FASN promotes the stemness of cancer stem cells and protects colorectal cancer cells from ferroptosis by inhibiting the activation of SREBP2.

Introduction: Fatty acid synthase (FASN) is a key regulator of lipid metabolism, but its role in colorectal cancer (CRC) stemness and ferroptosis remains unclear. Methods: FASN expression in CRC was analyzed using TCGA data and validated in CRC cell lines (CACO-2, HCT116, SW480) and normal HIEC-6 cells via qRT-PCR and Western blot. HCT116 cells (highest FASN expression) were used for experiments. FASN silencing (shRNA) effects on CSCs were assessed via 3D spheroid formation and CD133+CD44+ flow cytometry. In vivo tumor growth was tested in BALB/c nude mice. Mechanistic assays included cholesterol detection, SREBP2 Western blot, fatostatin rescue experiments, ferroptosis markers (ferrous ions, ROS, MDA, 4-HNE, mitochondrial function), and FASN-SREBP2 co-immunoprecipitation. Results: FASN was overexpressed in CRC tissues (TCGA) and cell lines, with highest levels in HCT116. It was upregulated in 3D spheroids and CD133+CD44+ CSCs. FASN silencing reduced spheroid formation, in vivo tumor growth, and CD133+CD44+ cells. Mechanistically, FASN knockdown decreased cholesterol, activated SREBP2, and induced ferroptosis (elevated ferrous ions, ROS, lipid peroxidation, mitochondrial dysfunction); these effects were reversed by fatostatin. Co-IP confirmed FASN-SREBP2 interaction. Discussion: FASN promotes CRC progression by enhancing CSC stemness and suppressing ferroptosis through SREBP2 inhibition, highlighting its potential as a therapeutic target.