CD81 and colorectal carcinoma: The major proteins associated with CRC progression, cell signaling, and metastasis are tetraspanins (CD9, CD63, CD81) [45], heat shock proteins (HSP70, HSP90) [46], tumor-associated antigens (CEA, CA19-9) [47], and proteins involved in cell adhesion, migration, and invasion (integrins, metalloproteases) [48].