RESUMEN
Objective To investigate and clarify the effect of Stat5a on proliferation of human breast cancer cells (MCF‐7) and to detect the changes of epigenetic signature on the promoter region of p53 gene .Methods Stat5a was over expressed in human breast cancer cells (MCF‐7) by using adenovirus mediated gene transfer technology .The cell proliferation was examined by MTS assay .ChIP assay was used to check the trimethylation of lysine 27 on histone 3 (H3K27Me3) of p53 gene promoter region .Fur‐thermore ,qRT‐PCR and western blot were also applied to confirm the expression of p53 gene .Results The number of MCF 7 in‐creased in a dose dependent manner .Compared with that of control group ,the cell density of MCF‐7 increased 7 .603 1% , 18 .123 7% and 24 .898 7% when the MOI were 10 ,20 and 30 .Chromatin Immunoprecipitation showed that Stat5a significantly in‐creased H3K27Me3 and down regulated the expression level of p53 gene .Conclusion Stat5a promotes proliferation of breast cancer cells through trimethylation of H3K27 and inhibition of p53 gene expression .