Abstract: The Effects of Annexin a2 Expression on the Proliferation, Migration and Invasion of HumanBreast Cancer CellsShuzhen CAO, Fei ZHANG, Peiqi ZHAO, Jinghua HAN, BingWU, Haichang ZHANG, Lin ZHANG, Ruifang NIUCorrespondence to: Ruifang NIU, E-mail: niurf1982@yahoo.com.cnKey Laboratory of Breast Cancer Prevention and Therapy, Tianjin Medical University, Ministry of Education; Key Laboratory of Can-cer Prevention and Therapy, Tianjin Medical University Cancer Institute and Hospital, Tianjin 300060, ChinaThis work was supported by National Natural Science Foundation of China (No. 81071731)Abstract Objective: To study the effects of Annexin a2 on the proliferation, migration and invasion of human breast cancer cellline MDA-MB-231. Methods: One pair of small interfering RNA (siRNA) sequences targeting Annexin a2 was transfected intoMDA-MB-231 cells and monoclonal cell strains were screened. The expression of Annexin a2 was detected by Western blot, prolifera-tion was examined by MTT assay, migration capacity was evaluated by wound healing assay and invasion was detected using Transwellchambers. In addition the proteins interacting with Annexin a2 were examined by immunoprecipitation analysis. Results: Annexin a2expression was significantly reduced and there was a notable decrease in the migration and invasion capability of transfected breast can-cer cells ( P < 0.05 ). Conclusion: MDA-MB-231 is a human breast cancer cell line with high migration and invasion ability, and the de-crease in Annexin a2 expression can notably inhibit the proliferation, migration and invasion capability of tumor cells. Annexin a2 inter-acts with HSP27 to play an important role in the progression and metastasis of breast cancer.Keywords Annexin a2; Breast cancer; Proliferation; Migration; Invasion