Highly and Broad-Spectrum <i>In Vitro</i> Antitumor Active <i>cis</i>-Dichloridoplatinum(II) Complexes with 7-Azaindoles

<div><p>The <i>cis</i>-[PtCl₂(<i>n</i>aza)₂] complexes (<b>1</b>–<b>3</b>) containing monosubstituted 7-azaindole halogeno-derivatives (<i>n</i>aza), showed significantly higher activity than <i>cisplatin</i> towards ovarian carcinoma A2780, its <i>cisplatin</i>-resistant variant A2780R, osteosarcoma HOS, breast carcinoma MCF7 and cervix carcinoma HeLa cell lines, with the IC₅₀ values of 3.8, 3.5, 4.5, 2.7, and 9.2 μM, respectively, obtained for the most active complex <b>3</b>. As for <b>4</b> and <b>5</b> having disubstituted 7-azaindoles in their molecule, the significant cytotoxicity was detected only for <b>4</b> against A2780 (IC₅₀ = 4.8 μM), A2780R (IC₅₀ = 3.8 μM) and HOS (IC₅₀ = 4.3 μM), while <b>5</b> was evaluated as having only moderate antiproliferative effect against the mentioned cancer cell lines with IC₅₀ = 33.4, 24.7 and 46.7 μM, respectively. All the studied complexes <b>1</b>–<b>5</b> effectively avoided the acquired resistance of ovarian carcinoma cell line. On the other hand, the complexes did not reveal any inhibition activity on the purified 20S proteasome from the A2780 cells. The representative complexes <b>3</b> and <b>5</b> showed low ability to be hydrolysed, but their stability was markedly lowered in the presence of physiological sulphur-containing biomolecule glutathione (GSH), as proved by the ¹H NMR spectroscopy and mass spectrometry studies. A rate of interaction of the studied complexes with GSH was affected by an addition of another mechanistically relevant biomolecule guanosine monophosphate. The differences in interactions of <b>3</b> and <b>5</b> with GSH correlate well with their different cytotoxicity profiles.</p>