Advances in engineered exosomes towards cancer diagnosis and therapeutics

Exosomes have emerged as natural nanocarriers and are advantageous in the field of nanomedicine due to their lipid bilayer membrane comprising many proteins, nucleic acids and cell debris. Exosomes are secreted from all types of living cells and play a role in cancer diagnosis and therapy because of their biological properties, such as intercellular communication, modulation of immune responses, biocompatibility and target specificity. Many studies have shown that exosomes can be engineered or modified with different therapeutic substances, including nucleic acids, proteins, drugs and other nanomaterials, to improve their specificity, efficiency and safety in nanomedicine. In this review, we summarize the methodologies of exosome biogenesis, purification, the possible mechanisms of cellular uptake and the important role of exosomes in cancer diagnosis, followed by the role of engineered exosomes in cancer therapy. Also, future trends and challenges are discussed. We strongly suggest that a clear articulation of the fundamental principles for the creation of exosome-based theranostic platforms will help reveal the unique powers of exosomes in early cancer diagnosis and therapeutics, including chemotherapy, gene therapy, immunotherapy and phototherapy.