Metnase mediates resistance to the Topo IIα inhibitor VP-16 in vitro. In vitro analysis of Topo IIα decatenation of kDNA was performed in the presence of Metnase and/or VP-16. The relaxed closed circle DNA is the fully decatenated species. kDNA decatenation (graph) was quantified by densitometric scans of the gel image. Pure Metnase (200 ng/μL) enhanced pure Topo IIα decatenation when added before or after VP-16.