Design, Synthesis and in vitro Characterization of Novel Topoisomerase II Inhibitors and Poisons

Cancer is a term used for diseases characterized by out of control cell-growth and rapid creation of abnormal cells able to grow beyond their usual borders, invading adjoining parts of the body and spreading to other organs. Several biochemical targets have been recognized to play a fundamental role in its development. In particular, in cancer therapy, DNA topoisomerases have raised much interest as potential anticancer targets. Topoisomerases are ubiquitous enzymes essential for cell survival that regulate the topological state of DNA. They modulate DNA supercoiling and remove DNA knots and tangles. There are two major classes of topoisomerases, type I and type II, that are distinguished by the number of DNA strands that they cleave and the mechanism by which they alter the topological properties of the genetic material. Type II regulate the topological state of DNA in the cell by generating transient double-stranded breaks in the double helix. In order to maintain genomic integrity while the DNA is cleaved, topoisomerase II forms a covalent attachment, known as the “cleavage complex”, which is normally short-lived and is present at low steady-state levels in order to be tolerated by normal cells. Considering the key role of this enzyme for cell surviving, in this thesis project new small entities have been designed and synthesized in order to provide molecules able to block the activity of topoisomerase II by inhibiting the overall catalytic activity of the enzyme or by enhancing the concentration of the cleavage complex. To this aim, four different scaffolds known to act against topoisomerase II were selected: i) 4ꞌ-demethylepipodophyllotoxin, ii) xanthone, iii) thiobarbituric acid, and iv) 4-amino-2-pyrido-bicyclic pyrimidine moieties. All the new derivatives were investigated in biological assays and computational studies to evaluate their inhibitory activity and to identify their mechanism of action against topoisomerase IIα.