title: High early growth response 1 (EGR1) expression correlates with resistance to anti-EGFR treatment in vitro and with poorer outcome in metastatic colorectal cancer patients treated with cetuximab.
abstract: OBJECTIVE
  Biomarkers, such as mutant RAS, predict resistance to anti-EGFR therapy in only a proportion of patients, and hence, other predictive biomarkers are needed. The aims were to identify candidate genes upregulated in colorectal cancer cell lines resistant to anti-EGFR monoclonal antibody treatment, to knockdown (KD) these genes in the resistant cell lines to determine if sensitivity to anti-EGFR antibody was restored, and finally to perform a pilot correlative study of EGR1 expression and outcomes in a cohort of metastatic colorectal cancer (mCRC) patients given cetuximab therapy.
  
  
  METHODS
  Comparative expression array analysis of resistant cell lines (SW48, COLO-320DM, and SNU-C1) vs sensitive cell lines (LIM1215, CaCo2, and SW948) was performed. The highest up-regulated gene in each resistant cell line was knocked down (KD) using RNA interference, and effect on proliferation was assessed with and without anti-EGFR treatment. Expression of the candidate genes in patients' tumours treated with cetuximab was assessed by immunohistochemistry; survival analyses were performed comparing high vs low expression.
  
  
  RESULTS
  Genes significantly upregulated in resistant cell lines were EGR1 (early growth response protein 1), HBEGF (heparin-binding epidermal growth factor-like growth factor), and AKT3 (AKT serine/threonine kinase 3). KD of each gene resulted in the respective cells being more sensitive to anti-EGFR treatment, suggesting that the resistant phenotype was reversed. In the pilot study of mCRC patients treated with cetuximab, both median PFS (1.38 months vs 6.79 months; HR 2.77 95% CI 1.2-19.4) and median OS (2.59 months vs 9.82 months; HR 3.0 95% CI 1.3-23.2) were significantly worse for those patients with high EGR1 expression.
  
  
  CONCLUSIONS
  High EGR1 expression may be a candidate biomarker of resistance to anti-EGFR therapy.
authors.affiliation: Basil Hetzel Institute, The Queen Elizabeth Hospital, 28 Woodville Road, Woodville, SA, 5011, Australia.|School of Medicine, University of Adelaide, Adelaide, SA, 5005, Australia.
authors.forename: S S
authors.initials: SS
authors.lastname: Kumar
authors.affiliation: School of Medicine, University of Adelaide, Adelaide, SA, 5005, Australia.|Basil Hetzel Institute and Department of Medical Oncology, The Queen Elizabeth Hospital, 28 Woodville Road, Woodville, SA, 5011, Australia.
authors.forename: Y
authors.initials: Y
authors.lastname: Tomita
authors.affiliation: Basil Hetzel Institute, The Queen Elizabeth Hospital, 28 Woodville Road, Woodville, SA, 5011, Australia.|School of Medicine, University of Adelaide, Adelaide, SA, 5005, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Wrin
authors.affiliation: Basil Hetzel Institute, The Queen Elizabeth Hospital, 28 Woodville Road, Woodville, SA, 5011, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Bruhn
authors.affiliation: Department of Anatomical Pathology, SA Pathology, The Queen Elizabeth Hospital, 28 Woodville Road, Woodville, SA, 5011, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Swalling
authors.affiliation: Department of Anatomical Pathology, SA Pathology, The Queen Elizabeth Hospital, 28 Woodville Road, Woodville, SA, 5011, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Mohammed
authors.affiliation: School of Medicine, University of Adelaide, Adelaide, SA, 5005, Australia.|Department of Medical Oncology, The Queen Elizabeth Hospital, 28 Woodville Road, Woodville, SA, 5011, Australia.
authors.forename: T J
authors.initials: TJ
authors.lastname: Price
authors.affiliation: Basil Hetzel Institute, The Queen Elizabeth Hospital, 28 Woodville Road, Woodville, SA, 5011, Australia. Jennifer.hardingham@adelaide.edu.au.|School of Medicine, University of Adelaide, Adelaide, SA, 5005, Australia. Jennifer.hardingham@adelaide.edu.au.
authors.forename: J E
authors.identifier: http://orcid.org/0000-0001-8277-1199
authors.initials: JE
authors.lastname: Hardingham
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000032:analysis; D000068818:Cetuximab / Q000627:therapeutic use*; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000401:mortality; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D051766:Early Growth Response Protein 1 / Q000096:biosynthesis*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors; D006801:Humans; D053208:Kaplan-Meier Estimate; D010865:Pilot Projects
chemical_list: D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; C512478:EGFR protein, human; D066246:ErbB Receptors; D000068818:Cetuximab
keywords: Anti-EGFR therapy; Colorectal cancer; EGR1; Predictive biomarker; Resistance