Molecular forms and microheterogeneity of the oligosaccharide chains of pregnancy-associated CA125 antigen

The cancer antigen CA125 has a very complex molecular architecture in terms of both protein backbone and oligosaccharide chains. In this study, we examined the molecular forms and microheterogeneity of oligosaccharide chains of pregnancy-associated CA125, as a first step towards gaining an insight into its possible involvement as a ligand in carbohydrate-dependent interactions. The glycobiochemical properties of CA125 may be of diagnostic and biomedical importance as specific markers of physiological and pathological conditions of early pregnancy, as well as targets in different therapeutic procedures.

Pregnancy-associated CA125 was characterized by gel filtration and ion-exchange chromatography, followed by lectin-affinity chromatography with a panel of plant lectins as ligands.

CA125 antigen isolated from first trimester placental extract was found to be heterogeneous in respect to molecular mass and the existence of different glyco-isoforms. Thus, elution profiles from the lectin-affinity columns demonstrated molecular subpopulations bound with low, intermediate and high affinity. Under the applied experimental conditions, CA125 bound most strongly to Triticum vulgaris agglutinin (WGA) and Ricinus communis agglutinin (RCA), but low affinity interactions occurred with the other lectins tested.

The assessment of the carbohydrate composition of N- and O-glycans of pregnancy-associated CA125 was in general agreement with available data on CA125 of cancer origin. The main difference was observed in reactivity to Canavalia ensiformis agglutinin (ConA) and Phaseolus vulgaris erythroagglutinin (PHA-E) binding.