Ascitic Antigen CA125: Study of Dissociaton Forms and its Final - Stem Structure

Aim: Study of dissociation forms of the ascites antigen СÐ125 and its stem structure – the final form of its dissociation.
Study Design: Resarch paper.
Place and Duration оf Study: Department of biochemistry, N.I. Pirogov Russian National Research Medical University, laboratory of immunochemistry and laboratory immunology, N. N. Blokhin Russian Oncological Scientific Center.
Methods: Next materials were used in the work: ascitic fluid from patients with ovary cancer (14 patients), blood serum from patients with ovary cancer (28 patients), 40 donors (24 women and 16 men). Electrochemoluminiscent method, ELISA, electrophoresis and direct binding of labeled antibodies with antigen in polyacrylamide gel, reaction of precipitation, chromatography were used to study forms of dissociation of the antigen СÐ125.
Results: Dissociation forms of the antigen СÐ125 isolated from ascites fluid of patients with ovary cancer, demonstrated at native conditions of electrophoresis in polyacrylamide gel three main forms: gamma – globulin with molecular weight (MW) ~500 kDa, alpha-globulin with MW ~ 230 kDa and beta-globulin with MW ~110 kDa. All 3 forms bound l-MAB to СA125 and were isolated from the polyacrylamide gel during preparative electrophoresis. All these forms dissociated to a single protein band with MW 55 kDa that migrated in the albumin zone and did not bind l-MAB to CA125 under denaturing conditions of polyacrylamide gel-electrophoresis with 2% sodium dodecyl sulfate. This form also demonstrated a sigle protein band corresponding to MW 75 kDa in reducing conditions of electrophoresis. It has been established that the form with MW of 55 kDa represents a complex of three different polypeptides, which are identical to heavy chains IgG, albumin and unknown thermostable protein coupled to albumin. This thermostable protein was revealed in all immunoreactive forms of CA125 and all investigated commercially available samples of albumins in the reaction of precipitation with polyclonal antibodies. Antibodies to these proteins have also been revealed in commercial antisera to human serum proteins in a titer 1:40.
Conclusion: The final form of dissociation of immunoreactive forms of the antigen CA125 is represented by a complex of three different polypeptides with MW of 55 kDa that did not bind l-MAB to CA125.