Acquired Resistance of EGFR-Mutant Lung Adenocarcinomas to Afatinib plus Cetuximab Is Associated with Activation of mTORC1

•mTORC1 activation in EGFR-mutant tumors with resistance to afatinib plus cetuximab•Afatinib plus cetuximab-resistant tumors have genomic alterations in NF2 and TSC1•NF2 loss and TSC1 loss lead to mTORC1 activation•mTOR inhibition resensitizes resistant tumors to afatinib plus cetuximab therapy

SummaryPatients with EGFR-mutant lung adenocarcinomas (LUADs) who initially respond to first-generation tyrosine kinase inhibitors (TKIs) develop resistance to these drugs. A combination of the irreversible TKI afatinib and the EGFR antibody cetuximab can be used to overcome resistance to first-generation TKIs; however, resistance to this drug combination eventually emerges. We identified activation of the mTORC1 signaling pathway as a mechanism of resistance to dual inhibition of EGFR in mouse models. The addition of rapamycin reversed resistance in vivo. Analysis of afatinib-plus-cetuximab-resistant biopsy specimens revealed the presence of genomic alterations in genes that modulate mTORC1 signaling, including NF2 and TSC1. These findings pinpoint enhanced mTORC1 activation as a mechanism of resistance to afatinib plus cetuximab and identify genomic mechanisms that lead to activation of this pathway, revealing a potential therapeutic strategy for treating patients with resistance to these drugs.

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