Endometrial carcinoma (EC) is one of the main gynecologic malignancies affecting women, but effective treatments are currently lacking. In the present study, we investigated the effect of sorafenib, a general kinase inhibitor, on several EC cell lines (HEC1A, HEC1B, and RL95-2). Sorafenib induced cell death in EC cells with the following order of sensitivity: HEC1A > HEC1B > RL95-2. Sorafenib suppressed several anti-apoptotic proteins in HEC1A cells, including myeloid cell leukemia 1 (Mcl-1). Ectopic overexpression of Mcl-1 prevented the cell killing effect of sorafenib. Sorafenib suppressed Mcl-1 at the gene transactivation level by inactivating the ERK/Elk-1 pathway. Accordingly, the inhibitory effect of sorafenib on Mcl-1 expression decreased following knockdown of Elk-1 using short-hairpin RNA (shRNA). Elk-1 overexpression rescued both the inhibitory effect of sorafenib on Mcl-1 expression and the cell killing effect of sorafenib. Furthermore, sorafenib reduced the stability of the Mcl-1 protein by enhancing its ubiquitination and degradation by the proteasome via the AKT/GSK3β and the ERK pathways. Similar results were detected in other EC cell lines. These results indicate that sorafenib induces apoptosis in EC cells by down-regulating the anti-apoptotic protein Mcl-1 via transcriptional inhibition and protein degradation. Our results thus support the notion that sorafenib may be used in endometrial cancer therapy. J. Cell. Biochem. 114: 1819–1831, 2013. © 2013 Wiley Periodicals, Inc.
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