Genomic Correlate of Exceptional Erlotinib Response in Head and Neck Squamous Cell Carcinoma

Abstract

Importance: Randomized clinical trials demonstrate no benefit for epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors in unselected patients with head and neck squamous cell carcinoma (HNSCC). However, a patient with stage IVA HNSCC received 13 days of neoadjuvant erlotinib and experienced a near-complete histologic response.

Objective: To determine a mechanism of exceptional response to erlotinib therapy in HNSCC.

Design, setting, and participants: Single patient with locally advanced HNSCC who received erlotinib monotherapy in a window-of-opportunity clinical trial (patients scheduled to undergo primary cancer surgery are treated briefly with an investigational agent). Whole-exome sequencing of pretreatment tumor and germline patient samples was performed at a quaternary care academic medical center, and a candidate somatic variant was experimentally investigated for mediating erlotinib response.

Intervention: A brief course of erlotinib monotherapy followed by surgical resection.

Main outcomes and measures: Identification of pretreatment tumor somatic alterations that may contribute to the exceptional response to erlotinib. Hypotheses were formulated regarding enhanced erlotinib response in preclinical models harboring the patient tumor somatic variant MAPK1 E322K following the identification of tumor somatic variants.

Results: No EGFR alterations were observed in the pretreatment tumor DNA. Paradoxically, the tumor harbored an activating MAPK1 E322K mutation (allelic fraction 0.13), which predicts ERK activation and erlotinib resistance in EGFR-mutant lung cancer. The HNSCC cells with MAPK1 E322K exhibited enhanced EGFR phosphorylation and erlotinib sensitivity compared with wild-type MAPK1 cells.

Conclusions and relevance: Selective erlotinib use in HNSCC may be informed by precision oncology approaches.

Trial registration: ClinicalTrials.gov NCT00779389.

Conflict of interest statement

Conflict of Interest Disclosures: Dr Garraway is a consultant and equity holder in Foundation Medicine. Dr Grandis receives research support from Novartis and Bristol-Myers Squibb. No other disclosures are reported.

Figures

Figure 1. Clinical Course and Histologic Findings

A, Time course for the patient’s clinical experience, highlighting the number of days receiving erlotinib and the time elapsed since surgery. D indicates day. B and C, Representative histologic analysis images of the pretreatment tumor biopsy confirm squamous cell carcinoma (hematoxylin-eosin; B, original magnification ×40; C, original magnification ×100). D and E, representative histology images from surgical specimens taken after 13 days of erlotinib therapy (hematoxylin-eosin; D, original magnification ×40; E, original magnification ×100).

Figure 2. Whole-Exome Sequencing of the Pretreatment Tumor

A, There is no evidence of EGFR amplification. B, Heuristic analysis of the somatic mutations, short insertions and deletions, and copy number alterations across the exome identifies 4 mutations for additional evaluation: TP53, ARID1A, ABL2, and MAPK1. The horizontal line denotes the separation between nonsynonymous and synonymous variants, and COSMIC indicates the Catalogue of Somatic Mutations in Cancer database. C, The location of E322 is near the terminal end of the MAPK1 protein, in the common docking domain. Numbers indicate the color-coded regions of the protein. D, The E322 locus is highly conserved across species.

Figure 3. MAPK1 E322K Mutations and EGFR Signaling

A, HSC-6 cells that harbor an endogenous MAPK1 E322K mutation express higher basal levels of phospho-p42/44 MAPK, p-EGFR(Y1068), and pAKT(S473) when compared with CAL-33 cells that endogenously express MAPK1 wild type. B, The head and neck squamous cell carcinoma cells with deleted MAPK1 (FaDu) were engineered to express increased levels of mutant E322K and demonstrate upregulation of phospho-p42/44 MAPK, p-EGFR(Y1068), and pAKT(S473) levels compared with vector-control transfectants. Similar results were observed at least 3 times. C, FaDu-MAPK1 E322K cells demonstrated significantly increased senescence compared with FaDu-vector and FaDu-wild-type MAPK1 following 48-hour treatment with erlotinib. β-Galactosidase activity at pH 6 was detected in senescent cells by means of light microscopy (original magnification ×100) following staining using the senescence staining kit (Cell Signaling Technology). Number of senescent cells and total number of cells per field were analyzed for at least 5 fields for each cell type and treatment condition. Mean (SD) percent of senescent cells from a representative of 3 independent experiments is presented.