Long Non­coding RNA SNHG16 Functions as Tumor Activator by Sponging hsa-miR-373-3p to Regulate TGFBR2/SMAD Pathway in Prostate Cancer

Abstract

Background: Long noncoding RNAs (lncRNAs) are one of the major causes of tumorigenesis. However, the roles and mechan­­isms of lncRNA SNHG16 in prostate cancer (PCa) remain unknown. The purpose of this study was to elucidate the mech­­anisms of lncRNA SNHG16 in the proliferation and metastasis of human PCa cells.Material and Methods: First, the quantitative polymerase chain reaction (qPCR) was used to measure SNHG16 expression in PCa tissues and adjacent normal tissues (n=80). Down-regulate and over-express SNHG16 in human PCa DU-145 cell. Then cell proliferation was detected by CCK8 assay, cell apoptosis was analyzed by flow cytometry, cell migration were determined by wound healing, and cell invasion was examined by transwell. Western blot assays were used to examine the expression of the TGFBR2, c-MYC, E2F4, SMAD2, p-SMAD2, SMAD3, and p-SMAD3. Second, the targeting relationship between SNHG16 and hsa-miR-373-3p was verified by dual-luciferase reporter assay and rescue experiments. Third, the targeting relationship between hsa-miR-373-3p and TGFBR2 was verified by dual-luciferase reporter assay and rescue experiments. Results: The expression of SNHG16 was significant increase in PCa tissues (Z=-8.405, P<0.001), and with significant correlation with patient's age (<60 and ≥60 years old, P=0.007). Silencing SNHG16 inhibited DU-145 cell proliferation, migration, and invasion, while induced cell apoptosis significantly (P<0.01, respectively). Overexpressing SNHG16 promoted cell proliferation, migration and invasion, and reduced cell apoptosis rate (P<0.05, respectively). SNHG16 overexpression observably increased TGFBR2, c-MYC, E2F4, p-SMAD2, and p-SMAD3 expression (P<0.001, respectively), but SNHG16 inhibition was opposite. However, SNHG16 did not regulate SMAD2 and SMAD3 expression. Next, hsa-miR-373-3p was found down-regulated in PCa tissues (Z=-8.344, P<0.001), and the down-regulation of hsa-miR-373-3p were closely linked to Gleason score (Gleason score: <7 and >7, P = 0.024). Hsa-miR-373-3p expression of hsa-miR-373-3p was negatively correlated with SNHG16 (r=-0.544, P<0.001). The result of dual-luciferase reporter assay and qPCR test revealed that hsa-miR-373-3p was a target of SNHG16. Hsa-mir-373-3p inhibitor could rescue sh-SNHG16-inhibited cell proliferation, migration and invasion by promoting TGFBR2, C-MYC, E2F4, P-Smad2, and P-smad3 expression. Finally, we found that TGFBR2 may be the target gene of hsa-mir-373-3p through TargetScan and starbase. Further research found that TGFBR2 was markedly up-regulated in PCa tissues (Z=-5.945, P<0.001), and the expression of TGFBR2 was negatively correlated with hsa-miR-373-3p (r=-0.627, P<0.001). Dual-luciferase reporter assay and qPCR test showed that TGFBR2 was a target of hsa-miR-373-3p. TGFBR2 knockdown could inhibit hsa-mir-373-3p inhibitor-induced cell proliferation, migration and invasion, and reversed the effect of hsa-mir-373-3p inhibitor on cell apoptosis. Based on the data, sh-TGFBR2 partially disabled hsa-mir-373-3p inhibitor effect. Conclusion: LncRNA SNHG16 might act as a ceRNA to regulate the proliferation and migration of DU-145 cells by modulating the hsa-miR-373-3p/TGFBR2/SMAD axis.