Natural Compound Alternol Induces Oxidative Stress-dependent Apoptotic Cell Death Preferentially In Prostate Cancer Cells

Objectives:Effective therapeutic options for castration resistant prostate cancer are limited, necessitating the development of novel therapies to ameliorate this disease. In this study, we evaluated the anti-cancer effect of a newly isolated natural compound Alternol in multiple prostate-derived cell lines with the properties of advanced prostate cancers and benign tissues.Methods:Utilizing western blot, flow cytometer and other indicators of apoptosis were done after Alternol incubation to test the apoptosis activation. Then ROS was detected after Alternol treated combined with or without ROS scavengers in three different cell lines-PC3, DU145and BPH1. To assess whether the Alternol induced apoptosis pathway was bax dependent, PC3cells were transfected with Bax siRNA meanwhile DU145cells were transfected with exogenous bax plasmid and then test the apoptosis indicators after Alternol treatment. Finally, the mitochondrial was observed via transmission electron microscopy and several Caspase inhibibors were used to explore the downstream of mitochondrial apoptoic pathway.Results:Western blot and flowcytometer analyses revealed that Alternol-induced cell death was an apoptotic response in a dose-and time-dependent manner, as evidenced by the appearance of apoptosis hallmarks such as Caspase-3processing and PARP cleavage. Interestingly, this compound induced a profound intracellular oxidative response and initiated the apoptotic cascade. Alternol-induced cell death was completely abolished by reactive oxygen species (ROS) scavengers, N-acetylcysteine (N-Ac) and dihydrolipoic acid (DHLA). We also demonstrated that the pro-apoptotic Bax protein was activated after Alternol treatment and was critical for Alternol-induced apoptosis. Reinstalling the Bax protein expression in bax deficient cell lines-DU145sensitized them to Alternol induced apoptotic cell death while knockdown the endogenous Bax in PC3cell lines facilitated them resistant to Alternol. Activated Bax damage the mitochondria and induce apoptosis via both Caspase dependent and independent pathway. These data suggest that Alternol might serve as a novel anticancer agent for late stage prostate cancer patient.Conclusion:Alternol is capable of inducing intracellular oxidative stress and subsequently Bax-dependent apoptotic cell death in prostate cancer cells.