Abstract 2447: Activation of Chk1 critical for Piperine induced cell cycle arrest and apoptosis in melanoma cells.

Abstract

Abstract The National Cancer Institute estimates that about 76,250 new cases of melanomas will be diagnosed in 2012 in the United States leading to at least 9810 related deaths. Therefore, novel strategies to control and treat melanoma are of prime importance. In this study, we determined the cytotoxic effects of Piperine, a major constituent of black (Piper nigrum Linn) and long pepper (Piper longum Linn), in melanoma cell lines. Piperine treatment inhibited the growth of SKMEL-28 and B16-F0 cells in a dose and time-dependent manner. The growth inhibitory effects of piperine were mediated by cell cycle arrest of both the cell lines in G1 phase. The G1 arrest by piperine was correlated with the down-regulation of cyclin D1 and induction of p21. The growth arrest was associated with DNA damage as indicated by phosphorylation of H2A.X at Ser139, activation of ataxia telangiectasia and Rad3-related protein (ATR) and checkpoint kinase 1 (Chk1). The G1 arrest by piperine was also associated with the down-regulation of E2F1 and decreased phosphorylation of retinoblastoma protein (Rb), hence indicating the inhibition of the dynamic transcription complex. In addition, apoptosis induced by piperine was associated with down-regulation of XIAP and Bid (uncleaved) and cleavage of Caspase-3 and PARP. Pretreatment of SK-MEL-28 with AZD 7762, a Chk1 inhibitor not only abrogated the activation of Chk1 but also piperine mediated G1 arrest. Silencing of Chk1 in SK-MEL28 cells with Chk1 siRNA completely protected the cells from G1 arrest induced by piperine treatment showing the involvement of Chk1. Through immunofluorescence of Phospho Chk1 (Ser 256), we found significant activation of Chk1 in the cells that were treated with piperine hence, establishing the role of Chk1 activation. Furthermore, our results showed that piperine treatment caused ROS generation in melanoma cells. Blocking ROS generation by Tiron pre-treatment prevented the cells from piperine mediated cell cycle arrest. Moreover, western-blotting results showed that Tiron pre treatment prevented the activation of Chk1 hence, confirming the role played by Chk1 in piperine mediated cell cycle arrest. Taken together, our results demonstrate that piperine induced G1 phase cell cycle arrest by generating ROS and inducing DNA damage with activation of Chk1 being a critical event. [Supported in part by R01 grants CA106953 and CA129038 (to S.K.S) awarded by the National Cancer Institute]. Citation Format: Neel M. Fofaria, Sanjay K. Srivastava. Activation of Chk1 critical for Piperine induced cell cycle arrest and apoptosis in melanoma cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2447. doi:10.1158/1538-7445.AM2013-2447