Synergetic inhibition effects of lysozyme and cisplatin against proliferation of human liver cancer SMMC-7721 cells

Aim:To study the effect of lysozyme combined with conventional cytotoxic agent cisplatin on proliferation of human liver cancer cells SMMC-7721,and to evaluate the toxicity of lysozyme in normal human liver cell line LO2. Methods: MTT assay was used to determine the inhibitory effect of the drugs on SMMC-7721 cells and RT-PCR used to determine the mRNA levels of PCNA and bcl-2.The toxic effect of lysozyme on proliferation of LO2 cells was also evaluated by MTT assay,and apoptosis of the cells incubated with or without drugs was analyzed by flow cytometry.Results: Our results showed that a significantly synergetic nhibitory effect on proliferation of SMMC-7721 cells was produced by combination of lysozyme with cisplatin,in a time-and dose-dependent manner.The inhibition rate ranged from 36% to 82%.The mRNA levels of either PCNA or bcl-2 in SMMC7721 cells were found decreased in the group of lysozyme combined with cisplatin,and apoptosis of the cells was found to be evidently induced by the combination of these two agents in a dose-dependent manner,tne greatest apotosis rate is 32.5%.Conclusion:Combination of lysozyme with conventional cytotoxic agent cisplatin can synergistically inhibit proliferation of SMMC-7721 cells in a time-and dos-dependent manner,and significantly induce apoptosis of the cancer cells.These may be resulted from the deceased expression of PCNA and bcl-2 in SMMC-7721 cells caused by lysozyme-cisplatin combination.