Abstract 3808: Tetrandrine blocks cell cycle progression and promotes growth arrest in prostate cancer cells by up-regulating CDK inhibitors (p21 and p27) and suppressing cyclin expression.

Abstract

Abstract Introduction: Prostate cancer (PCa) is the second leading cause of cancer deaths in men. De-regulated cell cycle progression is one of the hallmarks of cancer cells. While many agents are available to inhibit growth and proliferation of normal cells, we do not have efficient agents that inhibit growth and proliferation of tumor cells, and no agents are able to achieve growth arrest and inhibition of cell cycle progression in castrate resistant prostate cancer. In this study we evaluated effects of Tetrandrine (Tet: a bis-benzylisoquinoline alkaloid isolated from the root of Stephania tetrandra) that has been shown to have diverse biological properties, on cell growth, proliferation and cell cycle progression in prostate cancer cells. Methods: Prostate cancer cells, LNCaP cells (androgen dependent), LNCaP C-4 and C4-B (castrate resistant lineages derived from LNCaP cells) cells were obtained from ATTCC. Cells were maintained in select media and grown in 5% CO2 in a humidified incubator maintained at 37C. Where indicated Tet (1-20 uM) was added to the growth media for various time points as indicated. Cell growth and proliferation was monitored by MTT assay and cell cycle distribution was measured by FACS assay following labeling of the cells with Propedium Iodide. Western Blotting was used to monitor changes in the levels of various cell cycle related proteins. Results: Tet treatment inhibited cell growth and proliferation in all three cell lines tested. The effects of Tet on cell growth and proliferation were dose dependent with complete growth inhibition at 20 uM. Tet treatment resulted in a significant increase in cyclin dependent kinase inhibitory (CDKi) protein p21 (WAF1, Cip1) and p27 (Kip1) and with p21 increase being most prominent. Moreover, p21 was associated with Cyclin D kinases as monitored by IP assays. Gene expression analysis revealed that Tet decreased mRNA levels of cyclins. FACS analysis revealed that Tet treatment resulted in cell cycle arrest in G1/G0 phase of cell cycle. Finally TET inhibited growth of LNCaP-derived tumors in nude mice. These in vivo effects of TET were also associated with a dramatic increase in p21. Conclusions: Tet inhibits growth and proliferation of prostate cancer cells by effectively blocking cell cycle progression, in part by mediating increase in p21 (WAF1, Cip1) and p27 (Kip1) proteins and suppressing cyclin expression. 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 3808. doi:1538-7445.AM2012-3808