The Effect And Mechanisms Of Extracelluar Regulated Protein Kinase In Estrogen Promoting Proliferation Of Breast Cancer Line MCF-7

Objective To investigate the effect of extracellular regulated protein kinase in estrogen promting proliferation and transformation of cell cycle and inhibiting apoptosis of human breast cancer cells MCF-7 by a specific inhibitor for phosphorylation of ERK PD98059,and to analyze its molecular mechanisms.Methods Estrogen receptor-positive human breast cancer cells MCF-7 was used as the research model. The effect of 17β-E₂ on the proliferation of MCF-7 cells was investigated with MTT assay so as to determining the optimal concentration of 17β-E₂ in the following experiment;The effect of PD98059 in promting proliferation of MCF cells by 17β-E₂ was measured with MTT assay and the intermediate concentration was determined;apoptosis and cell cycle of the cell was analyzed by flow cytometry; Telomerase activity was detected with TRAP-PCR argentation;The expression of wild-type P53 and phosphorylated ERK1/2 and PCAF protein were detected by Western blot;The level of wild-type p53 mRNA and PCAFmRNA were detected by RT-PCR .Results With phosphorylation inhibitor of ERK PD98059 , the proliferation of MCF-7 cells treated with 17β-E₂ was inhibited on a time-dose-dependent manner. This difference had statistical significance(P <0.01).The intermediate concentrations of PD98059 were 89.28μmol/L in 24 h,39.81μmol/L in 48h and 21.87μmol/L in 72h respectively. when the cells treated with 20μmol/l PD98059 for 48h, the effect of 17β-estradiol in prmotting transformation of MCF-7 cell cycle was reversed, the number of G1 phase cells increased ,and the number of S and M phase cells decreased(P <0.05 ),and the effect of 17β-estradiol in inhibiting apoptosis of MCF-7 cell was reversed,the rate of early apoptosis increased(P<0.05 ); The action of 17β-estradiol on enhancing telomerase activity of MCF-7 cells was inhibited(P<0.05 ); The expression level of wild-type P53 protein and gene transcription of wild-type P53 were reinforced(P < 0.05 ) ;The expression level of PCAF protein and P-ERK1/2 protein decreased remarkably(P<0.05 ). While the difference of gene transcription of PCAF had no statistical significance(P>0.05).Conclusion ERK played an important role in promoting proliferation and transformation of cell cycle of MCF-7 by 17β-E₂ and also in resisting apoptosis of breast cancer cell MCF-7.The mechanism is probably associated with changes of gene transcription of wild-type p53 and telomerase activity and enhancing the signal of estrogen receptor through increaseing the expression of PCAF protein.