Mena Is A Transcriptional Target Of The Wnt/Beta-Catenin Pathway

Wnt/beta-catenin signalling pathway plays important roles in embryonic development and carcinogenesis. Overactivation of the pathway is one of the most common driving forces in major cancers such as colorectal and breast cancers. The downstream effectors of the pathway and its regulation of carcinogenesis and metastasis are still not very well understood. In this study, which was based on two genome-wide transcriptomics screens, we identify MENA (ENAH, Mammalian enabled homologue) as a novel transcriptional target of the Wnt/beta-catenin signalling pathway. We show that the expression of MENA is upregulated upon overexpression of degradation-resistant beta-catenin. Promoters of all mammalian MENA homologues contain putative binding sites for Tcf4 transcription factor - the primary effector of the Wnt/beta-catenin pathway and we demonstrate functionality of these Tcf4-binding sites using luciferase reporter assays and overexpression of beta-catenin, Tcf4 and dominant-negative Tcf4. In addition, lithium chloride-mediated inhibition of GSK3 beta also resulted in increase in MENA mRNA levels. Chromatin immunoprecipitation showed direct interaction between beta-catenin and MENA promoter in Huh7 and HEK293 cells and also in mouse brain and liver tissues. Moreover, overexpression of Wnt1 and Wnt3a ligands increased MENA mRNA levels. Additionally, knock-down of MENA ortholog in D. melanogaster eyeful and sensitized eye cancer fly models resulted in increased tumor and metastasis formations. In summary, our study identifies MENA as novel nexus for the Wnt/beta-catenin and the Notch signalling cascades.