Silencing of LOXL4 inhibits colorectal cancer progression via regulating GLS1-dependent glutamine metabolism

Abstract Lysyl oxidase-like 4 (LOXL4) is frequently overexpressed in colorectal cancer (CRC) and associated with poor clinical prognoses. However, the metabolic mechanisms underlying LOXL4-driven CRC progression remain poorly elucidated. This study investigated the biological function of LOXL4 in CRC and its potential as a therapeutic target. We detected LOXL4 expression in paired CRC and normal tissues via western blot, qRT-PCR, IHC and flow cytometry. CRISPR-Cas9 was used to construct LOXL4 knockout SW480 and HT-29 cells, and multiple functional assays assessed cell proliferation, migration and invasion. Integrated proteomics and targeted metabolomics screened glutamine metabolic alterations, with the glutaminase 1 (GLS1) inhibitor CB-839 for functional validation. AOM/DSS-induced CRC mouse models were built to evaluate in vivo tumor growth. LOXL4 was significantly upregulated in clinical CRC samples. LOXL4 knockout suppressed malignant behaviors of CRC cells in vitro. Combined proteomic and metabolomic profiling confirmed GLS1 downregulation in LOXL4-knockout cells, accompanied by glutamine accumulation and glutamate reduction. Exogenous glutamate supplementation enhances the proliferative and migratory capacities of LOXL4-knockout tumor cells. LOXL4-knockout mice developed fewer, smaller intestinal tumors and milder weight loss. CB-839-mediated GLS1 inhibition synergistically strengthened the anti-tumor effect of LOXL4 deletion. LOXL4 silencing restrains CRC progression via a novel mechanism of GLS1 downregulation and intracellular glutamine accumulation. GLS1 pharmacological blockade further potentiates the anti-cancer efficacy of LOXL4 depletion, highlighting complex metabolic dependence in CRC.