Chemoimmunotherapy of metastatic murine renal cell carcinoma using flavone acetic acid and interleukin 2

Metastatic renal cell carcinoma (RCC) remains largely incurable. We used a murine RCC (Renca) in BALB/c mice to investigate the treatment possibilities with chemoimmunotherapy using in vivo boosters of natural killer (NK) activity. Diffuse pulmonary metastases were induced by intravenous (i.v.) inoculation with 100,000 Renca cells. All untreated control animals died within one month from pulmonary metastases. Chemoimmunotherapy using the NK immunostimulator flavonic-8-acetic acid (FAA) at 200 mg./kg. i.v. was given on the third day post tumor inoculation, followed by four consecutive days of twice daily intraperitoneal (i.p.) administration of 10,000 units human recombinant interleukin-2 (rIL-2). This chemoimmunotherapy regimen consistently cured 70% of tumor-bearing animals. Mice cured by this chemoimmunotherapy regimen did not reject subsequent reinoculation with Renca, indicating absence of specific antitumor immunity as a result of the treatment. While FAA and rIL-2 have no demonstrable in vitro cytotoxicity for Renca, they are excellent boosters of in vivo NK activity. These data suggest a potential alternative treatment method for metastatic RCC, a tumor type for which no efficient cytostatic drugs are available.