title: Axl mediates acquired resistance of head and neck cancer cells to the epidermal growth factor receptor inhibitor erlotinib.
abstract: Elevated expression and activity of the epidermal growth factor receptor (EGFR) is associated with development and progression of head and neck cancer (HNC) and a poor prognosis. Clinical trials with EGFR tyrosine kinase inhibitors (e.g., erlotinib) have been disappointing in HNC. To investigate the mechanisms mediating resistance to these agents, we developed an HNC cell line (HN5-ER) with acquired erlotinib resistance. In contrast to parental HN5 HNC cells, HN5-ER cells exhibited an epithelial-mesenchymal (EMT) phenotype with increased migratory potential, reduced E-cadherin and epithelial-associated microRNAs (miRNA), and elevated vimentin expression. Phosphorylated receptor tyrosine kinase profiling identified Axl activation in HN5-ER cells. Growth and migration of HN5-ER cells were blocked with a specific Axl inhibitor, R428, and R428 resensitized HN5-ER cells to erlotinib. Microarray analysis of HN5-ER cells confirmed the EMT phenotype associated with acquired erlotinib resistance, and identified activation of gene expression associated with cell migration and inflammation pathways. Moreover, increased expression and secretion of interleukin (IL)-6 and IL-8 in HN5-ER cells suggested a role for inflammatory cytokine signaling in EMT and erlotinib resistance. Expression of the tumor suppressor miR-34a was reduced in HN5-ER cells and increasing its expression abrogated Axl expression and reversed erlotinib resistance. Finally, analysis of 302 HNC patients revealed that high tumor Axl mRNA expression was associated with poorer survival (HR = 1.66, P = 0.007). In summary, our results identify Axl as a key mediator of acquired erlotinib resistance in HNC and suggest that therapeutic inhibition of Axl by small molecule drugs or specific miRNAs might overcome anti-EGFR therapy resistance.
authors.affiliation: Corresponding Author: Peter Leedman, Western Australian Institute for Medical Research, Level 6, MRF Building, Rear 50 Murray Street, Perth, WA 6000, Australia. peter.leedman@waimr.uwa.edu.au.
authors.forename: Keith M
authors.initials: KM
authors.lastname: Giles
authors.forename: Felicity C
authors.initials: FC
authors.lastname: Kalinowski
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Candy
authors.forename: Michael R
authors.initials: MR
authors.lastname: Epis
authors.forename: Priscilla M
authors.initials: PM
authors.lastname: Zhang
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Redfern
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Stuart
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Goodall
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Leedman
mesh_terms: D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D001567:Benzocycloheptenes / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D000069347:Erlotinib Hydrochloride; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006258:Head and Neck Neoplasms / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008297:Male; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011799:Quinazolines / Q000494:pharmacology*; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014230:Triazoles / Q000494:pharmacology*; D000094963:Axl Receptor Tyrosine Kinase
chemical_list: D001567:Benzocycloheptenes; C522425:MIRN34 microRNA, human; D035683:MicroRNAs; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D011799:Quinazolines; D014230:Triazoles; C548378:bemcentinib; D000069347:Erlotinib Hydrochloride; D020794:Receptor Protein-Tyrosine Kinases; D000094963:Axl Receptor Tyrosine Kinase; C000722289:AXL protein, human