Zinc ion dyshomeostasis increases resistance of prostate cancer cells to oxidative stress via upregulation of HIF1α

// David Wetherell 1, 2 , Graham S. Baldwin 1 , Arthur Shulkes 1 , Damien Bolton 1, 2 , Joseph Ischia 1, 2 and Oneel Patel 1 1 Department of Surgery, University of Melbourne, Austin Health, Heidelberg, Victoria, 3084, Australia 2 Department of Urology, Austin Health, Heidelberg, Victoria, 3084, Australia Correspondence to: Oneel Patel, email: patelo@unimelb.edu.au Keywords: castrate resistant; hypoxia inducible factor 1 alpha; prostate cancer; zinc; iron Received: September 07, 2017      Accepted: November 14, 2017      Published: January 03, 2018 ABSTRACT Zinc ions (Zn 2+ ) are known to influence cell survival and proliferation. However the homeostatic regulation of Zn 2+ and their role in prostate cancer (PC) progression is poorly understood. Therefore the subcellular distribution and uptake of Zn 2+ in PC cells were investigated. Inductively coupled plasma mass spectroscopy and fluorescent microscopy with the Zn 2+ -specific fluorescent probe FluoZin-3 were used to quantify total and free Zn 2+ , respectively, in the normal prostate epithelial cell line (PNT1A) and three human PC cell lines (PC3, DU145 and LNCaP). The effects of Zn 2+ treatment on proliferation and survival were measured in vitro using MTT assays and in vivo using mouse xenografts. The ability of Zn 2+ to protect against oxidative stress via a HIF1α-dependent mechanism was investigated using a HIF1α knock-down PC3 model. Our results demonstrate that the total Zn 2+ concentration in normal PNT1A and PC cells is similar, but PC3 cells contain significantly higher free Zn 2+ than PNT1A cells ( p < 0.01). PNT1A cells can survive better in the presence of high concentrations of Zn 2+ than PC3 cells. Exposure to 10 μM Zn 2+ over 72 hours significantly reduces PC3 cell proliferation in vitro but not in vivo . Zn 2+ increases PC3 cell survival up to 2.3-fold under oxidative stress, and this protective effect is not seen in PNT1A cells or in a HIF1α-KD PC3 cell model. A state of Zn 2+ dyshomeostasis exists in PC. HIF1α is an integral component of a Zn 2+ -dependent protective mechanism present in PC3 cells. This pathway may be clinically significant through its contribution to castrate-resistant PC survival.