Dysregulated post-transcriptional control of COX-2 gene expression in cancer.

The cyclooxygenase-2 (COX-2) enzyme catalyzes the rate-limiting step of prostaglandin formation in pathogenic states. The molecular regulation of COX-2 gene expression is normally tightly regulated on transcriptional and post-transcriptional levels. However, loss of function at either level of COX-2 gene regulation promotes constitutive COX-2 overexpression which plays a key role in carcinogenesis, particularly colorectal tumorigenesis. Current work investigating the regulatory mechanisms of COX-2 expression has demonstrated post-transcriptional regulation to play a central role. Rapid COX-2 mRNA decay and translational inhibition is mediated through a conserved AU-rich element (ARE) present within the 3'-untranslated region (3'UTR). The COX-2 ARE exerts its control through association with ARE RNA-binding proteins. These trans-acting regulatory factors influence the fate of COX-2 mRNA by controlling mRNA degradation, stabilization, or translation. Recent evidence demonstrates the functional significance rapid mRNA decay and translational inhibition play in controlling COX-2 gene expression and that, if dysregulated, allow for overexpression of COX-2 and other associated angiogenic factors detected in neoplasia.