title: Oncogenic KRAS impairs EGFR antibodies' efficiency by C/EBPβ-dependent suppression of EGFR expression.
abstract: Oncogenic KRAS mutations in colorectal cancer (CRC) are associated with lack of benefit from epidermal growth factor receptor (EGFR)-directed antibody (Ab) therapy. However, the mechanisms by which constitutively activated KRAS (KRAS(G12V)) impairs effector mechanisms of EGFR-Abs are incompletely understood. Here, we established isogenic cell line models to systematically investigate the impact of KRAS(G12V) on tumor growth in mouse A431 xenograft models as well as on various modes of action triggered by EGFR-Abs in vitro. KRAS(G12V) impaired EGFR-Ab-mediated growth inhibition by stimulating receptor-independent downstream signaling. KRAS(G12V) also rendered tumor cells less responsive to Fc-mediated effector mechanisms of EGFR-Abs-such as complement-dependent cytotoxicity (CDC) and Ab-dependent cell-mediated cytotoxicity (ADCC). Impaired CDC and ADCC activities could be linked to reduced EGFR expression in KRAS-mutated versus wild-type (wt) cells, which was restored by small interfering RNA (siRNA)-mediated knockdown of KRAS4b. Immunohistochemistry experiments also revealed lower EGFR expression in KRAS-mutated versus KRAS-wt harboring CRC samples. Analyses of potential mechanisms by which KRAS(G12V) downregulated EGFR expression demonstrated significantly decreased activity of six distinct transcription factors. Additional experiments suggested the CCAAT/enhancer-binding protein (C/EBP) family to be implicated in the regulation of EGFR promoter activity in KRAS-mutated tumor cells by suppressing EGFR transcription through up-regulation of the inhibitory family member C/EBPβ-LIP. Thus, siRNA-mediated knockdown of C/EBPβ led to enhanced EGFR expression and Ab-mediated cytotoxicity against KRAS-mutated cells. Together, these results demonstrate that KRAS(G12V) signaling induced C/EBPβ-dependent suppression of EGFR expression, thereby impairing Fc-mediated effector mechanisms of EGFR-Abs and rendering KRAS-mutated tumor cells less sensitive to these therapeutic agents.
authors.affiliation: Division of Stem Cell Transplantation and Immunotherapy, 2nd Department of Medicine, Christian-Albrechts-University, Kiel, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Derer
authors.forename: Sven
authors.initials: S
authors.lastname: Berger
authors.forename: Martin
authors.initials: M
authors.lastname: Schlaeth
authors.forename: Tanja
authors.initials: T
authors.lastname: Schneider-Merck
authors.forename: Katja
authors.initials: K
authors.lastname: Klausz
authors.forename: Stefan
authors.initials: S
authors.lastname: Lohse
authors.forename: Marije B
authors.initials: MB
authors.lastname: Overdijk
authors.forename: Michael
authors.initials: M
authors.lastname: Dechant
authors.forename: Christian
authors.initials: C
authors.lastname: Kellner
authors.forename: Iris
authors.initials: I
authors.lastname: Nagelmeier
authors.forename: Andreas H
authors.initials: AH
authors.lastname: Scheel
authors.forename: Jeroen J
authors.initials: JJ
authors.lastname: Lammerts van Bueren
authors.forename: Jan G J
authors.initials: JG
authors.lastname: van de Winkel
authors.forename: Paul W H I
authors.initials: PW
authors.lastname: Parren
authors.forename: Matthias
authors.initials: M
authors.lastname: Peipp
authors.forename: Thomas
authors.initials: T
authors.lastname: Valerius
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D061067:Antibodies, Monoclonal, Humanized; D000920:Antibody-Dependent Cell Cytotoxicity / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology; D001483:Base Sequence; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D000068818:Cetuximab; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008297:Male; D051379:Mice; D008875:Middle Aged; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D015398:Signal Transduction / Q000187:drug effects; D014158:Transcription, Genetic; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D022782:CCAAT-Enhancer-Binding Protein-beta; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins; D000068818:Cetuximab