Cancer-testis antigens MAGEA proteins are incorporated into extracellular vesicles released by cells

// Anneli Kuldkepp 1 , Magda Karakai 1 , Eve Toomsoo 1 , Olavi Reinsalu 1 and Reet Kurg 1 1 Institute of Technology, University of Tartu, Tartu, Estonia Correspondence to: Reet Kurg, email: reet.kurg@ut.ee Keywords: cancer-testis antigens; MAGEA; extracellular vesicles; microvesicles Received: December 13, 2018     Accepted: May 13, 2019     Published: June 04, 2019 ABSTRACT Melanoma-associated antigen A (MAGEA) family proteins represent a class of tumor antigens that are expressed in a variety of malignant tumors, but their expression in normal tissues is restricted to germ cells. MAGEA family consists of eleven proteins that are highly conserved sharing the common MAGE homology domain (MHD). In the current study, we show that MAGEA4 and MAGEA10 proteins are incorporated into extracellular vesicles released by mouse fibroblast and human osteosarcoma U2OS cells and are expressed, at least partly, on the surface of released EVs. The C-terminal part of the protein containing MHD domain is required for this activity. Expression of MAGEA proteins induced the budding of cells and formation of extracellular vesicles with 150 to 1500 nm in diameter. Our data suggest that the release of MAGEA-positive EVs is at least to some extent induced by the expression of MAGEA proteins itself. This may be one of the mechanisms of MAGEA proteins to induce cancer formation and progression.