Abstract 1632: Paracrine Hedgehog as a mediator of stromal cell steroidogenesis that contributes to progression of prostate cancer to castration resistant disease.

Androgen deprivation therapy (ADT) is frontline treatment for metastatic prostate cancer (PCa). ADT initially blocks disease progression but eventually allows the outgrowth of castration resistant disease (CRPC) that is refractory to the diminished systemic androgen levels in ADT-treated patients. CRPC is associated with acquired intratumoral steroidogenesis (IS), a process that increases the androgen levels in the local microenvironment of prostate tumors and enables further tumor growth and progression. IS has mainly been attributed to a steroidogenic process linked to CRPC cells and here we present evidence that benign tumor-associated prostate stromal cells (PrSCs) can also contribute to IS through a paracrine Hedgehog (HH) tumor microenvironment associated with increased production and release ofHedgehog ligands (Hhs) from prostate cancer cells in response to ADT (Chen, et al., Mol Cancer, 9: 89, 2010). Primary human PrSCs upregulate expression of a large repertoire of steroidogenic genes upon treatment with HH chemical agonists, SAG (100 nM) or Hg 1.5 (1 nM). These effects are Gli2-dependent (Levina, et al., Prostate, 72: 817, 2012) and they can be inhibited by the HH antagonist, KAAD-cyclopamine. Previously we showed that this upregulation significantly increased output of testosterone (T) in PrSCs fed DHEA precursor. More comprehensive analysis (via LC/MS/MS) of androgen outputs from PrSCs fed 22 OH-cholesterol showed that Hg1.5 significantly increased the outputs of Progesterone, DHEA, androsterone, T and dihydrotestosterone (DHT) showing that HH signaling activity effects outputs throughout the androgen biosynthetic pathway. Upregulation of the RDH5 gene by Hg1.5 suggests that the effects on production of DHT from PrSCs might be generated by increased synthesis through both classical and back-door pathways. On a weight-to-weight basis, Hg1.5-stimulated PrSCs produce higher T and DHT outputs than LNCaP cells or an androgen growth-independent variant, LNCaP-AI. Finally, we found that treatment of Sonic Hh-producing LNCaP cells with simvastatin reduced the ability of conditioned medium from these cells to induce steroidogenic gene expression from PrSCs. In summary, this work provides evidence for a stromal cell contribution to IS in CRPC mediated by a paracrine-active HH signaling tumor microenvironment induced by ADT-treatment and identifies potential treatment strategies to interfere with this process.

Citation Format: Amy A. Lubik, Hans Adomat, Emma S. Guns, Ralph Buttyan. Paracrine Hedgehog as a mediator of stromal cell steroidogenesis that contributes to progression of prostate cancer to castration resistant disease. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1632. doi:10.1158/1538-7445.AM2013-1632