Large tumour-derived extracellular vesicles as prognostic indicators of metastatic cancer patient survival.
Extracellular vesicles (EVs) are released by all cells and produced at particularly high levels by many cancer cells, often inducing pro-tumorigenic effects. Since these cancer EVs carry tumour proteins and RNAs, they can potentially be used at biomarkers. The heterogeneity of surface markers and cargos carried by EVs, however, presents some challenges to developing such approaches. Nanou et al.  found that automated counting of large tumour-derived EVs (tdEVs) performed at least as effectively as counting circulating tumour-derived cells (CTCs) and with higher sensitivity, in distinguishing the survival of patients with castration-resistant prostate cancer (CRPC), metastatic colorectal cancer (mCRC) and metastatic breast cancer (MBC), but not for non-small cell lung cancer (NSCLC). Subsequent work has suggested that these tdEVs may also be used to assess tumour subtype and that the number of large EVs produced by endothelial cells can also be increased in cancer patients. While by itself, the tdEV imaging approach used by Nanou et al.  is not specific enough to predict the survival of individual patients, in combination with other EV-associated assays, this test, perhaps enhanced through the inclusion of other tumour antigens, could prove invaluable in predicting cancer survival and other outcomes in the clinic.