Quantification of the apoptotic Top1cc induced by TRAIL. A,
HCT116 cells were treated with 0.1 μg/ml TRAIL for 4 h. Top1cc were
quantitated by pooling the DNA-containing fractions and probing with an
antibody against Top1. The pools containing 10 μg of DNA were assayed by
sequential 2-fold dilutions. HCT116 cells treated by CPT (0.5
μm, 1 h), for which the number of Top1cc/cell has been
determined (39), were used to
determine the genomic frequency of apoptotic Top1cc. B,
quantification of the data shown in A. The curves displaying the
levels of Top1cc as a function of the dilution of the samples show a 7.4-fold
increased of Top1cc induced by TRAIL as compared with CPT (0.5
μm). C, table expressing the amount of rad equivalent
(Rad-eq) Top1cc, and the number of Top1cc per cell and per bp in
response to TRAIL. a, CPT (0.5 μm, 1 h)
induces 573 rad equivalent Top1cc in HCT116 cells
(39), and 1 rad equivalent
Top1cc corresponds to ∼1 Top1cc/0.9 × 109 nucleotides
(64). The values for the
TRAIL-treated cells were obtained by multiplying by 7.4 (see B) those
of the standard CPT.