Differences in Antioxidant and Lipid Handling Protein Expression Influence How Cells Expressing Distinct Mutant TP53 Subtypes Maintain Iron Homeostasis

Abstract

The tumor suppressor TP53 is the most commonly mutated gene in human cancers, and iron is necessary for cancer cell growth and proliferation, but there is a significant gap in knowledge for how the two cooperate to affect cellular physiology. Elucidating this role is complicated, however, because each TP53 mutation subtype exhibits unique phenotypic responses to changes in iron availability. The goal of this work was to determine how cells expressing distinct TP53 mutation subtypes respond to iron restriction. Utilizing a reverse genetics approach, we generated eight isogenic cell lines that either lacked TP53 expression, expressed wild-type TP53, or expressed one of the six most common TP53 “hotspot” mutations. We then employed isobaric peptide labeling and mass spectrometry to quantitively measure changes in global protein expression, both in response to induction of mutant TP53 expression, and in response to iron chelation. Our findings indicate that mutant TP53-dependent sensitivities to iron restriction are not driven by differences in responsiveness to iron chelation, but more so by mutant TP53-dependent differences in cellular antioxidant and lipid handling protein expression. These findings reinforce the importance of distinguishing between TP53 mutation subtypes when investigating approaches to target mutant TP53. We also identify unique TP53-dependent perturbances in protein expression patterns that could be exploited to improve iron-targeted chemotherapeutic strategies.

Iron regulatory proteins: players or pawns in ferroptosis and cancer?

“…The context-dependent differences in IRP involvement are likely multifaceted. Factors such as mode of ferroptosis induction ( Gryzik et al, 2021 ), metabolic state of the cell ( Novera et al, 2020 ), and differences in endogenous antioxidant capacities ( Cardona et al, 2022 ) that influence the ability to handle a given amount of labile iron could all contribute to IRP responsiveness. Regardless, increased IRP-IRE binding activity ( Chen et al, 2020 ), and even the increased expression of either IRP1 ( Yao et al, 2021 ; Zhang et al, 2022 ) or IRP2 ( Li et al, 2020 ) alone have been shown to augment ferroptosis sensitivity ( Figure 2 ).…”