TGFβ1 and RGD Cooperatively Regulate SMAD2/3-Mediated Oncogenic Effects in Prostate Cancer Cells in Bio-Orthogonally Constructed Hydrogels

To recapitulate prostate cancer metastasis, DU145 cells were cultured in a hyaluronic acid-based, bio-orthogonally constructed, protease-degradable hydrogels. In the presence of a covalently conjugated integrin-binding peptide (G RGD SP), DU145 cells formed tumoroids and exhibited small protrusions. Upon addition of soluble transforming growth factor beta 1 (TGFβ1), cells underwent morphological changes to form extended interconnected cellular networks. Contrarily, in RGD-free hydrogels, cells maintained spherical structures even in the presence of TGFβ1. In RGD-conjugated hydrogels, TGFβ1 induced nuclear localization of SMAD2/3, upregulating a wide range of TGFβ1 target genes and proteins. Prolonged exposure to TGFβ1 led to matrix remodeling and induced epithelial-to-mesenchymal transition in DU145 cells, with loss of epithelial markers and gain of mesenchymal markers. A pharmacological inhibitor of TGFβRI/ALK5, SB-431542, attenuated TGFβ1-induced morphological changes, abrogated nuclear localization of SMAD2/3, and restored the expression of key epithelial markers. Our findings highlight the cooperative role of TGFβ1 signaling and integrin-binding peptide in the acquisition of an aggressive phenotype and the promotion of tumor progression.