Evaluating tumor cell- and T cell-derived extracellular vesicles as potential biomarkers of cancer and immune cell competence

IntroductionExtracellular vesicles (EVs) produced by tumors, also called tumor-derived exosomes (TEX), have been implicated in inducing immune cell suppression in vitro and in vivo. The development of a novel category of noninvasive biomarkers for precision oncology remains an unmet need, and TEX emerge as a promising liquid tumor biopsy component.Areas coveredTEX play a critical role in monitoring cancer presence/progression and in reprograming of anti-tumor effector T cells to producers of EVs with pro-tumor activity. TEX are a subset of circulating EVs. Their separation by immune capture from EVs derived from nonmalignant cells allows for TEX phenotypic/functional assessments. TEX cross-talking with CD3(+) T cells induce the release of CD3(+) small EV (sEV), whose cargo of suppressor proteins resembles that of TEX and further contributes to cancer-induced immune suppression. While TEX recapitulate the genetic/molecular phenotype of tumor cells, CD3(+) sEV might serve as 'T cell liquid biopsy.'Expert opinionPreclinical explorations of the role in cancer body fluids of TEX and CD3(+) sEV as cancer biomarkers suggest that these EV subsets may qualify as liquid tumor biopsy noninvasive components in the near future. Their potential to simultaneously serve as noninvasive liquid tumor biopsy and T cell biopsy remains to be validated in future clinical trials.