Regulation of Epidermal Growth Factor Receptor Signaling and Erlotinib Sensitivity in Head and Neck Cancer Cells by miR-7

Elevated expression and activity of the epidermal growth factor receptor (EGFR)/protein kinase B (Akt) signaling pathway isassociated with development, progression and treatment resistance of head and neck cancer (HNC). Several studies havedemonstrated that microRNA-7 (miR-7) regulates EGFR expression and Akt activity in a range of cancer cell types via itsspecific interaction with the EGFR mRNA 39-untranslated region (39-UTR). In the present study, we found that miR-7regulated EGFR expression and Akt activity in HNC cell lines, and that this was associated with reduced growth in vitro andin vivo of cells (HN5) that were sensitive to the EGFR tyrosine kinase inhibitor (TKI) erlotinib (Tarceva). miR-7 actedsynergistically with erlotinib to inhibit growth of erlotinib-resistant FaDu cells, an effect associated with increased inhibitionof Akt activity. Microarray analysis of HN5 and FaDu cell lines transfected with miR-7 identified a common set ofdownregulated miR-7 target genes, providing insight into the tumor suppressor function of miR-7. Furthermore, weidentified several target miR-7 mRNAs with a putative role in the sensitization of FaDu cells to erlotinib. Together, these datasupport the coordinate regulation of Akt signaling by miR-7 in HNC cells and suggest the therapeutic potential of miR-7alone or in combination with EGFR TKIs in this disease.