Synthetic approaches, anticancer potential, HSP90 inhibition, multitarget evaluation, molecular modeling and apoptosis mechanistic study of thioquinazolinone skeleton: Promising antibreast cancer agent

New series of compounds bearing 2-thioquinazolinone scaffold were designed, synthesized as HSP90 inhibitors. Anti-proliferative activity of the synthesized compounds was evaluated against HCT-116, Hela and MCF-7 cell lines and compound 5k was found to be the most active member of the entire study with IC₅₀ of 4.47, 7.55 and 4.04 μM, respectively, compared to DOX (IC₅₀ of 5.23, 5.57 and 4.17 μM, respectively). Most of the tested compounds revealed lower cytotoxicity against normal fibroblast cells WI-38. Compounds 5b, 5k and 8a showed potent HSP90 inhibitory activities with IC₅₀ values in nanomolar range; 71.32, 25.07 and 56.78 nm, respectively, against Tanespimycin (IC₅₀ of 86.45 nm). Their HSP90 inhibitory activities were confirmed by their down regulation of HSP90 client protein Her2 and up regulation of chaperone HSP70 levels. Compound 5k had shown potent multi-target inhibitory activities against EGFR, VEGFR-2 and Topoisomerase-2 with IC₅₀ values in nanomolar range; 38.5, 126.95 and 25.85 nm, respectively. Compound 5k was further evaluated for cell cycle distribution and Apoptosis induction on MCF-7 cells using flow cytometry. Compound 5k arrested the cell cycle on MCF-7 at a G2/M phase by 35.06% and induced Apoptosis by 19.82%. Mechanistic evaluation of Apoptosis induction was studied by following ways triggering mitochondrial apoptotic pathway through inducing ROS accumulation, increasing Bax/Bcl-2 ratio and activation of caspases 6, 7 and 9. Comparative molecular modeling study was performed between active and inactive HSP90 inhibitors. Docking studies into the active site of HSP90 N-terminal domain showed good agreement with the obtained biological results. ADMET analysis and parameters of Lipinski's rule of five were calculated where compound 5k had reasonable drug-likeness with acceptable physicochemical properties so it could be used as promising orally absorbed antibreast targeted therapy.