MALDI Detection of Exosomes: A Potential Tool for Cancer Studies

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry is used to detect intact whole exosomes, yielding exosomal fingerprints within minutes. This rapid exosome detection approach is proposed as a potential tool for cancer studies. Melanoma, a dangerous form of skin cancer, is investigated as a cancer model. The approach allows classification of melanoma cell lines from the stage level through mathematical analysis of the fingerprints and enables the tracking of protein transfer from parental cells to the secreted exosomes by following up certain fingerprint peaks. Protein identities of exosomal fingerprint peaks were clarified by correlation with top-down and bottom-up proteomics. The protein-assigned fingerprints provide a qualitative and semi-quantitative detection of melanoma biomarkers and help to explore melanoma progression via exosome-mediated intercellular communication. Targeting bloodstream-circulating exosomes, the proposed exosome fingerprinting approach also promises fast detection of melanoma diseases and dynamic monitoring of the disease state with proof of concept in mouse and human.