Blood-group precursors and cancer-related antigens.

Glycoprotein extracts from colonic tumours were tested for blood-group precursor-like activities using human anti-I and anti-i cold agglutinins as reagents. Substantial activity was detected in the high-molecular-weight fractions of two metastatic tumours. A carcinoembryonic antigen (C.E.A.) fraction from one of these tumours was also active. The C.E.A. and the precursor-like activities were located on separate molecules. These data indicate that the levels of precursor-like antigens in entodermal tumours and their possible diagnostic value warrant detailed investigation.