Abstract A052: Inhibition of triple-negative and Her-2 resistant breast cancer proliferation and migration by Annexin A2 antibodies

Abstract

Abstract Introduction: The triple negative breast cancer (TNBC) phenotype, which lacks the presence of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (ErbB-2 or Her-2), is highly aggressive and resistant to chemotherapy. In fact, some of the patients under hormone deprivation and/or Herceptin therapy acquire resistance. Therefore, there is an urgent need to identify new diagnostic as well as therapeutic markers for treatment of such patients. Herceptin, an immunotherapy directed against the Her-2 receptor, inhibits cancer growth and progression in Her-2 positive breast cancer by blocking the downstream survival pathways. In these cells however, the expression of epidermal growth factor receptor (EGFR) is significantly low. Interestingly, EGFR expression is significantly increased in triple negative and Her-2 resistant breast cancer thereby contributing to cancer growth and progression. Present studies were designed to investigate whether or not Annexin A2 (AnxA2), a calcium dependent phospholipid binding protein, regulated EGFR downstream signaling pathway and if the functions of EGFR can be inhibited by the AnxA2 antibody in TNBC and Herceptin resistant cancer cell lines. Methods: AnxA2 function at cell surface of the triple negative breast cancer cell line MDA-MB-231 and Her-2 resistant breast cancer cell line JIMT-1 was blocked incubating with AnxA2 antibody (2μg/ml) after 12h of serum starvation. The cells were treated with/without EGF (50ng/ml) for 20 min after 2h of antibody treatment. The cell lysate was analyzed for pEGFR and EGFR mediated downstream signaling by Western blotting. Cell migration was analyzed by scratch wound healing assay. Results: The results of the present study indicate that AnxA2 interacts with EGFR at the cell surface and plays an important role in the regulation of EGFR mediated downstream signaling. Treatment of MDA-MB-231 and JIMT-1 cells with AnxA2 antibody causes significant decrease in EGF-induced phosphorylation of EGFR at Y845 and Y1068 sites. Our results also demonstrate that blocking cell surface AnxA2 functions causes the downregulation of proteins such as pAKT, and pERK1/2 which are regulated by EGFR resulting in lower cell survival, proliferation, and migration. Conclusions: Our data indicate that association of AnxA2 with EGFR in the membrane domain plays a positive regulatory role in keeping EGFR signaling events in an activated state in both triple negative and Her-2 resistant breast cancer cells, thus making AnxA2 an important therapeutic target. Citation Format: Pankaj Chaudhary, Jamboor K. Vishwanatha. Inhibition of triple-negative and Her-2 resistant breast cancer proliferation and migration by Annexin A2 antibodies. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr A052.