Platinum (IV) Derivatives with Cinnamate Axial Ligands as Potent Agents Against Both Differentiated and Tumorigenic Cancer Stem Rhabdomyosarcoma Cells

ctc-[Pt(NH3)2(cinnamate)(valproate)Cl2] is a highly potent and low-toxic triple action anticancer prodrug

Pt(iv) prodrugs have gained tremendous attention due to their indisputable advantages compared to cisplatin. Herein, new Pt(iv) derivatives with cinnamic acid at the first axial position, and inhibitor of matrix metalloproteinases-2 and -9, histone deacetylase, cyclooxygenase or pyruvate dehydrogenase at the second axial position are constructed to develop multi-action prodrugs. We demonstrate that Pt(iv) prodrugs are reducible and have superior antiproliferative activity with IC50 values at submicromolar concentrations. Notably, Pt(iv) prodrugs exhibit highly potent anti-tumour activity in an in vivo breast cancer model. Our results support the view that a triple-action Pt(iv) prodrug acts via a synergistic mechanism, which involves the effects of CDDP and the effects of axial moieties, thus jointly leading to the death of tumour cells. These findings provide a practical strategy for the rational design of more effective Pt(iv) prodrugs to efficiently kill tumour cells by enhancing their cellular accumulation and tuning their canonical mechanism.

The Discrete Breast Cancer Stem Cell Mammosphere Activity of Group 10-Bis(azadiphosphine) Metal Complexes

We report the anti-breast cancer stem cell (CSC) properties of a series of Group 10-bis(azadiphosphine) complexes 1-3 under exclusively three-dimensional cell culture conditions. The breast CSC mammosphere potency of 1-3 is dependent on the Group 10 metal present, increasing in the following order: 1 (nickel complex) <2 (palladium complex) <3 (platinum complex). Notably, 3 reduces the formation and size of mammospheres to a greater extent than salinomycin, an established CSC-active compound, or any reported anti-CSC metal complex tested under similar conditions. Mechanistic studies suggest that the most effective complexes 2 and 3 readily penetrate CSC mammospheres, enter CSC nuclei, induce genomic DNA damage, and trigger caspase-dependent apoptosis. To the best of our knowledge, this is the first study to systematically probe the anti-CSC activity of a series of structurally related Group 10 complexes and to be conducted entirely using three-dimensional CSC culture conditions.

A Multi-action PtIV Conjugate with Oleate and Cinnamate Ligands Targets Human Epithelial Growth Factor Receptor HER2 in Aggressive Breast Cancer Cells

HER2-positive breast cancer is an aggressive subtype that typically responds poorly to standard chemotherapy. To design an anticancer drug selective for HER2-expressing breast cancer, a Pt^IV prodrug with axial oleate and cinnamate ligands was synthesized. We demonstrate its superior antiproliferative activity in monolayer and 3D spheroid models; the antiproliferative efficiency increases gradually with increasing expression of HER2. The results also suggest that the released Pt^II compound inhibits the proliferation of cancer cells by a DNA-damage-mediated mechanism. Simultaneously, the released oleic and cinnamic acid can effectively inhibit HER2 expression. To our knowledge, this is the first platinum-based complex inhibiting HER2 expression that does not contain protein or peptide. Moreover, this Pt^IV prodrug is capable of overcoming the resistance of cancer stem cells (CSCs), inducing death in both CSCs and differentiated cancer cells. Thus, the results substantiate our design strategy and demonstrate the potential of this approach for the development of new, therapeutically relevant compounds.