Functional polymorphisms of cyclooxygenase-2 (COX-2) gene and risk for urinary bladder cancer in North India

Cyclooxygenase-2 (COX-2) is an enzyme involved in the synthesis of prostaglandins and thromboxanes, which are regulators of processes that are relevant to cancer development. It is involved in carcinogenesis, immune response suppression, apoptosis inhibition, angiogenesis, and tumor cell invasion and metastasis. The gene for COX-2, designated as prostaglandin-endoperoxide synthase 2 (PTGS-2), carries polymorphisms, such as -765G>C, 1195G>A in the promoter region, and 8473T>C in the 3'-untranslated region (UTR), which have been associated with susceptibility to malignant disease.

We undertook a case-control study of 212 urothelial bladder cancer (UBC) cases and 250 controls to investigate the association between COX-2 polymorphism and bladder cancer susceptibility, using the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method and also investigated gene-environment interactions.

Cox-2 765G>C, a variant(C) allele carrier, was at an increased risk of UBC (odds ratio [OR] = 1.90; P = .004); however, -1195G>A; -1290A>G; and 3'UTR 8473T>C polymorphisms of COX-2 gene were not significantly associated with UBC. 765G>C also was associated with the invasive stage of a bladder tumor (OR = 2.73; P = .033). High risk for UBC also was observed with respect to COX-2 haplotypes C-765T8473A-1195A-1290 (OR = 3.47; P = .014). In case-only analysis, COX-2 765 variant allele carrier genotypes also showed an increased risk among former and current smokers (OR = 3.06; P = .041 and OR = 4.39; P = .032, respectively).

COX-2 -765G>C polymorphism confers UBC susceptibility particularly in smokers and in patients with invasive tumors. 765C allele carrier genotypes also are influenced with a high risk of recurrence in Bacillus Calmette-Guérin-treated patients. Collectively, these findings confirm that the COX-2 -765G>C polymorphism is a risk factor for the development of bladder cancer and can provide a plausible mechanistic explanation. Further validation in large population-based studies is needed.