GSTP1 IleVal polymorphism among North Indian lung cancer patients treated using monotherapy and poly-pharmacy

Genetic polymorphism within the P1 isoenzyme of the Glutathione-S-Transferase (GST) family is found to modulate and alter the enzyme activity of GSTP1 protein and thus may result in a change of sensitivity to platinum-based chemotherapy. We investigated the relationship between GSTP1 IleVal polymorphisms and overall survival, treatment response, and for both hematological and non-hematological toxicity of advanced North Indian lung cancer patients undergoing platinum-based double chemotherapy.

The polymorphism of GSTP1 IleVal in North Indian lung cancer patients was assessed by polymerase chain reaction-restriction fragment length polymorphism. A total of 682 lung cancer patients were enrolled in the study, and it was observed that patients who were carrying both the mutant alleles (Val/Val) for the GSTP1 polymorphism showed a higher trend of median survival time (MST) as compared to the patients bearing the wild type of genotype (Ile/Ile) (MST = 8.30 vs. 7.47, p = 0.56). Based on toxicity profiling, we observed that lung cancer patients with the mutant genotype of GSTP1 (Val/Val) had an increased risk of leukopenia (OR = 2.41; 95% CI = 1.39-4.18, p = 0.001) as compared to subjects carrying both copies of the wild alleles (Ile/Ile). Our data suggested that patients with heterozygous genotype (Ile/Val) had a 2.14-fold increased risk of developing severe anemia (OR = 2.14, 95% CI = 0.97-4.62, p = 0.03). Our data also showed that in small cell lung carcinoma (SCLC) patients' polymorphism of GSTP1 was associated with thrombocytopenia (χ2 test = 7.32, p = 0.02).

Our results suggest that GSTP1 Ile¹⁰⁵Val polymorphism could be a predictive biomarker for hematological toxicity, like leukopenia and anemia, but not thrombocytopenia or neutropenia.