Download MendeleySynthesis and Mechanism of Action Studies of a Series of Norindenoisoquinoline Topoisomerase I Poisons Reveal an Inhibitor with a Flipped Orientation in the Ternary DNA-Enzyme-Inhibitor Complex As Determined by X-ray Crystallographic Analysis
Ioanoviciu, A., Antony, S., Pommier, Y., Staker, B.L., Stewart, L., Cushman, M.(2005) J Med Chem 48: 4803-4814
- PubMed: 16033260
- DOI: https://doi.org/10.1021/jm050076b
- Primary Citation of Related Structures:
1TL8 - PubMed Abstract:
Several norindenoisoquinolines substituted with methoxy or methylenedioxy groups have been prepared and their anticancer properties evaluated in cancer cell cultures and in topoisomerase I inhibition assays. 2,3-Dimethoxy-8,9-methylenedioxy-11H-indeno[1,2-c]isoquinoline hydrochloride (14) is a strong topoisomerase I inhibitor and also displays very high cytotoxicity in the NCI cancer cell culture screen (mean graph midpoint of 50 nM). The X-ray crystal structure of norindenoisoquinoline 14 in complex with topoisomerase I and DNA has been solved, providing insight into the structure-activity relationships within this class of new anticancer agents. The number and position of the norindenoisoquinoline substituents have a significant influence on biological activity and demonstrate that substitution on the nitrogen atom is not an absolute requirement for the antitumor effect of the indenoisoquinolines. Removal of the 11-keto group from the lead compound 1 and replacement of the N-alkyllactam with an unsubstituted pyridine ring causes the indenoisoquinoline ring system to flip over in the DNA-enzyme-inhibitor ternary complex. This allows the nitrogen atom to assume the hydrogen bond acceptor role of the 11-keto group, resulting in hydrogen bonding to Arg364.
Organizational Affiliation:
Department of Medicinal Chemistry and Molecular Pharmacology and the Purdue Cancer Center, School of Pharmacy and Pharmaceutical Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
