Upregulation of IRS1 Enhances IGF1 Response in Y537S and D538G ESR1 Mutant Breast Cancer Cells

Endocrinology. 2018 Jan 1;159(1):285-296. doi: 10.1210/en.2017-00693.

Abstract

Increased evidence suggests that somatic mutations in the ligand-binding domain of estrogen receptor [ER (ERα/ESR1)] are critical mediators of endocrine-resistant breast cancer progression. Insulinlike growth factor-1 (IGF1) is an essential regulator of breast development and tumorigenesis and also has a role in endocrine resistance. A recent study showed enhanced crosstalk between IGF1 and ERα in ESR1 mutant cells, but detailed mechanisms are incompletely understood. Using genome-edited MCF-7 and T47D cell lines harboring Y537S and D538G ESR1 mutations, we characterized altered IGF1 signaling. RNA sequencing revealed upregulation of multiple genes in the IGF1 pathway, including insulin receptor substrate-1 (IRS1), consistent in both Y537S and D538G ESR1 mutant cell line models. Higher IRS1 expression was confirmed by quantitative reverse transcription polymerase chain reaction and immunoblotting. ESR1 mutant cells also showed increased levels of IGF-regulated genes, reflected by activation of an IGF signature. IGF1 showed increased sensitivity and potency in growth stimulation of ESR1 mutant cells. Analysis of downstream signaling revealed the phosphoinositide 3-kinase (PI3K)-Akt axis as a major pathway mediating the enhanced IGF1 response in ESR1 mutant cells. Decreasing IRS1 expression by small interfering RNA diminished the increased sensitivity to IGF1. Combination treatment with inhibitors against IGF1 receptor (IGF1R; OSI-906) and ER (fulvestrant) showed synergistic growth inhibition in ESR1 mutant cells, particularly at lower effective concentrations. Our study supports a critical role of enhanced IGF1 signaling in ESR1 mutant cell lines, pointing toward a potential for cotargeting IGF1R and ERα in endocrine-resistant breast tumors with mutant ESR1.

Publication types

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

MeSH terms

  • Amino Acid Substitution
  • Antineoplastic Agents / chemistry
  • Antineoplastic Agents / pharmacology
  • Breast Neoplasms / drug therapy
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism*
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Drug Synergism
  • Estrogen Receptor Antagonists / pharmacology
  • Estrogen Receptor alpha / antagonists & inhibitors
  • Estrogen Receptor alpha / genetics
  • Estrogen Receptor alpha / metabolism*
  • Female
  • Gene Expression Regulation, Neoplastic* / drug effects
  • Humans
  • Insulin Receptor Substrate Proteins / antagonists & inhibitors
  • Insulin Receptor Substrate Proteins / genetics
  • Insulin Receptor Substrate Proteins / metabolism*
  • Insulin-Like Growth Factor I / agonists
  • Insulin-Like Growth Factor I / genetics
  • Insulin-Like Growth Factor I / metabolism*
  • Mutation
  • Neoplasm Proteins / agonists
  • Neoplasm Proteins / antagonists & inhibitors
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism
  • Phosphatidylinositol 3-Kinase / metabolism
  • Protein Kinase Inhibitors / pharmacology
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA Interference
  • Receptors, Somatomedin / agonists*
  • Receptors, Somatomedin / antagonists & inhibitors
  • Receptors, Somatomedin / genetics
  • Receptors, Somatomedin / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Signal Transduction* / drug effects

Substances

  • Antineoplastic Agents
  • Estrogen Receptor Antagonists
  • Estrogen Receptor alpha
  • IGF1 protein, human
  • IGF1R protein, human
  • IRS1 protein, human
  • Insulin Receptor Substrate Proteins
  • Neoplasm Proteins
  • Protein Kinase Inhibitors
  • Receptors, Somatomedin
  • Recombinant Proteins
  • estrogen receptor alpha, human
  • Insulin-Like Growth Factor I
  • Phosphatidylinositol 3-Kinase
  • AKT1 protein, human
  • Proto-Oncogene Proteins c-akt