Altering relative metal-binding affinities in multifunctional Metallochaperones for mutant p53 reactivation

Abstract

The p53 protein plays a major role in cancer prevention, and over 50% of cancer diagnoses can be attributed to p53 malfunction. p53 incorporates a structural Zn site that is required for proper protein folding and function, and in many cases point mutations can result in loss of the Zn²⁺ ion, destabilization of the tertiary structure, and eventual amyloid aggregation. Herein, we report a series of compounds designed to act as small molecule stabilizers of mutant p53, and feature Zn-binding fragments to chaperone Zn²⁺ to the metal depleted site and restore wild-type (WT) function. Many Zn metallochaperones (ZMCs) have been shown to generate intracellular reactive oxygen species (ROS), likely by chelating redox-active metals such as Fe^2+/3+ and Cu^+/2+ and undergoing associated Fenton chemistry. High levels of ROS can result in off-target effects and general toxicity, and thus, careful tuning of ligand Zn²⁺ affinity, in comparison to the affinity for other endogenous metals, is important for selective mutant p53 targeting. In this work we show that by using carboxylate donors in place of pyridine we can change the relative Zn²⁺/Cu²⁺ binding ability in a series of ligands, and we investigate the impact of donor group changes on metallochaperone activity and overall cytotoxicity in two mutant p53 cancer cell lines (NUGC3 and SKGT2).

Keywords: Cytotoxicity; Ligand design; Metallochaperones; ROS; p53 protein.