Introduction:
It has been unclear that ERK play the effects and relative mechanism in breast cancer development. The purpose of this work was to discuss the ERK play the effect in breast cancer and relative mechanisms.

Material and methods:
Evaluating ERK and CD59 proteins expression in difference tissue from patients by IHC assay. Using MCF-7 and MDA-MB-231 cell lines which were breast cancer cell lines as target cell lines in our study. In vitro study, evaluating cell biological activities including proliferation, apoptosis, cell cycle, invasion, adherent and migration by MTT, clone test, TUNEL assay, flow cytometry and wound healing. And measuring relative proteins expressions by WB assay. In vivo study, measuring tumor weight and volume, the apoptosis cell number were evaluated by TUNEL assay and relative proteins expressions by IHC assay.

Results:
Compared with adjacent normal tissue, the ERK and CD59 proteins expression were significantly increased in breast cancer tissues (P＜0.001, respectively).In vitro and vivo studies, with ERK knockdown, the cell biological activities were significantly depressed with CD59 suppressing (P＜0.001, respectively). And the relative proteins including CD59, PKD, P53, E-cadherin and Vimentin were significantly differences (P＜0.001, respectively).

Conclusions:
ERK play an oncology gene in breast cancer development, ERK inhibitor had effects to suppress breast cancer biological via regulation CD59 in vitro and vivo study.