Abstract B56: Activation of Chk1 by Piperine causes cell cycle arrest and apoptosis in melanoma cells

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 correlated with the down-regulation of cyclin D1 and induction of p21. Furthermore, this growth arrest was associated with DNA damage caused by piperine treatment as indicated by phosphorylation of H2A.X at Ser139, activation of ataxia telangiectasia and Rad3-related protein (ATR) and checkpoint kinase 1 (Chk1). Pretreatment with AZD 7762, a Chk1 inhibitor not only abrogated the activation of Chk1 but also piperine mediated G1 arrest. Furthermore, transfection of cells with Chk1 siRNA completely protected the cells from G1 arrest induced by piperine treatment. The G1 arrest by piperine was also confirmed with the down-regulation of E2F1 and decreased phosphorylation of retinoblastoma protein (Rb), 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. In addition, our results showed that piperine treatment generated ROS in melanoma cells. Blocking ROS generation by Tiron prevented the cells from piperine mediated cell cycle arrest. Taken together, our results demonstrate that activation of Chk1 is required for piperine induced G1 phase cell cycle arrest. [Supported in part by R01 grants CA 106953 and CA 129038 awarded to S.K.S by National Cancer Institute, NIH]

Citation Format: Neel Fofaria, Sanjay K. Srivastava. Activation of Chk1 by Piperine causes cell cycle arrest and apoptosis in melanoma 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 B56.