Expression of BDNF by malignant plasma cells. (A-B) Immunohistochemistry demonstrating BDNF expression by primary MM plasma cells. Representative cytospins of BM mononuclear cells freshly isolated from 2 patients with MM. Plasma cells show strong immunoreactivity using chicken anti–human BDNF but are not stained by chicken anti–human BDNF precleared with BDNF (inset). (C) Western blot demonstrating expression of both mature and pro-BDNF protein by HMCL. Expression was evident using either mouse anti-BDNF (shown) or rabbit (N-20) (not shown) antibodies. (D) Reverse transcriptase (RT)–PCR demonstrating BDNF mRNA expression by HMCL. No PCR products were evident in the absence of RT (not shown). (1) NCI H929, (2) RPMI 8226, (3) LP1, (4) ARP1, (5) OPM1, (6) KMS11, (7) JJN3, and (8) OPM2. (E) ELISA demonstrating increased BDNF in BM plasma of MM patients. Mean value for MM patients was 274 ± 71; patients without MM, 72 ± 22 (P < .05, Mann-Whitney test). * indicates significantly different from non-MM mean.