Background: Accumulating evidence suggests an antineoplastic role of MicroRNA-34a (miR-34a) in human cancer. However, its precise biological functions stay largely elusive. Purpose: Our study was aimed to investigate the impact of miR-34a on hepatocellular carcinoma (HCC) and its underlying apoptosis related mechanisms in vitro, as well as the association of miR-34a, E2F1 and E2F3 expression with patient survival of HCC using publicly accessed datasets. Methods: The HBV-expressing Hep3B and SNU-449 cell lines with or without enforced expression of miR-34a were in vitro cultured for cell proliferation, colony formation, wound healing, cell invasion, and 3D spheroid formation. Quantitative reverse transcription PCR (RT-qPCR) was performed for E2F1, E2F3 expression. Caspase-3 (CASP3) activity was determined using a CaspACETM Assay System. Kaplan-Meier survival curves were used to analyze the associations of miR-34a, E2F1 and E2F3 expression and overall survival in HCC. Meta-analysis was performed to examine the differential expression of E2F1 and E2F3 between primary HCC vs normal tissues. Results: The results in vitro showed that enforced miR-34a expression significantly inhibited cell proliferation, migration, and invasion of both Hep3B and SNU-449. RT-qPCR results demonstrated that miR-34a could significantly suppress E2F1 and E2F3 expression, particularly in SNU-449. CASP3 activity in both Hep3B and SNU-449 increased in miR-34a treatment group. Overexpressed E2F1 and E2F3 were observed in primary HCC vs normal tissues. Survival analyses showed that HCC patients with either high miR-34a, or low E2F1, or low E2F3 expression had better survival than their opposite counterparts, respectively. Conclusion: Our study suggested thatmiR-34a can modulate the expression of E2F1, E2F3, and CASP3 activity, thereby repressing tumor aggressiveness and expediting apoptosis in liver cancer cells.
Keywords: Caspase-3; E2Fs; hepatocellular carcinoma; microRNA-34a; prognosis.