MiR-577 inhibits papillary thyroid carcinoma cell proliferation, migration and invasion by targeting SphK2

OBJECTIVE: MiRNAs are small, noncoding RNA molecules that serve as important regulators of cancer-related processes. Abnormal expression of miR-577 has been found in several tumors. However, the expression pattern and biological function of miR-577 in progression of papillary thyroid cancer (PTC) remain unknown. This study is aimed to determine its expression pattern and explore the function underlying the mechanism of miR-577 in PTC. PATIENTS AND METHODS: Using quantitative RT-PCR, we detected miR-577 expression in PTC cell lines and primary tumor tissues. MTT assay and colony formation were performed to measure the viabilities of tumor cells. Transwell invasion and migration assays were used to test the invasion and migration of PTC cells transfected with miR-577 mimic. TargetScan, mi-Randa and PicTar were used to analyze whether sphingosine kinase 2 (SphK2) was a potential target gene. Next, the direct target gene of miR-577 was also identified by luciferase reporter assays and Western blot analysis. RESULTS: The results showed that miR-577 was significantly downregulated in PTC tissues and cell lines. The up-regulation of miR-577 inhibited the proliferation, migration and invasion of PTC cells in vitro. Furthermore, bioinformatics analysis indicated that SphK2 was a putative target of miR-577. A luciferase reporter assay further confirmed that SphK2 was a direct target of miR-577. The results of Western blot indicated that the expression level of miR-577 was negatively correlated with the expression level of SphK2 in PTC tissues. In addition, knockdown of SphK2 significantly suppressed PTC cells proliferation, migration and invasion. CONCLUSIONS: Our findings indicate that miR-577 is a potential tumor suppressor in PTC by targeting SphK2, and may be a potential therapeutic target in PTC.