Heparin and Liver Heparan Sulfate Can Rescue Hepatoma Cells from Topotecan Action

Figure 3

Differences of topoisomerase I plasmid cleavage activity trapped by TpT in liver samples and in hepatoma cells (representative image of three independent experiments). pBR322 plasmid was linearized and end-labeled with 5 μCi P ATP by using 20 U Klenow DNA polymerase. To remove the labeling from one end, the linearized plasmid was digested with Hind III restriction endonuclease. Ten microgram 0.35 M NaCI nuclear extracts of HepG2, Hep3B, and human HCC specimens were incubated with 8000 cpm linearized plasmid in the absence or presence of 100 and 200 μM topotecan. Lanes 1: cleavage reaction without topotecan, lane 2: cleavage reaction with 100 μM topotecan, and lane 3: cleavage reaction with 200 μM topotecan. The activity of Hep3B extract was much lower than that of HepG2 and human Iiver cancer.