Synthesis of two platinum(II) complexes with 2-methyl-8-quinolinol derivatives as ligands and study of their antitumor activities.

Two platinum(II) complexes, [Pt(ClQ)(DMSO)Cl] (ClQ-Pt) and [Pt(BrQ)(DMSO)Cl] (BrQ-Pt), with 5,7-dichloro-2-methyl-8-quinolinol (H-ClQ) and 5,7-dibromo-2-methyl-8-quinolinol (H-BrQ) as ligands, respectively, have been synthesized and characterized. The single-crystal X-ray diffraction characterization as well as other spectroscopic and analytical studies of ClQ-Pt and BrQ-Pt revealed that the coordination geometry of Pt(II) can be described as a four-coordinated square planar geometry. By MTT assay, ClQ-Pt displayed the most potent activity, with IC50 values of 5.02-34.38 μM against MGC80-3, T-24, Hep-G2 and BEL-7402 tumor cells. Among them, the T-24 cells the highest sensitivity to ClQ-Pt and BrQ-Pt with IC50 value of 5.02 ± 0.62 μM and 18.02 ± 1.05 μM, respectively. In addition, ClQ-Pt caused a higher percentage of apoptotic T-24 cells (ca. 33.75%) than that of BrQ-Pt (ca. 23.85%) and cisplatin (ca. 12.82%). Mechanistic studies revealed that ClQ-Pt and BrQ-Pt caused T-24 cell cycle arrest at the S phase, as shown by the down-regulation of cyclin A and CDK2 expression levels. In addition, ClQ-Pt and BrQ-Pt also caused mitochondrial dysfunction. Interestingly, the in vitro anticancer activity of ClQ-Pt was higher than those of BrQ-Pt and cisplatin, more selective for T-24 tumor cells than for normal HL-7702 cells. Taken together, we concluded that the 5- and 7-substitution groups of the ClQ ligands play an important role in determining the anti-proliferation activity of the corresponding Pt(II) complexes.