Abstract 119: Vitamin K2 targets castration-resistant prostate cancer VCaP cells by reactive oxygen species mediated apoptotic cell death

Abstract

Abstract Prostate Cancer (PCa) is the second most common cancer in western countries especially in US population, in which castration-resistant prostate cancer (CRPC) is the major cause for patient mortality. Current treatment options available for CRPC are not efficient and have undesirable side effects. Hence there is an urgent need to develop non-toxic and effective treatment strategies for CRPC. Vitamin K2 (VK2), a natural menaquinone has several medicinal values including anti-cancer activity and anti-osteoporosis effect. The aim of this study is to evaluate the therapeutic effects of Vitamin K2 (VK2) and its anti-cancer mechanism against CRPC. In this study, we have used VCaP cell line (ATCC) which is established from a patient with hormone refractory prostate cancer. VCaP cells were treated with various concentrations of VK2 to evaluate its effects on cell viability by MTT assay, anchorage independent growth by soft agar assay, cellular senescence by beta-galactosidase staining assay and cancer cell migration by wound healing assay. We have also assessed the VK2-induced production of intracellular reactive oxygen species (ROS) using DCF (2′,7′-dichlorofluorescein) probe based fluorescence assay. VK2 induced apoptosis was detected by Annexin-V FITC and TUNEL assays. Western blot analysis was utilized to uncover the anti-proliferative and anti-metastatic mechanisms of VK2 against CRPC. Our results showed that VK2 significantly inhibits the proliferation of VCaP cells in a dose dependent manner at 48 hrs treatment in vitro. MTT data also showed that anti-proliferative effects of VK2 were significantly abrogated in the presence of anti-oxidant N-acetyl cysteine (NAC) and caspase inhibitor Z-VAD-FMK suggesting that ROS and caspase activation as the underlying anti-cancer mechanisms of VK2 in CRPC cells. In addition, VK2 reduced the migration potential of VCaP cells in wound healing assay and inhibited anchorage independent growth of these cells when compared to untreated cells. Annexin-V and TUNEL assays confirmed that VK2 induces apoptosis in VCaP cells. Our results also suggested that the VK2 has the ability to enforce growth arrest in CRPC cells by activating cellular senescence. Western blot analysis revealed that VK2 downregulated the expression of BiP, survivin, MMP-2, and PCNA while activating PARP-1, p21 and DNA damage response marker, phospho-H2AX in VCaP cells. Furthermore, VCaP cells treated with VK2 resulted in the activation of Caspase-3 and-7 apoptotic mediators. These results correlated with translocation of Bax and Cytochrome C to cytoplasm following VK2 treatment in VCaP cells as determined by confocal immunofluorescence analysis. In conclusion our study suggests that VK2 might be an effective anti-proliferative and anti-metastatic agent for CRPC by specifically targeting key anti-apoptotic, cell cycle progression and metastasis promoting signaling molecules. Citation Format: Subramanyam Dasari, Maarten C. Bosland, Andre Kajdacsy- Balla, Gnanasekar Munirathinam. Vitamin K2 targets castration-resistant prostate cancer VCaP cells by reactive oxygen species mediated apoptotic cell death [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 119. doi:10.1158/1538-7445.AM2017-119