Under specific conditions, SCFAs can elicit immunosuppressive effects, primarily characterized by the following mechanisms: SCFAs, particularly butyrate, have the capacity to suppress immune responses through activating G Protein-Coupled Receptor 43 (GPR43) and promoting the differentiation of Forkhead Box P3-positive (Foxp3+) CD4+ Tregs.65,72 Excessive proliferation of Tregs can potentially suppress anti-tumor immune responses, thereby diminishing the therapeutic efficacy of ICIs. This evidence concerns the gene FFAR2 and neoplasm.