In Vivo CRISPR Screens Identify SLC1A5 as a Metabolic Checkpoint for Cancer Immunotherapy [ATAC]

Tumor cells often evade immune pressure via metabolic reprogramming, yet the key metabolic regulators orchestrating this process remain poorly defined. Here, using in vivo metabolic CRISPR screening under distinct immune pressures, we identified tumor cell–derived solute carrier family 1 member 5 (SLC1A5) as a critical metabolic node that sustains an immunosuppressive tumor microenvironment (TME). SLC1A5-mediated glutamine metabolism in tumor cells modulates CD8 T cell infiltration and effector function, reshaping tumor response to immune checkpoint blockade therapy. Mechanistically, glucose deprivation up-regulated SLC1A5 isoforms in tumor cells, enhancing glutamine uptake and metabolic flux remodeling to reset intracellular metabolic homeostasis. This program suppressed inflammatory tumor cell differentiation characterized by cyclic GMP-AMP synthase–stimulator of interferon genes (cGAS–STING) pathway activation, reducing interferon-β secretion and impairing CD8 immunity. These findings define a glutamine-fueled metabolic program as a critical barrier to tumor immunogenicity, positioning SLC1A5 as a metabolic immune checkpoint with therapeutic relevance.