Improved efficacy of doxorubicin by simultaneous treatment with interferon-gamma and interleukin-2

Doxorubicin (DOX) is a potent anticancer agent active against a wide range of human neoplasms, yet, as is characteristic of most chemotherapeutics, the treatment of cancer with DOX alone has met with only limited success. This study was designed to investigate the possibility that the therapeutic potential of DOX could be enhanced by combination with one or more biological response modifiers. Segments (1mm3) of a transplantable colonic adenocarcinoma were implanted into the hind limbs of male WAG rats (200-250g). Serial tumour measurements were taken 3 x weekly throughout the 4 week experimental period by measuring the longest and perpendicular lengths with calibrated calipers. All drug administration was via a chronic indwelling jugular catheter, commencing 12 days after tumour implant, with control animals receiving physiological saline. Treatment of animals with DOX (4.5mg/kg as a 15 minute i.v. infusion), interferon gamma (IFN-gamma) (5 x 10(5) U/kg/day bolus i.v. for 5 days) or interleukin-2 (IL-2) (1 x 10(5)U/rat/day continuous i.v. infusion for 5 days) retarded tumour growth by approximately 30% by the completion of the study period (P < 0.001). The combined administration of IFN-gamma with DOX did not significantly alter the antitumour activity of either DOX or IFN-gamma. Concurrent administration of IL-2 with DOX also showed this treatment to have no therapeutic activity over that achievable with either agent alone. However, treatment of animals with IL-2, IFN-gamma and DOX resulted in a significant increase in tumour growth inhibition compared to DOX with either single cytokine (P < 0.001) and this was achieved without any apparent increases in the gross toxicity of DOX.(ABSTRACT TRUNCATED AT 250 WORDS)