Detection of the tumour-associated antigens recognized by the monoclonal antibodies HMFG-1 and 2 in serum from patients with breast cancer.

The levels of the human milk fat globule 1 and 2 antigens have been measured in the sera of patients with advanced breast cancer, using a "sandwich" type radioimmune assay which exploits the carbohydrate nature of the antigenic determinants. In the series studied, 30% of sera from advanced breast cancer patients contained elevated levels of the HMFG-I antigen as compared with 6% of sera from healthy control women, whereas 53% of the advanced breast cancer patients showed elevated levels of HMFG-2 antigen compared with 16,6% of the controls. By means of the immune blotting technique, the components carrying the antigenic determinants in sera have been identified and compared for size with those molecules expressing the determinants in primary and secondary breast tumours. Both antibodies react with similar molecular weight components of 320kd and 280kd which are present in serum and tumour samples, although lower molecular weight bands of 230kd and 190kd can be seen in some tumours. These components are much smaller than the glycoprotein (greater than 400kd) present in the human milk fat globule, which carries the antigenic determinants recognized by HMFG-I and 2.