An antibody-tumor model for the targeting of CA125-producing gynecologic malignancies.

By immunizing a mouse with HOUA-1 cells established from an endometrial cancer patient, two murine monoclonal antibodies designated 196-14 and 196-28 were generated, which were reactive with ovarian cancer-associated antigen CA125, originally defined by OC125 antibody. Antigenic determinants of these antibodies, although overlapping each other, were different from that of OC125 and the combined use of 125I-labeled 196-14 and OC125-coated beads markedly increased the sensitivity of measuring CA125 antigen. Both radioiodinated and 111In-labeled 196-14 localized well in CA125-producing human ovarian cancer tissues OVA-5 xenografted in nude mice. The biodistribution of radioiodinated 196-14 was quite different from that of 111In-labeled 196-14. Radioiodine was cleared faster from the OVA-5 tumor, making a clear contrast to the prolonged retention of 111In the tumor. Initial tumor uptake of radioiodinated 196-14 was the same as that of 111In-labeled 196-14 but decreased thereafter, due to the dehalogenation of radioiodinated antibody in the tumor. This antibody-tumor model seems to be suitable for examining the usefulness of monoclonal antibody-conjugates in the diagnosis and therapy of CA125-producing endometrial or ovarian cancers.