IL4I1 and cancer: Tryptophan can be converted to indole-3-pyruvate (I3P) by interleukin-4-induced-1 (IL4i1), which protects cancer cells from ferroptosis through scavenging lipophilic radicals, increasing the GSH/ Glutathione disulfide (GSSG) ratio, upregulating the expression of SLC7A11 and targeting some genes in the antioxidant signaling pathway, such as hemeoxygenase-1 (HO-1) [87].