Anti‐colorectal carcinoma monoclonal antibodies reactive with human milk fat globular membranes

Abstract

Two monoclonal antibodies (MoAbs) were produced against human colorectal cancer and were found to react with many colorectal carcinomas (MoAb DH-1 detected 25 of 32 and MoAb SMA-1 detected 28 of 32) by the immunoperoxidase technique. These two antibodies were found to detect epitopes present on human milk fat globules (HMFG) by enzyme-linked immunosorbent assays (ELISAs). There have been few reports of anti-mucin antibodies being produced to colon cancer and so we examined the reactions of these and 13 other anti-HMFG MoAbs with colonic cancers. Thirty-two colonic tumours were examined and different staining patterns were noted. Staining was particularly marked on the cell membranes and glandular deposits of the tumours rather than in the cytoplasm of the cells. All colonic tumours tested were positive with at least one MoAb, but no single MoAb stained all tumours; this suggested that at least one epitope of HMFG could be found on all colonic tumours but no epitope detected by any one MoAb could be found on all colonic tumours. The 15 MoAbs were also tested on a panel of adult tissues, and with the exception of two, all had unique reaction patterns. Thus, at least 13 different epitopes associated with HMFG could be detected by the panel of MoAbs based on their different tissue distributions. However, no normal tissue expressed all the epitopes detected by all the MoAbs (i.e. none was positive with all the MoAbs) and no 'monomorphic' HMFG epitope could be found. The antibodies were shown to react with carbohydrate or peptide-based epitopes, but this reactivity had no relationship with the pattern of tissue reaction and the significance of the expression of different epitopes is not clear. Preliminary results of serum tests with three different anti-HMFG MoAbs showed that approximately 10% of colorectal cancer patients had elevated HMFG levels but with the cut-off level selected, 10% of normal subjects also had raised levels. From this study, antibodies to HMFG, commonly associated with breast cancer, can also react with carcinoma of the colon and can indeed be useful in detecting this disease histologically (e.g. MoAbs CC3, 4 and 5 which detect greater than 80% of colonic tumours). In addition it is clear that some of the mucins produced in carcinoma of the colon are similar to those produced by breast tumours.