Abstract 4023: Elevating the reactive oxygen species threshold in prostate cancer stem cells using VK3-OCH3 as a strategy to target prostate cancer

Abstract

Abstract Prostate cancer (PCa) is the second most leading cause of cancer related deaths in American men. Although several cancer treatments are available, these have a number of drawbacks and can leave the patient with cardiotoxicity, loss of libido and infertility. Androgen deprivation therapy (ADT) is a standard promising therapy for metastatic PCa patients. However, patients within 18-24 months suffer from relapse and progress into castration resistant prostate cancer (CRPC). Experimental evidences suggest that, cancer stem cells (CSC) which constitute as a subpopulation of cancer cells, play a pivotal role in carcinogenesis, metastasis and chemoresistance to therapies. Therefore, targeting CSC can decrease the PCa recurrence rates and can help to offer better treatment options. Elevating the reactive oxygen species (ROS) threshold has been shown to be an effective strategy to eliminate CSC. Hence, in the present study, we hypothesized that VK3-OCH3, a menadione derivative, as a potential ROS enhancer in prostate cancer stem cell line (PCSC). After conducting a cell viability assay with different vitamin K (VK) analogs, our data revealed that VK3-OCH3 was more effective against PCSC compared to other VK analogs. Subsequently, colony formation assay and Trans-well migration assays revealed that VK3-OCH3 exhibits anti-tumorigenic and anti-metastatic properties against PCSC. Further studies showed that antioxidants such as NAC and GSH antagonized the effects of VK3-OCH3 on PCSC survival inhibition, suggesting the activation of oxidative stress by VK3-OCH3 in PCSC. In addition, our data revealed that VK3-OCH3 imparts oxidative stress by increasing the ROS levels which were determined using a ROS probe (DCFDA) by fluorescence analysis. VK3-OCH3 treatment also induced marked elevations in mitochondrial ROS generation in PCSC by FACS analysis which correlated with significant apoptotic cell death in these cells. Furthermore, we tested the effect of VK3-OCH3 on cell cycle progression using FACS and observed a significant G0 cell cycle arrest. By using an oncogene array, it was found that survivin, an apoptotic inhibitor, was downregulated by VK3-OCH3, which was further confirmed by Western blot analysis. Our subsequent confocal studies showed that, VK3-OCH3 downregulates the expression levels of EMT markers such as vimentin and TCF-8. Real time data also revealed that there is a modulation in gene expression of beta-catenin upon VK3-OCH3 treatment in PCSC. Of note, VK3-OCH3 treated PCSCs had a significant reduction in stem cell markers such as CD44 and ALDH1. In conclusion, our results suggest that VK3-OCH3 could be used as a potential ROS targeted anti-CSC strategy in treating PCa. Citation Format: Mona Vudutha, Somaiah Chinnapaka, Pranav Volety, Gnanasekar Munirathinam. Elevating the reactive oxygen species threshold in prostate cancer stem cells using VK3-OCH3 as a strategy to target prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4023.