Abstract: Objective To investigate the effects of streptococcal protein on the growth of human hepatocellular carcinoma Bel-7402 cells and healthy human Chang's liver cells.Methods The Streptococci(NO:32080 strain)were cultured conventionally.The whole streptococcal protein was extracted according to related references.The streptococcal protein components SpⅠand SpⅡ were separated by using DEAE-Sepharose Fast Flow anion exchange chromatography.Bel-7402 cells and Chang's liver cells were treated with different concentrations(10,50,100 mg/L)of the whole bacterial protein,SpⅠor SpⅡ for 24～72 h.MTTassay was used to evaluate the effects of the proteins on the proliferation of two kinds of cells.The morphological changes of the two cells were observed by 50 mg/Lwhole streptococcal protein and SpⅡ under the phase-contrast microscope.Results The growth of Bel-7402 cells was inhibited significantly in a time and dose dependent manner by the whole protein and SpⅡ,while there was no significant growth inhibition of SpⅠ.The whole streptococcal protein and SpⅡ could promote the proliferation of Chang's liver cells after the cells treated by the proteins.After treating with the whole streptococcal protein and SpⅡ,Bel-7402 cells lost the normal morphology and changed sparsely and mussily,while Chang's liver cells changed little.Conclusion The whole protein and SpⅡ of Streptococcus(NO:32080 strain)can inhibit Bel-7402 cell proliferation and stimulate the growth of human normal liver cells in vitro.

Key words: streptococcus, human hepatocellular carcinoma Bel-7402 cell, human Chang's liver cell