Large-scale CRISPR screening in human T cells holds significant promise for identifying genetic modifications that enhance cellular immunotherapy. Yet, many regulators of T cell performance in solid tumours are not revealed in vitro(1,2). In vivo screening in tumour-bearing mice is more physiological but has been limited by low intratumoural T cell recovery. Here we developed an in vivo model that efficiently recovers human T cells from solid tumours, permitting genome-wide CRISPR screens with few mice. Tumour-infiltrating T cells from this model exhibit hallmarks of dysfunction compared with splenic T cells, creating an ideal screening context. We performed two genome-wide CRISPR knockout screens to identify regulators of intratumoural T cell abundance and effector function. The abundance screen revealed the P2RY8-G_13 GPCR signalling axis as a negative regulator of T cell tumour infiltration. The effector function screen identified GNAS as a key driver of T cell dysfunction in tumours, whose product, G_s, acts as a convergent node downstream of multiple GPCRs sensing distinct suppressive ligands. Knockout of GNAS rendered T cells resistant to multiple suppressive cues and significantly improved efficacy across diverse solid tumour models in chimeric antigen receptor (CAR) and T cell receptor (TCR) systems. Combinatorial knockout of P2RY8-GNAS further enhanced tumour control, demonstrating that complementary in vivo screens can identify orthogonal targets whose combined editing improves therapeutic potency. This flexible, scalable platform can be adapted for systematic discovery of genetic strategies to improve solid tumour T cell therapies.
Author Info: (1) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. qi.liu3@ucsf.edu. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA

Author Info: (1) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. qi.liu3@ucsf.edu. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. qi.liu3@ucsf.edu. (2) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (3) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (4) Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (5) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (6) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (7) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (8) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. UCSF CoLabs, University of California San Francisco, San Francisco, CA, USA. Department of Surgery, University of California San Francisco, San Francisco, CA, USA. Diabetes Center, University of California San Francisco, San Francisco, CA, USA. (9) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (10) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (11) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (12) Department of Microbiology and Immunology and Howard Hughes Medical Institute, University of California San Francisco, San Francisco, CA, USA. (13) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (14) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (15) Department of Microbiology and Immunology and Howard Hughes Medical Institute, University of California San Francisco, San Francisco, CA, USA. Division of Pediatric Rheumatology, Department of Pediatrics, University of California San Francisco, San Francisco, CA, USA. (16) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. (17) Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (18) Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA. (19) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (20) Department of Surgery, Stanford University School of Medicine, Stanford, CA, USA. (21) Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA. (22) Division of Immunology and Rheumatology, Department of Medicine, Stanford University, Stanford, CA, USA. Division of Computational Medicine, Department of Medicine, Stanford University, Stanford, CA, USA. (23) Division of Immunology and Rheumatology, Department of Medicine, Stanford University, Stanford, CA, USA. Division of Computational Medicine, Department of Medicine, Stanford University, Stanford, CA, USA. Parker Institute for Cancer Immunotherapy, San Francisco, CA, USA. Weill Cancer Hub West, Stanford University and University of California, San Francisco, CA, USA. (24) Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. Weill Cancer Hub West, Stanford University and University of California, San Francisco, CA, USA. Department of Laboratory Medicine, University of California San Francisco, San Francisco, CA, USA. UCSF Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA, USA. (25) Gray Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv, Israel. George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel. Dotan Center for Advanced Therapies, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel. (26) Weill Cancer Hub West, Stanford University and University of California, San Francisco, CA, USA. Department of Pathology, University of California San Francisco, San Francisco, CA, USA. (27) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Parker Institute for Cancer Immunotherapy, San Francisco, CA, USA. Weill Cancer Hub West, Stanford University and University of California, San Francisco, CA, USA. UCSF Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA, USA. (28) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. Parker Institute for Cancer Immunotherapy, San Francisco, CA, USA. Weill Cancer Hub West, Stanford University and University of California, San Francisco, CA, USA. (29) Department of OB/Gyn, Center for Reproductive Sciences, University of California San Francisco, San Francisco, CA, USA. (30) Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. (31) Department of Microbiology and Immunology and Howard Hughes Medical Institute, University of California San Francisco, San Francisco, CA, USA. (32) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. Parker Institute for Cancer Immunotherapy, San Francisco, CA, USA. Weill Cancer Hub West, Stanford University and University of California, San Francisco, CA, USA. UCSF Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA, USA. Institute for Human Genetics (IHG), University of California San Francisco, San Francisco, CA, USA. Department of Microbiology and Immunology, University of California San Francisco, San Francisco, CA, USA. Innovative Genomics Institute, University of California Berkeley, Berkeley, CA, USA. (33) Department of Medicine, University of California San Francisco, San Francisco, CA, USA. julia.carnevale@ucsf.edu. Gladstone-UCSF Institute of Genomic Immunology, San Francisco, CA, USA. julia.carnevale@ucsf.edu. Parker Institute for Cancer Immunotherapy, San Francisco, CA, USA. julia.carnevale@ucsf.edu. Weill Cancer Hub West, Stanford University and University of California, San Francisco, CA, USA. julia.carnevale@ucsf.edu. UCSF Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA, USA. julia.carnevale@ucsf.edu.
