GDF15 and carcinoma: Signaling mechanisms ascribed to GDF-15 in various carcinomas do not only involve Smad 2/3 signaling, which could also be attributable to contaminating TGF-β in preparations of GDF-15, but also IGFR1, PI3K, Akt, ERK1/2, β-catenin, p38, MAPK, Smad1/5/8, NF-κB, reactive oxygen species, mTOR, FAK–RhoA, EGFR, ErbB2, and c-myc signaling (among others).