title: Hedgehog signaling alters reliance on EGF receptor signaling and mediates anti-EGFR therapeutic resistance in head and neck cancer.
abstract: The EGF receptor (EGFR)-directed monoclonal antibody cetuximab is the only targeted therapy approved for the treatment of squamous cell carcinoma of the head and neck (HNSCC) but is only effective in a minority of patients. Epithelial-to-mesenchymal transition (EMT) has been implicated as a drug resistance mechanism in multiple cancers, and the EGFR and Hedgehog pathways (HhP) are relevant to this process, but the interplay between the two pathways has not been defined in HNSCC. Here, we show that HNSCC cells that were naturally sensitive to EGFR inhibition over time developed increased expression of the HhP transcription factor GLI1 as they became resistant after long-term EGFR inhibitor exposure. This robustly correlated with an increase in vimentin expression. Conversely, the HhP negatively regulated an EGFR-dependent, EMT-like state in HNSCC cells, and pharmacologic or genetic inhibition of HhP signaling pushed cells further into an EGFR-dependent phenotype, increasing expression of ZEB1 and VIM. In vivo treatment with cetuximab resulted in tumor shrinkage in four of six HNSCC patient-derived xenografts; however, they eventually regrew. Cetuximab in combination with the HhP inhibitor IPI-926 eliminated tumors in two cases and significantly delayed regrowth in the other two cases. Expression of EMT genes TWIST and ZEB2 was increased in sensitive xenografts, suggesting a possible resistant mesenchymal population. In summary, we report that EGFR-dependent HNSCC cells can undergo both EGFR-dependent and -independent EMT and HhP signaling is a regulator in both processes. Cetuximab plus IPI-926 forces tumor cells into an EGFR-dependent state, delaying or completely blocking tumor recurrence.
authors.affiliation: Division of Medical Oncology, Department of Medicine, Departments of Pharmacology, Pathology, Radiation Oncology, and Otolaryngology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Keysar
authors.forename: Phuong N
authors.initials: PN
authors.lastname: Le
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Anderson
authors.forename: J Jason
authors.initials: JJ
authors.lastname: Morton
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Bowles
authors.forename: Jeramiah J
authors.initials: JJ
authors.lastname: Paylor
authors.forename: Brian W
authors.initials: BW
authors.lastname: Vogler
authors.forename: Jackie
authors.initials: J
authors.lastname: Thorburn
authors.forename: Pamela
authors.initials: P
authors.lastname: Fernandez
authors.forename: Magdalena J
authors.initials: MJ
authors.lastname: Glogowska
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Takimoto
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Sehrt
authors.forename: Gregory N
authors.initials: GN
authors.lastname: Gan
authors.forename: Justin R
authors.initials: JR
authors.lastname: Eagles-Soukup
authors.forename: Hilary
authors.initials: H
authors.lastname: Serracino
authors.forename: Fred R
authors.initials: FR
authors.lastname: Hirsch
authors.forename: M Scott
authors.initials: MS
authors.lastname: Lucia
authors.forename: Andrew
authors.initials: A
authors.lastname: Thorburn
authors.forename: John I
authors.initials: JI
authors.lastname: Song
authors.forename: Xiao-Jing
authors.initials: XJ
authors.lastname: Wang
authors.forename: Antonio
authors.initials: A
authors.lastname: Jimeno
mesh_terms: D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D000068818:Cetuximab; D019008:Drug Resistance, Neoplasm; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020868:Gene Silencing; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D020239:Receptor Cross-Talk; D015398:Signal Transduction; D000077195:Squamous Cell Carcinoma of Head and Neck; D014704:Veratrum Alkaloids / Q000008:administration & dosage / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D053823:Hedgehog Proteins; C541444:IPI-926; D014704:Veratrum Alkaloids; D066246:ErbB Receptors; D000068818:Cetuximab