Clinical and tumor significance of tropomyosin-1 expression levels in renal cell carcinoma.

Renal cell carcinoma (RCC) is the most common type of kidney cancer in adults and has been described as one of the deadliest of cancers affecting the genitourinary tract. Tropomyosin is a two-stranded α-helical coiled coil protein found in cell cytoskeletons. One of its isoforms, tropomyosin-1 (TPM1) has been reported as a novel tumor-suppressor gene and is downregulated in many solid tumors. However the expression level and function of TPM1 in RCC have not yet been determined. In the present study, we evaluated the TPM1-4 mRNA and TPM1 protein levels in RCC tissue samples. TPM1-overexpressing OSRC-2 and 786-O cell lines were also used to investigate the impact of TPM1 on RCC cells. We found that TPM1 was significantly and specifically downregulated in the RCC tissues. TPM1 expression was associated with tumor size, smoking status, Fuhrman grade and the prognosis of RCC patients. After TPM1 transfection, the migratory and invasive abilities of the OSRC-2 and 786-O cell lines were both reduced when compared to the control groups. Meanwhile, apoptosis was also enhanced in these two RCC cell lines following TPM1 transfection. Taken together, TPM1 exhibits characteristics of a tumor-suppressor gene while being overexpressed in RCC cell lines.