[Regulatory effect of hepatic stimulator substance on the proliferation of human hepatoma cells].

The hepatic stimulator substance (HSS) was prepared from weanling rat livers by ultracentrifugation and Sephadex G-75 chromatography. The stimulatory effects of HSS on cell proliferation, EGF receptor expression and receptor tyrosine phosphorylation were investigated in serum-free cultured human hepatoma cell line SMMC-7721. The results showed: (1) The relative percentage of S-phase cells was increased in HSS-treated cells. (2) EGF receptor protein level was increased after the cells were treated with HSS for 12-24 h and this effect was dose- and time-dependent. (3) Treatment of the cells with HSS for 0.5-15 min resulted in the autophosphorylation of EGF receptor tyrosine residue dramatically. The above results suggest that the proliferative action of HSS on hepatocytes might be due to its modulation of EGF receptor expression and the signaling pathway.