Description of the PhD thesis project
The activities of our team aim the design, synthesis, and studies of novel small-molecule ligands and probes able to recognize unusual DNA and RNA structures, in particular damaged DNA structures that represent intermediates in enzymatic DNA repair. We assume that these compounds could interfere with the native functions of nucleic acids or enzymatic DNA repair, thereby finding applications in cancer therapy.
Along these lines, the present PhD project focuses on the development of DNA-binding ligands for indirect inhibition of O6-methyguanine-DNA-methyltransferase (MGMT). MGMT is a DNA repair enzyme responsible for the resistance of glioblastoma to temozolomide (TMZ), a clinically used DNA-alkylating drug. MGMT induces direct repair of a significant part of TMZ-induced DNA lesions, namely O6-methylguanine (O6-MeG), which leads to chemoresistance of MGMT-expressing tumors. Inhibition of MGMT represents an attractive strategy for the improvement of glioblastoma treatment; nevertheless, currently known inhibitors acting at the protein level failed to demonstrate clinical efficiency. Herein, we consider an alternative strategy for MGMT inhibition, namely “substrate masking” using highly selective DNA ligands binding to O6-MeG:C mispairs (which represent the primary TMZ-induced DNA damage). Specifically, this interdisciplinary project involves:
1. design and chemical synthesis of novel ligands, namely heterocyclic heterodimers and heterocycle–nucleobase conjugates;
2. biophysical characterization of their interaction with O6-MeG:C mispairs in DNA in vitro,
3. investigation of their MGMT inhibition activity, and (iv) cell culture studies in a TMZ-resistant glioblastoma model.
The final goals of this project are:
1. the identification of novel DNA ligands, binding to O6-MeG:C mispairs, as indirect inhibitors of MGMT,
2. validation of the indirect MGMT inhibition pathway as a putative strategy for improvement of chemotherapy of TMZ-resistant glioblastoma.
International, interdisciplinary & intersectoral aspects of the project
This project crosses several domains (bioorganic chemistry, molecular biophysics, biochemistry and cellular biology). The required expertise is ensured by the project consortium involving the PhD supervisor (Dr. A. Granzhan) and co-supervisor (Dr. S. Bombard).
Novel indirect inhibitors of MGMT discovered within the framework of this project may be protected, through patent applications, as potential drugs for use in combination chemotherapy.
The project involves a collaboration with the team of Dr. L. Trantirek at CEITEC (Czech Republic). Specifically, the interaction of novel ligands with DNA substrates bearing O6-MeG:C mispairs, and inhibition of the MGMT-induced demethylation, will be assessed in living cells using in-cell NMR spectroscopy developed by the Trantirek lab.
1. Granzhan A, Kotera N, Teulade-Fichou MP. Finding needles in a basestack: recognition of mismatched base pairs in DNA by small molecules. Chem Soc Rev. 2014 May 21;43(10):3630-65.
2. Kotera N, Poyer F, Granzhan A, Teulade-Fichou MP. Efficient inhibition of human AP endonuclease 1 (APE1) via substrate masking by abasic site-binding macrocyclic ligands. Chem Commun (Camb). 2015 Nov 14;51(88):15948-51.
3. Kotera N, Granzhan A, Teulade-Fichou MP. Comparative study of affinity and selectivity of ligands targeting abasic and mismatch sites in DNA using a fluorescence-melting assay. Biochimie. 2016 Sep-Oct;128-129:133-7.
4. Guyon L, Pirrotta M, Duskova K, Granzhan A, Teulade-Fichou MP, Monchaud D. TWJ-Screen: an isothermal screening assay to assess ligand/DNA junction interactions in vitro. Nucleic Acids Res. 2017 Nov 15. doi: 10.1093/nar/gkx1118.
5. Kotera N, Guillot R, Teulade-Fichou MP, Granzhan A. Copper(II)-Controlled Molecular Glue for Mismatched DNA. ChemBioChem. 2017 Apr 4;18(7):618-622.