Relative CAT expression in untreated, TNFα-, PTX-, or TNFα/PTX-treated HL-60 cells transfected with the plasmids p4-19PCAT (A) or p4-18PCAT (B). Following transfection the cells were incubated for 48 hours in the absence or presence of TNFα (5 ng/mL) and/or PTX (200 μg/mL). PTX was added immediately after transfection and 1 hour before TNFα. The graph represents CAT conversion rates obtained in four independent experiments (mean average ± SD).