Loss of exogenous androgen dependence by prostate tumor cells is associated with elevated glucuronidation potential

Prostate epithelial cells control the potency and availability of androgen hormones in part by inactivation and elimination. UDP-glucose dehydrogenase (UGDH) catalyzes the NAD+-dependent oxidation of UDP-glucose to UDP-glucuronate, an essential precursor for androgen inactivation by the prostate glucuronidation enzymes UGT2B15 and UGT2B17. UGDH expression is androgen stimulated, which increases the production of UDP-glucuronate, and fuels UGT-catalyzed glucuronidation. In this study, we compared the glucuronidation potential and its impact on androgen-mediated gene expression in an isogenic LNCaP model for androgen dependent versus castration resistant prostate cancer. Despite significantly lower androgen-glucuronide output, LNCaP 81 castration resistant tumor cells expressed higher levels of UGDH, UGT2B15, and UGT2B17. However, the magnitude of androgen-activated UGDH and PSA expression, as well as the AR-dependent repression of UGT2B15 and UGT2B17, was blunted several-fold in these cells. Consistent with these results, the ligand-activated binding of AR to the PSA promoter and subsequent transcriptional activation were also significantly reduced in castration resistant cells. Analysis of the UDP-sugar pools and flux through pathways downstream of UDP-glucuronate production revealed that these glucuronidation precursor metabolites were channeled through proteoglycan and glycosaminoglycan biosynthetic pathways, leading to increased surface expression of Notch 1. Knockdown of UGDH diminished Notch1 and increased glucuronide output. Overall, these results support a model in which the aberrant partitioning of UDP-glucuronate and other UDP-sugars into alternative pathways during androgen deprivation contributes to the loss of prostate tumor cell androgen sensitivity by promoting altered cell surface proteoglycan expression

Loss of exogenous androgen dependence by prostate tumor cells is associated with elevated glucuronidation potential

Prostate epithelial cells control the potency and availability of androgen hormones in part by inactivation and elimination. UDP-glucose dehydrogenase (UGDH) catalyzes the NAD+-dependent oxidation of UDP-glucose to UDP-glucuronate, an essential precursor for androgen inactivation by the prostate glucuronidation enzymes UGT2B15 and UGT2B17. UGDH expression is androgen stimulated, which increases the production of UDP-glucuronate, and fuels UGT-catalyzed glucuronidation. In this study, we compared the glucuronidation potential and its impact on androgen-mediated gene expression in an isogenic LNCaP model for androgen dependent versus castration resistant prostate cancer. Despite significantly lower androgen-glucuronide output, LNCaP 81 castration resistant tumor cells expressed higher levels of UGDH, UGT2B15, and UGT2B17. However, the magnitude of androgen-activated UGDH and PSA expression, as well as the AR-dependent repression of UGT2B15 and UGT2B17, was blunted several-fold in these cells. Consistent with these results, the ligand-activated binding of AR to the PSA promoter and subsequent transcriptional activation were also significantly reduced in castration resistant cells. Analysis of the UDP-sugar pools and flux through pathways downstream of UDP-glucuronate production revealed that these glucuronidation precursor metabolites were channeled through proteoglycan and glycosaminoglycan biosynthetic pathways, leading to increased surface expression of Notch 1. Knockdown of UGDH diminished Notch1 and increased glucuronide output. Overall, these results support a model in which the aberrant partitioning of UDP-glucuronate and other UDP-sugars into alternative pathways during androgen deprivation contributes to the loss of prostate tumor cell androgen sensitivity by promoting altered cell surface proteoglycan expression

Role of UDP-glucose Dehydrogenase in Prostate Cancer Therapeutic Resistance

Prostate cancer is the most frequently diagnosed male cancer and the second leading cause of cancer related death in U.S. men. Treatment of locally advanced and metastatic tumors involves androgen deprivation therapy. Despite this treatment, more aggressive and metastatic tumors recur in a low circulating androgen environment. Availability of hormones in prostate epithelial cells are limited by their inactivation pathways. The enzymes that catalyze the inactivation reaction are UDP-glucuronsyltransferases (UGTs), which catalyze the covalent conjugation of the hormone using UDP-glucuronate as a precursor. Our lab has shown that the enzyme UDP-glucose dehydrogenase (UGDH), which provides this precursor, is upregulated by androgen and drives hormone elimination even in the presence of suppressed UGT. The goal of this work was to evaluate the effect of differential UGDH expression on androgen sensitivity in culture, to examine the underlying mechanisms responsible for directed channeling of UDP-glucuronate, and to evaluate UGDH as a target to control UDP-glucuronate partitioning. To evaluate the effect of differential UGDH expression on androgen sensitivity in culture, we used an isogenic LNCaP human prostate tumor cell culture model for androgen-dependent (LNCaP33) versus castration-resistant (LNCaP81) prostate cancer. We showed that the androgen-dependent line produced significantly more steroid glucuronides and exhibited a potent response to androgen exposure relative to castration-resistant cells, which channeled UDP-glucuronate precursors to producing proteoglycans as measured by increased surface expression of Notch1.^ To examine the underlying mechanisms responsible for directed channeling of UDP-glucuronate, we used the isogenic culture model to compare the impact of UGDH manipulation on androgen receptor-mediated gene expression, UDP-sugar content and the proliferative capacity of tumor cells. UGDH overexpression in LNCaP33 cells led to increased expression of UGT2B17 and Notch1, blunted responses to exogenous androgen, and increased growth rate compared to controls, consistent with the role and response of UGDH in castration-resistant cells. Furthermore, co-immunoprecipitation of FoxA1, the transcription factor necessary for UGT expression, revealed greater pulldown of AR in LNCaP33 relative to LNCaP81 cells. These results provide novel insights to metabolite-mediated gene expression, explain biomarker profiles associated with loss of androgen sensitivity, and improve the understanding of prostate cancer recurrence mechanisms following hormone deprivation therapy.

Search for gamma-ray emission from DES dwarf spheroidal galaxy candidates with Fermi-LAT data

Due to their proximity, high dark-matter (DM) content, and apparent absence of non-thermal processes, Milky Way dwarf spheroidal satellite galaxies (dSphs) are excellent targets for the indirect detection of DM. Recently, eight new dSph candidates were discovered using the first year of data from the Dark Energy Survey (DES). We searched for gamma-ray emission coincident with the positions of these new objects in six years of Fermi Large Area Telescope data. We found no significant excesses of gamma-ray emission. Under the assumption that the DES candidates are dSphs with DM halo properties similar to the known dSphs, we computed individual and combined limits on the velocity-averaged DM annihilation cross section for these new targets. If the estimated DM content of these dSph candidates is confirmed, they will constrain the annihilation cross section to lie below the thermal relic cross section for DM particles with masses 20 GeV annihilating via the bb¯ or τ+τ− channels