APMIS : acta pathologica, microbiologica, et immunologica Scandinavica
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Three of the proteins protecting cells from autologous lysis by complement are: membrane cofactor protein (MCP; CD46), an inhibitor of the membrane attack complex formation (CD59), and decay accelerating factor (DAF; CD55). We have investigated the expression of these proteins in breast and colorectal carcinoma by immunohistochemistry and immunoblotting of breast tissue for CD46. CD46 was consistently and strongly expressed in the epithelial compartment in 26/28 ductal carcinomas of the breast, 9/9 fibroadenomas, and 9/11 cases of control non-neoplastic breast tissue. ⋯ In contrast, tissue samples from colorectal adenocarcinomas showed clear staining for both CD59 (10/18) and, more markedly, CD46 (15/18). There was no association between the pattern or intensity of CD46 and CD59 expression and tumour differentiation. As the complement regulatory proteins CD46 and CD59 are also strongly expressed by trophoblast at the feto-maternal tissue interface, these results support the concept that similar mechanisms are employed both by the genetically dissimilar fetus and certain tumours to evade immune attack by their host.