Transmembrane and Coiled-Coil Domain 1 Impairs the AKT Signaling Pathway in Urinary Bladder Urothelial Carcinoma: A Characterization of a Tumor Suppressor.

Abstract

<b>Purpose:</b> Urinary bladder urothelial carcinoma (UBUC) is a common malignant disease in developed countries. Cell-cycle dysregulation resulting in uncontrolled cell proliferation has been associated with UBUC development. This study aimed to explore the roles of <i>TMCO1</i> in UBUCs.<b>Experimental Design:</b> Data mining, branched DNA assay, immunohistochemistry, xenograft, cell culture, quantitative RT-PCR, immunoblotting, stable and transient transfection, lentivirus production and stable knockdown, cell-cycle, cell viability and proliferation, soft-agar, wound-healing, transwell migration and invasion, coimmunoprecipitation, immunocytochemistry, and AKT serine/threonine kinase (AKT) activity assays and site-directed mutagenesis were used to study <i>TMCO1</i> involvement <i>in vivo</i> and <i>in vitro</i><b>Results:</b> Data mining identified that the <i>TMCO1</i> transcript was downregulated during the progression of UBUCs. In distinct UBUC-derived cell lines, changes in TMCO1 levels altered the cell-cycle distribution, cell viability, cell proliferation, and colony formation and modulated the AKT pathway. TMCO1 recruited the PH domain and leucine-rich repeat protein phosphatase 2 (PHLPP2) to dephosphorylate pAKT1(serine 473) (S473). Mutagenesis at S60 of the TMCO1 protein released TMCO1-induced cell-cycle arrest and restored the AKT pathway in BFTC905 cells. Stable <i>TMCO1</i> (wild-type) overexpression suppressed, whereas T33A and S60A mutants recovered, tumor size in xenograft mice.<b>Conclusions:</b> Clinical associations, xenograft mice, and <i>in vitro</i> indications provide solid evidence that the <i>TMCO1</i> gene is a novel tumor suppressor in UBUCs. TMCO1 dysregulates cell-cycle progression via suppression of the AKT pathway, and S60 of the TMCO1 protein is crucial for its tumor-suppressor roles. <i>Clin Cancer Res; 23(24); 7650-63. ©2017 AACR</i>.