fig5

Figure 5. Factors affecting levels of the Top1-DNA cleavage complex and irinotecan resistance. Levels of irinotecan-causing DNA damage response depends upon formation of the Top1-DNA cleavage complex through Top1 function. Decreases in cellular Top1 activities, Top1 gene copy number, and Top1 protein levels result in cellular irinotecan resistance. Top1: Topoisomerase I.