| Objective: Lung cancer is one of the most common maglinant tumors. Non-small cell lung cancer (NSCLC) accounts for approximately 85% of all histologic types of lung cancer. Chemotherapy is the main treatment in advanced NSCLC and platinum-based combination chemotherapy regimens are currently recognized as standard first-line one. The RAD51 protein is the key protein for homologous recombination, DNA damage repair and maintains of genetic diversity. The purpose of this study is to investigate the relationship between DNA repair gene RAD51 5'-UTR G135C polymorphisms and chemotherapeutic sensibility of platinum-based regimens in advanced non-small cell lung cancer and to provid theory basis for individual treatment module.Methods: Total of 152 advanced NSCLC patients, who diagnosis pathologically, receiving platinum-based chemotherapy, containing two drugs with cisplatin or carboplatin combined to others, were involved,and clinical response was evaluated after 2 cycles according to response evaluation criteria in solid tumor(RECIST). DNA in peripheral blood leukocytes was obtained, and genotypes were detected by PCR-RFLP method. The PCR amplification was performed by using the following primers: forward (5′- TGGGAACTGCAACTCATCTGG-3′) and reverse (5′- GCGCTCCTCTCTCCAGCAG-3′). PCR system: template DNA 3μl, forward and reverse primers each 2μl, 2.5 mmol / L dNTP mix 2μl, PCR buffer 5μl, 25 mmol / L MgCl2 3.5μl, High Fidelity PCR Enzyme Mix 0.3μl. Conditions for PCR were an initial denaturation at 95°C for 5 min, followed by 35 cycles at 94°C for 1 min, 53°C for 30s (annealing temperature), 72°C for 1 min, and ending with 72°C for 5 min. The resulting 157-bp product was incubated at 37°C/10min with 1U of the restriction enzyme FastDigest MvaI (Fermentas, #FD0554). The restriction fragments were then visualized by 4% (p/v) agarose gel electrophoresis, with ethidium bromide staining. Three types of band patterns were obtained: will type homozygote (G/G), two bands corresponding to 71 and 86bp; heterozygote (G/C), three bands corresponding to 157, 86 and 71bp; and polymorphic homozygote (C/C), only one band with 157bp. Statistical analysis: Analysis of data was performed using the computer software Statistical Package for Social Sciences (SPSS) for Windows (version 17.0). Differences in proportions were evaluated by theχ~2 and Fisher′s exact test (when expectation<5). Odds ratio (OR) and its 95% confidence intervals (CI) represents various genotypes on the effects of chemotherapy.Results:○1 There were no statistically significant differences between the groups of NSCLC patients with the different genotypes regarding gender, smoking history, tumour stage, histologic type(P>0.05).○2 The response rate to the chemotherapy in all 152 patients is 46.7%. Compared with the genotype, the response rates to the chemotherapy in RAD51 C-allele (G/C+C/C) carriers and the wild genotype (G/G) carriers are 56.7% vs. 40.2%. The former had a significant higher response rate than the latter (OR=1.944, 95% CI: 1.006-3.758,χ~2= 3.948, P=0.047).○3 Regarding smoking history, the response rates to the chemotherapy in RAD51 C-allele (G/C+C/C) carriers and the wild genotype (G/G) carriers are 62.1% vs. 36.9%. The former had a significant higher response rate than the latter (OR=2.847, 95% CI: 1.261-6.430,χ~2=2.847, P=0.011). No statistically significantly differences were found in the genotypes frequencies and response rate among non-smoker patients (P>0.05).Conclusions: DNA repair gene RAD51 5'-UTR G135C polymorphism has a significant impact on response rate in advanced NSCLC patients treated with platinum-based chemotherapy. Regarding smoking history, RAD51 C-allele (G/C+C/C) carriers had a significant higher response rate than the wild genotype (G/G) carriers . |
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