CD81 and cancer: Tumor cell‐generated exosomes (TEXs) are crucial to the occurrence, development, and metastasis of various cancers, for example, glioma, breast cancer, lung cancer, prostate cancer and melanoma, among others, as well as immune response and therapy resistance.[172, 173, 174, 175, 176, 177, 178, 179] TEXs carry rich cancer information that includes MHC molecules, heat shock proteins (HSPs), tetraspanin (CD9, CD63, and CD81), immunosuppressive cytokines, and characteristic tumor antigens.