Human carcinoma cell lines xenografted in athymic mice: biological and antigenic characteristics of an intraabdominal model

Summary In order to investigate in vivo clinical applications of murine monoclonal antibodies directed against human ovarian carcinoma a preclinical in vivo model was developed using BALB/c athymic mice. Three human carcinoma cell lines (MCF7, HT29, and SW626) were injected into the peritoneal cavity of pristane-primed animals and the biological and antigenic characteristics of the i.p. grown tumors were studied. The animals were killed when moribund or 6–8 weeks after tumor injection. At autopsy tumor take was observed in 85% of the injected animals, whereas palpable nodules were evident in only 83%. Examination of the peritoneal cavity revealed intraabdominal carcinomatosis with tumor masses varying in size between 0.2 and 0.5 cm in diameter and tumor sheets. The most frequently affected organs were the diaphragm, the liver, and the reproductive system. Ascitic fluid formation was rare and no animal developed tumors outside the peritoneal cavity. To determine whether the in vivo tumors retained the same antigenic characteristics as the in vitro cell lines, four monoclonal antibodies (MBrl, MOv2, MOv8, and MOv15) directed against ovarian carcinoma-associated antigens and two different experimental approaches (immunofluorescence and immunoblotting) were used. Variations at either a quantitative or a qualitative level were observed for some antigens, whereas no evident changes were apparent for others. In particular, the antigens detected by MBr1 and MOv15 on the MCF7 line both maintained high levels of expression and immunoblotting staining pattern, whereas the antigens detected by MOv2 on the HT29 and SW626 lines, although present at a high level, clearly changed their staining pattern. As regards the antigens recognized by MOv8 and MOv15 on the HT29 and SW626 lines, we observed a drastic decrease in the level of their expression and in many cases a drop below the threshold of detectability of the test. The intraabdominal carcinomatosis described partially mimics the growth characteristics of human ovarian cancer and maintains the expression of some antigenic markers associated with epithelial tumors of the ovary and may therefore be useful in devising immunodiagnostic and/or immunotherapeutic strategies for ovarian carcinoma.