Abstract A09: Activation of the CD45 receptor on leukocytes by the C24D peptide results in immune-mediated head and neck squamous cell carcinoma apoptosis

Objectives: CD45 is a highly conserved receptor-linked protein tyrosine phosphatase that is expressed on all leucocytes. C24D, a novel 24-amino acid dimer peptide, previously shown to activate immune-modulated breast cancer cell killing, binds to CD45, triggering leukocyte activation against cancer cells. The aim of this study was to evaluate the efficacy of C24D in activating leukocytes against head and neck squamous cell carcinoma (HNSCC). Methods: We performed a series of in vitro studies using 3 HNSCC cell lines (Cal33, FaDu, and A431). HNSCC cells were cocultured with peripheral blood mononuclear cells (PBMC) from healthy donors and subsequently treated with either C24D peptide or a scrambled control version. C24D activity was evaluated by tumor cell density and apoptosis analysis. Leukocyte activation by the peptide was evaluated by interferon gamma (IFN-γ) secretion. Results: Cocultures of HNSCC cells and PBMCs treated with C24D resulted in a substantial decrease in tumor cell density and increased apoptosis. IFN-γ levels were significantly elevated in the C24D treated PBMCs cocultured with HNSCC, suggesting leukocyte activation. Conclusions: C24D peptide activates leukocytes via CD45, causing immune cell-mediated killing of HNSCC cell lines. Citation Format: Aviram Mizrachi, Elad Hikri, Amit Ritter, Julia Dick-Lipovetsky, Sivan Simchi, Aron Popovtzer, Rinat Yerushalmi, Gideon Bachar, Anat Raiter. Activation of the CD45 receptor on leukocytes by the C24D peptide results in immune-mediated head and neck squamous cell carcinoma apoptosis [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr A09.