Purpose Hormone refractory metastatic prostate cancer is a major obstacle in clinical treatment. The key focus of this study was the discovery and development of a potential agent for this disease. Materials and Methods Several pharmacological and biochemical assays were used to characterize the apoptotic signaling pathways of moniliformediquinone, a natural product, in hormone refractory metastatic prostate cancer. Results Moniliformediquinone induced cell cycle arrest at the S-phase and subsequent apoptosis in the hormone refractory metastatic prostate cancer cell lines PC-3 and DU-145. Further examination showed that moniliformediquinone induced a DNA damage response associated with Chk1, Chk2, c-Jun and JNK activation. Mitochondrial apoptosis pathways were also activated, including loss of mitochondrial membrane potential, cytochrome c release, and activation of caspase-9 and 3. The antioxidant and glutathione precursor N-acetylcysteine, and the antioxidant Trolox™ completely abolished moniliformediquinone induced generation of reactive oxygen species. However, N-acetylcysteine but not Trolox blocked moniliformediquinone mediated apoptosis and related signaling cascades. Further identification showed that moniliformediquinone alone did not conjugate glutathione but significantly decreased cellular glutathione levels. The in vivo study revealed that moniliformediquinone completely inhibited tumor growth with no weight loss. Conclusions Our data suggest that moniliformediquinone is a potential anticancer agent for hormone refractory metastatic prostate cancer by decreasing cellular glutathione, leading to a DNA damage response and cell cycle arrest at the S-phase. Mitochondrial stress also occurs due to moniliformediquinone action through loss of mitochondrial membrane potential and cytochrome c release, which in turn induce the activation of caspase cascades and apoptotic cell death.
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