Macrophages and Fc-receptor interactions contribute to the antitumour activities of the anti-CD40 antibody SGN-40.

SGN-40 is a therapeutic antibody targeting CD40, which induces potent anti-lymphoma activities via direct apoptotic signalling cells and by cell-mediated cytotoxicity. Here we show antibody-dependent cellular phagocytosis (ADCP) by macrophages to contribute significantly to the therapeutic activities and that the antitumour effects of SGN-40 depend on Fc interactions.

Recombinant CD40 ligand therapy has significant antitumor effects on CD40-positive ovarian tumor xenografts grown in SCID mice and demonstrates an augmented effect with cisplatin.

CD40 is a member of the tumor necrosis factor receptor family and was first identified with a monoclonal antibody raised against bladder carcinoma. Recombinant human CD40L has been shown previously to have a direct antitumor effect on an ovarian cancer cell line and ovarian carcinoma cells isolated from ascites fluid. We show here that rhuCD40L inhibits the growth of several ovarian adenocarcinomas derived from surgical specimens and grown as xenografts in severe combined immunodeficient mice. Two 14-day treatment cycles were more effective than one. This effect is apparently not mediated by natural killer cells, because blocking natural killer cell activity by antiasialo GM-1 did not diminish this effect. In addition to suppression of tumor growth, treatment with rhuCD40L resulted in an increased expression of FasL, an increase in apoptosis, and histological changes including increased fibrosis and areas of tumor destruction. Using this model, we examined the efficacy of rhuCD40L in combination with chemotherapeutic agents. The antitumor effect of rhuCD40L in combination with 4 mg/kg cisplatin (CDDP) was increased over the effect of CDDP alone. Furthermore, rhuCD40L increased the efficacy of a suboptimal dose of CDDP (2mg/kg) such that it matched that of high-dose CDDP alone. These data suggest a role for rhuCD40L therapy in combination with platinum based regimens for primary treatment of epithelial ovarian tumors.

Characterization of human ovarian carcinomas in a SCID mouse model.

This study characterizes a murine model which is promising for the study of the growth and natural history of ovarian cancer and for testing of new therapies for its treatment. Intact portions of 20 different human ovarian cancer surgical specimens were implanted in over 60 severe combined immunodeficient (SCID) mice using techniques previously developed in our laboratory. Growth of xenografts was evaluated by gross examination and histopathologic analysis. Confirmation of the human origin of the tumor outgrowth was obtained using in situ hybridization analysis. By histological evaluation, all of the patients' tumors showed evidence of invasive growth in at least 1 of the mice implanted with portions of each surgical specimen and these tumors remained morphologically similar to the parent tumors for a long period of time. Furthermore, 65% (13/20) of the xenografts grew rapidly enough (i.e., reached a diameter of 1-2 cm within 2-6 months) to allow passage to subsequent SCID mice. Among the passaged xenografts, 3 eventually developed metastases in a distribution pattern similar to that of naturally occurring ovarian cancer and 2 developed ascites without evidence of further metastatic spread. Upon evaluation of sera from tumor-bearing mice, human antibodies presumably derived from immunoglobulin-secreting cells present in the original tumor specimen were identified. In support of this, human B cells and plasma cells could be seen within the tumor xenograft for more than 6 months following implantation. In summary, transplantation of surgical specimens from ovarian cancer patients into SCID mice results in an attractive model for the study of the natural history of ovarian cancer and may also be useful for analysis or new experimental therapeutic approaches for the treatment of this disease.