Abstract
A series of triple action Pt(iv) prodrugs was designed to test the hypothesis that multi-action compounds, where each bioactive moiety intervenes in several cellular processes, might be more effective than a single agent at killing cancer cells. In particular, "triple action" Pt(iv) derivatives of cisplatin, where the axial ligands are inhibitors of cyclooxygenase (COXi), histone deacetylase (HDACi) or pyruvate dehydrogenase kinase (PDKi) were developed. All compounds, ctc-[Pt(NH3)2(COXi)(PDKi)Cl2], ctc-[Pt(NH3)2(COXi)(HDACi)Cl2] and ctc-[Pt(NH3)2(HDACi)(PDKi)Cl2], where COXi = aspirin or ibuprofen, PDKi = dichloroacetate and HDACi = valproate or phenylbutyrate, were significantly more cytotoxic than cisplatin against all cell lines of an in-house panel of human cancer cells. They were particularly effective against thyroid and pancreatic cancer cells in monolayer cytotoxicity tests. Remarkably, in 3D spheroid cancer cell cultures, some triple action compounds showed an antitumor potency up to 50-fold higher than cisplatin against a KRAS mutated pancreatic cancer cell line (PSN-1 cells). Standard biochemical assays classically employed to explore structure activity relationships of platinum drugs, such as cellular uptake and binding to potential biological targets (DNA, HDAC, mitochondria, and COX), do not provide linear correlations with the overall cytotoxicity data. We observed a preferential induction of ROS production and of an anti-mitochondrial effect in cancer cells compared to rapidly dividing non-cancerous cells. Thus, we propose that these new triple action Pt(iv) derivatives of cisplatin are a novel and interesting class of potent and selective cytotoxic agents.