Background: Zinc is vital to normal prostate function and uniquely concentrates in healthy prostate. A hallmark of prostate cancers is diminished zinc levels. Results: The miR-183 family is overexpressed in prostate cancer and regulates intracellular zinc via suppression of zinc transporters. Conclusion: Prostatic zinc homeostasis is regulated by microRNAs. Significance: The miR-183 family regulates zinc and may contribute to prostate carcinogenesis.

Oral vitamin D3 raised prostate calcitriol levels (level 1 evidence) and modestly lowered both PSA and PTH. Although Ki67 expression did not differ among dose groups, its levels correlated inversely with prostate calcitriol. These suggestions of clinical benefit justify continued clinical research.

MiR-100 and miR-125b are lost in many cancers and have potential function as tumor suppressors. Using both primary prostatic epithelial cultures and laser-capture-microdissected prostate epithelium from 45 patients enrolled in a vitamin D3 randomized trial, we identified miR-100 and -125b as targets of 1,25-dihydroxyvitamin D3 (1,25D). In patients, miR-100 and -125b levels were significantly lower in tumor tissue than in benign prostate. Similarly, miR-100 and -125b were lower in primary PCa cells than in cells derived from benign prostate. Prostatic concentrations of 1,25D positively correlated with these miRNA levels in both PCa and benign epithelium, demonstrating that PCa patients may still benefit from vitamin D3. In cell assays, upregulation of these miRNAs by 1,25D was vitamin D receptor-dependent. Transfection of pre-miR-100 and pre-miR-125b in the presence or absence of 1,25D decreased invasiveness of cancer cell, RWPE-2. Pre-miR-100 and pre-miR-125b decreased proliferation in primary cells and cancer cells respectively. Pre-miR-125b transfection suppressed migration and clonal growth of PCa cells while knockdown of miR-125b in normal cells increased migration indicates a tumor suppressor function. 1,25D suppressed expression of previously bona fide mRNA targets of these miRNAs, E2F3 and Plk1, in a miRNA-dependent manner. Together, these findings demonstrate that vitamin D3 supplementation augments tumor suppressive miRNAs in patient prostate tissue, providing evidence that miRNAs could be key physiologic mediators of vitamin D3 activity in prevention and early treatment of PCa.