Genetically determined polymorphism of the circulating human breast cancer-associated DF3 antigen

The murine monoclonal antibody (MAb) DF3 was prepared against a human breast carcinoma. Previous studies have demonstrated that DF3 antigen levels are elevated in plasma of patients with breast cancer. Furthermore, MAb DF3 reacts with circulating glycoproteins of different molecular weights ranging from approximately 300 to 450 kd. The present study demonstrates that plasma DF3 antigen is comprised of at least four moieties with slow (S), intermediate (I), rapid (R) and very rapid (VR) electrophoretic mobilities. The electrophoretic mobility patterns for circulating DF3 antigen differ among individuals. Moreover, DF3 antigen is detectable in urine, and the electrophoretic mobility of the urinary moieties is similar, but not identical, to that in the plasma. Studies in family members suggest that the electrophoretic heterogeneity of plasma DF3 antigen is determined by codominant expression of multiple alleles at a single locus. This locus may code for the core protein of DF3 antigen. These findings thus identify a genetically determined polymorphism of a circulating tumor-associated glycoprotein.