title: Oncogenic KRAS desensitizes colorectal tumor cells to epidermal growth factor receptor inhibition and activation.
abstract: Epidermal growth factor receptor (EGFR)-targeting therapeutics have shown efficacy in the treatment of colorectal cancer patients. Clinical studies have revealed that activating mutations in the KRAS protooncogene predict resistance to EGFR-targeted therapy. However, the causality between mutant KRAS and resistance to EGFR inhibition has so far not been demonstrated. Here, we show that deletion of the oncogenic KRAS allele from colorectal tumor cells resensitizes those cells to EGFR inhibitors. Resensitization was accompanied by an acquired dependency on the EGFR for maintaining basal extracellular signal-regulated kinase (ERK) activity. Deletion of oncogenic KRAS not only resensitized tumor cells to EGFR inhibition but also promoted EGF-induced NRAS activation, ERK and AKT phosphorylation, and c-FOS transcription. The poor responsiveness of mutant KRAS tumor cells to EGFR inhibition and activation was accompanied by a reduced capacity of these cells to bind and internalize EGF and by a failure to retain EGFR at the plasma membrane. Of 16 human colorectal tumors with activating mutations in KRAS, 15 displayed loss of basolateral EGFR localization. Plasma membrane localization of the EGFR could be restored in vitro by suppressing receptor endocytosis through Rho kinase inhibition. This caused an EGFR-dependent increase in basal and EGF-stimulated ERK phosphorylation but failed to restore tumor cell sensitivity to EGFR inhibition. Our results demonstrate a causal role for oncogenic KRAS in desensitizing tumor cells not only to EGFR inhibitors but also to EGF itself.
authors.affiliation: Department of Surgery, University Medical Center Utrecht, Heidelberglaan 100, Utrecht, The Netherlands.
authors.forename: Winan J
authors.initials: WJ
authors.lastname: van Houdt
authors.forename: Frederik J H
authors.initials: FJ
authors.lastname: Hoogwater
authors.forename: Menno T
authors.initials: MT
authors.lastname: de Bruijn
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Emmink
authors.forename: Maarten W
authors.initials: MW
authors.lastname: Nijkamp
authors.forename: Danielle A E
authors.initials: DA
authors.lastname: Raats
authors.forename: Petra
authors.initials: P
authors.lastname: van der Groep
authors.forename: Paul
authors.initials: P
authors.lastname: van Diest
authors.forename: Inne H M
authors.initials: IH
authors.lastname: Borel Rinkes
authors.forename: Onno
authors.initials: O
authors.lastname: Kranenburg
mesh_terms: D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D016762:Genes, fos / Q000235:genetics; D006801:Humans; D007124:Immunoenzyme Techniques; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras); D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D046888:Tissue Array Analysis; D014407:Tumor Cells, Cultured; D018631:ras Proteins / Q000502:physiology*
chemical_list: C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D004815:Epidermal Growth Factor; C512478:EGFR protein, human; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins