<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>Any substance that inhibits topoisomerase-I, a topoisomerase that relieves torsional stress in a DNA molecule by cutting only one strand of the DNA double helix. Inhibition of topoisomerase-I causes DNA damage, inhibition of DNA replication, and apoptosis.</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>