Combination therapy with metformin and IL-12 to inhibit the growth of hepatic carcinoma by promoting apoptosis and autophagy in HepG2-bearing mice.

OBJECTIVE: To investigate the effects and mechanism of metformin (Met) combined the interleukin-12 (IL-12) on inhibiting hepatoma HepG2 cell proliferation via in vitro and in vivo assays. MATERIALS AND METHODS: MTT assay was used to detect inhibitory effects of Met, IL-12 alone or combination on HepG2 cells proliferation. Half inhibitory concentration (IC50) and combination index (CI) were also calculated. Anti-tumor effects of combination or monotherapy on the HepG2-bearing mice were investigated and protein expression levels of apoptosis, as well as the Akt/mTOR/STAT3 signaling pathway-related factors were detected by Western blot. RESULTS: MTT results showed that the inhibitory effect of Met combined with IL-12 on HepG2 cell proliferation was significantly enhanced (both p<0.01) compared with monomer therapy group with a significant synergistic effect (CI<1). The apoptosis rate of HepG2 cells treated with Met combined with IL-12 were 88.12±7.15% and significantly higher than the others (all p<0.01). Moreover, combination treatment significantly suppressed hepatoma growth and increased the survival rate of HepG2-bearing mice without evident body weight loss. Western blot analysis showed that Met combined with IL-12 significantly increased the expression of autophagy-related marker proteins, downregulated the protein expression levels of Bcl-2, p-Akt, p-mTOR, p-STAT3, upregulated the expression level of BAX in both HepG2 cells and tumor tissues. CONCLUSIONS: Met combined with IL-12 exhibited a synergistic antitumor effect on hepatoma HepG2 cells, and the mechanism may be related to its common inhibition of Akt/mTOR/STAT3 signaling pathway and increase of autophagy in HepG2-bearing mice.