We identified MIG6 (gene symbol ERRFI1) as a phosphorylation target of mutant EGFRs in our mass spectrometry-based experiments. MIG6, also known as ERBB receptor feedback inhibitor 1 (ERRFI1) and receptor-associated late transducer (RALT), is a scaffolding adaptor protein whose expression is rapidly induced by a variety of growth factors (including EGF) and by hormones and other stressors. MIG6 negatively regulates EGFR, ERBB2, and several other receptor tyrosine kinases and their signaling pathways. We hypothesized that loss of MIG6 may cooperate with mutant EGFR to induce lung tumorigenesis. To test this hypothesis we crossed doxycycline inducible mutant EGFR transgenic mice with Mig6 null mice. Upon doxycycline induction of mutant EGFRs that are expressed in type II epithelial cells, lung tumorigenesis is indeed accelerated upon loss of Mig6 expression. We have completed the survival curve upon doxycycline induction of mutant EGFRs in wild type, heterozygous and knock-out mice. We convincingly show that tumorigenesis is accelerated in Mig6 null background suggesting that Mig6 is indeed a tumor suppressor in mutant EGFR-induced lung tumorigenesis. We have completed the evaluation of histology of mouse lung tumor in various genotypes in collaboration with Dr. Ilona Linnoila. We have also initiated a collaboration with Dr. Mark Simpson to quantify immunohistochemical staining of various targets in these tumors. We have performed biochemical experiments to elucidate the functional role of increased tyrosine phosphorylation at Y394 and Y395 of ERRFI1. We have also initiated a collaboration with Dr. Debbie Morrison in the NCI intramural program to understand the biochemical implication of Mig6 phosphorylation and interaction with EGFR. We have now convincingly showed that there is increased interaction of mutant EGFRs and Mig6. In addition Y394/395 are the predominant sites of phosphorylation in Mig6. Phosphorylation at these sites is increased in lung adenocarcinoma cells harboring mutant EGFRs. Most interestingly, Mig6 cannot promote recycling of mutant EGFRs contrary to its effects on WT EGFR. A manuscript is in preparation describing these findings.

National Institute of Health (NIH)
National Cancer Institute (NCI)
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National Cancer Institute Division of Basic Sciences
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