CD9 and cancer: For cancer-derived exosomes, the PPI network was mainly concentrated on the connections among UPF3B, SRSF6, SRSF5, RBMX, PRPF38A, KCNC4, RPS27I, VAMP8, EFNB2, CD9, CD63, CD81, ADAM10, and MMP9, among which 11 exosomal proteins formed two clusters: in addition to the cluster of major proteins identified by molecular cargo analysis of primary endotheliocytes, one cluster was identified that enhanced the malignant potential of MCF-7 and BT-474 cells (Figure 5).