Abstract 2122: Pharmacologic interconversion of EMT to MET for prostate cancer

Introduction and objection: Dysregulation of transforming growth factor-β (TGF-β) and insulin-like growth factor (IGF) axis has been linked to reactive stroma dynamics in the tumor microenvironment during prostate cancer progression. IGFBP3 induction is initiated by stroma remodeling and represents a potential therapeutic target for advanced prostate cancer. A lead quinazoline-based Doxazosin® derivative, DZ-50, generated in our laboratory (US Patent # 8377948), inhibits prostate tumor growth via inducing anoikis and disrupting focal adhesions. Molecular profiling revealed that the process of epithelial-mesenchymal-transition (EMT) is 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 invasive properties of prostate cancer cells. 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. The 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 cytokine, on prostate tumor cell migration and invasion, was assessed in co-cultures with CAFs. The functional contribution of IGFBP3 to EMT-MET interconversion in response to DZ-50 was assessed using siRNA approaches. 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 promoted EMT-MET conversion in both LNCaP and LNCaPTβRII cells. IGFBP3 knockdown in LNCaPTβRII cells led to E-cadherin upregulation and MET induction, implicating IGFBP3 as a potential target of DZ-50 to reverse EMT to MET. Moreover exposure to TGF-β reversed DZ-50-induced MET by upregulating IGFBP3 in LNCaPTβRII cells. Co-cultures of LNCaPTβRII with CAFs promoted prostate cancer cell invasion via TGF-β and IGFBP3, an effect that was inhibited by the drug. Conclusions: Treatment of prostate cancer cells with the novel agent DZ-50 inhibits cell migration and invasion and causes reversal of EMT to MET by regulating IGFBP3. This study integrates IGFBP3 as new signaling effector driving the antitumor action of DZ-50 via targeting the EMT-MET phenotypic landscape in the prostate tumor microenvironment. Ongoing work in pre-clinical models will establish the therapeutic value of this novel compound in advanced metastatic prostate cancer. Citation Format: Zheng Cao, Shahriar Koochekpour, Stephen E. Strup, Natasha Kyprianou. Pharmacologic interconversion of EMT to MET for prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2122. doi:10.1158/1538-7445.AM2017-2122