LTA4H promotes intrahepatic cholangiocarcinoma progression via mTOR activation and T-cell exhaustion

Introduction: Intrahepatic cholangiocarcinoma (ICC) is a highly aggressive liver cancer with a poor prognosis. Immune evasion plays a critical role in ICC progression. Leukotriene A4 hydrolase (LTA4H), a key enzyme in eicosanoid metabolism, is overexpressed in multiple cancer types; however, its role and mechanism in ICC remain entirely unexplored. Methods: LTA4H expression and its prognostic significance were assessed in two independent ICC cohorts (n=130) and cell lines using bioinformatics, immunohistochemistry (IHC), and western blot (WB). LTA4H was genetically modulated in ICC cell lines via lentiviral transduction. Functional impacts on proliferation, migration, and invasion were evaluated by colony formation, real-time cellular analysis, wound healing, and Transwell assays. Spontaneous ICC was modeled in mice via hydrodynamic tail vein injection of a plasmid combination comprising pT3-EF1alpha-myr-AKT, pT3-EF1alpha-myr-NICD, and pCMV-SB. Mechanistic insights were investigated through RNA sequencing, metabolomics, and WB. Tumor immune microenvironment was profiled by flow cytometry. The therapeutic efficacy of the LTA4H-specific inhibitor LYS006 was tested in vivo and in patient-derived organoids. Results: LTA4H was significantly overexpressed in ICC tissues and correlated with poor patient survival. LTA4H overexpression enhanced ICC cell proliferation, migration, and invasion in vitro, and accelerated tumor progression in vivo. Conversely, LTA4H knockdown suppressed these malignant phenotypes. Mechanistically, LTA4H activated the mTOR signaling pathway and induced T-cell exhaustion in the tumor microenvironment. Therapeutic inhibition of LTA4H with LYS006 significantly suppressed tumor growth in mouse models and organoids. Conclusions: Our study identifies LTA4H as a novel oncoprotein in ICC that drives tumor progression by activating the mTOR pathway and fostering an immunosuppressive microenvironment via T-cell exhaustion. Targeting LTA4H represents a promising therapeutic strategy for ICC. Clinical Significance: This work unveils the dual pro-tumorigenic functions of LTA4H in ICC and provides a strong rationale for targeting LTA4H, potentially alone or in combination with immunotherapy, for the treatment of this lethal disease.