background: Uncontrolled cell proliferation and suppressed apoptosis are the critical events transforming a normal cell to a cancerous one wherein the inflammatory microenvironment supports this oncogenic transformation. The process of colon carcinogenesis may be aggravated in chronic inflammatory conditions such as ulcerative colitis where non-steroidal anti-inflammatory drugs (NSAIDs) may effectively prevent the cellular and molecular events. methods: Western blots and immunofluorescent analysis of DNA mismatch repair enzymes, cell cycle regulators and pro- and anti-apoptotic proteins were performed in dextran sulfate sodium (DSS)-induced ulcerative colitis and 1,2-dimethyl benz(a)anthracene (DMH)-induced colon cancer. Also, apoptotic studies were done in isolated colonocytes using fluorescent staining and in paraffin sections using TUNEL assay. results: An upregulation of cell cycle regulators: cyclin D1/cdk4 and cyclin E/cdk2 and anti-apoptotic Bcl-2, along with the suppression of DNA repair enzymes: MLH1 and MSH2; tumour suppressors: p53, p21and Rb and pro-apoptotic proteins: Bax and Bad were observed in the DSS, DMH and DSS+DMH groups. Proliferating cell nuclear antigen (PCNA) was also overexpressed in these groups. The ultimate executioner of the apoptotic pathway; caspase-3, was suppressed in these groups. Apoptotic studies in colonocytes and paraffin sections revealed suppressed apoptosis in these groups. These effects were corrected with the administration of a second generation NSAID, celecoxib along with the treatment of DSS and DMH. conclusions: The chemopreventive action of celecoxib in colitis mediated colon carcinogenesis may include the regulation of DNA mismatch repair enzymes, cell cycle check points, cell proliferation and apoptosis.