Abstract
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.
Highlights
Transglin/SM22-α/WS3-10/mp27 (TAGLN), a kind of 22-kDa protein, presents primarily in smooth muscle-containing tissues of vertebrates
Results of RT-qPCR assays revealed that levels of TAGLN were higher in both HBdSMC and human normal primary bladder epithelial cells (HBdEC) cells than the bladder carcinoma cells (Figure 1A)
Further immunoblot assays showed that T24 cells expressed the highest TAGLN protein levels among the four carcinoma cell lines (Figure 1B) which were similar to the results of RT-qPCR assays presented in the Figure 1A
Summary
Transglin/SM22-α/WS3-10/mp (TAGLN), a kind of 22-kDa protein, presents primarily in smooth muscle-containing tissues of vertebrates. Study indicated that abolition of TAGLN expression is an important early event in tumor progression and a diagnostic marker for breast and colon cancer development [5]. Studies have reported that TAGLN is an antitumor gene in esophageal squamous cell carcinoma and regarded as an oncogene for gastric cancer [6,7,8]. Contrary results from different independent laboratories showed that overexpression of TAGLN causes a poor prognosis in colon cancer in vivo and contributes to colorectal cancer progression and metastasis [14,15]. Previous studies indicated that TAGLN is one of the common differentially-expressed genes which is significantly decreased in bladder cancer compared with normal bladder tissues [19,20]. We determined the expressions of TAGLN in both bladder carcinoma cells and bladder tissues, and examined the regulatory mechanisms and potential functions of TAGLN in bladder carcinoma cells
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