Exosomes: A role for naturally occurring nanovesicles in cancer growth, diagnosis and treatment

Exosomes are 30 - 100 nm bodies secreted from almost all types of cells into the extracellular spaces. They enclose in their lumen active genetic information in the form of messenger RNA (mRNA), micro RNA (miRNA), DNA and active peptides that are representative of the parental cell and can be isolated from different body fluids. Exosomes can participate in inter-cellular communication by trafficking molecules to their target cells. Because they can stably carry cargo including miRNA, mRNA, and proteins and can pass through stringent biological barriers (e.g., blood brain barrier) without eliciting an immune response, they are considered as an ideal acellular vehicle for drug delivery. In this review, we describe the structure and biogenesis of exosomes and new directions related to their role in diagnosis and treatment of diseases, especially for cancer. We also discuss potential challenges associated with exosomes that should be addressed before exosome-based therapy can be applied to clinical settings.