Abstract 542: Camalexin, the phytoalexin from Cruciferous Plants, decreases cell proliferation and induces apoptosis in prostate cancer cells

Abstract

Abstract Camalexin, the phytoalexin produced in the model plant Arabidopsis thaliana, accumulates in various cruciferous plants upon exposure to environmental stress and plant pathogens. Besides moderate antibacterial and antifungal activity, camalexin was reported to also exhibit antiproliferative and cancer chemopreventive effects. We studied the effects of camalexin treatment on viability of several prostate cancer (PCa) cell lines and whether cytostatic/cytotoxic effects of camalexin-treated prostate cancer cells were due to reactive oxygen species (ROS) generation. As models, we utilized LNCaP and its aggressive subline, C4-2, as well as ARCaP cells stably transfected with empty vector (Neo) control or constitutively active Snail cDNA that represents an EMT model. Previous studies have shown that C4-2 and ARCaP-Snail cells express more ROS than LNCaP and ARCaP-Neo, respectively. We hypothesized that camalexin would decrease cell proliferation and increase apoptosis in PCa cell lines and that the more aggressive cell lines expressing more ROS would be more sensitive to camalexin. Our results showed that camalexin treatments led to higher ROS as shown spectrofluorometrically by the oxidation of H2DCFDA, and this was decreased by co-treatment with NAC. Cell viability using MTS proliferation assay indicated that camalexin treatments decreased cell proliferation more significantly in C4-2 and ARCaP-Snail cells, as compared to LNCaP and ARCaP-Neo cells, respectively, while PrEC normal prostate epithelial cells were unaffected. Conversely, camalexin treatments increased apoptosis and mitocasp activity, which assesses caspase3/7 activity. This was associated with increased p21 and p27 anti-proliferative markers and cleaved PARP apoptotic marker as shown by western blot analysis. NAC reduced camalexin-induced ROS in ARCaP-Snail cells and abrogated camalexin-mediated cell proliferation decrease and apoptosis increase, showing that camalexin is mediating its effects through ROS. In conclusion, camalexin retarded prostate cancer cell proliferation and induced apoptosis via increased ROS generation. Interestingly, it was more potent in aggressive PCa cells expressing higher levels of ROS and did not affect normal cells. Hence, this phytoalexin has a strong potential as a novel therapeutic agent for the treatment of especially metastatic prostate cancer cells that express high levels of ROS. Supported by grants P20MD002285-01 & G12RR003062-22. 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 542. doi:1538-7445.AM2012-542