Addiction of lung cancer cells to GOF p53 is promoted by up-regulation of epidermal growth factor receptor through multiple contacts with p53 transactivation domain and promoter

Catherine A Vaughan,Sumitra Deb,Swati P Deb,Shilpa Singh,Brad Windle,Isabella Pearsall,W Andrew Yeudall,Steven R Grossman

doi:10.18632/oncotarget.6998

Catherine A Vaughan, Sumitra Deb + Show 6 more

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https://doi.org/10.18632/oncotarget.6998

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Abstract

Human lung cancers harboring gain-of-function (GOF) p53 alleles express higher levels of the epidermal growth factor receptor (EGFR). We demonstrate that a number of GOF p53 alleles directly upregulate EGFR. Knock-down of p53 in lung cancer cells lowers EGFR expression and reduces tumorigenicity and other GOF p53 properties. However, addiction of lung cancer cells to GOF p53 can be compensated by overexpressing EGFR, suggesting that EGFR plays a critical role in addiction. Chromatin immunoprecipitation (ChIP) using lung cancer cells expressing GOF p53 alleles showed that GOF p53 localized to the EGFR promoter. The sequence where GOF p53 is found to interact by ChIP seq can act as a GOF p53 response element. The presence of GOF p53 on the EGFR promoter increased histone H3 acetylation, indicating a mechanism whereby GOF p53 enhances chromatin opening for improved access to transcription factors (TFs). ChIP and ChIP-re-ChIP with p53, Sp1 and CBP histone acetylase (HAT) antibodies revealed docking of GOF p53 on Sp1, leading to increased binding of Sp1 and CBP to the EGFR promoter. Up-regulation of EGFR can occur via GOF p53 contact at other novel sites in the EGFR promoter even when TAD-I is inactivated; these sites are used by both intact and TAD-I mutated GOF p53 and might reflect redundancy in GOF p53 mechanisms for EGFR transactivation. Thus, the oncogenic action of GOF p53 in lung cancer is highly dependent on transactivation of the EGFR promoter via a novel transcriptional mechanism involving coordinated interactions of TFs, HATs and GOF p53.

Highlights

Wild-type (WT) p53 acts as a tumor suppressor protein, yet single amino acid substitutions prevalent in many cancers, including lung cancer, abrogate the tumor suppressor function and endow it with dominant proliferative and oncogenic properties. p53 is found to be mutated at a high frequency [1, 2]
Once we found that GOF p53 binds to the epidermal growth factor receptor (EGFR) promoter region, coupled with our knowledge that GOF p53 transactivates the EGFR promoter [17, 18], we tested whether H1299 cells expressing p53-R175H and -R273H show higher levels of EGFR mRNA compared to vector transfected cells
Our data show that lung cancer cells with endogenous GOF p53 are addicted to GOF p53 (Figure 4A), and one pathway used in the addiction is the EGFR pathway as the defect can be rectified by overexpressing EGFR in H1975 cells (Figure 4D, 4G)

Summary

Introduction

P53 is found to be mutated at a high frequency In small cell lung carcinoma) [1, 2]. GOF p53, in general, is expressed at a relatively high level in cancer cells, while WT p53 is found only in low amounts in unstressed normal cells. Clinical and laboratory studies suggest that lung cancers with p53 mutations carry a worse prognosis and are more resistant to chemotherapeutic drugs and radiation [3, 4]. The molecular mechanism behind GOF revolves around two mutually non-exclusive concepts. One involves transcriptional modulation of target genes by tumor-derived GOF p53. The other concept implicates protein-protein interactions between GOF p53 and other cellular protein(s) such as the p53 family members, p63 and p73 [13], or interference with AMPK [14]

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