Tardis assay of cleavable complex levels. Cells were treated with etoposide in the presence or absence of 10 μM NU7026 for 24 hours. Original magnification × 10. (A) Immunofluorescent micrographs of control cells and cells treated with 1 and 10 μM etoposide. The blue stain indicates DNA; green stain, topo IIα cleavable complexes. (B) Scattergram. (C) Averaged data from scattergram (topo IIα-specific antisera). □ indicates etoposide alone; and ▪, etoposide + NU7026. Results are means of 3 experiments ± SE.