Acquisition of aneuploidy drives mutant p53-associated gain-of-function phenotypes

Lindsay N Redman-Rivera,Rachel A Hongo,Jennifer A Pietenpol,Brian D Lehmann,Clayton B Marshall,Quanhu Sheng,Ferrin C Wheeler,Hailing Jin,Johanna M Schafer,Timothy M Shaver,Kathryn E Beckermann

doi:10.1038/s41467-021-25359-z

Abstract

p53 is mutated in over half of human cancers. In addition to losing wild-type (WT) tumor-suppressive function, mutant p53 proteins are proposed to acquire gain-of-function (GOF) activity, leading to novel oncogenic phenotypes. To study mutant p53 GOF mechanisms and phenotypes, we genetically engineered non-transformed and tumor-derived WT p53 cell line models to express endogenous missense mutant p53 (R175H and R273H) or to be deficient for p53 protein (null). Characterization of the models, which initially differed only by TP53 genotype, revealed that aneuploidy frequently occurred in mutant p53-expressing cells. GOF phenotypes occurred clonally in vitro and in vivo, were independent of p53 alteration and correlated with increased aneuploidy. Further, analysis of outcome data revealed that individuals with aneuploid-high tumors displayed unfavorable prognoses, regardless of the TP53 genotype. Our results indicate that genetic variation resulting from aneuploidy accounts for the diversity of previously reported mutant p53 GOF phenotypes.

Highlights

P53 is mutated in over half of human cancers
To select cell lines that would provide controlled model systems for the study of p53 mutation, we evaluated p53 status and the fraction of the genome altered (FGA) across cancer cell lines (Cancer Cell Line Encyclopedia, n = 957)
We selected two TP53 WT lines derived from breast epithelium that are near-diploid and have a low FGA (MCF10A = 13%, CAL-51 = 3%) compared to pan- or breast cancer cell lines (Fig. 1a and Supplementary Fig. 2a)

Summary

Introduction

P53 is mutated in over half of human cancers. In addition to losing wild-type (WT) tumorsuppressive function, mutant p53 proteins are proposed to acquire gain-of-function (GOF) activity, leading to novel oncogenic phenotypes. To study mutant p53 GOF mechanisms and phenotypes, we genetically engineered non-transformed and tumor-derived WT p53 cell line models to express endogenous missense mutant p53 (R175H and R273H) or to be deficient for p53 protein (null). The study of mutant p53 GOF activities is made even more challenging because mutations in p53 are positively correlated with the development of aneuploidy[20,21,22], which can increase heterogeneity through diverse chromosomal alterations and contribute to tumorigenesis[23,24,25,26]. Mutant p53-containing cell lines did not have increased tumorigenicity or metastasis in vivo, and analysis of human tumors revealed that loss of p53 function and increased aneuploidy were associated with unfavorable prognoses. Our results reveal aneuploidy as a mechanism contributing to the diversity of reported mutant p53 GOF phenotypes

Methods

Results

Conclusion