In Vitro Evaluation of Novel Hsp90 Inhibitors Determined with In Silico Drug Repurposing Approach

Hsp90 is an evolutionarily conserved molecular chaperone that modulates many cellular processes in eukaryotes through

signaling pathways regulated by Hsp90-related proteins such as proliferation, cell cycle, and gene expression. Thanks to

control of the Hsp90 protein, cellular functions such as cell proliferation and apoptosis are stabilized [1,2]. In addition,

Hsp90 inhibitors have a wide therapeutic window for cancer therapy, since the level of Hsp90 between cancer cells and

normal cells is distinctive. Therefore, targeting Hsp90 today is a promising strategy for developing a new anticancer drug

[3]. For this purpose, the interactions of all drugs (FDA approved, experimental, research) with Hsp90 protein in the

Drugbank database were determined using structure-based virtual screening. In this study, all molecules (~10767) in the

Drugbank database were downloaded and examined for interactions with the Hsp90 protein and potential hit inhibitors

were identified. DB00157, DB00581, DB00256, DB0786, DB00577, DB00415 targeting the active site of Hsp90 were

identified by virtual screening and molecular dynamics simulations were performed. After MD simulation (200 ns), the

effects of NADH, Lactulose and Ampicillin (DB00157, DB00581 and DB00415) drugs on human breast cancer cell lines

(MCF-7 and MCF10) were determined as in vitro. IC50 values of 17-AAG, Ampicillin, Lactulose and NADH applied (48

hours) on MCF-7 and MCF10A cell lines were determined experimentally. It was determined that three of these six target

drugs (Lactulose, NADH and Ampicillin) determined by in silico modeling according to their IC50 values, acted against

MCF-7 and MCF10A human breast cancer cell lines at moderate micromolar concentrations. The antiproliferative effects

of Lactulose, Ampicillin, NADH and reference 17-AAG drugs were evaluated in MCF-7 breast cancer and MCF10A

cells after prolonged incubation with increasing compound concentrations. These results accelerated their identification

as new Hsp90 inhibitors that could be used in cancer therapy. Considering the ligand RMSD values obtained as a result

of molecular dynamic simulation studies of these target compounds, new Hsp90 target compounds can be designed by

removing the groups with high fluctuations on the ligand.