KITLG and neoplasm: These tumor-derived factors include granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-SCF), macrophage colony-stimulating factor (M-CSF), IL-1β, IL-6, VEGF, IL-13, IL-10, prostaglandin E2 (PGE2), TNF, bombina variegate peptide 8 (Bv8, also known as prokineticin 2 or Prok2), and stem cell factor (SCF) [51–61].