Lee, Dong-hee Ahn, Hyejin Sim hye in Choi, Eunji Choi, Seung hyun JO, YUNJU Yun, Bohwan Song, Hyun Kyu Oh, Soo Jin Denda-Nagai, Kaori Park, Chan-Sik Irimura, Tatsuro Park, Yoon Jin, Hyung-seung 2024-01-12T06:33:14Z 2024-01-12T06:33:14Z 2023-11-23 2023-10 0392-9078 https://pubs.kist.re.kr/handle/201004/79788 Background: Immunotherapy has significantly advanced cancer treatments, but many patients do not respond to it, partly due to immunosuppressive mechanisms used by tumor cells. These cells employ immunosuppressive ligands to evade detection and elimination by the immune system. Therefore, the discovery and characterization of novel immunosuppressive ligands that facilitate immune evasion are crucial for developing more potent anti-cancer therapies. Methods: We conducted gain-of-function screens using a CRISPRa (CRISPR activation) library that covered the entire human transmembrane sub-genome to identify surface molecules capable of hindering NK-mediated cytotoxicity. The immunosuppressive role and mechanism of MUC21 were validated using NK and T cell mediated cytotoxicity assays. Bioinformatics tools were employed to assess the clinical implications of mucin-21 (MUC21) in cancer cell immunity. Results: Our genetic screens revealed that MUC21 expression on cancer cell surfaces inhibits both the cytotoxic activity of NK cells and antibody-dependent cellular cytotoxicity, but not affecting complement-dependent cytotoxicity. Additionally, MUC21 expression hinders T cell activation by impeding antigen recognition, thereby diminishing the effectiveness of the immune checkpoint inhibitor, anti-PD-L1. Moreover, MUC21 expression suppress the antitumor function of both CAR-T cells and CAR-NK cells. Mechanistically, MUC21 facilitates immune evasion by creating steric hindrance, preventing interactions between cancer and immune cells. Bioinformatics analysis revealed elevated MUC21 expression in lung cancer, which correlated with reduced infiltration and activation of cytotoxic immune cells. Intriguingly, MUC21 expression was higher in non-small cell lung cancer (NSCLC) tumors that were non-responsive to anti-PD-(L)1 treatment compared to responsive tumors. Conclusions: These findings indicate that surface MUC21 serves as a potent immunosuppressive ligand, shielding cancer cells from NK and CD8 English BioMed Central A CRISPR activation screen identifies MUC-21 as critical for resistance to NK and T cell-mediated cytotoxicity Article 10.1186/s13046-023-02840-9 1 Journal of Experimental and Clinical Cancer Research, v.42, no.1 Journal of Experimental and Clinical Cancer Research 42 1 Y scie scopus 001100173800003 2-s2.0-85174496486 Oncology Oncology Article CANCER PERSPECTIVE GLYCOFORM MUCINS MUC1 Cancer immunotherapy CRISPR library screening MUC21 CAR