Dna Damage Repair Genetic Polymorphisms And Lung Cancer Susceptibility And Pharmacogenomics Research

PartⅠDNA Repair Gene Polymorphisms and Lung Caneer CharpterⅠGenetic variants in GTF2H1 and risk of lung cancerLung cancer is the most common cause of cancer deaths worldwide. Although the risk of lung cancer is associated with exposure to cigarette smoke, which accounts for about 80-90% of lung cancer incident cases, only 10-15% of smokers develop lung cancer, suggesting possible involvement of predisposing genetic factors. It has been hypothesized that these differences may be due, in part, to genetically determined variation in DNA repair capacity.GTF2H1, the p62 subunit of the multiprotein complex TFIIH, participates in both the nucleotide excision repair process and transcription control by specifically interacting with a variety of factors important in carcinogenesis. To elucidate the role of genetic variations in GTF2H1 in the etiology of lung cancer, we conducted a case-control study of 500 incident lung cancer cases and 517 controls in a Chinese population by genotyping six common single nucleotide polymorphisms (SNPs) in GTF2H1.An increased risk was associated with the variant genotypes of rs3802967 [adjusted odds ratios (OR)= 1.38,95% confidence interval (CI)= 1.04-1.82], rs4150606 (adjusted OR= 1.44,95% CI= 1.08-1.92), and rs4150678 (adjusted OR= 1.37,95% CI=1.04-1.81) in a dominant genetic model. The risk for rs3802967 C/T+T/T genotypes was more pronounced among males subjects (P= 0.002). In contrast, a decreased risk was associated with the rs4150667 T/T genotype (adjusted OR= 0.59,95% CI= 0.38-0.93) in a recessive model. Haplotype analysis showed that the haplotype "222212" (1 for common alleles and 2 for minor alleles) was associated with increased risk of lung cancer (P= 0.03). Further evaluation using luciferase reporter constructs showed that the T allele of rs3802967 had higher luciferase expression, suggesting that the-79C→T change may affect transcriptional activation of GTF2H1. Taken together, these results suggest that GTF2H1 polymorphisms/haplotypes may contribute to genetic susceptibility to lung cancer. CharpterⅡRad52 Polymorphisms in Chinese Lung Cancer Patients: Association with Lung Cancer SusceptibilityThe removal of tobacco induced adducts is carried out by homologous recombination repairing DNA double strand breaks. Rad52 is one of the key enzymes of homologus recombination repair, and has been shown to plays an important role in the maintenance of genome stability, as well as the progression of carcinogenesis.Here, we investigated 9 common polymorphisms in the Rad52 gene in a case-control study of 500 incident lung cancer patients and 517 cancer-free controls in a Chinese population. We observed statistically significant differences between case patients and control subjects in genotype distributions for three SNPs (P= 0.002 for rs10774474 and P= 1.647×10-5 for rs11571378, P= 0.002 for rs1051669) and the significance remained after applying Bonferroni correction. Haplotype analysis revealed significant differences in haplotype (rs10774474-rs11571378) distributions between cases and controls (Global P=0.007), and the significance remained after applying 100,000-time permutation tests. Haplotype'12'(in the order of rs10774474-rs11571378,1 for common alleles and 2 for minor alleles) was associated with increased risk of lung cancer. The 104A allele for rs1051669 3'UTR construct exhibited decreased luciferase reporter gene expression.104G→A was predicted with reduced mRNA stability, which is consistent with the luciferase results.Further SPR experiments showed another explanation in that the A variant may enhance the affinity of cytoplasmic posttranslational repression binding protein or miRNA, resulting in reduced Rad52 expression. Our results suggest that the 104G>A polymorphism of rs1051669 may be functional thus influencing the DNA repair efficacy.These data indicate that the Rad52 polymorphisms may play a role in mediating susceptibility to lung cancer. It can help us construct genetic profiles directing the prediction for cancer susceptibility. Part II Pharmacogenetic Analysis of Platinum-based Chemotherapy in Non-Small Cell Lung Cancer PatientsCharpter I Effect of XPD Polymorphisms on Outcome and Prognosis in Non-Small Cell Lung Cancer PatientsNon-small cell lung cancer (NSCLC) accounts for approximately 80% of such deaths. Most NSCLC patients are diagnosed in the advanced (stage III or