Figure 2 summarizes the reported interaction between butyrate and GPR109a and the subsequent cytokines production. Despite the observed tumor suppressor effects of GPR109a receptors, some reports highlighted that the activation of this receptor leads to the activation of inflammatory signaling pathways, which suggest that GPR109a could act as a tumor activator and suppressor depending on the affected sites and tissues [46]. This evidence concerns the gene HCAR2 and neoplasm.