In vivo bioassay to detect irinotecan‐stabilized DNA/topoisomerase I complexes in rats

Abstract

Irinotecan is an anticancer agent that stabilizes topoisomerase I/DNA complexes. So far, no test system has been reported for directly determining irinotecan‐induced stabilization of topoisomerase I/DNA complexes in organs in vivo. We adapted an ‘in vivo complexes of enzyme to DNA’ (ICE) bioassay to assess irinotecan activity in the stomach, duodenum, colon and liver of male Wistar rats after a single treatment with irinotecan (100 mg/kg body weight, intraperitoneally). This was compared to the control group receiving 0.9% sodium chloride intraperitoneally. In addition, the DNA strand breaking properties of irinotecan were measured in mucosal cells from the distal colon by single‐cell gel electrophoresis (comet assay) to investigate the association of topoisomerase poisoning and DNA damage in vivo. A single dose of irinotecan significantly increased amounts of topoisomerase I covalently bound to DNA in stomach, duodenum, colon and liver. Concomitantly, the irinotecan‐treated group showed significantly higher amounts of DNA strand breaks in colon mucosa cells compared to the control group. The ICE bioassay and the comet assay represent two test systems for investigating the impact of topoisomerase I poisons on DNA integrity in colon tissues of Wistar rats.

A Novel Small Molecule FL118 That Selectively Inhibits Survivin, Mcl-1, XIAP and cIAP2 in a p53-Independent Manner, Shows Superior Antitumor Activity

“…It is known that the major mechanism of action (MOA) for irinotecan is to inhibit DNA topoisomerase 1 (Top1) activity [53]–[57]. We therefore compared the effect of FL118 with SN-38 (the in vitro active form of irinotecan) on the inhibition of DNA Top1 activity at different concentrations.…”

Topoisomerase as target for antibacterial and anticancer drug discovery

“…They bind with a brief topo I DNA covalent complex and shows inhibitory action on resealing of a single strand nick which the enzyme creates to aid superhelical tension in paired DNA. The topo I targeted drugs are S-phase specific 46,[55][56][57] .…”

“…The limitation of hCPTs is that they get permanently inactivated when the lactone E ring is opened. Ketonic derivatives which are active Topo I poisons are the second novel family of lactone derivative of CPT 55 . 55 Non-camptothecin inhibitors which have structural difference from camptothecins include the (8) indolocarbazoles, phenanthridines and indenoisoquinolines 55,61 as shown in Figure 4.…”

“…Ketonic derivatives which are active Topo I poisons are the second novel family of lactone derivative of CPT 55 . 55 Non-camptothecin inhibitors which have structural difference from camptothecins include the (8) indolocarbazoles, phenanthridines and indenoisoquinolines 55,61 as shown in Figure 4. In recent times, three Topo I-DNA co-crystal structures: one with an indenoisoquinoline, one with an indolocarbazole and the other with the natural CPT bound to Topo I-DNA complexes have been observed 62 .…”

Assessment of mechanisms driving non-linear dose–response relationships in genotoxicity testing

“…immunostaining (TARDIS) [203,204] or the in vivo complex of 1572 enzyme (ICE) assays [205,206]. The formation of the stabilized 1573…”