CD81 and cancer: - Within glioma, proneural stem cells release EVs largely devoid of markers, while those derived from mesenchymal stem cells uniquely express CD9, CD63, and CD81, indicating intra-disease heterogeneity [60].- Up to 5000 distinct protein signals have been detected in the EV-associated proteome of a typical cancer cell population [61,62,63,64,65,66,67].