Apoptosis - Related Gene Single Nucleotide Polymorphism And Platinum Therapy For Advanced Non - Small Cell Lung Cancer

The development of predictive markers to identify patients who will derive significant benefit with minimal toxicity from chemotherapy is a continuing focus in lung cancer research. In this study,10putative functional single nucleotide polymorphisms in8apoptosis-related genes (BCL2, BAX, CASP3, CASP8, CASP9, CASP10, TNF-a and MIF) were selected. We then investigated whether these polymorphisms were associated with severe hematological toxicity, gastrointestinal toxicity or objective response rate among445platinum-based chemotherapy treated advanced NSCLC patients.The incidence of severe hematological toxicity was significantly lower in variant C allele carriers of CASP3rs6948polymorphism (adjusted OR of0.588and95%CI of0.369-0.940for carriers of one C allele, adjusted OR of0.174and95%CI of0.038-0.784for carriers of two C alleles), compared with their wild-type homozygotes AA and the significance levels of the increasing trend were apparent for an indication of a dose-dependent relationship between the polymorphism and severe hematological toxicity risk (P for trend=0.010). The GA genotype of TNF-α rs1800629was significantly associated with increased gastrointestinal toxicity risk compared with the GG genotype (adjusted OR=3.354;95%CI=1.302-8.640,P=0.012). No severe throbocytopenia observed in52variant A allele carriers of BAX rs4645878polymorphism among389samples suggested that this SNP was associated with lower risk for thrombocytopenia. The heterozygotes of CASP8rs3834129(adjusted OR=0.557;95%CI=0.334-0.930, P=0.025), CASP10rs13006529(adjusted OR=0.587;95%CI=0.325-0.980, P=0.041) and CASP10rs3900115(adjusted OR=0.575;95%CI=0.344-0.959, P=0.034) were significantly associated with lower risk for leukocytopenia compared with their wild type homozygotes, respectively. The three polymorphisms are in high linkage disequilibrium in Chinese population. In the subgroup analysis for patients receiving Navelbine in combination with cisplatin treatment, poor response was significantly associated with the minor A allele of BCL2rs2279115in a dominant genetic model (adjusted OR=0.454;95%CI=0.207-0.998, P=0.049). BCL2rs1564483polymorphism was related to response in both elder patients (>57years old) C allele carriers of CASP3rs6948and younger (≤57years old) patients. However, the effects on response were distinct in age-stratified patients. The variant C allele increased the possibility to have objective response in elder patients (adjusted OR=3.088;95%CI=1.528-6.239, P=0.002), but decreased the possibility in younger patients (adjusted OR=0.327;95%CI=0.116-0.924, P=0.035) in a dominant genetic model.Further studies with larger group of study subjects or other samples are warranted to validate the associations as indicated above.To validate the association between rs6948and hematological toxicity, we recruited other52patients with newly diagnosed lung cancer treated with platinum combination chemotherapy and examined the relative CASP3mRNA levels in the peripheral blood leukocytes of these patients by real-time PCR, whose CASP3rs6948SNP genotypes were also determined. We found that the CASP3rs6948C variant in the3’UTR was associated with a relatively lower mRNA level. The average mRNA level of CASP3C variant genotypes was about72.5%compared to that of wild genotype AA. The result is consistent with the assumption that the minor C allele suppresses CASP3expression and lowers the risk for hematological toxicity.Besides rs6948we detected another SNP, rs1049216in the CASP33’UTR from20samples. Using PHASE2.0.2program we found only two haplotypes, A/C (A for rs6948, C for rs1049216) and C/T (C for rs6948, T for rs1049216) in this region, which suggested that the two SNPs were highly linked. By cloning the CASP33’UTR into pGL3-Promoter vector, we constructed two recombinants, pGL3-PromoterA/C and pGL3-PromoterC/T. Luciferase assays revealed that reporter expression levels of pGL3-PromoterA/C were significantly lower than those of pGL3-PromoterC/T in ECV304, HEK293, H1299and HeLa cell line, separately.TargetScan predicts that rs6948is located in miR-24seed region and rs1049216is located in miR-664seed region. Further studies are needed to verify whether rs6948or rs1049216causes the translation suppression. If does, whether miR-24or miR-664contributes to the translation suppression.