In Vitro Activity of Monofunctional Pt-II Complex Based on 8-Aminoquinoline against Human Glioblastoma

The Chemistry of Anticancer Mononuclear and N-Bridged Dinuclear 8-Aminoquinoline Half-sandwich Metal Complexes

Piano-stool complexes of ruthenium and other platinum group metals have shown promising preclinical results as anticancer agents, often with alternative modes of action to traditional platinum-based compounds. Quinoline is considered a privileged structure in medicinal chemistry and many complexes with potent anticancer activity have been reported. To assess the effect of incorporating bidentate 8-aminoquinoline-η2N-1,N-8 (AQH) ligands in half-sandwich piano-stool metal complexes of the general formula [M(L)(AQH)Cl]+, the respective Ru, Os (L=η6-p-cymene), Rh and Ir (L=η5-pentamethylcyclopentadienyl) complexes were prepared. Deprotonation of AQH during the reaction gave dinuclear [M(L)(AQ)]2 2+ complexes with the deprotonated μ-κ1N-8-aminoquinolinato-η2N-1,N-8 (AQ) ligands acting as bridges between the metal centers. Conversion of the mononuclear Ru, Rh and Ir compounds to the dimetallic analogues was facilitated under basic conditions and improved for the Ru derivative by the addition of AgNO3 to abstract the chlorido ligand. In in vitro anticancer activity studies, the dimetallic complexes were in general more potent than mononuclear analogues. The higher activity of the dimetallic compounds can be explained by higher uptake into cancer cells, as demonstrated for the respective Ru complexes, while zebrafish embryo studies demonstrated low toxicity, irrespective of the number of metal centers in the complexes.

Effect of Glycoconjugation on Cytotoxicity and Selectivity of 8-Aminoquinoline Derivatives Compared to 8-Hydroxyquinoline

Numerous emerging chemotherapeutic agents incorporate N-heterocyclic fragments in their structures, with the quinoline skeleton being particularly significant. Our recent works have focused on glycoconjugates of 8-hydroxyquinoline (8-HQ), which demonstrated enhanced bioavailability and solubility compared to their parent compounds, although they fell short in selectivity. In this study, our objective was to improve the selectivity of glycoconjugates by replacing the oxygen atom with nitrogen by substituting the 8-HQ moiety with 8-aminoquinoline (8-AQ). The 8-AQ derivatives were functionalized through the amino group and linked to sugar derivatives (D-glucose or D-galactose) that were modified with an azide, alkylazide, or propargyl group at the anomeric position by copper(I)-catalyzed 1,3-dipolar azido-alkyne cycloaddition (CuAAC). The resulting glycoconjugates, as well as their potential metabolites, were evaluated for their ability to inhibit the proliferation of cancer cell lines (including HCT 116 and MCF-7) and a healthy cell line (NHDF-Neo). Two of the synthesized glycoconjugates (17 and 18) demonstrated higher cytotoxicity than their oxygen-containing counterparts and showed improved selectivity for cancer cells, thus enhancing their anticancer potential. Furthermore, it was found that glycoconjugates exhibited greater cytotoxicity in comparison to their potential metabolites.

Cytotoxic Pt(II) complexes containing alizarin: a selective carrier for DNA metalation

Many efforts have been made in the last few decades to selectively transport antitumor agents to their potential target sites with the aim to improve efficacy and selectivity. Indeed, this aspect could greatly improve the beneficial effects of a specific anticancer agent especially in the case of orphan tumors like the triple negative breast cancer. A possible strategy relies on utilizing a protective leaving group like alizarin as the Pt(II) ligand to reduce the deactivation processes of the pharmacophore enacted by Pt resistant cancer cells. In this study a new series of neutral mixed-ligand Pt(II) complexes bearing alizarin and a variety of diamine ligands were synthesized and spectroscopically characterized by FT-IR, NMR and UV-Vis analyses. Three Pt(II) compounds, i.e., 2b, 6b and 7b, emerging as different both in terms of structural properties and cytotoxic effects (not effective, 10.49 ± 1.21 μM and 24.5 ± 1.5 μM, respectively), were chosen for a deeper investigation of the ability of alizarin to work as a selective carrier. The study comprises the in vitro cytotoxicity evaluation against triple negative breast cancer cell lines and ESI-MS interaction studies relative to the reaction of the selected Pt(II) complexes with model proteins and DNA fragments, mimicking potential biological targets. The results allow us to suggest the use of complex 6b as a prospective anticancer agent worthy of further investigations.

Enhancing Pt(IV) Complexes' Anticancer Activity upon Encapsulation in Stimuli-Responsive Nanocages

Platinum-based chemotherapy is the first-line treatment for different cancer types, and in particular, for malignant pleural mesothelioma patients (a tumor histotype with urgent medical needs). Herein, a strategy is presented to stabilize, transport, and intracellularly release a platinumIV (PtIV ) prodrug using a breakable nanocarrier. Its reduction, and therefore activation as an anticancer drug, is promoted by the presence of glutathione in neoplastic cells that also causes the destruction of the carrier. The nanocage presents a single internal cavity in which the hydrophobic complex (Pt(dach)Cl2 (OH)2 ), (dach = R,R-diaminocyclohexane) is encapsulated. The in vitro uptake and the internalization kinetics in cancer model cells are evaluated and, using flow cytometry analysis, the successful release and activation of the Pt-based drug inside cancer cells are demonstrated. The in vitro findings are confirmed by the in vivo experiments on a mice model obtained by xenografting MPM487, a patient-derived malignant pleural mesothelioma. MPM487 confirms the well-known resistance of malignant pleural mesothelioma to cisplatin treatment while an interesting 50% reduction of tumor growth is observed when mice are treated with the PtIV , entrapped in the nanocages, at an equivalent dose of the platinum complex.

The Challenging Treatment of Cisplatin-Resistant Tumors: State of the Art and Future Perspectives

One of the main problems in chemotherapy using platinum drugs as anticancer agents is the resistance phenomenon. Synthesizing and evaluating valid alternative compounds is challenging. This review focuses on the last two years of progress in the studies of platinum (II)- and platinum (IV)-based anticancer complexes. In particular, the research studies reported herein focus on the capability of some platinum-based anticancer agents to bypass resistance to chemotherapy, which is typical of well-known drugs such as cisplatin. Regarding platinum (II) complexes, this review deals with complexes in trans conformation; complexes containing bioactive ligands, as well as those that are differently charged, all experience a different reaction mechanism compared with cisplatin. Regarding platinum (IV) compounds, the focus was on complexes with biologically active ancillary ligands that exert a synergistic effect with platinum (II)-active complexes upon reduction, or those for which controllable activation can be realized thanks to intracellular stimuli.