FFAR4 negatively regulates colorectal cancer growth via blocking oxidative phosphorylation.

[BACKGROUND] Colorectal cancer (CRC) is closely associated with dietary factors and genetic alterations. As lipid-sensing receptors, FFARs may transduce dietary fatty acid cues into tumor-related signaling pathways. However, the role of FFAR4 in CRC remains unclear.

[METHODS] Integrative multi-omics approaches were used to identify FFAR4 as a key candidate within the FFAR family in CRC. FFAR4 expression and clinical relevance were evaluated using transcriptomic datasets, ROC analysis, and immunofluorescence in clinical CRC tissues. FFAR4 function was assessed by pharmacological activation with TUG891 in CRC cell lines and an MC38 syngeneic tumor model, with proliferation, cell-cycle, and metabolic assessments.

[RESULTS] FFAR4 expression was reduced in CRC tissues, and higher FFAR4 levels were associated with improved overall survival. Single-cell RNA sequencing analysis showed that FFAR4 was predominantly expressed in early differentiation states, and ROC analysis yielded an AUC > 0.8 for CRC diagnosis. TUG891-mediated FFAR4 activation inhibited CRC cell proliferation and induced cell-cycle arrest in vitro, and reduced tumor volume and tumor weight in vivo without affecting body weight. Metabolic profiling and extracellular flux analyses showed decreased mitochondrial respiration (OCR), accompanied by reduced NAD⁺ levels, a lower NAD⁺/NADH ratio, and decreased ATP/ADP, indicating altered NADH redox balance and cellular energy deficit. Consistently, aspartate was downregulated, whereas GOT1 and MDH1 were upregulated, suggesting alterations in the malate-aspartate shuttle. Meanwhile, glycolytic activity increased, as reflected by elevated ECAR and lactate levels; however, inhibition of glycolysis with 2-deoxyglucose (2-DG) did not reverse the TUG891-induced anti-proliferative effect or cell-cycle arrest, suggesting that enhanced glycolysis may represent a compensatory response.

[CONCLUSIONS] FFAR4 suppresses CRC growth by modulating mitochondrial function and cellular metabolism, supporting its potential as a diagnostic biomarker and therapeutic strategy for CRC.