meanwhile, the rs4713354C variant genotypes contributed to a significant increase for lung cancer risk (OR = 1.32, 95%CI = 1.02–1.71) in comparison to the rs4713354AA genotype. We then merged the two populations to increase the study power. We found that individuals carrying the rs4713354C variant genotypes had 1.33-folds increased risk of lung cancer compared with those carrying the rs4713354AA genotype (OR = 1.33, 95%CI = 1.14–1.55). The gene-based association analysis further revealed that the MDC1 gene to be associated with lung cancer risk with an approaching statistical significance (P = 0.057) based on the results from above five SNPs, and the most significant associated-SNP was rs4713354A>C (P = 0.003). In addition, the frequency distributions of demographic characteristics of the discovery set and validation set are shown in Table S2 in File S1.
Table 1. Distribution of genotypes of MDC1 and associations with the risk of lung cancer.
| Genotypes/Alleles | Case n (%) | Controlsa n (%) | P valueb | Crude OR (95%CI) | Adjusted OR (95%CI)c |
| Discovery set | |||||
| Total no. of subjects | 1056 | 1056 | |||
| rs4713354A>C | |||||
| AA | 750(71.0) | 811(76.8) | 0.006 | 1.00 (ref.) | 1.00 (ref.) |
| CA | 278(26.3) | 229(21.7) | 1.31(1.07–1.61) | 1.32(1.08–1.61) | |
| CC | 28(2.7) | 16(1.5) | 1.89(1.02–3.53) | 1.93(1.03–3.61) | |
| CA+CC | 306(29.0) | 345(23.2) | 1.35(1.11–1.64) | 1.36(1.12–1.65) | |
| rs9262152G>A | |||||
| GG | 915(86.6) | 932(88.2) | 0.357 | 1.00 (ref.) | 1.00 (ref.) |
| AG | 138(13.1) | 119(11.3) | 1.18(0.91–1.53) | 1.17(0.90–1.52) | |
| AA | 3(0.3) | 5(0.5) | 0.61(0.15–2.27) | 0.62(0.15–2.62) | |
| rs2075015G>A | |||||
| GG | 922(87.3) | 911(86.3) | 0.226 | 1.00 (ref.) | 1.00 (ref.) |
| AG | 132(12.5) | 138(13.1) | 0.95(0.73–1.22) | 0.97(0.75–1.25) | |
| AA | 2(0.2) | 7(0.6) | 0.28(0.06–1.36) | 0.29(0.06–1.39) | |
| rs28986465C>T | |||||
| CC | 899(85.1) | 919(87.0) | 0.449 | 1.00 (ref.) | 1.00 (ref.) |
| TC | 146(13.8) | 128(12.1) | 1.17(0.90–1.50) | 1.16(0.90–1.49) | |
| TT | 11(1.1) | 9(0.9) | 1.25(0.52–3.03) | 1.25(0.51–3.03) | |
| rs9461623T>C | |||||
| TT | 901(85.3) | 908(86.0) | 0.339 | 1.00 (ref.) | 1.00 (ref.) |
| CT | 154(14.6) | 144(13.6) | 1.08(0.84–1.38) | 1.08(0.85–1.38) | |
| CC | 1(0.1) | 4(0.4) | 0.25(0.03–2.26) | 0.26(0.03–2.37) | |
| Validation set | |||||
| Total no. of subjects | 503 | 623 | |||
| rs4713354A>C | |||||
| AA | 336(66.8) | 453(72.7) | 0.098 | 1.00 (ref.) | 1.00 (ref.) |
| CA | 150(29.8) | 153(24.6) | 1.32(1.01–1.72) | 1.31(1.00–1.72) | |
| CC | 17(3.4) | 17(2.7) | 1.35(0.68–2.68) | 1.36(0.68–2.72) | |
| CA+CC | 167(33.2) | 170(27.3) | 1.32(1.03–1.71) | 1.32(1.02–1.71) | |
| Merge set | |||||
| Total no. of subjects | 1559 | 1679 | |||
| rs4713354A>C | |||||
| AA | 1086(69.7) | 1264(75.3) | 0.001 | 1.00 (ref.) | 1.00 (ref.) |
| CA | 428(27.4) | 382(22.7) | 1.30(1.11–1.53) | 1.30(1.11–1.53) | |
| CC | 45(2.9) | 33(2.0) | 1.58(1.01–2.51) | 1.63(1.03–2.57) | |
| CA+CC | 473(30.3) | 415(24.7) | 1.33(1.14–1.55) | 1.33(1.14–1.55) |
The genotype distributions of above SNPs in controls were all in Hardy-Weinberg equilibrium (P>0.05).
