Relative CAT expression in HL-60 cells incubated with TNFα and PTX in combination, with TNFα alone, or in the absence of either. PTX was added to the culture medium immediately after transfection and 1 hour before TNFα. After 48 hours at 37°C cell extracts were prepared for CAT assay. The diagram shows mean value of relative CAT conversion rates (±SD) measured in four independent experiments.