EFFECT OF HUMAN RECOMBINANT INTERFERON-CR ON THE ACTIVITY OF CIS-DIAMMINEDICHLOROPLATINUM(II) IN HUMAN NON-SMALL-CELL LUNG-CANCER XENOGRAFTS

Interferons (IFNs) augment the effect of some antitumor agents, includ ing cis-diamminedichloroplatinum(II) (cDDP), in experimental systems. The effect of human recombinant interferon-alpha(2b) (rIFN alpha) on t he cDDP-dependent growth delay of a human non-small cell lung cancer e stablished as a xenograft in nude mice (NX002) has been investigated. IFN (10(5) IU/mouse, s.c.) as a single agent had no effect on the grow th of the xenograft. cDDP (4.2 mg/kg, i.p.) caused a specific growth d elay of 0.42, and this delay was significantly enhanced (to 1.08) by c oncomitant dosing with the otherwise inactive IFN, Possible mechanisms for this supra-additive relationship between IFN and cDDP have been i nvestigated: increased intratumoral accumulation of platinum was seen at late time points (maximally at 36 hr) during the pharmacokinetic be ta-phase cDDP elimination from the plasma of the nude mice. Tumor:plas ma platinum concentration ratios at 36-48 hr indicated significantly i ncreased accumulation of platinum in tumors from IFN-treated mice comp ared to controls (p < 0.05). Scheduling experiments suggest that this IFN-mediated effect can persist for 4 hr. These differences may accoun t for the enhanced antitumor activity of cDDP when coadministered with IFN.