title: Mitogen-Inducible Gene-6 Mediates Feedback Inhibition from Mutated BRAF towards the Epidermal Growth Factor Receptor and Thereby Limits Malignant Transformation.
abstract: BRAF functions in the RAS-extracellular signal-regulated kinase (ERK) signaling cascade. Activation of this pathway is necessary to mediate the transforming potential of oncogenic BRAF, however, it may also cause a negative feedback that inhibits the epidermal growth factor receptor (EGFR). Mitogen-inducible gene-6 (MIG-6) is a potent inhibitor of the EGFR and has been demonstrated to function as a tumor suppressor. As MIG-6 can be induced via RAS-ERK signaling, we investigated its potential involvement in this negative regulatory loop. Focus formation assays were performed and demonstrated that MIG-6 significantly reduces malignant transformation induced by oncogenic BRAF. Although this genetic interaction was mirrored by a physical interaction between MIG-6 and BRAF, we did not observe a direct regulation of BRAF kinase activity by MIG-6. Interestingly, a selective chemical EGFR inhibitor suppressed transformation to a similar degree as MIG-6, whereas combining these approaches had no synergistic effect. By analyzing a range of BRAF mutated and wildtype cell line models, we could show that BRAF V600E causes a strong upregulation of MIG-6, which was mediated at the transcriptional level via the RAS-ERK pathway and resulted in downregulation of EGFR activation. This feedback loop is operational in tumors, as shown by the analysis of almost 400 patients with papillary thyroid cancer (PTC). Presence of BRAF V600E correlated with increased MIG-6 expression on the one hand, and with inactivation of the EGFR and of PI3K/AKT signaling on the other hand. Importantly, we also observed a more aggressive disease phenotype when BRAF V600E coexisted with low MIG-6 expression. Finally, analysis of methylation data was performed and revealed that higher methylation of MIG-6 correlated to its decreased expression. Taken together, we demonstrate that MIG-6 efficiently reduces cellular transformation driven by oncogenic BRAF by orchestrating a negative feedback circuit directed towards the EGFR.
authors.affiliation: Systems Biology Ireland, University College Dublin, Dublin, Ireland.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Milewska
authors.affiliation: Systems Biology Ireland, University College Dublin, Dublin, Ireland.
authors.forename: David
authors.initials: D
authors.lastname: Romano
authors.affiliation: Systems Biology Ireland, University College Dublin, Dublin, Ireland.
authors.forename: Ana
authors.initials: A
authors.lastname: Herrero
authors.affiliation: Systems Biology Ireland, University College Dublin, Dublin, Ireland.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Guerriero
authors.affiliation: Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.
authors.forename: Marc
authors.initials: M
authors.lastname: Birtwistle
authors.affiliation: Institute of Medical Informatics, Statistics and Documentation, Medical University of Graz, Graz, Austria.
authors.forename: Franz
authors.initials: F
authors.lastname: Quehenberger
authors.affiliation: Division of Hematology, Medical University of Graz, Graz, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Hatzl
authors.affiliation: Systems Biology Ireland, University College Dublin, Dublin, Ireland; Conway Institute of Biomolecular & Biomedical Research, University College Dublin, Dublin, Ireland; School of Medicine and Medical Science, University College Dublin, Dublin, Ireland.
authors.forename: Boris N
authors.initials: BN
authors.lastname: Kholodenko
authors.affiliation: Laboratory of Immunology, Regina Elena Cancer Institute, Rome, Italy.
authors.forename: Oreste
authors.initials: O
authors.lastname: Segatto
authors.affiliation: Systems Biology Ireland, University College Dublin, Dublin, Ireland; Conway Institute of Biomolecular & Biomedical Research, University College Dublin, Dublin, Ireland; School of Medicine and Medical Science, University College Dublin, Dublin, Ireland.
authors.forename: Walter
authors.initials: W
authors.lastname: Kolch
authors.affiliation: Division of Hematology, Medical University of Graz, Graz, Austria.
authors.forename: Armin
authors.initials: A
authors.lastname: Zebisch
mesh_terms: D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000328:Adult; D000818:Animals; D019556:COS Cells; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D025461:Feedback, Physiological; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008875:Middle Aged; D020125:Mutation, Missense; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics / Q000378:metabolism*; D013964:Thyroid Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C484017:ERRFI1 protein, human; D025521:Tumor Suppressor Proteins; D066246:ErbB Receptors; D048493:Proto-Oncogene Proteins B-raf