The frequency distribution of genotypes of SNPs between cases and controls by the chi-square test.
Adjusted in a logistic regression model that included age, sex, smoking status, drinking status, and family history of cancer.
Stratification analysis of the association between rs4713354A>C and lung cancer risk
Table 2 shows the the frequency distributions of rs4713354A>C genotypes in cases and controls and associations between the SNP and lung cancer risk in each sub-group stratified by the confounding factors. No significant association between the SNP rs4713354A>C and lung cancer risk was observed in individuals with pack-years smoked <20 or ≥20 and in individuals with a history of cancer. However, this may be due to the limited sample size because the homogeneity test indicated that there was no significant difference between these stratum-ORs in each sub-group (P>0.05 for all). Moreover, no significant interaction was observed for the selected factors and the SNP on increasing lung cancer risk (P>0.05 for all), which might be due to a lack of study power for interaction analysis. In addition, results from the multivariable logistic regression analysis showed that smoking and the risk genotype of SNP rs4713354A>C were still associated with increased risks of lung cancer as shown in Table 3 (P<0.001 for both).
Table 2. Stratification analysis of the MDC1 rs4713354A>C genotypes by selected variables in cases and controls.
| Patients (n = 1559) | Controls (n = 1679) | Adjusted OR (95% CI)a | P b | P c | |||
| CA+CC n (%) | AA n (%) | CA+CC n (%) | AA n (%) | CA+CC vs AA | |||
| Age (years) | |||||||
| ≤60 | 245(30.3) | 564(69.7) | 227(25.9) | 650(74.1) | 1.24(1.00–1.54) | 0.387 | 0.338 |
| >60 | 228(30.4) | 522(69.6) | 188(23.4) | 614(76.6) | 1.46(1.16–1.83) | ||
| Sex | |||||||
| Male | 331(30.3) | 760(69.7) | 299(25.2) | 886(74.8) | 1.29(1.07–1.55) | 0.584 | 0.559 |
| Female | 142(30.3) | 326(69.7) | 116(23.5) | 378(76.5) | 1.44(1.08–1.92) | ||
| Smoking status | |||||||
| Ever | 244(29.6) | 580(70.4) | 194(25.4) | 571(74.6) | 1.24(1.00–1.55) | 0.366 | 0.089 |
| Never | 229(31.2) | 506(68.8) | 221(24.2) | 693(75.8) | 1.43(1.14–1.77) | ||
| Pack-years smoked | |||||||
| ≥20 | 175(28.0) | 449(72.0) | 118(24.6) | 361(75.4) | 1.20(0.91–1.57) | 0.564 | 0.339 |
| <20 | 69(34.5) | 131(65.5) | 76(26.6) | 210(73.4) | 1.43(0.97–2.12) | ||
| 0 | 229(31.2) | 506(68.8) | 221(24.2) | 693(75.8) | 1.43(1.14–1.77) | ||
| Drinking status | |||||||
| Ever | 93(31.7) | 200(68.3) | 80(23.4) | 262(76.6) | 1.47(1.02–2.17) | 0.390 | 0.463 |
| Never | 380(30.0) | 886(70.0) | 335(25.1) | 1002(74.9) | 1.29(1.08–1.53) | ||
| Family history of cancer | |||||||
| Yes | 31(24.0) | 98(76.0) | 37(26.1) | 105(73.9) | 0.90(0.51–1.29) | 0.147 | 0.131 |
| No | 442(30.9) | 988(69.1) | 378(24.6) | 1159(75.4) | 1.38(1.17–1.62) | ||
| Histological types | 415(24.7) | 1264(75.3) | |||||
| Adenocarcinoma | 194(31.5) | 421(68.5) | 1.40(1.14–1.72) | 0.831 | |||
| Squamous cell carcinoma | 159(30.2) | 368(69.8) | 1.31(1.06–1.64) | ||||
| Large cell carcinoma | 21(31.8) | 45(68.2) | 1.41(0.83–2.40) | ||||
| Small cell lung cancer | 56(29.0) | 137(71.0) | 1.25(0.90–1.74) | ||||
| Other carcinomas | 38(26.4) | 106(73.6) | 1.08(0.73–1.59) | ||||
| Stages | |||||||
| I | 63(31.5) | 137(68.5) | 415(24.7) | 1264(75.3) | 1.40(1.02–1.93) | 0.683 | |
| II | 39(26.5) | 108(73.5) | 1.09(0.74–1.59) | ||||
| III | 156(31.8) | 334(68.2) | 1.42(1.14–1.77) | ||||
| IV | 215(29.8) | 507(70.2) | 1.29(1.06–1.57) | ||||
ORs were adjusted for age, sex, smoking status, drinking status, and family history of cancer.
