Identification a Novel Tumor-suppressive Hsa-miR-599 Regulates Cells Proliferation, Migration and Invasion by Targeting Oncogenic MYC in Hepatocellular Carcinoma

Increasing evidences have demonstrated that microRNAs (miRNAs) act an essential role in regulating tumor progression and metastasis. Previous miRNAs microarray data showed that hsa-miR-599 is lower expressed in hepatocellular carcinoma (HCC); however, the function and molecular mechanism of hsa-miR-599 on HCC has not been well illustrated. Here, we first analyzed the expression level of hsa-miR-599 in HCC tissues and cell lines by real-time reverse-transcription PCR (qRT-PCR). Interestingly, we found that hsa-miR-599 was significantly down-regulated in the examined HCC tissues and cell lines. Then cells proliferation, migration and invasion were assessed by MTT, wound-healing and trans-well assay respectively. The results showed that over-expression of hsa-miR-599 resulted in inhibited HCC cells proliferation, migration and invasion in vitro. In addition, dual-luciferase reporter assay, qRT-PCR and Western blot analyzes were used to confirm MYC (v-myc avian myelocytomatosis viral oncogene homolog) as a target gene of hsa-miR-599. MYC expression was up-regulated in HCC tissues and cell lines, and restoration of hsa-miR-599 could remarkably decreased the mRNA and protein levels of MYC. Moreover, over-expression of MYC partly reversed hsa-miR-599-mediated inhibition of HCC cells proliferation, migration and invasion in vitro. Taken together, our data demonstrate that hsa-miR-599 acts as a tumor suppressor and inhibits HCC cells proliferation, migration and invasion by partly targeting oncogenic MYC, which hints that hsa-miR-599 can be a diagnostic and therapeutic biomarker in HCC.