SNP analysis in ATP-binding cassette, Solute carrier transporters and Thymidylate synthase genes in North Indian lung cancer patients

Abstract

Background: Lung carcinoma is the second most common type of cancer (accounting for 13% of all occurrences) and the leading cause of carcinoma fatalities. Drug transporters are well-known mediators of drug disposition that facilitate drug influx and efflux from cells. Polymorphisms in transporter genes and drug targets alters intracellular concentrations of drugs that determine the efficacy, toxicity, and clinical outcomes in lung cancer patients. Objective: To evaluate the sequence variants of ABC (ABCB1, ABCC1, ABCC2, and ABCG2) and SLC (SLC19A1, SLCO1B1, and SLCO1B3) drug transporters and Thymidylate synthase gene (chemotherapeutic target) in North Indian population. Methodology: Lung cancer patients undergoing platinum-based chemotherapy were recruited in the current study. Genotyping of ABCB1 (C1236T, C3435T, and G2677T/A), ABCC1 (G3173A and G2168A), ABCC2 (G4544A), ABCG2 (C421A), SLC19A1 (G80A), SLCO1B1 (A388G, T521C), SLCO1B3 (A1683-5676G), TS TSER (2R/3R), and TS 1494del6 polymorphisms were evaluated using polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP). The univariate Kaplan-Meier method was used to assess overall survival in lung cancer patients. Cox regression analysis was employed to retrieve the adjusted hazard ratio. Stratified analysis was carried out to estimate risk for subgroups based on different clinicopathological parameters, clinical outcome, and toxicity by odds ratios (ORs) and 95% confidence intervals (CIs). In all analyses, a p-value of <0.05 was chosen to be significant. Results: Poor survival outcomes were noted in patients carrying heterozygous genotype (CT) for ABCB1 C1236T polymorphism as compared to the wild-type genotype (CC) (p=0.04). Patients with ADCC harboring heterozygous (CT) genotype for ABCB1 C1236T had lower survival as compared to the patients having wild type (CC) genotype (p=0.03). The patients administered with cisplatin/carboplatin and docetaxel and having both copies of the mutant allele (TT) for ABCB1 C1236T polymorphism showed higher survival as compared to the wild-type genotype (CC) (p=0.04). The lung cancer subjects harboring heterozygous genotype (CT) for ABCB1 C1236T and treated with the pemetrexed and cisplatin/carboplatin had substantially poor survival as compared to the patients with wild type (CC) genotype (p=0.02). The patients harboring heterozygous x genotype (CT) for ABCB1 C1236T polymorphism had lower survival than those with wild-type genotype (CC) in stage IV lung cancer patients (p=0.002). For ABCB1 C3435T, a drastic decrease in survival was observed in the ADCC patients having heterozygous genotype (CT) as compared to the wild-type genotype (CC) (p=0.04). For ABCB1 C3435T, individuals who carried heterozygous (CT) (p=0.03) and mutant (TT) genotypes (p=0.04) had poor survival as compared to the wild-type (CC) genotype in patients treated with pemetrexed and cisplatin. SCLC patients with ABCB1 G2677A polymorphism having heterozygous genotype (GA) showed poor survival as compared to the wild-type genotype (GG) (p=0.03).The patients administered with cisplatin and irinotecan and having mutant alleles (AA) for ABCB1 G2677A polymorphism showed lower survival as compared to the individuals carrying wild-type alleles (GG) (p=0.007). The mutant genotype (AA) for ABCC1 G3173A exhibited a lower survival time as compared to the reference genotype (GG) (p=0.01). For ABCC1 G3173A, ADCC patients having mutant genotype (AA) had reduced survival as compared to the wild-type (GG) genotype (p=0.001). Lower survival was observed in individuals carrying heterozygous genotype (GA) for ABCC2 G4544A polymorphism as compared to the wild-type genotype (GG) (p=0.04). Patients having SCLC and carrying heterozygous genotype (GA) for ABCC2 G4544A polymorphism showed a poor survival time as compared to the wild-type genotype (GG) (p=0.03). The patients administered with cisplatin/carboplatin and pemetrexed and harboring heterozygous genotype for the ABCC2 G4544A variant exhibited poorer survival than those carrying the wild-type genotype (p=0.03). ADCC patients harboring mutant genotype (AA) showed better survival outcomes as compared to the ADCC subjects with wild-type genotype (GG) for SLC19A1 G80A (p=0.04). SCLC patients' with SLC19A1 G80A polymorphism showed increased survival in patients with the mutant genotype (p=0.04). Patients with mutant genotype (GG) for SLCO1B1 A388G polymorphism depicted lower survival as compared to the wild-type genotype (AA) (p=0.008). In SLCO1B3 A1683-5676G, patients carrying heterozygous alleles and administered with platinum and docetaxel showed inferior survival (p=0.006). TSER polymorphism was associated with poor overall survival in lung