Abstract: PD33-03
Sources of Funding: Urology Care Foundation Postdoctoral Research Scholarship (ZC), and the James F. Hardymon Endowment in Urologic Research.

Introduction

Dysregulation of transforming growth factor-β (TGF-β) and insulin-like growth factor (IGF) axis has been linked to reactive stroma dynamics in tumor microenvironment during prostate cancer progression. IGFBP3 induction is initiated by stroma remodeling and could represent a potential therapeutic target for prostate cancer treatment. A lead quinazoline-based Doxazosin® derivative, DZ-50, generated in our laboratory, inhibits prostate tumor growth and vascularity via inducing anoikis and disrupting focal adhesions. Molecular profiling revealed that process of epithelial-mesenchymal-transition (EMT) is also targeted by DZ-50. In this study, we investigated the effect of DZ-50 on EMT landscape, EMT to mesenchymal-epithelial-transition (MET) conversion, and migratory ability of prostate cancer cells within prostate tumor microenvironment.

Methods

Human prostate cancer cells LNCaP, LNCaP overexpressing TGF-β type II receptor (TβRII), and cancer associated fibroblasts (CAFs) derived from human prostate cancer specimens, were used. Antitumor effect of DZ-50 against prostate cancer epithelial cells and CAFs was evaluated using cell viability assays. Effect of the drug on EMT key regulators (including IGFBP3) was determined using RT-PCR and Western blot analysis. Drug-induced phenotypic conversions of EMT were evaluated by confocal microscopy. Impact of TGF-β from the stroma microenvironment or exogenous addition of the cytokine, on migration of prostate tumor cells, was assessed using Matrigel assays.

Results

DZ-50 induced cell death in prostate cancer epithelial cells and CAFs, in a concentration-dependent manner. DZ-50 downregulated IGFBP3 mRNA and protein expression and contributed to MET in LNCaP cells. DZ-50 decreased nuclear IGFBP3 expression with no effect on total protein and promoted MET in LNCaPTβRII cells. In addition, TGF-β reversed DZ-50-induced MET by upregulating IGFBP3 expression in LNCaPTβRII cells. Co-cultures of LNCaPTβRII with CAFs promoted prostate cancer cell migration via TGF-β, an effect that was inhibited by DZ-50.

Conclusions

Our results demonstrate that DZ-50 inhibits prostate cancer cell migration and invasion. DZ-50 caused reversal of EMT to MET by regulating IGFBP3 and potentially targeting the prostate stroma in tumor microenvironment. This evidence integrates new signaling mechanisms underlying the antitumor effect of DZ-50 and calls for pre-clinical studies to establish the therapeutic value of this compound in advanced metastatic prostate cancer.

Funding

Urology Care Foundation Postdoctoral Research Scholarship (ZC), and the James F. Hardymon Endowment in Urologic Research.