The Mechanism And Effect Of HL-60 Cell Apoptosis Induced By (-)-epigallocatechin Gallate

Objective: Apoptosis inducing effect of the main ingredient, (-)-epigallocatechin gallate (EGCG), of tea polyphenols on the cultured human promyelocytic Leukemia HL-60 cells was studied to clarify the genes and signal pathways involved and to further elucidate their effect mechanisms.Methods: ①The growth inhibition of EGCG treated HL-60 cells was observed under light microscopy; ②The cytotoxicity of EGCG on HL-60 cells was tested by MTT assay; ③The biochemical change of apoptosis cells was observed on agrarose gel electrophoresis.The cell DNA cleavage induced by EGCG and the optimal duration and concentration of the EGCG action was selected; ④The change of ultrastructure of HL-60 cells was observed on TEM; ⑤The genes significantly expressed were screened by using gene chip; ⑥The gene chip data was certified by RT-PCR.Results: ①EGCG obviously inhibited the growth of the cultured HL-60 cells. The inhibition showed a dose-dependent manner; ②EGCG had cytotoxicitic effect on cells and its ICso is 220ug/ml; ③The DNA ladder presented on agrarose gel electrophoresis was charateristic. Within a certain range, the degree of DNA cleavage showed in a concentration-time-dependent manner and at the concentration of 250ug/ml for 6h showed the most evident apoptosis effect; ④The HL-60 cells nuclei fragments and apoptotic vehicles were observed under TEM; ⑤Among the total 8444 genes, 97 genes were involved in the apoptotic process. Within the 97 genes, 58 were down-regulated, they were the protein translation, synthesis and degradation and the DNA duplication and repair related genes. While another 39 genes were up-regulated, which were associated with the cell cycle, signal pathway and transcription; ⑥The results of RT-PCR agreed with the gene chip data.Conclusion:①EGCG inhibits the growth of HL-60 cells, and induces apoptosis in vitro; ②The apoptosis of HL-60 cells induced by EGCG was involved with multiple genes. The proteasome genes, ADPRT, BGT1, gadd45, MAP2K1 play important role in the apoptotic processes.