The MIF homologue D-dopachrome tautomerase promotes COX-2 expression through β-catenin-dependent and -independent mechanisms.

The cytokine/growth factor, macrophage migration inhibitory factor (MIF), contributes to pathologies associated with immune, inflammatory, and neoplastic disease processes. Several studies have shown an important contributing role for MIF-dependent COX-2 expression in the progression of these disorders. We now report that the MIF homologue, D-dopachrome tautomerase (D-DT), is both sufficient and necessary for maximal COX-2 expression in colorectal adenocarcinoma cell lines. D-DT-dependent COX-2 transcription is mediated in part by β-catenin protein stabilization and subsequent transcription. Also contributing to D-DTs regulation of COX-2 expression are the activities of both c-jun-N-terminal kinase and the MIF-interacting protein, Jab1/CSN5. Interestingly, D-DT-dependent β-catenin stabilization is regulated by COX-2 expression, suggesting the existence of an amplification loop between COX-2- and β-catenin-mediated transcription in these cells. Because both COX-2- and β-catenin-mediated transcription are important contributors to colorectal cancer (CRC) disease maintenance and progression, these findings suggest a unique and novel regulatory role for MIF family members in CRC pathogenesis.