Reversal of DOX resistance by transfection of antisense TNF cDNA with retroviral vector pRXhTNFanti into leukemic cells. The leukemic cells obtained freshly from five patients were used (cases 2, 5, 6, 10, and 11) for the cytotoxic assay as described in Materials and Methods. The data represent the mean (±SD) of three independent experiments and statistical significance was determined by Student's t-test. *P < .01; **P < .02; ***P < .05.