Transgelin, a p53 and PTEN-upregulated gene, inhibits the cell proliferation and invasion of human bladder carcinoma cells in vitro and in vivo

Transgelin (TAGLN/SM22-α) is a regulator of the actin cytoskeleton, affecting the survival, migration, and apoptosis of various cancer cells divergently; however, the roles of TAGLN in bladder carcinoma cells remain inconclusive. We compared expressions of TAGLN in human bladder carcinoma cells to the normal human bladder tissues to determine the potential biological functions and regulatory mechanisms of TAGLN in bladder carcinoma cells. Results of RT-qPCR and immunoblot assays indicated that TAGLN expressions were higher in bladder smooth muscle cells, fibroblast cells, and normal epithelial cells than in carcinoma cells (RT-4, HT1376, TSGH-8301, and T24) in vitro. Besides, the results of RT-qPCR revealed that TAGLN expressions were higher in normal tissues than the paired tumor tissues. In vitro, TAGLN knockdown enhanced cell proliferation and invasion, while overexpression of TAGLN had the inverse effects in bladder carcinoma cells. Meanwhile, ectopic overexpression of TAGLN attenuated tumorigenesis in vivo. Immunofluorescence and immunoblot assays showed that TAGLN was predominantly in the cytosol and colocalized with F-actin. Ectopic overexpression of either p53 or PTEN induced TAGLN expression, while p53 knockdown downregulated TAGLN expression in bladder carcinoma cells. Our results indicate that TAGLN is a p53 and PTEN-upregulated gene, expressing higher levels in normal bladder epithelial cells than carcinoma cells. Further, TAGLN inhibited cell proliferation and invasion in vitro and blocked tumorigenesis in vivo. Collectively, it can be concluded that TAGLN is an antitumor gene in the human bladder.