Characterisation of the molecular structure and function of topoisomerase I using anticancer agents as molecular probes acting in a new allosteric binding-site

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INTRODUCTION: Topoisomerases (Topo) are important therapeutic targets to treat many cancers. To that end, inhibitors of these enzymes are amongst the most widely used anticancer drugs. For example, Topo I is an enzyme essential to maintain the integrity of our genetic code to avoid introducing harmful mutations while inhibitors of these enzymes induce breakages of this code and death of the cells. I have developed for nearly two years as an independent researcher a new family of promising anticancer drugs referred to “N-phenyl ureidobenzenesulfonates” (PUB-SOs) blocking the activity of this enzyme. PUB-SOs are different from known Topo I inhibitors used in clinic or in development. They are based on a genuine new molecular template easily prepared and modifiable to produce efficient anticancer drugs at low costs. Indeed, I have shown that these compounds block the activity of Topo I by a mechanism that still not identified but different from the drugs used in the clinic. This suggests that they might not be plagued with the same side effects such as diarrhoea and neutropenia and other problems related to their chemical instability and induction of chemoresistance. RESEARCH PROGRAM: My research program aims to locate and study the site where PUB-SOs binds to Topo I. To that end, I will use PUB-SO derivatives and analogs to study that binding site in 3D. Aim 1: Design and preparation of PUB-SOs derivatives and analogs that will be used as “special probes”. Aim 2: Localization of the site on Topo I binding PUB-SOs to block its repairing activity of the genetic code. Aim 3: Study this binding site using tools of biology and pharmacology such as a measure of the effect of new compounds on the repair activity of Topo I and the reproduction of cancer cells. Aim 4: Construction of 3D computer models of Topo I where the PUB-SOs are fixed in order to understand the mechanism of action of these molecules. Aim 5: Design and development of a new test to identify quickly promising compounds inhibiting the activity of Topo I. CONCLUSION: My research program is a unique opportunity to expand on a short-term level our understanding of the tridimensional structure of Topo I when it forms complexes with PUB-SOs. These studies provide a new method for rapid identification of new molecules of interest inhibiting Topo I. Finally, this research program will allow on a longer term to develop new tools for the design and development of the next generations of inhibitors and anticancer drugs. My research program will also offer a stimulating multidisciplinary training for highly qualified personnel in the drug design sector, notably in organic synthesis, molecular pharmacology, cellular biology, mass spectrometry and molecular modeling.