PTHLH and plasma cell myeloma: Myeloma cells adhere to the stromal cells and induce secretion of OAFs including interleukin (IL)-6, IL-1, tumor necrosis factor (TNF), IL-11, macrophage inflammatory protein-1α (MIP-1α), hepatocyte growth factor (HGF), parathyroid hormone-related peptide (PTHrP), and others.