Topoisomerase I InhibitorsCamptothecinDNA Topoisomerases, Type ITopotecanTopoisomerase II InhibitorsDNA DamageDNA Topoisomerases, Type IIAntineoplastic Agents, PhytogenicTopoisomerase InhibitorsTeniposideIndenesEnzyme InhibitorsAntineoplastic AgentsDrug Screening Assays, AntitumorDNA CleavageDNA, SuperhelicalIntercalating AgentsEtoposideTumor Cells, Cultured