Abstract 546: Impact of therapeutic EGFR inhibition on immune checkpoint blockade in head and neck squamous cell carcinoma

Abstract

Abstract Patients with advanced recurrent and/or metastatic head and neck squamous cell carcinoma (HNSCC) have few effective treatment options and a poor median survival of 6-8 months. Limited improvement in overall survival has been observed in HNSCC patients treated with EGFR inhibitors despite high expression of epidermal growth factor receptor (EGFR) in these tumors. Remarkable clinical results are emerging from immunotherapy targeting programmed death-1 (PD1) and its ligand programmed death ligand-1 (PDL1). Blockade of the PD1/PDL1 interaction is believed to enhance endogenous anti-tumor immunity by restoring T cell cytotoxic action. PDL1 is highly expressed in primary, recurrent, and metastatic HNSCC and phase 1 clinical trials are ongoing for monoclonal antibodies targeting the PD1/PDL1 axis in HNSCC. We found that activation of EGFR in HNSCC cells by epidermal growth factor (EGF) significantly increases PDL1 expression in a dose dependent manner. EGFR inhibition using tyrosine kinase inhibitors (TKI) or cetuximab suppresses this EGF-induced PDL1 expression in cells with both wild type and constitutively active EGFR. This is consistent with published data that constitutively active EGFR in lung cancer cells correlates with higher PDL1 expression, and this can be reversed by EGFR inhibition. These results suggest there may be interactions between EGFR-targeted therapy and immunotherapy involving the PD1/PDL1 axis. To evaluate potential therapeutic interactions, we used an immunocompetent, syngeneic mouse model of human EGFR-expressing TUBO cancer cells on a BALB/c background. The murine TUBO-EGFR cells are sensitive to human EGFR inhibitors both in vitro and in vivo. Initial studies show that treatment of tumors with EGFR inhibitor (erlotinib) results in increased intratumoral CD8+ T cell infiltration and tumor regression, suggesting that EGFR inhibition can impact the anti-tumor T cell response. We are currently evaluating the effects of EGFR inhibition on PDL1 expression and tumor response to PD1/PDL1 blockade using this model. Further, a clinical trial investigating the impact of cetuximab treatment on intratumoral expression of PDL1 in HNSCC patients is planned to open shortly. We conclude that signaling mediated by EGFR can impact expression of PDL1 by HNSCC. Understanding the interactions between EGFR inhibitors and immune checkpoint blockade could lead to new approaches to combining TKI and cancer immunotherapy. Citation Format: Laura M. Rogers, Madelyn M. Espinosa-Cotton, Andrean L. Simons, George J. Weiner. Impact of therapeutic EGFR inhibition on immune checkpoint blockade in head and neck squamous cell carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 546.