Abstract A71: Curcubitacin B exhibits cytotoxic effects by inhibiting Integrin-HER2 signaling in breast cancer cells

Abstract

Abstract Integrins have recently been shown to play an important role in promotion of cell motility and survival in various cancers through cooperative signaling with EGFRs. Integrins transmit cell survival signals through ILK-Paxillin complex and further play role in activating AKT signaling. Curcubitacin B (CuB) is a steroidal class of chemical present in the plants belonging to cucurbitaceae family. CuB has shown cytotoxic potential in several cancers by causing G2/M cell cycle arrest and inhibition of JAK/STAT3 pathway. However, the exact mechanism of CuB and its role in metastasis and cell survival is not known. Our results show that CuB significantly suppressed the growth of MDA-MB-231, SKBR3, HCC1806 and MCF-7 breast cancer cells in a concentration and time-dependent manner. CuB also induced apoptosis and down-regulated ILK1 expression. In addition, CuB down-regulated ITGB4 and ITGA6 protein expression and suppressed the phosphorylation of AKT at Ser473, paxillin at Tyr118. Previous studies have shown that TGFβ mediates physical association of ITGB4 and HER2, through Src kinase to enhance cell survival and motility. Interestingly we observed significant downregulation of Src, EGFR and HER2 in different breast cancer cells, suggesting that CuB suppresses cooperative signaling of Integrins and HER2. We also observed that TGFβ pretreatment imparted protection from CuB's cytotoxic effects, indicating that CuB modulates TGFβ mediated Integrin signaling. Taken together our results indicate the anti-cancer effects of CuB in breast cancer cells by targeting ITGB4/ITGA6, Src, ILK and TGFβ. Further detailed mechanistic work is in progress. [Supported in part by R01 grants CA106953 and CA129038 (to S.K.S) awarded by the National Cancer Institute]. Citation Format: Parul Gupta Gupta, Sanjay K. Srivastava. Curcubitacin B exhibits cytotoxic effects by inhibiting integrin-HER2 signaling in breast cancer cells. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr A71.