Targeting DHEA-S transport and steroid sulfatase for more efficient androgen deprivation therapy

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Androgen deprivation therapy (ADT) is used to treat locally advanced or metastatic prostate cancer (CaP). Patients treated with ADT respond well initially, but develop castration-resistant prostate cancer (CRPC) eventually. Failure of ADT is attributed to intra-tumoral steroidogenesis that produces testosterone (T) and dihydrotestosterone (DHT). Adrenal androgens dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEA-S) are the most abundant circulating androgens in adult males, with circulating DHEA-S and DHEA in the μM and nM ranges, respectively. ADT reduces only modestly circulating DHEA-S and DHEA levels. Tumor cells are believed to produce T/DHT from DHEA-S or DHEA through the "front-door" steroidogenesis pathway. The high concentration of DHEA-S in circulation suggests that DHEA-S is the most available substrate for intra-tumoral T/DHT production. However, whether, and to what extent, benign prostate tissue and CaP tissue produce T/DHT from DHEA-S remains unsettled. Demonstration of production of T/DHT from DHEA(-S) is critical to designing novel neo-adjuvant therapies to synergize with ADT based on inhibitors of androgen metabolizing/transport proteins.


Fresh benign prostate tissue and CaP tissue specimens were received in phenol red-free RPMI1640 medium supplemented with 10% charcoal-stripped fetal bovine serum. Tissue specimens were cut into -3 mm3 pieces and 2-3 pieces were placed in each well of 48-well plates. Samples were treated with DHEA or DHEA-S for various numbers of days. Medium samples were collected at the end of experiments, and DHT and DHEA in the medium analyzed using ELISA.


1) DHEA-S at a physiological concentration (3.5 μM) was a suitable substrate for DHT production, resulting in final tissue DHT concentrations > 100 nM; 2) DHEA at a physiological concentration (10 nM) was not an effective substrate for DHT production; 3) DHEA at a supra-physiological concentration (3.5 μM) was an effective substrate for DHT production; 4) the steroid sulfatase (STS)inhibitor STX64 completely inhibited production of DHT from DHEA-S.


Benign prostate tissue and CaP tissue produced DHT from DHEA-S at physiologic concentrations, and DHEA only at supra-physiologic concentrations. Therefore, DHEA-S is the adrenal androgen most likely to be a substrate for intracrine DHT production, with STS critical to DHT production from DHEA-S. Therefore, targeting transport of DHEA-S from circulation into CaP cells or desulfation by STS represent significant new therapeutic targets.

Funding: NIH grant: 1R01CA193829-01A1.