OBJECTIVETo investigate the effects of epigallocatechin-3-gallate (EGCG) on proliferation and cell cycle of acute promyelocytic leukemia NB4 cell line and to clarify the molecular mechanism.

METHODSNB4 cells were treated with 0,50,75,100 and 125µmol/L of EGCG for 24, 48, 72 and 96 h, respectively. The proliferation level of NB4 cells was measured by CCK-8 assay. The cell cycle progression of NB4 cells was assayed by flow cytometry. The mRNA expression levels of DNMT1, DNMT3a and DAPK1 were detected by RT-PCR. The methylation status of gene was tested by methylation specific PCR, and the expression level of DAPK1 protein was detected by Western blot.

RESULTSThe proliferation and cell cycle progression of NB4 cells treated with EGCG were inhibited and showed the characteristic of time-dependent and dose-dependent manner. The expression level of DAPK1 and DNMT3a decreased in NB4 cells treated with EGCG. The expression level of DAPK increased in NB4 cells treated with EGCG, while the methylation of DAPK1 gene decreased.

CONCLUSIONEGCG inhibits the proliferation and cell cycle progression of NB4 cells by inhibiting the expression of DNMT1 and DNMT3a and down-regulating the methylation status of DAPK1 gene.