The Cancer Stem Cell Potency of Group 10-Azadiphosphine Metal Complexes

The cancer stem cell (CSC) potency of a series of structurally analogous Group 10-azadiphosphine metal complexes is reported. The complexes comprise a Group 10 metal (Ni for 1, Pd for 2, or Pt for 3), an azadiphosphine ligand, and two chloride ligands. The complexes exhibit micromolar potency towards bulk breast cancer cells and breast CSCs cultured in monolayer systems. The cytotoxicity of the complexes is comparable to or better than clinically used metallopharmaceuticals, cisplatin and carboplatin, and the gold-standard anti-breast CSC agent, salinomycin. Notably, the breast CSC mammosphere inhibitory effect and potency of the complexes is dependent on the Group 10 metal present, increasing in the following order: 3<2<1. This study highlights the importance of the metal within a given series of structurally related compounds to their breast CSC mammosphere activity and reinforces the therapeutic potential of Group 10 coordination complexes as anti-CSC agents.