[p53-dependent antiproliferation and apoptosis of H22 cell induced by melatonin].

BACKGROUND & OBJECTIVE: It has been shown that melatonin has a direct inhibitory effect on the proliferation of H22 mouse hepatoma cells in our research. This study was designed to investigate its molecular mechanism. METHODS: (1) Animal models were established by transplanting H22 cells and treated with melatonin, and then the p53 and cyclin E of the tumor tissue were determined by immunohistochemical analysis. (2) After treatment of H22 cells with melatonin in vitro, the percentage of cells in each cell cycle phase and apoptosis rate were analyzed by flow cytometry. p53 and cyclin E were determined again by immunohistochemical analysis. The level of Fas mRNA was examined by real time polymerase chain reaction (RT-PCR). RESULTS: (1) After treated with melatonin (1 x 10(-6) mol/L), the number of the H22 cells in phase G(0)/G(1) were elevated from 75.24% to 85.46%, while which in phase S almost decreased from 10.32% to 0, and at the same time, the number of apoptotic cells increased from 5.07% to 12.77%. (2) Compared with the control, the level of p53 elevated 42.5% (in vitro) and 19.5% (in vivo), however, the level of cyclin E decreased 31.7% (in vitro) and 39.9% (in vivo). (3) Fas mRNA increased about 44.2% after melatonin treatment (P< 0.01). CONCLUSION: Melatonin inhibits the proliferation of H22 cells by arrest and apoptosis, and the mechanism perhaps interferes with increasing p53 that results in down-regulation of cyclin E indirectly and stimulates the expression of Fas gene.