Topo I band depletion assay in clinical leukemia samples. Aliquots of freshly isolated blasts from 4 different leukemia patients were incubated at 37°C for 30 minutes in buffer A containing 0 (lane 1), 3 μmol/L (lane 2), 10 μmol/L (lane 3), 30 μmol/L (lane 4), or 100 μmol/L TPT (lane 5); lysed; and subjected to SDS-polyacrylamide gel electrophoresis followed by Western blotting with anti-topo I antibody.