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 (125)I‐labeled 196–14 and OC125‐coated beads markedly increased the sensitivity of measuring CA125 antigen. Both radioiodinated and (111)In‐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 (111)In‐labeled 196–14. Radioiodine was cleared faster from the OVA‐5 tumor, making a clear contrast to the prolonged retention of (111)In in the tumor. Initial tumor uptake of radioiodinated 196–14 was the same as that of (111)In‐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.