In these studies, different formulations of zinc have been utilized. Unfortunately, in vivo measurements regarding the bio-pharmocokinetics of these different zinc salts are lacking. For this study, we have selected zinc acetate as it is pH neutral in aqueous solution with minimal effect on osmalarity, relative to other formulations of zinc. Cytotoxic effects of zinc acetate PXD101 clinical trial have not been reported. In order to examine the general effectiveness of zinc in inducing cell death in prostate cancer cells, we selected three cell lines with distinct properties, representative of the distinct forms in which prostate
cancers emerge. For example, PC3 and DU145 cells are androgen-independent, while LNCaP cells are androgen-dependent[19]. The molecular pathways associated with carcinogenesis vary as well between these cell lines[20] as determined by gene expression analysis. For example, PSA is upregulated in LNCaP but not expressed in PC3 or DU145. Using markedly different prostate cancer cell lines allowed us to analyze the effect of zinc irrespective of underlying pathways of transformation. Induction of apoptosis of prostate cancer cells by zinc In figure 1, we show that treatment with zinc acetate leads to widespread cell death within 18 hours in three different prostate cancer cell lines
(figure 1A). Importantly, cell death is sharply dose-dependent over a broad SHP099 solubility dmso range from 100–600 μM and the APO866 chemical structure cytotoxicity curves indicate that 300–400 μM zinc acetate, depending on cell line, is effective at inducing
cell death in ~80% of the cell population within just 18 hours (figure 1A). Having established that zinc acetate has a rapid Regorafenib cell line cytotoxic effect on prostate cancer cell lines, we next established the time course of cell killing in vitro. Although only data for PC3 cells are shown, for all three cell lines, 400 μM zinc acetate induced cell death quite rapidly, with 50% cell death occurring by 6 hours (figure 1B and data not shown). By 24 hours, greater than 95% of the cells had perished. Interestingly, zinc dose had minimal effect on the kinetics of cell death, as doubling the dose to 800 μM zinc only reduced the EC50 by approximately 90 minutes (figure 1B). Figure 1 Kinetics and Toxicity of Zinc Acetate on Prostate Cancer Cell Lines. Prostate cancer cell lines (Panel A: PC3, DU145, and LNCaP; Panels B and C: PC3) were treated with the indicated concentrations of zinc acetate for either 18 hours (A) or indicated length of time (B and C). Data represent mean cell viability as assessed by MTT assay (n = 3 independent cell populations) and error bars represent standard deviation. Although maximal cytotoxicity is seen within 24 hours with doses of 400 μM zinc or higher, we reasoned that longer incubations with lower doses of zinc might also have a cytotoxic effect on prostate cancer cells.