Zinc is a vital micronutrient that has structural, catalytic and regulatory functions in cells. Given the diverse and central functions of zinc, organisms tightly regulate zinc homeostasis. The prostate uniquely concentrates zinc 10-fold higher than other organs. Furthermore, it is well established that prostate cancer lesions are zinc depleted compared to normal prostate. Zinc levels inversely associate with aggressive disease and low dietary zinc increases prostate cancer risk, supporting a protective role for zinc in the prostate. High levels of zinc are required to maintain the normal differentiated state of th prostate and lower zinc may increase dedifferentiation and lead to the development or outgrowth of prostate tumors. Zinc depletion in prostate cells causes metabolism changes that increase cellular respiration and cell proliferation. Thus, diminished zinc in prostate cancer may to contribute to the cancer etiology and is a viable selective biomarker for the disease. Using patient specimens and primary prostatic cell cultures we recently identified the microRNAs miR- 183, miR-96 and miR-182, which are expressed as together as the miR-183 family cluster, as regulators of zinc homeostasis in the prostate via regulation of several zinc transporters. MicroRNAs (miR) are small non- coding regulatory RNAs that suppress expression of their target mRNAs via binding to the 3'UTR. Consistent with zinc depletion, higher levels of the miR-183 cluster was present in prostate tumors compared to benign epithelium from the same patients. Others have shown that individually or as a cluster, miRs-183, 96 and 182 are overexpressed in prostate cancer and several other cancers. miR clusters, such as the miR-183 family, are co-expressed as a single polycystronic RNA then processed into the mature miR. miR clusters are thought to exist as a mechanism to more efficiently coordinate complex cell processes than regulation by a single miR can provide. In summary, our preliminary data show that the miR-183 cluster is a regulator of intracellular zinc concentrations in prostate cells. To our knowledge, these data are the first to report a miRNA cluster targeting a family of metal transport proteins. Furthermore, we and others have shown overexpression of this miR cluster in prostate cancer, strongly supporting a role for this miR-cluster in carcinogenesis. The present proposal is an extension of our recent data and will further analyze regulation of the miR- 183 cluster and its role in cell phenotype, zinc sequestration, prostate carcinogenesis and progression. The results of this project will have clear implications not only in prostate cancer, but also in other cancers in which the miR-183 cluster is highly expressed. Specifically we will examine the following hypotheses: 1) Sequestration of zinc in differentiated prostate epithelium is regulated by the coordinated expression of miRs-183, 96 and 182 as a cluster. 2) MiRs-183, 96 and 182 are oncomiRs that reduce zinc levels and promote dedifferentiation when over-expressed during prostate carcinogenesis.
Zinc is a vital micronutrient that has structural, catalytic and regulatory functions in cells. The prostate gland uniquely concentrates zinc and zinc depletion is a hallmark of prostate cancer. This proposal investigates how dysregulation of a microRNA cluster contributes to prostate carcinogenesis by regulation of zinc homeostasis. MicroRNAs have become attractive therapeutic targets and therefore, it is imperative to understand the regulation and physiological role of specific microRNAs.
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