Abstract 188: EphrinA1 induces microRNA-302b expression in malignant mesothelioma cells and suppresses tumor growth via repression of Mcl-1 gene

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Abstract Introduction: EphA2 is a receptor tyrosine kinase (RTK) and is over expressed in malignant mesothelioma (MM). In earlier studies we demonstrated that receptor EphA2 activation with ephrinA1 suppressed growth of MM. In addition there is evidence that ephrin ligand induces some MicroRNAs expression in cancer cells. MicroRNAs belonging to the miR-302 family are emerging as key players in the control of proliferation and cell fate determination during differentiation. However, the mechanisms whereby EphrinA1 activation attenuates the MM cell growth are not clear. Our study identified a novel mechanism of Ephrin-A1 tumor suppressor signaling in MM cells. Ephrin-A1 activation up regulates miR-302b expression in MM cells and attenuates tumor growth via repression of Mcl-1. Methods: MM cell lines (CRL-2081 and CRL-5830) were activated with recombinant-Ephrin-A1 for the indicated period of time. The expression of miR-302b was analyzed by quantitative real time RT-PCR, and the expression Mcl-1 was analyzed by RT-PCR, immuno-blotting and Immunofluorescence staining. To confirm that Ephrin-A1 regulates the expression of Mcl-1 mRNA through miR302-b up regulation, cultured cells were transfected with and without miR302-b and miR-302b inhibitor prior to activation. The cell proliferation and tumor growth was measured by WST-1 and 3 D matrigel assay in vitro assays respectively. Luciferase assay was performed to confirm the binding of miR-302b to the 3′UTR of Human Mcl-1. Results: Ephrin-A1 activation induced several fold increases of miR-302b expression in MM cells when compared to resting cells. In Ephrin-A1 activated MM cells, Mcl-1 expression was significantly down regulated when compared to resting cells. Moreover, Ephrin-A1 activation significantly inhibited MM cell proliferation and tumor growth. The present data suggests that Ephrin-A1 targets MM cells by inducing the expression of miR-302b and inhibits MM cell and tumor growth by targeting Mcl-1 protein. Conclusion: Our data suggest that over expression of Mcl-1 enhances tumor proliferation in MM cells. During Ephrin-A1 activation miR-302b expression is up regulated in MM cells. The up regulation of miR-302b leads to repression of Mcl-1 gene and attenuation of tumor growth. EphrinA1 could be a promising therapeutic agent for the treatment of MM. Funding Source: NIR and RC1 Department of Health Florida; VA Merit Review Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 188. doi:1538-7445.AM2012-188