IV) stages. Five-year survival rates for NSCLC remain less than 15%. Standard treatment for NSCLC involves chemotherapy with a platinum agent and another cytotoxic agent.Platinum agents cause DNA cross-linking and adducts. Xeroderma pigmentosum group D (XPD) plays a key role in the nucleotide excision repair pathway of DNA repair. Genetic polymoiphisms of XPD may affect the capacity to remove the deleterious DNA lesions and lead to individual variability. This study aimed to investigate the association of three polymorphisms of XPD at codons 156, 312, and 711 with the outcomes in advanced NSCLC patients.We used matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to genotype the three polymorphisms in 445 stage III and IV NSCLC patients treated with platinum combination chemotherapy. The variant homozygotes of XPD p. Arg156Arg (rs238406) polymorphism were associated with a significantly increased risk of grade 3 or 4 hematologic toxicity, and more specifically, severe leukopenia toxicity (P for trend=0.007). Consistent with these results of single-locus analysis, both the haplotype and the diplotype analyses revealed a protective effect of the haplotype 'CG' on the risk of grade 3 or 4 leukopenia toxicity.In the subgroup analysis for patients receiving Navelbine in combination with cisplatin treatment, XPD p.Arg156Arg A/A genotype was associate with increased platinum sensitivity (P=0.003), grade 3-4 hematologic toxicity risk (P=0.012) and severe leukopenia toxicity (P=0.003).We observed significant associations between XPDp.Asp312Asn, p.Asp711Asp polymorphisms and overall survival(log-rank P=0.006,0.006 respectively).The survival of patients in stageⅢB with XPD p.Asp312Asn A/G+A/A genotypes was significant shorter than that of G/G genotype (log-rank P=7.25×10-5).This investigation, for the first time, provides suggestive evidence of XPD p.Arg156Arg, p.Asp312Asn, p.Asp711Asp polymorphisms effects on toxicity and prognosis variability among platinum-treated non-small cell lung cancer patients.Charpter II Pharmacogenetic Assessment of Outcome and Survival after Platinum Chemotherapy in Non-Small Cell Lung Cancer PatientsThe large individual variability for NSCLC in both outcome and survival from chemotherapy makes the identification of pharmacogenetic markers that can be used to screen patients before therapy selection an attractive prospect.We assessed 17 selected polymorphisms based on previously described associations or putative functional effects in 11 key genes from pathways that may influence cellular sensitivity to platinum (XPC, XPF, XPG, MLH1, MSH2, MTHFR, XRCC3, lig4, Rad52, IL-1a and IL-1b) using matrix-assisted laser desorption /ionization time-of-flight mass spectrometry in 445 NSCLC patients.MTHFR rs1801131 was associated with risk of response rate. Rad52 rs1051669 A/A genotype increased response rate in subgroup analysis for patients receiving Navelbine plus platinum treatment. We observed significant associations between 9 SNPs in 7 genes and toxicity risk. Statistically significant associations for IL-1 b rs16944 (-511 C>T), rs1143627 (-31T>C) and severe leukocytopenia, agranulocytosis toxicities remained after False discovery rate correction. The risk for leukopenia was increased for rs16944 among nonsmokers (adjusted OR=5.10, 95%CI= 2.31-11.19, P=5.41×10-5); and the association between this SNP and agranulocytosis was more significant in nonsmokers (adjusted OR=16.38, 95%CI=5.88-45.61, P=8.84×10-8), female (adjusted OR=12.87,95%CI=3.70-44.76, P=5.92×10-5) patients. Further gene-environment interaction analysis suggests interactive effects between IL-1 b rs16944, rs1143627 with smoking status and gender. The interaction P value for rs16944-smoking status, rs16944-gender in agranulocytosis toxicity was 0.001,0.007 respectively.The survival of patients with XPC rs222800 T/T genotype was shorter than that of C/C+C/T genotypes(MST,14 months v 18 months), and survival of patients with Rad52 rs1051669 A/A genotypes was shorter than that of G/G+A/G genotypes (MST, 7months v 18 months), the difference was statistically significant.This exploratory study suggests that polymorphisms in specific genes encoding for DNA repair, methylenetetrahydrofolate reductase enzyme and anti-inflammatory cytokines are associated with platinum-related response, toxicities and overall survival. It can help us understand the functional consequences of chemotherapy and construct genetic profiles directing the choice of optimal therapy.