BDNF and plasma cell myeloma: Several studies have implicated BDNF and TrkB in the pathogenesis of various human malignancies, including not only neuronal tumors such as neuroblastoma [9] but also non-neuronal tumors such as lung cancer, hepatocellular carcinoma, ovarian cancer, breast cancer, pancreatic ductal carcinoma, prostate cancer, and multiple myeloma [10–14].