Elevated systemic phenylalanine disrupts glutamate-dependent STING signaling in neutrophils and impairs cancer immunotherapy
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ABSTRACT: Immune checkpoint inhibitors (ICIs) have transformed cancer therapy, yet acquired immune resistance remains a major barrier to durable response. Here, we identify a previously unrecognized immunometabolic axis in which elevated systemic phenylalanine (Phe) - driven by dietary intake or ICI-induced hepatic dysfunction - promotes immune evasion. Mechanistically, ICI-induced IL-6 and IFN-γ trigger proteasomal degradation of phenylalanine hydroxylase (PAH) via a TOPK-HECTD1 pathway in hepatocytes, leading to increased circulating Phe. Excess Phe suppresses antitumor immunity by impairing STING activation in tumor-associated neutrophils (TANs), through antagonism of glutamate-GRIK1-CaMKIV signaling. We uncover a key STING phosphorylation site (S324/326) essential for ER-to-Golgi trafficking and type I interferon responses, which is disrupted by Phe. These effects are independent of cGAS-cGAMP and define a glutamate-sensing checkpoint in neutrophil immunity. Therapeutically, restoring PAH function using liver-targeted synthetic RNA mimetics of HULC - a noncoding RNA shown to allosterically enhance PAH enzymatic activity - or activating GRIK1 with SYM2081 reprograms the tumor microenvironment, enhances CD8⁺ T cell function, and overcomes ICI resistance. This work reveals hepatic metabolic reprogramming as a central mechanism of immune escape and highlights new therapeutic opportunities to boost immunotherapy efficacy.
ORGANISM(S): Mus musculus
PROVIDER: GSE303168 | GEO | 2025/07/21
REPOSITORIES: GEO
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