Characterization of a MAb to ovarian cancer and its possible diagnostic application

We report the distribution pattern of the target antigen of an IgG1 monoclo nal antibody, KI-OC III raised in BALB/C mice against solubilised ovarian a denocarcinoma, in normal tissue and in a collection of human tumour types. Special reference was made to benign and malignant ovarian tumours. The rea ctive antigen protein purified to homogeneity for a planned amino acid anal ysis showed three bands between 37-40 kDa. Immunohistochemical analysis rev ealed a specificity of 98% and a sensitivity of 77%. The tracer kinetics of the radiolabelled antibody were tested on a human ovarian carcinoma cell l ine in athymic mice. The results were compared to cell lines derived from b reast and stomach carcinomas as well as to a human glioblastoma cell line. The results show the preferential uptake by ovarian cancer cells followed b y breast cancer cell lines. In animal models, scintigraphic monitoring and direct measurement of the radio-labelled monoclonal antibody showed a prefe rential accumulation in tumours, in addition to high level signals in the l iver, kidney, spleen and heart which were related to degradation, excretion and high circulation. The Ki-OC III reactive antigen could be a potential candidate for immunomon itoring of ovarian and possibly also of breast cancer, for in vivo tumour i maging as well as for histopathologic examinations..