Assessing the Binding Affinity of a Small Molecule for the c-Myc oncogene guanine quadruplex for targeted anticancer applications

Abstract

Cancer is a group of diseases defined by abnormal cell growth that can invade different tissues and is caused by mutations to certain genes leading to uncontrolled cellular proliferation.[1] Found in all cells, deoxyribonucleic acid (DNA) encodes through five bases the genes needed to make every protein in the body. Aside from its conventional double helical structure, DNA can form higher-order architectures called guanine quadruplexes (G4s). G4s are composed of planar tetrads of four hydrogen-bonded guanines stabilized by a central cation that help limit the expression of cancer-related genes (Figure 1).[2] c-Myc is a gene that is overexpressed in the majority of human cancers.[3] Overexpression of c-Myc upregulates cellular growth and metabolism pathways central to cancer.[3] The region of the c-Myc gene that controls its expression (‘promoter region’) can fold into a G4.[4] Enforcing the folding of the c-Myc promoter into a G4 using small molecules can prevent c-Myc expression leading to cancer. Two years ago, the Petitjean Group made an exciting discovery of a binder which showed uniquely high affinity for G4s, while not associating with duplex DNA.[5] In my research presented here, I am using the fluorescence indicator displacement assay to indirectly assess binding constants and determine the degree of stabilization this binder offered to the c-Myc G4. Knowing the stabilization offered by this binder to c-Myc G4 can allow further research into a second generation of binders for targeted anticancer applications. 
 Figure 1. Planar tetrads of hydrogen-bonded guanines (left) stacked to form a G4 (right). G4-selective binder (yellow).
 References
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 [2] Ruggiero, E.; Richter, S. N. Nucleic Acids Res. 2018, 46, 3270-3283.
 [3] Brooks, T. A.; Hurley, L. H. Genes Cancer. 2010, 6, 641-649.
 [4] You, H.; Wu, J.; Shao, F.; Yan, J. J. Am. Chem. Soc. 2015, 7, 2424-2427.
 [5] a) Caitlin E. Miron, PhD Thesis, Queen’s University, 2018; b) C. E. Miron, J.-L. Mergny, A.
 Petitjean, Platinum Compounds for Binding Guanine Quadruplexes, PCT/C2018/051399.