CD63 [NKI-C3]

CD63 is a 53 kDa lysosomal membrane glycoprotein that has been identified as a platelet activation molecule that belongs to the tetraspanin family, which is characterized by the presence of four hydrophobic domains. CD63 can mediate signal transduction events that play a role in the regulation of cellular adhesion, cell differentiation, migration, carcinogenesis and tumor progression. CD63 shows a broad tissue distribution and is predominantly localized in cytoplasmic lysosomes. It is mainly present on platelet lysosomes, granulocytes, basophils and a small percentage of resting T cells, while it is also strongly expressed in early melanoma, breast carcinoma, merkel cell carcinoma, astrocytoma and lung adenocarcinoma. Recent reports also indicate that CD63 is a good prognostic biomarker for human astrocytomas and earlier stages of lung carcinoma. Additionally, CD63 has been useful in differentiating renal oncocytomas (RO) from eosinophilic variants of chromophobe renal cell carcinomas (RCCs).