Annexin A1 (ANXA1) is a
calcium-dependent
phospholipid-linked
protein, involved in anti-inflammatory effects, regulation of cellular differentiation, proliferation and apoptosis. While many studies have investigated the ANXA1 expression in various
tumor types, the role of ANXA1 is not fully understood. Therefore, in the present study, we evaluated the ANXA1 expression in 211
breast cancer patients and compared the levels with clinicopathological factors. ANXA1 was positively expressed in 31 (14.7%) of the 211 cases in our cohort, and these positive cases were associated with
triple-negative breast cancer (TNBC) (P=0.007) and venous invasion (P=0.028). The in vitro cell experiment found that the MDA-MB-231 cell line, which is a TNBC cell line, highly expressed ANXA1. Using this cell line, the functional role of ANXA1 in
breast cancer was revealed and the knockdown of ANXA1 by specific
siRNA demonstrated a significant reduction in cellular invasion. Further experiments indicated that ANXA1 was induced by
hypoxia with
hypoxia-inducible factor-1α induction. These results suggested that ANXA1, which enhanced
breast cancer invasion and
metastasis under
hypoxia, were significantly associated with the worst patient outcome. This is particularly noted in TNBC, the group of
breast cancer with the worst outcome for which new therapeutic implications are required.