PTGS2 and colorectal adenoma: The current study analysed the following: (1) the cellular effects of exogenous PGE2 on the expression of COX-2, c-jun and c-fos in LT97 human colorectal adenoma cells as well as Caco2 colorectal carcinoma cells that also express little COX-2, (2) the consequences of sustained COX-2 expression in VACO235 cells that have a high level of endogenous expression of the enzyme (Willson et al, 1987) and in LT97 cells infected with a COX-2-expressing adenovirus.