Clinical And Tumor Significance Of Tropomyosin-1Expression Levels In Renal Cell Carcinoma

OBJECTIVE:To explore the expression levels of tropomyosin1(TPM1) and some othertropomyosins in renal cell carcinoma (RCC) tissue and cell lines, we evaluatedTPM1expression status from mRNA level to protein and tissue levels. We thenanalyzed the relationships between TPM1expression and many clinical features,including tumor size, grade, stage, survival status and so on. We also furtherobserved the tumor biological significance of TPM1in two RCC cell lines.MATERIALS AND METHODS:The TPM1expression levels was mainly detected by real-time polymerasechain reaction (RT-PCR), Western blotting and immunohistochemistry (IHC) fortissue sections. The analysis involved tissue blocks and cases data of49patientsunderwent partial or radical nephrectomy for kidney neoplasms. Reconstructedplasmid transient transfection was used as treatment to OSRC-2and786-O cells andthen viability, migration, invasion, apoptosis and cell cycle assays were completedby cell counting kit8(CCK-8), scratch assay, Transwell migration or invasion assaysand flow cytometery (FCM) respectively.RESULTS:TPM1expression was down-regulated at mRNA, protein and tissue levels inmost RCC tumor tissues (p=0.0297, p=0.0074and p<0.0001) while up-regulated inOSRC-2and786-O cells (p=0.006and p=0.003). TPM2, TPM3and TPM4mRNAexpression levels did not show any significant difference in RCC tumor tissues(p=0.591, p=0.104and p=0.191) compared to paired normal renal tissues while nearly all of them significantly changed in both OSRC-2and786-O cells (p=0.025,p=0.019, p<0.001and p<0.001, p=0.23, p=0.006). An association was foundbetween obvious lower TPM1mRNA level (decreased more than two fold) andlarger (larger than4.5cm) RCC tumor size (p=0.011). Similarly, an association wasfound between lower TPM1staining weaken degree and lower Fuhrman grade(p=0.009) but not clinical stage (p=0.263). Another significant association wasobserved between down-regulated TPM1expression and relatively lowerdisease-specific survival (DSS) rate (p=0.039), but not for the overall survival (OS)rate(p=0.137). After TPM1transfection, the migration and invasion abilities ofOSRC-2cells (p=0.0013and p=0.0155) and786-O cells (p=0.0039and p=0.0411)were both weaken compared with the empty vector transfection groups. At the sametime, early stage apoptosis and all stage apoptosis were enhanced in OSRC-2cells(p=0.0051and p=0.0022) and786-O cells (p=0.0361and p=0.0318). Its effects oncell cycle arrest in these two cell lines were not specific or consistent. In addition,TPM1had no significant effect on cell proliferation as we observed.CONCLUSION:TPM1was significantly and specifically down-regulated in the RCC tissuescompared with normal renal tissues. The TPM1expression was associated with thetumor size, Fuhrman grade and prognosis of RCC patients. Restoring expression ofTPM1in RCC cells could significantly inhibit migration and invasion besidespromoting tumor cell apoptosis and nonspecific cell cycle arrest, which were thecharacteristics of a tumor suppressor gene (TSG).