P value of Breslow-Day test.
P value of test for the multiplicative interaction.
Table 3. A multivariable logistic regression analysis for lung cancer risk.
| Variable | ß | SE | OR | 95%CI | P |
| age | −0.004 | 0.004 | 1.00 | 0.99–1.00 | 0.208 |
| sex | 0.198 | 0.125 | 1.22 | 0.95–1.56 | 0.113 |
| Smoking status | 0.475 | 0.086 | 1.61 | 1.36–1.90 | <0.001 |
| Drinking status | −0.012 | 0.131 | 0.99 | 0.77–1.28 | 0.927 |
| Family history of cancer | −0.054 | 0.128 | 0.95 | 0.74–1.22 | 0.674 |
| rs4713354A>C | 0.285 | 0.079 | 1.33 | 1.14–1.55 | <0.001 |
Genotype-phenotype correlation by bioinformatics analysis
The SNP rs4713354A>C is located at the 5′-untranslated region (5′-UTR) of MDC1 gene, it may affect the transcript activity of MDC1 promoter. We therefore performed bioinformatics analyzes to explore the possible function of this SNP on MDC1 expression. By querying the Snpexp database (http://app3.titan.uio.no/biotools/tool.php?app=snpexp), we found a significant correlation between the rs4713354A>C genotypes and mRNA expression levels of MDC1 in 260 cases of lymphoblastoid cells in all population under the dominant genetic model (P = 0.002). Cells carrying the rs4713354C variant genotypes expressed significantly lower mRNA levels of MDC1 (CA: 9.066±0.184; CC: 9.030±0.185) than cells carrying the rs4713354AA genotype (9.138±0.237). We further used the SNPinfo Web server (http://snpinfo.niehs.nih.gov/) to predict the possible molecular mechanism of this SNP on affecting gene expression and found that the A to C transvertion of rs4713354A>C would result in a loss of binding sites of three transcription factors (TFs) that are CEBPA, CEBP and NR2F2.
Discussion
Multiple evidences supported that the MDC1 gene to be a potential tumor suppressor resting with its essential roles in repairing DNA damage and its interactions with several important tumor-related genes, such as P53, NBS1 and 53BP1 [19]–[24], [39], [40]. Here, we found that the SNP rs4713354A>C of MDC1 was associated with risk of lung cancer in Chinese. The rs4713354C variant genotypes could cause a low expression of MDC1 in vivo and thus contributed to an increased lung cancer risk. However, we did not find any significant associations between other four putatively functional SNPs of MDC1 and lung cancer risk. Further analysis supported the MDC1 gene to be a susceptible gene and rs4713354A>C to be a susceptible loci of lung cancer. To the best of our knowledge, this is the first report on genetic variants of MDC1 and susceptibility of cancer.
