Vitamin K2, a menaquinone present in dairy products targets castration-resistant prostate cancer cell-line by activating apoptosis signaling

The aim of this study was to evaluate the therapeutic effects of vitamin K2 (VK2) on castration-resistant prostate cancer (CRPC) and its anti-cancer mechanisms in a pre-clinical study using a VCaP cell line (ATCC (R) CRL-2876 (TM)) which was established from a vertebral bone metastasis from a patient with hormone refractory prostate cancer. Our data showed that VK2 significantly inhibited CRPC VCaP cell proliferation in a dose-dependent manner at 48 h treatment in vitro. In addition, VK2 reduced the migration potential of VCaP cells and inhibited anchorage-independent growth of these cells. Our results also showed that VK2 induces apoptosis in VCaP cells. Furthermore, VK2 enforced growth arrest in VCaP cells by activating cellular senescence. Notably, VK2 treatment elevated the levels of reactive oxygen species in VCaP cells. Western blot analysis revealed that VK2 downregulated the expression of androgen receptor, BiP, survivin, while activating caspase-3 and -7, PARP-1 cleavage, p21 and DNA damage response marker, phospho-H2AX in VCaP cells. In conclusion, our study suggests that VK2 might be a potential anti-cancer agent for CRPC by specifically targeting key anti-apoptotic, cell cycle progression and metastasis-promoting signaling molecules.