Oxorhenium(V) complexes in the drug combination study

Abstract

Rhenium complexes merit particular attention in the area of metallodrug design due to rhenium’s broad spectrum of oxidation states and consequently, the possibility to design compounds of a great structural diversity. Thus, the synthesis, chemical characterization and antitumor activity in vitro of the three Re(V) complexes is described. Novel compounds were obtained via reaction of [ReOCl3(PPh3)2] with corresponding ligands (pyridine-2-carboxylic acid, 3-methylpyridine-2-carboxylic acid and 6-methylpyridine- 2-carboxylic acid) in acetonitrile at 78 °C for 3h. The complexes were fully characterized using NMR, IR, MS and elemental analysis. Their octahedral geometry with bidentate N^O ligand was confirmed by X-ray diffraction analysis. Antiproliferative effect was determined by MTT assay and only the complex with pyridine-2-carboxylic acid (1) showed dose-dependent cytotoxic potential, particularly toward triple-negative breast adenocarcinoma cells MDA-MB-231 with IC50 68.90 ± 1.73 μM and pancreatic adenocarcinoma cells PANC-1 with IC50 69.8 ± 2.3 μM. Drug combination studies in PANC-1 cells with 1 and Verapamil hydrochloride (VRP) showed slight arrest of cell cycle in the S phase and also it increase its antiproliferative potential to IC50 51.4 ± 2.8 μM. Part of the research included a depletion of the glutathione (GSH) level by L-buthionine-sulfoximine (L-BSO) at sub-toxic concentrations (100 μM) in PANC-1 cells which caused an increase of activity of 1 to the IC50 57.67 ± 6.51 μM.