Fumaric acid (2-Butenedioic acid) attenuates the eotaxin-1 expression in TNF-α-stimulated fibroblasts by suppressing p38 MAPK-dependent NF-κB signaling. Fumaric acid has recently been identified as an oncometabolite or an endogenous, cancer-causing metabolite. High levels of this organic acid can be found in tumors or biofluids surrounding tumors. Its oncogenic action appears due to its ability to inhibit prolyl hydroxylase-containing enzymes.