Aberrant reduction or lack of MDC1 was observed in lung cancer tissues [25], and down-regulation of MDC1 expression in lung cancer cells would result in defective radiation-induced apoptosis [41]. Moreover, the toxin cantharidin can cause DNA damage by inhibiting MDC1 expression in lung cancer cells [42]. Thus, loss expression of MDC1 is an important condition during lung carcinogenesis. The SNP rs4713354A>C is located at the 5′-UTR of MDC1, a region generally recognized as promoter or exonic splicing element of genes. Bioinformatics analyses showed that the A to C transvertion of rs4713354A>C causes a loss of binding sites of three TFs that are CEBPA, CEBP and NR2F2, and the rs4713354C variant genotypes exert a decreased MDC1 expression in vivo. This is consistent in biological plausibility with our observation of rs4713354C variant genotypes conferred an increased risk of lung cancer. Interestingly, not only the three TFs involves lung cancer development [43]–[45], but also CEBPA plays an important role in cell cycle [46]. It is possible that the two molecules, CEBPA and MDC1 might have a cross-talk on regulating cell cycle, which needs to further study.
A few studies have investigated the association between MDC1 SNPs and risk of human diseases. However, the results were controversial. One synonymous variant of MDC1 was reported to be associated with increased radiosensitivity but not prostate cancer risk [29]. An Chinese study reported a variant allele of MDC1 exhibited a significant association with EBV seropositivity [28]. A Caucasian study reported no variant of MDC1 was associated with breast cancer risk as well as DNA-damaging effects of radiation therapy [47]. However, the above studies were all lack of study power because of their limited sample sizes. In the current study, based on a two-stage case-control study with a relatively large sample size, we showed that a promoter SNP of MDC1 contributed to a significant increased risk of lung cancer in Chinese. The study power was strong in the current study, as we achieved a 94.47% study power (two-sided test, α = 0.05) to detect an OR of 1.33 for the rs4713354C variant genotypes, which occurred at a frequency of 24.7% in the controls. Further analysis based on the results from the five putatively functional SNPs of MDC1 suggested MDC1 to be a susceptible gene for lung cancer.
Since our study was a hospital-based case-control study, it had some limitations such as bias, including selection bias and information bias. These may cause spurious associations between the studied SNPs and cancer risk. However, four points supported our results were not achieved by chance and the significant association was credible. The first was that we have achieved two consistent results in two independent populations. The second was that we have achieved a strong study power. The third was that the bioinformatics analyses demonstrated a consistence in biological plausibility with our observation. In addition, results from the Chinese GWAS also showed that the frequency of rs4713354A>C genotypes was different between cases and controls with approaching statistical significance (P = 0.078) [48].
In conclusion, our data showed that the promoter SNP rs4713354A>C of MDC1 and the MDC1 gene were associated with lung cancer risk in Chinese by influencing MDC1 expression. Both the SNP rs4713354A>C and MDC1 might be a genetic biomarker for susceptibility of lung cancer in Chinese. Validations with larger population based studies in different ethnic groups are warranted.
Supporting Information
(DOC)
The primers and probes for the five putatively functional SNPs of MDC1.
(DOC)
Frequency distributions of selected variables in cases and controls.
(DOC)
Acknowledgments
We thank Dr. Zhanhong Xie, Ms. Wanmin Zeng and Ling Liu for their assistances in recruiting subjects.
Data Availability
The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files.
