LETTER TO THE EDITOR Double-stranded DNA in exosomes: a novel biomarker in

Exosomes, small membrane vesicles (30-100 nm) of endocytic origin secreted by most cell types, contain functional biomolecules, which can be horizontally transferred to recipient cells [1]. Exosomes bear a spe-cific protein and lipid composition, and carry a select set of functional mRNAs and microRNAs [2]. Recently, our group has shown that c-Met shed in exosomes can promote a proangiogenic and prometastatic phenotype in bone marrow-derived progenitor cells during melanoma progression [3]. In previous research, retrotransposon RNA transcripts, single-stranded DNA (ssDNA), mito-chondrial DNA, and oncogene amplifications (i.e., c-myc) have been detected in microvesicles [4-6]. In this report, we provide evidence that tumor-derived exosomes carry double-stranded DNA (dsDNA), as demonstrate