Annexin A3 is associated with a poor prognosis in breast cancer and participates in the modulation of apoptosis in vitro by affecting the Bcl-2/Bax balance.

OBJECTIVE: Annexins are a family of intracellular proteins that bind membrane phospholipids in a Ca(2+) concentration-dependent manner. Several annexins play important roles during tumor progression. However, little is known about the clinical implications and biological functions of Annexin A3 in breast cancer.
METHODS: Using immunohistochemistry, we analyzed 60 breast cancers for the levels of annexin A3 and investigated the correlation of its expression change with patient's survival via Kaplan-Meier survival analysis. Furthermore, via knockdown of Annexin A3 expression in breast cancer cells with special siRNA, the role of Annexin A3 in the proliferation and apoptosis of breast cancer cells was examined.
RESULTS: Annexin A3 was expressed at higher level in breast cancer than that in normal breast tissue. The expression of Annexin A3 in human breast carcinoma closely correlated with tumor size and axillary lymph node metastasis. Kaplan-Meier survival analysis revealed a significant inverse correlation between strong Annexin A3 expression and overall patient survival. Moreover, Annexin A3 overexpression was inversely associated with Bax staining and the apoptosis index. Annexin A3 small interfering RNA in MCF-7 and MDA-MB-435 could inhibit cell proliferation, decrease Bcl-2 mRNA and protein expression, and increase Bax mRNA and protein expression.
CONCLUSION: Our findings indicated that Annexin A3 might be a novel and potential prognostic marker for patients with breast cancer and be involved in regulating apoptosis by affecting Bcl-2/Bax balance.