Funding Statement
This study was supported by the National Natural Scientific Foundation of China grants 30671813, 30872178, 81072366, 81273149 (JCL), and partly by 81001278 and 81171895 (YFZ), 81271350 (WJ); the Guangdong Provincial Scientific Research Grants 8251018201000005 (JCL), Guangdong Provincial High Level Experts Grants 2010-79, Changjiang Scholars and Innovative Research Team in University grant IRT0961 and Guangdong natural science foundation team grant 10351012003000000 (JCL). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
References
- 1. Lagerwerf S, Vrouwe MG, Overmeer RM, Fousteri MI, Mullenders LH (2011) DNA damage response and transcription. DNA Repair (Amst) 10: 743–750. [DOI] [PubMed] [Google Scholar]
- 2. Ermolaeva MA, Schumacher B (2014) Systemic DNA damage responses: organismal adaptations to genome instability. Trends Genet 30: 95–102. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3. Rai R, Peng G, Li K, Lin SY (2007) DNA damage response: the players, the network and the role in tumor suppression. Cancer Genomics Proteomics 4: 99–106. [PubMed] [Google Scholar]
- 4. Petrini JH, Stracker TH (2003) The cellular response to DNA double-strand breaks: defining the sensors and mediators. Trends Cell Biol 13: 458–462. [DOI] [PubMed] [Google Scholar]
- 5. Stewart GS, Wang B, Bignell CR, Taylor AM, Elledge SJ (2003) MDC1 is a mediator of the mammalian DNA damage checkpoint. Nature 421: 961–966. [DOI] [PubMed] [Google Scholar]
- 6. Goldberg M, Stucki M, Falck J, D'Amours D, Rahman D, et al. (2003) MDC1 is required for the intra-S-phase DNA damage checkpoint. Nature 421: 952–956. [DOI] [PubMed] [Google Scholar]
- 7. Lou Z, Minter-Dykhouse K, Wu X, Chen J (2003) MDC1 is coupled to activated CHK2 in mammalian DNA damage response pathways. Nature 421: 957–961. [DOI] [PubMed] [Google Scholar]
- 8. Shibata A, Barton O, Noon AT, Dahm K, Deckbar D, et al. (2010) Role of ATM and the damage response mediator proteins 53BP1 and MDC1 in the maintenance of G(2)/M checkpoint arrest. Mol Cell Biol 30: 3371–3383. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9. Peng A, Chen PL (2005) NFBD1/Mdc1 mediates ATR-dependent DNA damage response. Cancer Res 65: 1158–1163. [DOI] [PubMed] [Google Scholar]
- 10. Xu X, Stern DF (2003) NFBD1/MDC1 regulates ionizing radiation-induced focus formation by DNA checkpoint signaling and repair factors. FASEB J 17: 1842–1848. [DOI] [PubMed] [Google Scholar]
- 11. Dimitrova N, de Lange T (2006) MDC1 accelerates nonhomologous end-joining of dysfunctional telomeres. Genes Dev 20: 3238–3243. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12. Zhang J, Ma Z, Treszezamsky A, Powell SN (2005) MDC1 interacts with Rad51 and facilitates homologous recombination. Nat Struct Mol Biol 12: 902–909. [DOI] [PubMed] [Google Scholar]
- 13. Xie A, Hartlerode A, Stucki M, Odate S, Puget N, et al. (2007) Distinct roles of chromatin-associated proteins MDC1 and 53BP1 in mammalian double-strand break repair. Mol Cell 28: 1045–1057. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14. Luo K, Yuan J, Chen J, Lou Z (2009) Topoisomerase IIalpha controls the decatenation checkpoint. Nat Cell Biol 11: 204–210. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15. Townsend K, Mason H, Blackford AN, Miller ES, Chapman JR, et al. (2009) Mediator of DNA damage checkpoint 1 (MDC1) regulates mitotic progression. J Biol Chem 284: 33939–33948. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16. Lou Z, Minter-Dykhouse K, Franco S, Gostissa M, Rivera MA, et al. (2006) MDC1 maintains genomic stability by participating in the amplification of ATM-dependent DNA damage signals. Mol Cell 21: 187–200. [DOI] [PubMed] [Google Scholar]
