NTSR1 and plasma cell myeloma: We previously demonstrated interactions between NTSR3 and epidermal growth factor receptor (EGFR) and TrkB.18 Interestingly, NTSR1 also interacts with EGFR, although, as mentioned above, neither NTSR1 nor EGFR is detectably expressed in B-CLL cells.20 Based on our previous findings showing that TrkB and its ligand BDNF are involved in fine-tuning endogenous B-cell survival,21 as well as in several malignancies22 including myeloma,23, 24 we speculated that TrkB might serve as a co-receptor for NTSR2.