LH-A

The p53 protein plays an important role in preventing cancer and is critical in inducing an antiproliferative response. Unfortunately, the p53 pathway is compromised in almost all cancers, and mutations to p53 lead to loss of function due to protein unfolding, compromised Zn²⁺ binding, aggregation and amyloid formation. Herein, two new multidentate N,O donor ligands L^I-A and L^H-A were tested to potentially restore Zn²⁺ binding to mutant p53, while also inhibiting protein aggregation. The design of these ligands centered on combining an iminodiacetate (IDA) metal binding moiety which was previously determined to exhibit favourable Zn²⁺ binding affinity and Cu²⁺/Zn²⁺ selectivity ratio, with a benzothiazole unit that has been demonstrated to limit mutant p53 protein aggregation. The new ligands were shown to exhibit Zn²⁺ K_d values in the low nM range based on a fluorophore competition assay, while also inhibiting mutant p53 aggregation via a Thioflavin-T (ThT) assay. In cell-based assays and NCI-60 screening, neither of the new ligands displayed significant cytotoxicity. A reactive oxygen species (ROS) assay showed that neither of the new ligands increased intracellular ROS, however, the previously studied L^I compound did show an increase in ROS, providing further information on the mechanism of action of this class of compounds. The current results highlight that the dipicolylamine (DPA) unit is important for anticancer activity, and that phenolate substitution has an important role in dictating the mechanism of cytotoxicity.