A High-Throughput Immune-Oncology Screen Identifies EGFR Inhibitors as Potent Enhancers of Antigen-Specific Cytotoxic T-lymphocyte Tumor Cell Killing

• Published in: Cancer immunology research 2018-12, Vol.6 (12), p.1511-1523
• Main Authors: Lizotte, Patrick H, Hong, Ruey-Long, Luster, Troy A, Cavanaugh, Megan E, Taus, Luke J, Wang, Stephen, Dhaneshwar, Abha, Mayman, Naomi, Yang, Aaron, Kulkarni, Meghana, Badalucco, Lauren, Fitzpatrick, Erica, Kao, Hsiang-Fong, Kuraguchi, Mari, Bittinger, Mark, Kirschmeier, Paul T, Gray, Nathanael S, Barbie, David A, Jänne, Pasi A
• Format: Article
• Language: English
• ISSN: 2326-6066; 2326-6074
• DOI: 10.1158/2326-6066.CIR-18-0193

We developed a screening assay in which luciferized ID8 expressing OVA was cocultured with transgenic CD8 T cells specifically recognizing the model antigen in an H-2b-restricted manner. The assay was screened with a small-molecule library to identify compounds that inhibit or enhance T cell-mediated killing of tumor cells. Erlotinib, an EGFR inhibitor, was the top compound that enhanced T-cell killing of tumor cells. Subsequent experiments with erlotinib and additional EGFR inhibitors validated the screen results. EGFR inhibitors increased both basal and IFNγ-induced MHC class-I presentation, which enhanced recognition and lysis of tumor cell targets by CD8 cytotoxic T lymphocytes. The ID8 cell line was also transduced to constitutively express Cas9, and a pooled CRISPR screen, utilizing the same target tumor cell/T-cell assay, identified single-guide (sg)RNAs targeting that sensitized tumor cells to T cell-mediated killing. Combination of PD-1 blockade with EGFR inhibition showed significant synergistic efficacy in a syngeneic model, further validating EGFR inhibitors as immunomodulatory agents that enhance checkpoint blockade. This assay can be screened in high-throughput with small-molecule libraries and genome-wide CRISPR/Cas9 libraries to identify both compounds and target genes, respectively, that enhance or inhibit T-cell recognition and killing of tumor cells. Retrospective analyses of squamous-cell head and neck cancer (SCCHN) patients treated with the combination of afatinib and pembrolizumab demonstrated a rate of clinical activity exceeding that of each single agent. Prospective clinical trials evaluating the combination of an EGFR inhibitor and PD-1 blockade should be conducted.