Abstract 2081 Cancer Exosome Biogenesis Occurs Primarily by an Endocytosis-Independent Pathway

Exosomes are small extracellular vesicles (sEVs) that play major roles in cancer biology. Exosomes are though to arise by the formation and exocytosis of endosomal intralumenal vesicles (ILVs). Here we tested this model by interrogating the biogenesis of key exosome marker proteins CD63, CD81, and CD9. CD63 has an endocytosis signal, is constitutively endocytosed, requires syntenin for its exosomal secretion, but is loaded into exosomes at far lower efficiency than the exosome markers CD81 or CD9, which reside at the plasma membrane.