Voreloxin Is an Anticancer Quinolone Derivative that Intercalates DNA and Poisons Topoisomerase II
Figure 2
Voreloxin poisons topoisomerase II and induces site-selective DNA DSB.
A, CCRF-CEM cells were untreated (No drug) or treated for 4 h with voreloxin (0.1–20 µM), doxorubicin (1 µM) or etoposide (1 or 10 µM), DNA harvested through a caesium chloride pad, DNA quantities normalized, and topoisomerase II levels analyzed following a slot blot using anti-topoisomerase IIα or β antibodies. The immunoblot is a representative of three independent experiments. Quantitative analysis was performed using the Alpha Innotech digital imaging system and each condition was compared relative to the level of cleavage complex induced by 1 µM etoposide. Error bars represent the standard deviations for three independent experiments. B, pBR322 was incubated in vitro with either purified topoisomerase IIα or β and a dose-titration of voreloxin (0.1–10 µM) or etoposide (5 µM). DNA cleavage was assessed using SDS-PAGE, with untreated reaction mix (0) or DNA alone (DNA) as controls. Densitometry quantification of the indicated band, and the sequence surrounding the cleavage site, are shown in Figure S2.