Personalized Medicine and Imaging Increased Expression of HER2, HER3, and HER2:HER3 Heterodimers in HPV-Positive HNSCC Using a Novel Proximity-Based Assay: Implications for Targeted Therapies

Purpose: In other cancer types, HPV infection has been reported to coincide with overexpression of HER2 (ERBB2) and HER3 (ERBB3); however, the association between HER2 or HER3 expression and dimer formation in HNSCC has not been reported. Overexpression of HER2 and HER3 may contribute to resistance to EGFR inhibitors, including cetuximab, although the contribution of HPV in modulating cetuximab response remains unknown.Determinationof heterodimerization ofHER receptors is challenging and has not been reported in HNSCC. The present study aimed to determine the expression ofHERproteins inHPVþ versus HPV HNSCC tumors using a proximity-based protein expression assay (VeraTag), and to determine the efficacy of HERtargeting agents in HPVþ and HPV HNSCC cell lines. Experimental Design: Expression of total HER1, HER2, and HER3, p95HER2, p-HER3, HER1:HER1 homodimers, HER2: HER3 heterodimers, and the HER3–PI3K complex in 88 HNSCC was determined using VeraTag, including 33 baseline tumors from individuals treated in a trial including cetuximab. Inhibition of cell growth and protein activation with cetuximab and afatinib was compared in HPVþ and HPV cetuximab-resistant cell lines. Results: Expression of total HER2, total HER3, HER2:HER3 heterodimers, and the HER3:PI3K complex were significantly elevated in HPVþ HNSCC. Total EGFR was significantly increased in HPV HNSCCwhereVeraTag assay results correlatedwith IHC.Afatinib significantly inhibited cell growth when compared with cetuximab in the HPVþ and HPV cetuximab-resistant HNSCC cell lines. Conclusions: These findings suggest that agents targeting multiple HER proteins may be effective in the setting of HPVþ HNSCC and/or cetuximab resistance. Clin Cancer Res; 21(20); 4597–606. 2015 AACR.