Abstract 3335: Role of TGF-beta type III receptor in cell migration, invasion, and proliferation

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Abstract This study aims to investigate the role of Transforming Growth Factor-beta type III receptor on tumor metastasis through cell migration and invasion. Metastasis is responsible for 90% of cancer related deaths. An important step in the metastatic process is the epithelial to mesenchymal transition (EMT) of cancer cells, which is stimulated by TGFβ. The binding of TGFβ to its type II receptor (TβRII) triggers the phosphorylation of ser/thr kinase TGFβ type I receptor (TβRI), and receptor-regulated Smad (R-Smad) which translocates to the nucleus and alters gene transcription. The activity of this pathway is affected by receptor localization on the cell membrane, while the presence of TβRI/II complex in clathrin-coated pits propagates TGFβ signaling. However, TβRI/II complex relocation to membrane lipid rafts reduces signaling. A TGFβ receptor that lacks kinase activity, type III (TβRIII), regulates TGFβ signaling through multiple roles. Previous investigations have determined TβRIII sequesters TGFβ ligand to reduce signaling, while also presenting TGFβ to TβRII to increase signaling. TβRIII has also been shown to bind type I and type II TGFβ receptors independently, and reverse their membrane partitioning from membrane lipid rafts to clathrin-coated pits. This TβRIII induced relocation of TβRI/II increases receptor half-life, altering TGFβ signaling. Many cancers demonstrate increased expression of TβRIII, suggesting that this protein is influential in the metastatic pathway. Interestingly, conflicting studies have shown that metastasis is stimulated when TβRIII is either overexpressed or knocked-down. Overexpression of exogenous TβRIII and knockdown of endogenous TβRIII using siRNA were used to explore alterations in cell migration and invasion potential. TGFβ signaling, receptor expression, membrane partitioning, and protein interaction analyses were performed using Western blotting, sucrose-density ultracentrifugation, and immunoprecipitation techniques. Immunofluorescent transwell assays measured relative cell migration and invasion through Matrigel. Transfection of TβRIII demonstrated both the punctate and membrane localization of TβRIII, while inhibiting transwell migration. The ability of transfected cells to migrate and invade through transwell assays clarified the impact of TβRIII expression on metastatic processes. Finally, both the overexpression and silencing of TβRIII resulted in significantly different cancer cell migration and invasion profiles when compared to untransfected cell lines. TβRIII expression and activity modify cellular migratory and invasive potential through the modulation of the TGFβ signaling pathway, altering epithelial to mesenchymal transitioning and therefore tumor metastasis. Citation Format: Anthony Ziccarelli, John Di Guglielmo. Role of TGF-beta type III receptor in cell migration, invasion, and proliferation [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 3335. doi:10.1158/1538-7445.AM2017-3335