Gene environment interaction in urinary bladder cancer with special reference to organochlorine pesticide: A case control study

Urinary bladder cancer (UBC) is a common disease worldwide with a higher incidence rate in developed countries. Organochlorine pesticides (OCPs), potent endocrine disrupters, are found to be associated with several cancers such as prostate, breast, bladder, etc. Glutathione S-transferase (GST) is a polymorphic supergene family involved in the detoxification of numerous environmental toxins including OCPs. The present study was carried out in UBC subjects (n = 50) and healthy control subjects (n = 50) with an aim to determine the role of GSTM1 and GSTT1 polymorphism and its implication on the OCP detoxification or bioaccumulation which may increase the risk of UBC in humans. This study was also designed to identify the "gene-environment interaction" specifically between gene polymorphism in xenobiotic metabolizing genetic enzyme(s) and blood OCP levels. GSTM1/GSTT1 gene polymorphism was analysed by using multiplex PCR. OCPs levels in whole blood were estimated by Gas chromatography equipped with electron capture detector. The results demonstrated a significant (p < 0.05) increase in frequency of GSTM1(-)/GSTT1(-) (null) genotype in UBC cases without interfering the distribution of other GSTT1/GSTM1 genotypes. The blood levels of alpha(alpha), Beta(beta), Gamma(gamma), total - Hexachlorcyclohexane (HCH) and para-para - dichlorodiphenyltrichloroetane (p,p'-DDT) were found to be significantly (p < 0.05) high in UBC cases as compared to controls. Multiple regression analysis revealed a significant interaction between beta-HCH and GSTM1(-) genotype (p < 0.05) as well as in beta-HCH and GSTT1(-) genotype (p < 0.05) respectively. These findings indicate that "gene-environment interaction" may play a key role in increasing the risk for UBC in individuals who are genetically more susceptible due to presence of GSTM1/GSTT1 null deletion during their routine encounter with or exposure to OCPs.