Abstract 3676: Selective modulation of CHOP/GADD153 in prostate cancer cells by alpha-mangostin promotes cell death.

Abstract

Abstract Background: It is well-established that during endoplasmic reticulum (ER) stress cells utilize several cell signal pathways collectively named “unfolded protein reaction (UPR)” to re-establish homeostasis and promote cell survival. The upregulation of UPR proteins to an extent is thought to be a growth advantage for cancer cells. However, chronic ER stress or prolonged UPR will lead to apoptosis. Alpha-mangostin, a xanthone from mangosteen fruit, has been reported to effectively induce prostate cancer cell apoptosis in vitro and suppress xenograft tumor growth. Thus, we investigated the alteration of ER stress-related proteins in mangosteen fruit extract (MFE)- or α-Mangostin-treated prostate cancer cells as well as its correlation with apoptosis. Methods: Two human prostate cancer cell lines, 22Rv1 and LNCaP, and a prostate epithelial cell line were treated with MFE or α-mangostin. Flow cytometry, MTT and BrdU were used to evaluate cell apoptosis, viability and proliferation. Western blot and fluorescent microscopy were used to detect proteins involved in apoptosis or ER stress. We also evaluated the anti-cancer activity of MFE and α-mangostin in nude mice inoculated with 22Rv1 cells. In addition, pharmacokinetics data of α-mangostin was collected on wild type C57BL6 mice for toxicity concern. Results: MFE increased apoptosis, decreased viability and inhibited proliferation in prostate cancer cell lines. Both MFE and α-mangostin significantly upregulated the expression of ER stress proteins, such as PERK, CHOP and IRE1α. Both MFE and α-mangostin also effectively suppressed tumor growth in a xenograft tumor model without affecting body weight. Interestingly, CHOP knockdown enhanced apoptosis in α-mangostin-treated prostate cancer cells; both MFE and α-mangostin decreased PERK expression and did not induce ER stress in prostate epithelial cells (PrECs) from prostate cancer patients. Conclusions: Both MFE and α-mangostin selectively promote ER stress in prostate cancer cells and inhibit prostate cancer cell growth in a xenograft mouse model without observable toxicity, suggesting further research is needed to evaluate its potential as an anti-cancer agent. Citation Format: Gongbo Li, Sakina Petiwala, Dana Pierce, Jeremy Johnson. Selective modulation of CHOP/GADD153 in prostate cancer cells by alpha-mangostin promotes cell death. [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 3676. doi:10.1158/1538-7445.AM2013-3676