Abstract 2591: Caffeic acid phenethyl ester (CAPE) suppresses melanoma tumor growth by inhibiting AKT/XIAP pathway

Abstract

Abstract The incidence of melanoma is constantly on the rise indicating that current available therapies are not very effective. Moreover, melanoma is highly metastatic and resistant to chemotherapeutic drugs. Our previous studies have demonstrated that caffeic acid phenethyl ester (CAPE) suppress the growth of melanoma cells and induce ROS generation. However, the exact mechanism of the growth suppressive effects of CAPE was not clear. Here we determined the potential mechanism of CAPE against melanoma in vitro and in vivo. In a concentration and time-dependent study, CAPE treatment suppressed the activating phosphorylation of PI3K at Tyr-458, PDK1 at Ser-241, mTOR at Ser-2448 and AKT at Ser-473 in B16F0 and SK-MEL-28 melanoma cells. Furthermore, the expression of XIAP, survivin and BCl2 were down-regulated by CAPE treatment in both the cell lines. Significant apoptosis was observed in both the cell lines by CAPE treatment as indicated by cleavage of caspase-3 and PARP. AKT kinase activity was inhibited by CAPE in a concentration-dependent manner. Since Akt regulates XIAP, their interaction was examined by immunoprecipitation studies. Our results show that CAPE treatment decreased the interaction of AKT with XIAP. To establish the involvement of Akt in the apoptosis-inducing effects of CAPE, cells were transfected with Akt. Our results reveal that AKT over-expression attenuated the decrease in XIAP and significantly blocked CAPE-mediated apoptosis. Similarly, over-expression of XIAP further decreased CAPE-induced apoptosis. To confirm the involvement of ROS in the inhibition of AKT/XIAP pathway, cells were treated with antioxidant NAC prior to CAPE treatment. Our results indicate that NAC blocked CAPE mediated AKT/XIAP inhibition and protected the cells from apoptosis. In addition, oral administration of 10mg/kg/day CAPE substantially suppressed the growth of B16F0 tumor xenografts in C57BL/6 mice. Tumors from CAPE treated mice showed reduced phosphorylation of PI3K, AKT, mTOR and protein level of XIAP and enhanced the cleavage of caspase-3 and PARP. Taken together, our results suggest that CAPE suppresses AKT/XIAP pathway leading to apoptosis in melanoma tumor cells in vitro and in vivo. [Supported in part by R01 grant CA129038 (to S.K.S) awarded by the National Cancer Institute]. 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 2591. doi:1538-7445.AM2012-2591