The majority of patients with head and neck squamous cell carcinoma (HNSCC) present with advanced-stage disease. Current standard of care is surgery followed by adjuvant radiation therapy with or without chemotherapy or chemoradiation alone. The addition of cetuximab for the treatment of patients with locally advanced or recurrent/metastatic HNSCC has improved overall survival and locoregional control; however, responses are often modest, and treatment resistance is common. A variety of therapeutic strategies are being explored to overcome cetuximab resistance by blocking candidate proteins implicated in resistance mechanisms such as HER2. Several HER2 inhibitors are in clinical development for HNSCC, and HER2-targeted therapy has been approved for several cancers. This review focuses on the biology of HER2, its role in cancer development, and the rationale for clinical investigation of HER2 targeting in HNSCC.

The angiotensin II receptor AGTR1, which mediates vasoconstrictive and inflammatory signaling in vascular disease, is overexpressed aberrantly in some breast cancers. In this study, we established the significance of an AGTR1-responsive NFκB signaling pathway in this breast cancer subset. We documented that AGTR1 overexpression occurred in the luminal A and B subtypes of breast cancer, was mutually exclusive of HER2 expression, and correlated with aggressive features that include increased lymph node metastasis, reduced responsiveness to neoadjuvant therapy, and reduced overall survival. Mechanistically, AGTR1 overexpression directed both ligand-independent and ligand-dependent activation of NFκB, mediated by a signaling pathway that requires the triad of CARMA3, Bcl10, and MALT1 (CBM signalosome). Activation of this pathway drove cancer cell-intrinsic responses that include proliferation, migration, and invasion. In addition, CBM-dependent activation of NFκB elicited cancer cell-extrinsic effects, impacting endothelial cells of the tumor microenvironment to promote tumor angiogenesis. CBM/NFκB signaling in AGTR1 breast cancer therefore conspires to promote aggressive behavior through pleiotropic effects. Overall, our results point to the prognostic and therapeutic value of identifying AGTR1 overexpression in a subset of HER2-negative breast cancers, and they provide a mechanistic rationale to explore the repurposing of drugs that target angiotensin II-dependent NFκB signaling pathways to improve the treatment of this breast cancer subset. These findings offer a mechanistic rationale to explore the repurposing of drugs that target angiotensin action to improve the treatment of AGTR1-expressing breast cancers. .

Purpose In other cancer types, HPV infection has been reported to coincide with overexpression of HER2 and HER3, however the association between HER2 or HER3 expression or 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. Determination of heterodimerization of HER receptors is challenging and has not been reported in HNSCC. The present study aimed to determine the expression of HER proteins in HPV[+] versus HPV[−] HNSCC tumors using a proximity-based protein expression assay (VeraTag), and to determine the efficacy of HER targeting agents in HPV[+] 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 HPV[+] 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 HPV[+] HNSCC. Total EGFR was significantly increased in HPV[−] HNSCC where VeraTag assay results correlated with IHC. Afatinib significantly inhibited cell growth when compared to cetuximab in the HPV[+] and HPV[−] cetuximab-resistant HNSCC cell lines. Conclusion These findings suggest that agents targeting multiple HER proteins may be effective in the setting of HPV[+] HNSCC and/or cetuximab resistance.

Aberrant activation of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) 3 has been implicated in cell proliferation and survival of many cancers including head and neck squamous cell carcinoma (HNSCC). AZD1480, an orally active pharmacologic inhibitor of JAK1/JAK2, has been tested in several cancer models. In the present study, the in vitro and in vivo effects of AZD1480 were evaluated in HNSCC preclinical models to test the potential use of JAK kinase inhibition for HNSCC therapy. AZD1480 treatment decreased HNSCC proliferation in HNSCC cell lines with half maximal effective concentration (EC50) values ranging from 0.9 to 4 μM in conjunction with reduction of pSTAT3Tyr705 expression. In vivo antitumor efficacy of AZD1480 was demonstrated in patient-derived xenograft (PDX) models derived from two independent HNSCC tumors. Oral administration of AZD1480 reduced tumor growth in conjunction with decreased pSTAT3Tyr705 expression that was observed in both PDX models. These findings suggest that the JAK1/2 inhibitors abrogate STAT3 signaling and may be effective in HNSCC treatment approaches.

Structure-activity relationship studies of a 1,2,4-triazolo-[3,4-b]thiadiazine scaffold, identified in an HTS campaign for selective STAT3 pathway inhibitors, determined that a pyrazole group and specific aryl substitution on the thiadiazine were necessary for activity. Improvements in potency and metabolic stability were accomplished by the introduction of an α-methyl group on the thiadiazine. Optimized compounds exhibited anti-proliferative activity, reduction of phosphorylated STAT3 levels and effects on STAT3 target genes. These compounds represent a starting point for further drug discovery efforts targeting the STAT3 pathway.