Design, molecular modeling and anticancer evaluation of thieno[2,3-d] pyrimidine derivatives as inhibitors of topoisomerase II

Synthesis of 4-(3,5-dimethyl-1H-pyrazol-1-yl)-5,6,7,8-tetrahydrobenzo[4,5]thieno [2,3-d]pyrimidine 1 and its functionalized reactions as nucleophile with various electrophilic reagents were performed through facile methods to yield different cyclic and acyclic derivatives (2-17). The structures of the newly synthesized compounds were established by their elemental analysis and spectral data. Derivatives 4, 14, 16, and 17 in addition to the parent compound 1 had IC50 at similar to 4-10 mu M against HepG2 and MCF7 and were selected for further investigations. All derivatives had high IC50, values ( > 60 mu M) against normal fibroblasts WI38 indicating selectivity against cancer cell lines. Derivatives 4, 14, and 17 up-regulated the expression of p53 by similar to 3-4 folds. All derivatives caused a significant similar to 3-fold increase in the expression of executive caspase 3 and significant elevation in cleaved caspase 3 activity. The elevation in the expression of caspase 3 by compound 1 and derivative 16 was not accompanied by an increase in p53 expression or cleaved caspase 3 activity. These two thienopyrimidines may act directly on caspase 3. Derivative 17 was unique in reducing the expression of Topo II by similar to 60%. The molecular docking showed that derivatives 4 and 17 with high binding energies could bind and inhibit Topoisomerase II (Topo II). In accordance with the docking modelling, derivatives 4 and 17 reduced the Topo II concentration by 82 and 90%, respectively, compared to the untreated cells. However, the parent compound 1 also caused a significant 34% reduction in the enzyme concentration although it was not predicted as a ligand for the enzyme in the docking study. Taken together, derivatives 4, 14 and 17 showed selective cytotoxicity, could arrest cell cycle, and induce apoptosis. Furthermore, they could serve as cytostatic agents by inhibiting/reducing Topo II.