Abstract 2107: CHMP2A regulates NK cell-mediated anti-tumor activity in a syngeneic HNSCC model
Authors: Yun Jiyoung , Saddawi-Konefka Robert , Goldenson Benjamin , Al-msari Riyam , Gutkind J Silvio , Kaufman Dan S. 
Published: June 2022

Abstract
Natural killer (NK) cells are a key effector in antitumor immunity. However, tumors often acquire resistance programs to escape NK cell-mediated immunosurveillance. Identifying targetable vulnerabilities that reinvigorate NK cell-driven antitumor immunity can enable new therapeutic strategies to improve NK cell-mediated anti-tumor activity. Previous studies from our group used a whole genome CRISPR-Cas9 screen that identified CHMP2A as a gene that mediates tumor-intrinsic resistance to NK cell cytotoxicity. CHMP2A is a member of the ESCRTIII complex and regulates secretion of tumor-derived chemokines and extracellular vehicles (EVs) that express NK cell-activating ligands MICA/B and TRAIL, which induce NK apoptosis. Previously, we demonstrated that the deletion of CHMP2A in glioblastoma and head and neck squamous cell carcinoma (HNSCC) increases allogeneic NK cell-mediated killing both in vitro and in vivo. Here, we extend these studies to explore whether CHMP2A may serve as a targetable regulator of NK cell-mediated immunity. Employing our recently characterized syngeneic, tobacco-signature murine HNSCC model, 4MOSC (PMID: 31804466), we deleted CHMP2A in both the immune-responsive 4MOSC1 and immune-insensitive 4MOSC2 cell line. In vitro NK cell cytotoxicity assays reveal that 4MOSC1-CHMP2A-KO cells were more potently killed by NK cells compared to 4MOSC1-WT cells (53% increased cytotoxicity, p&lt;0.001). In contrast, there was no significant difference in NK cell-mediated killing of 4MOSC2-WT versus CHMP2A-KO cells. Following orthotopic transplantation into immunocompetent hosts, we find that 4MOSC1-KO, but not 4MOSC2-WT, tumors spontaneously regress in vivo compared to wild type tumors (4MOSC1 KO with 80% regression, p=0.0476). Moreover, we find that NK cell depletion, achieved with systemic delivery of the blocking antibody PK136, was sufficient to reverse the complete response of 4MOSC1 tumors to anti CTLA-4 immune checkpoint inhibition (p&lt;0.01), implying promise for combination therapeutic strategies in immunotherapy insensitive tumors. Ongoing studies are using IHC and mass cytometry (Cytof) to characterize the immune infiltrates to better define immune cell populations regulated by CHMP2A-mediated resistance of tumor cells to NK cell and possibly T-cell-mediated responses. Together, these studies demonstrate that CHMP2A provides a targetable, tumor-derived inhibitor of NK cell-driven antitumor immunity. Moreover, our preclinical model features HNSCC cell lines with variable sensitivity to CHMP2A-deletion to enable future studies to target key pathways to overcome resistance programs and mediate improved anti-tumor activity.
Citation Format: Jiyoung Yun, Robert Saddawi-Konefka, Benjamin Goldenson, Riyam Al-msari, J Silvio Gutkind, Dan S. Kaufman. CHMP2A regulates NK cell-mediated anti-tumor activity in a syngeneic HNSCC model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2107.