GDF15 and neoplasm: Through direct cell-cell contacts, paracrine factors, and tumor-generated physical forces, tumor cells stimulate secretion of growth factors, (e.g., growth-derived factor 15 (GDF15)), chemokines (e.g., chemokine (C-C motif) ligand 5 (CCL5)) and metalloproteases, that promote proliferation, migration, and invasion of several cancer types including prostate, breast and lung [117,118].