Exosomal AnnexinA2′s Role In Angiogenesis And Breast Cancer Metastasis

Abstract

Early detection of cancer using circulating biomarkers is a realistic possibility with the discovery of exosomes which are 40‐100nm in size and comprise a major portion of secretory vesicles. Annexin A2 (AnxA2) is a 36 KD Ca+2 dependent phospholipid‐binding protein up‐regulated in many cancer types and implicated in promoting tumorigenesis and angiogenesis. Although AnxA2 is highly expressed in exosomes, its function has never been studied. We propose to explore the correlation and functionality of exosomal AnxA2 (exo‐AnxA2) in breast cancerMethodsExosomes were isolated from MCF10 progression model,MDA‐MB‐231 and its organ specific metastatic variants and characterized via Western blotting and particle size analyzer. Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) were used to study the correlation between exo‐AnxA2 and breast cancer progression. In vitro and in vivo angiogenesis assays explored the role of exo‐AnxA2 in angiogenesis. Experimentally induced (intracardiac injection) and spontaneous (mammary fat pad) metastasis models were used to study the role of exo‐AnxA2 in metastasis. To study AnxA2 specific function, LCKLSL inhibitory peptide or shAnxA2 were used.ResultsAFM and Western analysis showed increased levels of exo‐AnxA2 along the progression modelimageAngiogenesis studies with LCKLSL showed exo‐AnxA2 to be a potent inducer of angiogenesisimageBoth the metastasis models showed exo‐AnxA2 to be a potent inducer of metastasisConclusionWe found increased expression of exo‐AnxA2 in cancer exosomes vs. normal. Further, we found that exo‐AnxA2 is a potent inducer of angiogenesis and breast cancer metastasis indicating a possible role of exo‐AnxA2 in tumor‐ microenvironment signaling and cancer progression(Supported by NIMHHD grant under Award Number P20MD006882)