Multifunctional ligand design for modulating protein stability and aggregation for cancer treatment

Referred to as the “guardian of the genome”, p53 is the most frequently mutated protein in cancer and accounts for over 50% of cancer diagnoses. p53 regulates the cellular network by signaling for the activation of various pathways including apoptosis and cell cycle arrest to avoid propagation of damaged cells. Consequently, in 50% of cancer diagnoses, single point mutations render the protein inactive, prohibiting its antiproliferative response and allowing for accumulation of damaged cells. The majority of mutations are localized to the DNA-binding domain, a domain that contains a Zn2+ ion that is essential for proper protein folding and function. These mutations typically affect the proteins’ tertiary structure, resulting in a loss or alteration of Zn-binding which can lead to unfolding and enhanced aggregation. As an overexpressed and tumour-specific target, the past two decades have seen considerable dedication to the development of small molecules that aim to restore wild-type function in mutant p53. Previous efforts have been monofunctional in design, targeting specific characteristics of a given p53 mutant including thermal denaturation, aggregation, or loss of zinc. This thesis explores small molecule design strategies to restore wild-type function in mutant p53. Considering the multifaceted nature of p53 mutants, a multifunctional approach was employed to simultaneously target various characteristics. Chapter 2 features a bifunctional scaffold targeting zinc loss and thermal denaturation. The utility of this scaffold in increasing intracellular zinc and restoring transcriptional function in mutant p53-Y220C is described. Modifications to the ligand scaffold to extend the structures into subsite cavities of this mutant are explored in Chapter 3. These modifications increased the cytotoxicity of the ligands and restored apoptotic activity, however, resulted in a loss in their ability to serve as zinc metallochaperones. Lastly, a combination of fragments targeting zinc loss and protein aggregation found success in restoring wild-type function in mutant p53 in Chapter 4. These studies highlighted the possible advantages of halogenation in modulating mutant p53 aggregation, as an iodinated scaffold limited mutant p53 aggregation and restored wild-type function. This work represents a foundation to simultaneously target the multiple characteristics of p53 mutants and provides important information for drug design moving forward.