A novel mononuclear
platinum(II) complex, [Pt(L-H)Cl] (1, where L= N-(4-(benzo[d]thiazol-2-yl)phenyl)-2-((2-pyridylmethyl)(2-hydroxyethyl)-amino)
acetamide), was obtained by covalently tethering a
benzothiazole derivative
2-(4-aminophenyl)benzothiazole to the 2-pyridylmethyl-2-hydroxyethylamine chelating PtII center. In vitro tests indicated that complex 1 displayed excellent antiproliferative activity against the tested
cancer cell lines, especially
liver cancer HepG-2 and SMMC-7221 cells. Importantly, the complex possessed 4.33-fold higher antiproliferative activity as compared with
cisplatin against HepG-2 cells, but was less toxic to the normal cell line L02 with the selectivity index (SI = IC50(L02)/IC50(HepG-2)) value of 8.36 compared to
cisplatin (SI, 1.40). The results suggested that 1 might have the potential to act as a candidate for the treatment of
hepatocellular carcinoma (HCC). Cellular uptake and distribution studies showed that 1 could effectively pass through the membrane of cells, enter the nuclei and mitochondria, induce the platination of cellular
DNA. The interaction of 1 with CT-
DNA demonstrated that 1 could effectively bind to
DNA in a dual binding mode, i.e., the intercalation of the
2-(4-aminophenyl)benzothiazole unit plus monofunctional platination of the
platinum(II) moiety. In addition,
Hoechst 33342 staining and flow cytometry analysis illustrated that 1 arrested the cell cycle in HepG-2
cancer cells at G2/M phases, induced mitochondrial membrane depolarization, increased ROS generation, and caused obvious cell apoptosis. Further cellular mechanism studies elucidated that 1 triggered HepG-2 cell apoptosis via the mitochondrial-mediated pathway by upregulating the gene and
protein expression levels of Bax, downregulating the gene and
protein expression levels of Bcl-2, and activating the
caspase cascade.