Formation of the eIF4F Translation–Initiation Complex Determines Sensitivity to Anticancer Drugs Targeting the EGFR and HER2 Receptors

Elucidating how cancer cells respond to antagonists of HER receptor family members is critical to understand mechanisms of therapeutic resistance that arise in patients. In large part, resistance to such agents appears to arise from deregulation of the PI3K/Akt/mTOR pathway. mTOR-dependent phosphorylation of the translation repressor 4E-BP1 leads to its dissociation from eIF4E, thereby causing an increase in the formation of the eIF4F complex also comprising eIF4G and eIF4A. In this study we show that trastuzumab, cetuximab and erlotinib all decrease the formation of the eIF4F complex in breast, colon and head and neck cancer cells, respectively. Ectopic expression of eIF4E restores the trastuzumab-dependent defect in eIF4F formation, renders cells resistant to the trastuzumab-mediated decrease in cell proliferation and rescues breast cancer xenografts from inhibition by trastuzumab. In breast tumor specimens, the level of eIF4E expression is associated with the therapeutic response to trastuzumab based regimen. Together, our findings suggest that formation of the eIF4F complex may be a critical determinant of the response to anti-cancer drugs which target HER2 and EGFR.