Abstract 1677: Annexin A2 antibody inhibits the progression of triple-negative and herceptin-resistant breast cancer by blocking epidermal growth factor receptor functions

Abstract

Abstract Short Description: Annexin A2 (AnxA2), a calcium-dependent phospholipid binding protein, is abundantly present at the surface of triple-negative and Herceptin-resistant breast cancer cells. Interactions between cell-surface AnxA2 and tyrosine kinase receptors have an important role in the tumour microenvironment and act together to enhance tumour growth. The mechanism supporting this role is still unknown. Methods: Triple-negative (MDA-MB-231) and Herceptin-resistant (JIMT-1) breast cancer cell lines were grown in complete DMEM and DMEM/F12 medium respectively, in a humidified incubator at 37°C with 5% CO2. The membrane function of AnxA2 was blocked by incubating cells with anti-AnxA2 antibodies. Western blotting, immunoprecipitation, immunofluorescence, 1-(4,5-Dimethylthiazol-2-yl)-3,5-diphenylformazan (MTT), flow cytometry, Clonogenic, and wound-healing assays were performed in this study Results: We demonstrate that in triple-negative and Herceptin-resistant breast cancer cells a large amount of AnxA2 is specifically translocated to the outer membrane domain. In addition, AnxA2 interacts with extracellular domain of epidermal growth factor receptor (EGFR) at the cell surface and has an important role in cancer cell proliferation and migration by modulating EGFR functions. Blocking AnxA2 function at the cell surface by anti-AnxA2 antibody suppressed the EGF-induced EGFR tyrosine phosphorylation and internalization by blocking its homodimerization. Furthermore, addition of AnxA2 antibody significantly inhibited the EGFR-dependent PI3K-AKT and Raf-MEK-ERK downstream pathways under both EGF-induced and basal growth conditions, resulting in lower cell proliferation and migration. Conclusions: These studies indicate that association of AnxA2 with EGFR in the membrane domain might play a positive regulatory role in keeping EGFR signaling events in an activated state in triple negative and Herceptin-resistant breast cancer thus making AnxA2 an important therapeutic target. Citation Format: Pankaj Chaudhary, Lee Daniel Gibbs, Jamboor K. Vishwanatha. Annexin A2 antibody inhibits the progression of triple-negative and herceptin-resistant breast cancer by blocking epidermal growth factor receptor functions. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1677. doi:10.1158/1538-7445.AM2015-1677