Experiments in CBA mice with transplanted CaO 1 ovarian carcinoma possessing common antigenic determinants with human ovarian carcinoma showed that specific immunotherapy with mucin containing CA 125 antigen inhibited tumor growth by 60% and prolonged animal lifespan by 40-60% in comparison with the control. The correlation coefficient between the tumor size and antibody titer after injection of mucin was -0.4 for IgM and -0.6 for IgG. Titration of IgG may be used for monitoring of the efficiency of specific immunotherapy.

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The interactions between tumor cells and autoantibodies to tumor-associated human ovarian cancer antigen isolated from the plasma of a non-cancer patient are demonstrated using an original model of pseudomucinous murine ovarian carcinoma CaO-1. The use of natural autoantibodies for active immunotherapy of tumors may be more effective and safe than murine monoclonal antibodies to CA 125, because there will be no reaction to a toreign protein. Key Words: natural autoantibodies; human ovarian cancer; murine ovarian cancerStudy of tumor-associated antigens (TAA) detected in cancer patients and their role in the diagnosis and treatment of malignant tumors is an important trend of cancer research [3]. TAA are high-molecular-weight glycoproteins with extremely conservative structure, which may be indicative of their important biological role. For example, the peptide sequences of human and chimpanzee MUC 1 antigen differ by only 1% [2].There are no published data on the homology of glycoproteins expressed in human and murine ovarian cancer. In the present study we attempted to detect common antigenic determinants for glycoproteins expressed in human ovarian cancer and experimental mouse tumors of the same origin. This study was prompted by the detection of high titers of autoantibodies (autoAB) to human ovarian cancer TAA in the plasma of a non-cancer patient. Natural autoAB purified by affinity chromatography were used for examining the TAA of homologous murine tumors. The data can be used for studying natural autoAB and TAA to glycoprotein CA 125 expressed in patients with ovarian cancer and for detecting TAA homology in humans and mice with histologically similar tumors. MATERIALS AND METHODSThe study was carried out on an original model of murine mixed pseudomucinous ovarian carcinoma CaO-1 obtained and maintained in CBA mice. Similar tumors often occur in humans. This cell strain (frozen at the second generation) is highly sensitive to cytostatics routinely used in human ovarian cancer. We assume that the antigenic characteristics of this tumor remained unchanged. Relatively rapid growth of the tumor also is an important factor.Female CBA mice aged 2-3 months were used. CaO-1 ovarian cancer cells were transplanted subcutaneously in a dose of 10 6 cells in 0.3 ml medium 199. The cells were isolated from the tumor node on day 21 after tumor transplantation.