Disruption of Ribosome Biogenesis and Induction of Nucleolar Stress by Platinum(II)-based Chemotherapeutics

Abstract

Platinum(II) metal complexes—cisplatin, carboplatin, and oxaliplatin—represent a major class of antineoplastics agents used in a majority of cancer treatment regimens throughout the world. Despite their ubiquitous use, the precise mechanisms and targets responsible for cancer cell death are not fully understood. Overcoming these deficiencies will be necessary to address the limitation associated with current Pt-based chemotherapeutics in the clinical setting. Current literature has revealed, unlike cisplatin and carboplatin, oxaliplatin primarily kills cells through disruption of ribosome biogenesis. Ribosome biogenesis is intimately connected to the nucleolus, a phase-separated nuclear condensate, which also functions as a central hub for sensing and coordinating cellular stress response through nucleolar stress response.This work provides insight on the relationship between Pt(II) compounds and disruptions in ribosome biogenesis, and the impact on nucleolar structure. Chapter I summarizes the significance and current understanding of Pt-based chemotherapeutics in the context of ribosome biogenesis and the nucleolus. Chapter II identifies structural and chemical properties of Pt(II) compounds necessary for nucleolar stress induction through a novel immunofluorescence imaging approach for quantifying nucleolar stress. Chapter III applies this framework to a subset of monofunctional Pt(II) compounds which are also shown to induce nucleolar stress. Chapter IV examines spatiotemporal differences in nucleolar stress induced by Pt(II) compounds identified in previous studies—ruling out connections with intracellular accumulation and DNA binding. Chapter V discusses current progress on elucidating the molecular mechanisms for inhibition of rRNA synthesis by oxaliplatin by adapting a ChIP-based sequencing techniques to map the occupancy of RNA Polymerase I machinery along rDNA. Chapter VI provides a comprehensive review on the coordination metal ions with nucleic acids, highlighting recent examples of NMR and x-ray crystallography structures from the literature. This dissertation includes published and unpublished co-authored material