Trans-platinum(II)/(IV) Complexes with Acetylpyridine Ligands as Antivascular Agents in vitro: Cytotoxic and Antiangiogenic Potential

In vitro biological studies of four trans-platinum complexes of structural formulas trans-[PtCl2(n-acetylpyridine)2] (n = 3 or 4, complex 1 or 2) and [Pt(n-acetylpyridine)2Cl4] (n = 3 or 4, complex 3 or 4) were performed in human endothelial EA.hy 926 cells, in order to evaluate and compare their cytotoxic and antiangiogenic potential. MTT results revealed that trans-Pt(II) complexes exhibited significantly lower IC50 values: 4.0±0.9 μM (1) and 2.1±0.0 μM (2), than cisplatin (27.7±1.3 μM). Combinational drug treatment with N-Acetyl-L-cysteine and L-buthioninesulfoximine strongly counteracted effect of 1 and 2, while the same treatment rather enhanced cytotoxicity of Pt(IV) analogues. ICP-MS results suggested that differential endothelial toxicity of cisplatin and trans-platinum complexes correlated to the differences in their cellular accumulation, rather than to the different affinity of DNA binding. Intracellular accumulation of complexes (ng Pt/106 cells) for 24 h treatment, decreased in order: 1>2>4>3>CDDP, while ratio of DNA binding (pg Pt/μg DNA) decreased as following: 2>1>CDDP>4>3. FACS/Annexin-V-FITC analysis, and morphological study demonstrated that the enhanced cytotoxic and apoptotic potential (18.1%) of complex 2 was related to its highest affinity to bind nuclear DNA. Pt(IV) complexes exhibited the lowest reactivity to cellular DNA and proteins. Regardless of their antiproliferative action, 1-4 at subtoxic concentrations demonstrated in vitro inhibitory effect on tubulogenesis and matrix metalloproteinases (MMPs) 2 and 9 gelatinolitic activity, while 1 and 2 additionally downregulated MMP-2 gene expression.