Abstract 5940: Inhibition of β-catenin/CBP signaling alters EGFR fucosylation status in head and neck squamous cell carcinoma

Abstract

Abstract Head and neck squamous cell carcinoma (HNSCC) is the sixth most common malignancy in the world with oral squamous cell carcinomas (OSCC) accounting for the majority of HNSCC cases. A major driver of OSCC is the epidermal growth factor receptor (EGFR), a receptor tyrosine kinase (RTK) with 12 N-glycosylation sites. Fucosylated N-linked glycans on EGFR are associated with survival e.g., they suppress receptor dimerization and signaling. High levels of fucosylated glycan epitopes have been observed in OSCC, where invasive regions lose expression of linkage-specific fucosylated epitopes, suggesting that fucosylated glycans are involved in the suppression of cell growth and invasion. Previously, it was shown that inhibition of the interaction between nuclear β-catenin and CREB-binding protein (CBP) in human OSCC cells and in mouse tumor xenografts with a small molecule inhibitor ICG-001, interfered with OSCC proliferation and aggressive features in cellular, zebrafish, and murine models. E7386, a novel β-catenin/CBP modulator displays activity profile that closely overlaps with that of ICG-001 and exhibits ~50 - 100-fold lower EC50 values. Treatment with ICG-001 and E7386, increased expression of two glycosyltransferases, FUT2 and FUT3 coincident with decreased EGFR abundance that was accompanied by higher fucosylation of EGFR and upregulated expression of E-cadherin and junctional β-catenin. Further, genomic analyses showed a positive correlation between the ICG-001 and E7386 treatments and EGFR inhibition, suggesting that higher expression of antennary fucosyltransferase genes suppresses EGFR signaling. We now show using nLC-MS/MS analyses that EGFR from metastatic HSC-3 cells had low levels of fucosylated N-glycans, while EGFR from indolent CAL27 cells displayed higher levels of fucosylation at multiple EGFR N-linked glycosylation sites, and that these changes were statistically significant. In-depth characterization of multiply-fucosylated N-glycans via tandem mass spectrometry of EGFR glycopeptides revealed new insights into the identity of fucosylated glycan epitopes. Collectively, these results suggest that the β-catenin/CBP axis promotes EGFR signaling through downregulation of fucosyltransferase expression and activity. We conclude that inhibition of β-catenin/CBP signaling with a novel small molecule E7386 may serve as a therapeutic approach to downregulate EGFR pro-tumorigenic activity in HNSCC patients. Citation Format: Kevin B. Chandler, Khalid Alamoud, Bac-Cuc Nguyen, Vanessa L. Stahl, Takashi Owa, Kenichi Nomoto, Stefano Monti, Maria A. Kukuruzinska, Catherine E. Costello. Inhibition of β-catenin/CBP signaling alters EGFR fucosylation status in head and neck squamous cell carcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5940.