cancer patients (p=0.04). Stage IV patients having mutant genotype (3R3R) for TSER polymorphism showed reduced survival as compared to the combined wild and heterozygous genotype (2R2R+3R3R) (p=0.02). Analysis of combined genotypes of TS polymorphism showed a better prognosis in subjects carrying both the wild and heterozygous alleles [ (2R3R) + (+6/-6) and (2R2R) + (+6/+6)] as compared to patients having the homozygous variant alleles for both the genotypes (3R3R+ -6/-6 bp) (p=0.04). xi Additionally, a substantial improvement was observed in patients' survival time with the genotypic combination of 2R2R &-6/-6 (low TS expression) as compared to patients harboring the 3R3R & +6/+6bp genotype (p=0.04). Patients harboring heterozygous (GA) genotype for ABCC1 G3173A had an increased risk of developing anemia (AOR=2.70, p=0.03). For ABCC2 G4544A polymorphism, patients harboring one copy of the mutant (GA) allele showed an increased risk of developing anemia (p=0.03). The ABCB1 G2677A (OR=0.37, p=0.008) and ABCC1 G3173A (OR=0.54, p=0.04) polymorphism showed a lower incidence of developing nephrotoxicity. For ABCC1 G3173A polymorphism, a lower incidence of anorexia was observed in patients with one copy of the mutant allele (GA) as compared to patients having both copies of wild-type alleles (GG) (p=0.04). There was an increased risk of developing diarrhea in the patients with heterozygous genotype (GA) for ABCC1 G3173A polymorphism (AOR=2.78, p=0.04). Also, patients harboring heterozygous (CT) (p=0.015) and mutant genotype (AA) (p=0.02) for ABCB1 C1236T variant were associated with a reduced risk of having nausea/vomiting as compared to the wild type (CC) genotype. An increased risk of liver injury was noted in patients having heterozygous genotype for ABCB1 C1236T as compared to the wild-type (CC) genotype (p=0.04). Patients with SLCO1B1 A388G polymorphism harboring a single copy of mutant allele (AG) were associated with a lower incidence of thrombocytopenia when compared to the patients carrying wild-type alleles (AA) (p=0.02). Patients with SLCO1B3 A1683-5676G variants showed a lower incidence of nephrotoxicity. For SLCO1B1 A388G, lung cancer patients with heterozygous genotype (AG) revealed a 3.87-fold increased risk of having constipation (p=0.04) as compared to the patients with wild-type genotype (AA). Patients with the mutant (-6/-6) genotype showed a 2.57-fold elevated risk of developing leukopenia (p=0.03). Lung cancer patients with mutant genotype (-6/-6bp) for 1494 ins/del6 polymorphism had a roughly 2-fold risk of developing anemia as compared to patients with wild genotype (+6/+6bp) (p=0.04). A substantial risk of 4.76-fold constipation was found in the individuals having heterozygous genotype (2R3R) for TSER polymorphism (p=0.0016). The combined mutant and heterozygous genotype (3R3R+2R3R) revealed a 4.09-fold elevated risk of having constipation (p=0.02). An increased risk of nausea/vomiting was observed in patients with mutant genotype (-6/-6bp) for 1494del6 polymorphism compared to patients with wild-type genotype (+6/+6bp) (p=0.03). xii Conclusion: Survival analysis revealed that three variants (C1236T, C3435T, and G2677A) of the ABCB1 gene predicts survival of lung cancer patient. ADCC patients having polymorphism of ABCC1 G3173A appear to be a potential prognostic marker as mutant genotype (AA) was associated with poor survival outcomes. Pemetrexed cisplatin/pemetrexed carboplatin therapy is associated with poor prognosis for lung cancer patients having ABCC2 G4544A polymorphism. The SLC19A1 G80A polymorphism appears to be a potential prognostic factor for OS of SCLC and ADCC patients. SLCO1B1 A388G was associated with poor survival outcomes in lung cancer patients. SLCO1B3 A1683-5676G independently affects the OS of patients treated with docetaxel and cisplatin/carboplatin regimen. TSER polymorphism was associated with poor overall survival in lung cancer patients. Our results showed a strong association between ABCC1 G3173A and ABCG2 G4544A in causing anemia in lung cancer patients who underwent platinum-based doublet chemotherapy. We also report a correlation between ABCB1 C1236T, C3435T, and ABCC1 G3173A polymorphism in predicting gastrointestinal toxicity. Additionally, ABCB1 C1236T polymorphism had a strong association in causing hepatic toxicity in lung cancer patients undergoing platinum-based doublet chemotherapy. SLCO1B1 A388G and SLCO1B3 A1683-5676G polymorphisms modify the associated adverse events. Patients with TS polymorphisms might impact the development of platinum-related toxicities such as hematological and gastrointestinal toxicity. This study in the future can facilitate the assessment of genetic variations of ABC/SLC/TS and help patients to make therapeutic decisions for individualized therapy in advanced lung cancer patients.