CyA-induced apoptosis is suppressed by phorbol myristate acetate (PMA). B-lineage ALL cell line NALM6 was incubated for 1 hour with the compounds indicated before addition of CyA (5 μmol/L). After 48 hours of culture, the number of viable cells in cultures with and without CyA was compared. Only preincubation with PMA (1 ng/mL) inhibited CyA-induced apoptosis, while fumonisine B1 (FMN B1, 50 μmol/L), sphingosine 1-phosphate (SPP, 10 μmol/L), staurosporine (3 μmol/L), genistein (10 μmol/L), and wortmannin (WM, 100 nmol/L) had no effect. At higher concentrations, these compounds were markedly toxic. Bars represent the mean ± SD of 4 measurements per test.