Histone lactylation-mediated up-regulation of IGF2BP2 enhances ferroptosis resistance via Nrf2 in colorectal cancer.

BACKGROUND: Emerging evidence suggests that ferroptosis resistance may drives colorectal cancer (CRC) pathogenesis and limits therapeutic efficacy. A previous study has reported that lactate can enhance ferroptosis in CRC cells. The objective of this study was to elucidate how lactate regulates ferroptosis in CRC and to identify potential therapeutic targets. METHODS: Cellular viability and proliferative capacities were determined via cell counting kit-8 (CCK-8) and colony formation. Ferroptosis-related and inflammatory markers, including malondialdehyde (MDA), Fe(2+), glutathione (GSH), IL-1β, IL-12 and IL-10, were quantified by commercial kits. Protein and RNA interactions were investigated using co-immunoprecipitation (Co-IP), RNA pull-down, dual-luciferases reporter and RNA immunoprecipitation （RIP) assays. Flow cytometry analysed M1 and M2 macrophage populations. Chromatin immunoprecipitation followed by quantitative polymerase chain reaction (ChIP-qPCR) examined histone H3 lysine 18 lactylation (H3K18la) and EP300 binding at the insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2)promoter. Methylated RNA Immunoprecipitation-qPCR (MeRIP-qPCR) measured the m(6)A modification of nuclear factor erythroid 2-related factor 2 (Nrf2) mRNA. Transmission electron microscopy determined mitochondrial morphology. C11-BODIPY immunofluorescence staining analysed lipid peroxidation. RESULTS: Our findings revealed that lactate up-regulates IGF2BP2 through H3K18la-mediated transcriptional activation in both CRC cells and tumour-associated macrophages. Elevated IGF2BP2 directly bound to and stabilised Nrf2 mRNA, resulting in increased Nrf2 levels and enhanced resistance to ferroptosis in CRC cells. Notably, this lactate-IGF2BP2-Nrf2 axis also promoted M2 macrophage polarisation, fostering an immunosuppressive tumour microenvironment (TME). In xenograft models, lactate-driven Nrf2 up-regulation accelerated CRC tumour growth and metastasis. Conversely, pharmacological inhibition of ferroptosis resistance with dichloroacetate (DCA) or depletion of IGF2BP2 significantly reduced tumour burden. CONCLUSION: Our study identified a novel lactate-IGF2BP2-Nrf2 signalling pathway that drives ferroptosis resistance and immune evasion in CRC. KEY POINTS: Lactate drives H3K18la-mediated transcriptional activation of IGF2BP2 in CRC. IGF2BP2 protein stabilises Nrf2 mRNA by binding to its m(6)A modification site. The lactate-IGF2BP2-Nrf2 axis confers ferroptosis resistance in CRC cells. This pathway simultaneously promotes M2 macrophage polarisation in the tumour microenvironment.