Hypoxia Alters the Response to Anti-EGFR Therapy by Regulating EGFR Expression and Downstream Signaling in a DNA Methylation-Specific and HIF-Dependent Manner

Cancer Res. 2020 Nov 15;80(22):4998-5010. doi: 10.1158/0008-5472.CAN-20-1232. Epub 2020 Oct 6.


Intratumoral hypoxia occurs in 90% of solid tumors and is associated with a poor prognosis for patients. Cancer cells respond to hypoxic microenvironments by activating the transcription factors, hypoxia-inducible factor 1 (HIF1) and HIF2. Here, we studied the unique gene expression patterns of 31 different breast cancer cell lines exposed to hypoxic conditions. The EGFR, a member of the ErbB (avian erythroblastosis oncogene B) family of receptors that play a role in cell proliferation, invasion, metastasis, and apoptosis, was induced in seven of the 31 breast cancer cell lines by hypoxia. A functional hypoxia response element (HRE) was identified, which is activated upon HIF1 binding to intron 18 of the EGFR gene in cell lines in which EGFR was induced by hypoxia. CpG methylation of the EGFR HRE prevented induction under hypoxic conditions. The HRE of EGFR was methylated in normal breast tissue and some breast cancer cell lines, and could be reversed by treatment with DNA methyltransferase inhibitors. Induction of EGFR under hypoxia led to an increase in AKT, ERK, and Rb phosphorylation as well as increased levels of cyclin D1, A, B1, and E2F, and repression of p21 in an HIF1α-dependent manner, leading to cell proliferation and migration. Also, increased EGFR expression sensitized cells to EGFR inhibitors. Collectively, our data suggest that patients with hypoxic breast tumors and hypomethylated EGFR status may benefit from EGFR inhibitors currently used in the clinic. SIGNIFICANCE: Hypoxia sensitizes breast cancer cells to EGFR inhibitors in an HIF1α- and a methylation-specific manner, suggesting patients with hypoxic tumors may benefit from EGFR inhibitors already available in the clinic. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/22/4998/F1.large.jpg.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agammaglobulinaemia Tyrosine Kinase / metabolism
  • Animals
  • Antineoplastic Agents / pharmacology*
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Breast Neoplasms / drug therapy
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism*
  • Cell Line, Tumor
  • Cell Movement
  • Cell Proliferation
  • CpG Islands
  • Cyclin D1 / metabolism
  • Cyclin-Dependent Kinase Inhibitor p21 / metabolism
  • Cytosine / metabolism
  • DNA Methylation*
  • ErbB Receptors / antagonists & inhibitors
  • ErbB Receptors / genetics
  • Female
  • Genes, erbB-1
  • HSP70 Heat-Shock Proteins / metabolism
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / genetics
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism*
  • MAP Kinase Signaling System
  • Methyltransferases / antagonists & inhibitors
  • Mice
  • Phosphorylation
  • Retinoblastoma Protein / metabolism
  • Signal Transduction / physiology
  • Tumor Hypoxia / physiology*


  • Antineoplastic Agents
  • Basic Helix-Loop-Helix Transcription Factors
  • CDKN1A protein, human
  • Cyclin-Dependent Kinase Inhibitor p21
  • HSP70 Heat-Shock Proteins
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Retinoblastoma Protein
  • oxygen-regulated proteins
  • Cyclin D1
  • endothelial PAS domain-containing protein 1
  • Cytosine
  • Methyltransferases
  • EGFR protein, human
  • ErbB Receptors
  • Agammaglobulinaemia Tyrosine Kinase
  • BTK protein, human