Abstract 5901: Involvement of VEGF-A signaling in the acquisition and maintenance of human prostate carcinoma-associated fibroblast phenotype

Abstract

Abstract Introduction: Progression of prostate cancer (CaP) is modulated by the carcinoma-associated fibroblasts (CAFs) within the tumor microenvironment. However, little is known about the specific mechanisms involved in the activation of the benign prostate fibroblasts (BAFs) to CAFs in CaP and the specific signaling altered in CAFs that are needed to maintain its activated phenotype. Vascular endothelial growth factor-A (VEGF-A) is overexpressed in CaP and, additionally to the angiogenic effect, a non-angiogenic effects of VEGF-A on cancer cells have been recently reported. This study seeks to evaluate the potential role of VEGF-A signaling in the activation of BAFs and/or in the maintenance of the activated phenotype presented in CAFs. Material and Methods: Primary cultures of BAFs and CAFs were characterized by gene expression profile, qPCR, WB and ELISA for the expression and/or secretion of VEGF-A and its receptors. Dose-response and time course analysis for the effect of exogenous VEGF-A, TGF-β1 and conditioned medium from CAFs (CM-CAFs) were analyzed by RT-qPCR, immunocytochemistry and WB for the stroma cell markers: Vimentin, Pro-collagen, α-SMA, Tenascin, Fibronectin and FSP-1. The contribution of VEGF-A signaling to the pgenotype of CAFs was determined by siRNA assays for the VEGFRs and the functional effect of CAFs on cancer progression was studied using CM-CAFs or CM from VEGFR siRNA-CAFs over PC3 cancer cells growth in vitro and in vivo. Results: Exposure of primary cultures of BAFs to exogenous VEGF-A, TGF-β1 and CM-CAFs upregulate stroma cell markers associated with the appearance of CAFs phenotype and it is reversed with the pre-treatment of the VEGF-A antibody Bevacizumab. Furthermore, CAFs, but not BAFs, produced massive levels of VEGF-A and overexpress its cognate receptors. siRNA studies demonstrated that knock down VEGFRs in CAFs reverse the activated phenotype and CM from VEGFRsiRNA-CAFs failed to increase the migration and invasion potential of PC3 cells in vitro and tumor growth in vivo. Discussion: Our data indicate that VEGF-A signaling plays a key role in the activation of human prostate fibroblasts. Furthermore, VEGF-A and TGF-β1 interactions may cooperatively regulate activation of fibroblasts within the tumor microenvironment in CaP. These findings also suggest that blockade of this signaling cascade in the activated fibroblasts could be a potential therapeutic target designed to prevent disease progression. Citation Format: Javier Cerda Infante, Marianela Sanchez, Paola Conejeros, Alejandra Alarcón, Alejandro Godoy, Enrique Brandan, Viviana P. Montecinos. Involvement of VEGF-A signaling in the acquisition and maintenance of human prostate carcinoma-associated fibroblast phenotype [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 5901. doi:10.1158/1538-7445.AM2017-5901