Therapy of peritoneal murine cancer with biological response modifiers

We have used a murine renal adenocarcinoma of spontaneous origin (Renca) inplanted in the peritoneal cavity to study the therapeutic potential of biological response modifiers (BRMs) used alone or in conjunction with chemotherapy. This tumor model is therapeutically challenging since following intraperitoneal (i.p.) injection, the tumor grows progressively with hemorrhagic ascites, abdominal metastases to lymph nodes, liver, spleen, most serous membranes, and, in some animals, metastases to extra-abdominal sites (lungs). In the absence of therapy, death invariably occurs within 36 +/- 2 days. The tumor is efficiently lysed in 4 hours by peritoneal cells isolated from mice treated with BRMs. Both MVE-2 and rIL-2 significantly increased the survival time of tumor-bearing mice, but only treatment with MVE-2 led to definite cures of i.p. Renca. A single i.p. injection of MVE-2 cured 20% of the tumor-bearing mice, while repeated i.p. administration of this drug at 12 day intervals cured 70% of i.p. Renca-bearing mice. Combined therapy with doxorubicin hydrochloride and a single dose of MVE-2 cured 90% of tumor-bearing animals. The superior therapeutic efficiency of MVE-2 compared to that of the rIL-2 may be due to its ability, after i.p. inoculation, to generate and maintain high levels of cytotoxic effector cell activity for an elevated period of time within the peritoneal cell population. Additionally, MVE-2 augments effector cell activity in the liver, lungs, spleen, and blood and may therefore more efficiently interfere with metastasis formation in those compartments. The additive effects of MVE-2 and the chemotherapeutic agent suggest that more effective therapy may be achieved by the combination of immunotherapy with BRMs with chemotherapeutic drugs.