Abstract 538: ROS differentially regulates prostate cancer cell survival

Abstract

Abstract In vitro and in vivo studies have shown that ROS accumulation correlates with increasing aggressiveness of prostate cancer cells, and increased expression of oncogenic molecules, such as CXCR4. CXCR4 is a G-Protein Coupled Receptor that is heavily implicated in the metastatic dissemination of prostate tumor cells to bone marrow. In cancer and other cell models, CXCR4 expression and activity increases in response to hypoxic environments and/or oxidative stress. Cells react by inducing expression of a HIF1α transcription factor, which enhances expression of targeted genes involved in adjusting to oxidative stress and cell survival. HIF1α has been shown to directly induce the expression of CXCR4 in prostate cancer cells. Therefore, generation of ROS in tumor tissues may critically influence CXCR4-mediated expression and functions, ultimately encouraging cancer progression. In this study, we elucidate a mechanism by which ROS induces CXCR4 expression and function in prostate cancer cells. We initially investigated the role of ROS on the phosphorylation of AKT (p-AKT) and ERK1/2 (p-ERK1/2) in DU145 and 22Rv1 prostate cancer cell lines. Using H2O2 as our model of ROS, we found that H2O2 induced a gradual expression of p-AKT and p-ERK1/2 by western blot analysis, which was abrogated by the ROS scavenger N-acetyl cysteine (NAC). It has been shown that PTEN is a negative regulator of AKT and ERK1/2 signaling, and that ROS accumulation inactivates PTEN phosphatase function; hence, we determined whether the increase in p-AKT and p-ERK1/2 expression was due to loss of PTEN function. By performing a phosphatase assay, we found that H2O2 inhibited PTEN catalytic activity compared to untreated cells, while NAC abrogated these effects in both cell lines. The increase in ROS and loss of PTEN has been shown to correlate with CXCR4-mediated function; therefore, we determined the role of H2O2 on CXCR4 expression. We found that H2O2 induced CXCR4 expression in DU145 cells, but not in 22Rv1 cells. Furthermore, we investigated whether ROS-mediated induction of CXCR4 was HIF1α dependent. Interestingly, H2O2 induced expression of HIF1α in DU145 cells, which was abrogated by siRNA for HIF1α. HIF1α expression decreased in 22Rv1 cells, which correlated with apoptosis, as confirmed by Annexin-V analysis. Finally, we observed that the H2O2-mediated increase in CXCR4 enhanced transendothelial invasion and migration in DU145 cells in a CXCR4 dependent manner. Our study suggests that ROS differentially regulates CXCR4 expression and function in prostate cancer cells, suggesting that ROS plays a differential role on heterogeneous tumor mass. 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 538. doi:1538-7445.AM2012-538