Abstract 1499: Vitamin D promotes differentiation in patient-derived organoids in benign and cancer prostate models

Abstract

Abstract Deficiency in the prohormone vitamin D is associated with increased risk of lethal prostate cancer (PCa) and less-differentiated, more aggressive tumors. As cancer progresses there is aberrant expression of vitamin D metabolic genes causing dysregulation of the vitamin D pathway, indicating its role in disease. Vitamin D has many chemopreventive actions in vitro, including promotion of differentiation and apoptosis. The ability for vitamin D to drive differentiation has been explored in various cell types and cancer lines, but its mechanism of action in the prostate is not well defined. Our lab found that vitamin D treatment globally upregulates microRNAs (miRs) in prostate cell lines, primary cells and patient samples. Temporal regulation of miRs is critical for differentiation and levels of mature miRs are globally lower in PCa. Given the relationship between vitamin D and microRNAs, and their influence over differentiation, we hypothesize that vitamin D promotes differentiation in the prostate in a microRNA-dependent manner and that this process is disrupted during cancer. Here we examined organoid differentiation in the presence of 1,25D, the active metabolite of vitamin D. Organoids were grown in matrigel from human primary prostate epithelial progenitor cells. Differentiation was assessed by organoid size and branching, and by expression of epithelial markers. Organoids grown in the presence of 1,25D were strikingly larger and formed more complex branching structures than those treated with control. Whole mount immunofluorescence revealed expression of basal and luminal epithelial cells in the organoids. Flow-sorted organoids had a greater composition of basal cells when grown in the presence of 1,25D. RT-qPCR analysis of the flow-sorted epithelial populations revealed an enhancement in the WNT pathway with 1,25D, this pathway is critical in prostate development and dysregulated in cancer. The role of miRNAs was determined by reducing global miRNA levels via knockdown of Drosha, an essential miRNA-processing protein. Knockdown abrogated the effect of 1,25D, as evidenced by reduced size, round shape, and protein expression. Together our findings indicate a role of 1,25D in normal prostate development and branching, a phenotype that is lost when mature miR levels are reduced. Ongoing studies examine these phenotypes in PCa organoids. Citation Format: Tara N. McCray, Giovani Lugli, Larisa Nonn. Vitamin D promotes differentiation in patient-derived organoids in benign and cancer prostate models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1499.