Background: Prostate cancer is one of the most prevalent forms of cancer among men, especially in the United States. Previously, we have shown that carnosol, a dietary diterpene from rosemary (Rosmarinus officinalis), has a unique function in that it is a dual disruptor of androgen and estrogen receptor alpha. Herein, we examined how carnosol and another dietary diterpene from rosemary, carnosic acid, promote endoplasmic reticulum (ER) stress and modulate the activity and expression of androgen receptor (AR). Materials and Methods: Experiments were performed using the prostate cancer cell lines 22Rv1 and LNCaP cells. Cell proliferation and cell viability were studied using BrdU and MTT assay respectively. Western blotting, ELISA and siRNA were used to evaluate the relationship between ER stress and androgen receptor degradation. Results: Both, carnosic acid and carnosol, inhibited growth and decreased the cell viability of 22Rv1 and LNCaP cells in a dose-dependent manner. The anti-proliferative effect was associated with apoptosis as evidenced by a significant increase in levels of cleaved caspase-3 protein. Interestingly, these diterpenes modulated proteins associated with ER stress including BiP, IRE1 and CHOP. Furthermore, we saw a dose-dependent decrease in expression of AR in 22Rv1 and LNCaP cells when treated with either carnosol or carnosic acid. The proteasome has been shown to be regulated by multiple proteins including proteins associated with ER stress. The AR expression increased in presence of proteasome inhibitor, MG-132, suggesting that decrease in AR expression was due to proteasomal degradation. Carnosic acid and carnosol, also showed a decrease in expression of prostate-specific antigen (PSA) levels in a dose-dependent manner. Conclusion: Both, carnosic acid and carnosol, induce ER stress-mediated apoptotic cell death in prostate cancer cell lines, 22Rv1and LNCaP cells, leading to disruption of AR expression. Our data suggests that these natural diterpenes possess strong anticancer activity and should be evaluated further as potential chemopreventive and/or chemotherapeutic agents for controlling prostate cancer.

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 2573. doi:1538-7445.AM2012-2573

©2012 American Association for Cancer Research
2012