Celecoxib treatment alters the gene expression profile of normal colonic mucosa

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Nonsteroidal anti-inflammatory drugs, including inhibitors of cyclooxygenase 2, suppress colorectal carcinogenesis and decrease the risk of death from colorectal cancer as shown in several epidemiological studies. A clinical trial was recently conducted to evaluate the safety and efficacy of selective inhibitor of cycloxygenase 2, celecoxib, in hereditary nonpolyposis colon cancer (HNPCC) patients. As part of this trial, we analyzed gene expression in normal descending (rectal) colonic mucosa of patients before and after 12 months of treatment with celecoxib or placebo. Total RNAs were isolated from 25 pairs of pre-treatment and post-treatment descending colon pinch biopsies from HNPCC patients exposed to celecoxib (from 14 patients receiving 200 mg BID and 11 patients receiving 400 mg BID of celecoxib) and from 14 pairs of biopsies of HNPCC patients treated with placebo, and analyzed on arrays containing 9128 cDNAs. We found that treatment of patients with celecoxib, in contrast to treatment with placebo, leads (according to Significance Analysis of Microarrays) to changes in expression of more than 1400 genes in the healthy colon. In general the magnitude of the changes is not greater than two-fold. Twenty three out of 25 pairs of colon biopsies taken before and after celecoxib treatment can be classified correctly by the pattern of expression of 173 genes (significant at a univariate paired t-test p<0.001) in leave-one-out cross-validation. In contrast, less than half of the samples from placebo-treated patients were correctly classified in cross-validation by the pattern of expression of 14 genes whose changes in expression are significant at a univariate paired t-test p<0.001. Most (130 genes or 75%) of the 173 genes whose differences in expression are significant at p<0.001 showed greater fold differences in expression between pre-treatment and post-treatment biopsies for patients treated with 400 mg of celecoxib compared to patients who received 200 mg of celecoxib. Immune response, particularly T- and B-lymphocyte activation and early steps of inflammatory reaction, cell signaling and cell adhesion, response to stress, transforming growth factor beta (TGF-beta) signaling, and regulation of apoptosis are the main biological processes targeted by celecoxib as suggested by over-representation analysis of the distribution of celecoxib affected genes across Gene Ontology categories. Analysis of possible cumulative effects of celecoxib-induced changes in gene expression indicates that in healthy colon, celecoxib may suppress the immune response and early steps of inflammation, inhibit formation of focal contacts, and stimulate TGF-beta signaling.