- 17. Coster G, Goldberg M (2010) The cellular response to DNA damage: a focus on MDC1 and its interacting proteins. Nucleus 1: 166–178. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18. Bohgaki T, Bohgaki M, Cardoso R, Panier S, Zeegers D, et al. (2011) Genomic instability, defective spermatogenesis, immunodeficiency, and cancer in a mouse model of the RIDDLE syndrome. PLoS Genet 7: e1001381. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19. Yang Z, Bu Y, Wang C, Liu G, Song F (2010) Growth inhibition, morphology change, and cell cycle alterations in NFBD1-depleted human esophageal cancer cells. Mol Cell Biochem 342: 1–6. [DOI] [PubMed] [Google Scholar]
- 20. Patel AN, Goyal S, Wu H, Schiff D, Moran MS, et al. (2011) Mediator of DNA damage checkpoint protein 1 (MDC1) expression as a prognostic marker for nodal recurrence in early-stage breast cancer patients treated with breast-conserving surgery and radiation therapy. Breast Cancer Res Treat 126: 601–607. [DOI] [PubMed] [Google Scholar]
- 21. Belgnaoui SM, Fryrear KA, Nyalwidhe JO, Guo X, Semmes OJ (2010) The viral oncoprotein tax sequesters DNA damage response factors by tethering MDC1 to chromatin. J Biol Chem 285: 32897–32905. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22. Nakanishi M, Ozaki T, Yamamoto H, Hanamoto T, Kikuchi H, et al. (2007) NFBD1/MDC1 associates with p53 and regulates its function at the crossroad between cell survival and death in response to DNA damage. J Biol Chem 282: 22993–23004. [DOI] [PubMed] [Google Scholar]
- 23. Wilson KA, Colavito SA, Schulz V, Wakefield PH, Sessa W, et al. (2011) NFBD1/MDC1 regulates Cav1 and Cav2 independently of DNA damage and p53. Mol Cancer Res 9: 766–781. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24. Motoyama N, Naka K (2004) DNA damage tumor suppressor genes and genomic instability. Curr Opin Genet Dev 14: 11–16. [DOI] [PubMed] [Google Scholar]
- 25. Bartkova J, Horejsi Z, Sehested M, Nesland JM, Rajpert-De Meyts E, et al. (2007) DNA damage response mediators MDC1 and 53BP1: constitutive activation and aberrant loss in breast and lung cancer, but not in testicular germ cell tumours. Oncogene 26: 7414–7422. [DOI] [PubMed] [Google Scholar]
- 26. Zhang ZZ, Liu YJ, Yin XL, Zhan P, Gu Y, et al. (2013) Loss of BRCA1 expression leads to worse survival in patients with gastric carcinoma. World J Gastroenterol 19: 1968–1974. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27. Shiraishi K, Kunitoh H, Daigo Y, Takahashi A, Goto K, et al. (2012) A genome-wide association study identifies two new susceptibility loci for lung adenocarcinoma in the Japanese population. Nat Genet 44: 900–903. [DOI] [PubMed] [Google Scholar]
- 28. Shen GP, Pan QH, Hong MH, Qin HD, Xu YF, et al. (2011) Human genetic variants of homologous recombination repair genes first found to be associated with Epstein-Barr virus antibody titers in healthy Cantonese. Int J Cancer 129: 1459–1466. [DOI] [PubMed] [Google Scholar]
- 29. Pugh TJ, Keyes M, Barclay L, Delaney A, Krzywinski M, et al. (2009) Sequence variant discovery in DNA repair genes from radiosensitive and radiotolerant prostate brachytherapy patients. Clin Cancer Res 15: 5008–5016. [DOI] [PubMed] [Google Scholar]
- 30. Lu J, Yang L, Zhao H, Liu B, Li Y, et al. (2011) The polymorphism and haplotypes of PIN1 gene are associated with the risk of lung cancer in Southern and Eastern Chinese populations. Hum Mutat 32: 1299–1308. [DOI] [PubMed] [Google Scholar]
- 31. Yang L, Li Y, Cheng M, Huang D, Zheng J, et al. (2012) A functional polymorphism at microRNA-629-binding site in the 3′-untranslated region of NBS1 gene confers an increased risk of lung cancer in Southern and Eastern Chinese population. Carcinogenesis 33: 338–347. [DOI] [PubMed] [Google Scholar]
- 32. Yang L, Yang X, Ji W, Deng J, Qiu F, et al. (2014) Effects of a functional variant c.353T>C in snai1 on risk of two contextual diseases. Chronic obstructive pulmonary disease and lung cancer. Am J Respir Crit Care Med 189: 139–148. [DOI] [PubMed] [Google Scholar]
