[Inhibition of SMYD3 gene expression by RNA interference induces apoptosis in human hepatocellular carcinoma cell line HepG2].

Background & Objective: SET and MYND domain-containing protein 3 (SMYD3) gene was found to encode a histone methyltransferase involved in the proliferation and apoptosis of cancer cells. This study was to detect the expression of SMYD3 in hepatocellular carcinoma (HCC) cell lines, and reveal its function of regulating proliferation and apoptosis of HCC cell line through gene silencing.

Methods: The expression of SMYD3 in HCC cell lines HepG2, Hep3B, SMMC7721, and normal hepatic cell line L-02 was detected by reverse transcription-polymerase chain reaction (RT-PCR); its expression in 24 specimens of HCC and peri-cancer tissue was detected by immunohistochemistry. Short hairpin RNA (shRNA) plasmids Pgenesil-1-s1 and Pgenesil-1-s2 (with interfering effect), and Pgenesil-1-hk (without interfering effect) were constructed and transfected into HepG2 cells. Western blot was used to detect the expression of SMYD3 protein after transfection. Cell proliferation was analyzed by MTT assay; cell apoptosis was analyzed by flow cytometry (FCM) and TUNEL.

Results: SMYD3 was overexpressed in the HCC cell lines and HCC tissue. After transfection with shRNA, SMYD3 expression in HepG2 cells was down-regulated by 75%-85%, and the cell growth was inhibited by 60.95%-72.14%. The apoptosis rate of HepG2 cells was significantly higher in Pgenesil-1-s1 and Pgenesil-1-s2 groups than in Pgenesil-1-hk and Pgenesil-1 groups [(17.68+/-2.36)% and (19.07+/-1.78)%, vs. (1.44+/-0.28)% and (0.47+/-0.12)%, P<0.01].

Conclusion: SMYD3 is overexpressed in various HCC cell lines and HCC tissue; RNA interference can down-regulate SMYD3 expression, inhibit proliferation and promote apoptosis of HepG2 cells.