CD81 and cancer: Interestingly, a significant increase in HPA binding was observed in CD81-positive MCF-7 sEVs, from cells derived from metastatic cancer, showing a 1.5-fold higher binding compared to sEVs from hTERT-HME1, cells derived from healthy breast epithelium, and a 2.5-fold increase compared to sEVs from BT-474, cells derived from primary cancer (p < 0.01).