The -1195G allele increases the transcriptional activity of cyclooxygenase-2 gene (COX-2) in colon cancer cell lines.

Up-regulation of cyclooxygenase-2 (COX-2) is an early and key event in human colorectal carcinogenesis (CRC). Nevertheless, the molecular mechanisms leading to this over-expression are largely unknown. We previously reported an association between the -1195G allele and higher predisposition for CRC in a Caucasian population. The biological explanation for the involvement of this polymorphism in CRC remains elusive. We aimed to functionally characterize the influence of the -1195A>G promoter region polymorphism on COX-2 transcription activity in colon cancer cell lines. Luciferase reporter assays were performed to assess whether the -1195A/G alleles influenced COX-2 transcription. The COX-2 promoter's region containing either the -1195A or -1195G alleles was cloned into pGL3-basic reporter vector. The reporter vectors were transiently co-transfected with the pGL4.73 control plasmid to HCT-116 and HCA-7 colon cancer cell lines. The levels of reporter gene expression driven by the -1195G allele-containing COX-2 promoter were significantly higher in both colon cancer cell lines. A 2.2-fold increase in promoter activity was observed in the HCT-116 cell line (P < 0.001), and this over-expression was even more noticeable in the HCA-7 COX-2 expressing cell line with a threefold higher transcriptional activity (P = 0.001). The -1195G allele appeared to enhance COX-2 transcription, providing a molecular basis underlying the increased susceptibility for CRC and potentially a new mechanism for COX-2 overexpression.