- 33. Yang L, Liu B, Huang B, Deng J, Li H, et al. (2013) A functional copy number variation in the WWOX gene is associated with lung cancer risk in Chinese. Hum Mol Genet 22: 1886–1894. [DOI] [PubMed] [Google Scholar]
- 34. Liu B, Yang L, Huang B, Cheng M, Wang H, et al. (2012) A functional copy-number variation in MAPKAPK2 predicts risk and prognosis of lung cancer. Am J Hum Genet 91: 384–390. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 35. Yang L, Li Y, Ling X, Liu L, Liu B, et al. (2011) A common genetic variant (97906C>A) of DAB2IP/AIP1 is associated with an increased risk and early onset of lung cancer in Chinese males. PLoS One 6: e26944. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 36. Liu JZ, McRae AF, Nyholt DR, Medland SE, Wray NR, et al. (2010) A versatile gene-based test for genome-wide association studies. Am J Hum Genet 87: 139–145. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 37. Liu B, Chen D, Yang L, Li Y, Ling X, et al. (2010) A functional variant (−1304T>G) in the MKK4 promoter contributes to a decreased risk of lung cancer by increasing the promoter activity. Carcinogenesis 31: 1405–1411. [DOI] [PubMed] [Google Scholar]
- 38. Dupont WD, Plummer WD Jr (1998) Power and sample size calculations for studies involving linear regression. Control Clin Trials 19: 589–601. [DOI] [PubMed] [Google Scholar]
- 39. Shahar OD, Gabizon R, Feine O, Alhadeff R, Ganoth A, et al. (2013) acetylation of lysine 382 and phosphorylation of serine 392 in p53 modulate the interaction between p53 and MDC1 in vitro. PLoS One 8: e78472. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 40. Noon AT, Shibata A, Rief N, Lobrich M, Stewart GS, et al. (2010) 53BP1-dependent robust localized KAP-1 phosphorylation is essential for heterochromatic DNA double-strand break repair. Nat Cell Biol 12: 177–184. [DOI] [PubMed] [Google Scholar]
- 41. Lou Z, Chen J (2004) Use of siRNA to study the function of MDC1 in DNA damage responses. Methods Mol Biol 281: 179–187. [DOI] [PubMed] [Google Scholar]
- 42.Hsia TC, Lin JH, Hsu SC, Tang NY, Lu HF, et al.. (2014) Cantharidin induces DNA damage and inhibits DNA repair-associated protein levels in NCI-H460 human lung cancer cells. Environ Toxicol. [DOI] [PubMed]
- 43. Min Y, Ghose S, Boelte K, Li J, Yang L, et al. (2011) C/EBP-delta regulates VEGF-C autocrine signaling in lymphangiogenesis and metastasis of lung cancer through HIF-1alpha. Oncogene 30: 4901–4909. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 44. Safe S, Jin UH, Hedrick E, Reeder A, Lee SO (2014) Minireview: role of orphan nuclear receptors in cancer and potential as drug targets. Mol Endocrinol 28: 157–172. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 45. Sato A, Yamada N, Ogawa Y, Ikegami M (2013) CCAAT/enhancer-binding protein-alpha suppresses lung tumor development in mice through the p38alpha MAP kinase pathway. PLoS One 8: e57013. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 46. Wang H, Iakova P, Wilde M, Welm A, Goode T, et al. (2001) C/EBPalpha arrests cell proliferation through direct inhibition of Cdk2 and Cdk4. Mol Cell 8: 817–828. [DOI] [PubMed] [Google Scholar]
- 47. Brooks JD, Teraoka SN, Reiner AS, Satagopan JM, Bernstein L, et al. (2012) Variants in activators and downstream targets of ATM, radiation exposure, and contralateral breast cancer risk in the WECARE study. Hum Mutat 33: 158–164. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 48. Hu Z, Wu C, Shi Y, Guo H, Zhao X, et al. (2011) A genome-wide association study identifies two new lung cancer susceptibility loci at 13q12.12 and 22q12.2 in Han Chinese. Nat Genet 43: 792–796. [DOI] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
(DOC)
The primers and probes for the five putatively functional SNPs of MDC1.
(DOC)
Frequency distributions of selected variables in cases and controls.
(DOC)
Data Availability Statement
The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files.