Topoisomerase-I inhibitor SN-38 can induce DNA damage and chromosomal aberrations independent from DNA synthesis.

Background: SN-38 is the active metabolite of the topoisomerase-I (topo-I) inhibitor Irinotecan (CPT-11). Generally, topo-I inhibitors stabilize the complex between topo-I and DNA which collide with moving DNA replication forks, eventually leading to double stranded DNA damage. Therefore, topo-I inhibitors are regarded as S-phase specific.