CP-115,953 stimulates cytokine production by lymphocytes

The cytotoxic quinolone CP-115,953 specifically exerts its inhibitory effect upon eukaryotic topoisomerase II. CP-115,953 stimulates DNA cleavage mediated by topoisomerase II with a potency approximately 600 times greater than that of ciprofloxacin, a quinolone antibacterial agent that currently is in clinical use. Because ciprofloxacin has been reported to strongly enhance interleukin-2 production, we considered it important to study the effect of CP-115,953 on interleukin-2 and gamma interferon (IFN-γ) mRNA and protein expression in mitogen-stimulated human peripheral blood lymphocytes. For comparison, novobiocin and the antineoplastic drug etoposide were also included in the study. CP-115,953 (25 μM) enhanced interleukin-2 mRNA levels up to 8-fold and IFN-γ mRNA concentrations up to 6.5-fold. In contrast, ciprofloxacin (282 μM) induced mRNAs for interleukin-2 and IFN-γ up to 20- fold and 7.8-fold, respectively. However, CP-115,953 showed more prolonged kinetics of IFN-γ mRNA production than ciprofloxacin. At high concentrations (≥141 μM), ciprofloxacin was a greater inducer of interleukin-2 production and exhibited a higher level of stimulatory action than CP-115,953 on IFN-γ synthesis. At low concentrations, however, CP-115,953 (≤25 μM) was more potent than ciprofloxacin in inducing interleukin-2 and IFN-γ synthesis. Etoposide or novobiocin did not influence cytokine mRNA expression. Thus, among the topoisomerase II inhibitors tested, fluoroquinolones are unique in stimulating cytokine synthesis in lymphocyte cultures