MiR-299-3p functions as a tumor suppressor via targeting Sirtuin 5 in hepatocellular carcinoma

Hepatocellular carcinoma(HCC) is one of the most common cancers in the world, with the characteristics of high morbidity and mortality. Though the levels of diagnosis and treatment of HCC have been largely improved recently, the prognosis of these patients remains unacceptable. Thus, it is urgent for us to discover the exact mechanisms and determine some new biomarkers for HCC. Previous studies revealed that microRNAs (miRNAs) played a critical role in the occurrence and progression of HCC. And miR-299-3p has been reported to be closely related to the progression of colon carcinoma, lung cancer and clear cell renal cell carcinoma and so on. However, the exact expression and functions of miR-299-3p in HCC are still uncovered. Here, we reported for the first time that miR-299-3p was downregulated in HCC. Clinically, statistical analysis showed that miR-299-3p expression was significantly associated with tumor size (P = 0.007), venous infiltration (P = 0.028), Edmondson-Steiner grading (P = 0.042) and TNM stage (P = 0.012). In addition, HCC patients with lower miR-299-3p expression had worse 3-year overall survival and disease-free survival (P = 0.0012, P = 0.0002). Functionally, Transwell assays, Wound healing assay, MTT assay and plate clone formation assay revealed that miR-299-3p inhibited the migration, invasion and proliferation of HCC cells. Furthermore, bioinformatics tools, luciferase reporter assay, real-time PCR, Pearson's correlation coefficient analysis, immunohistochemistry and Western blot showed that Sirtuin 5 (SIRT5) was a downstream target of miR-299-3p in HCC cells. In addition, rescue experiments indicated that SIRT5 mediated the effects of miR-299-3p on migration, invasion and proliferation of HCC cells. Thus, we conclude that miR-299-3p suppresses migration, invasion and proliferation of HCC cells via directly targeting SIRT5. MiR-299-3p may be a potential prognosis indicator and therapeutic target for HCC.