[Expression and significance of brain-derived neurotrophic factors and receptors in multiple myeloma]

Abstract

Objective: To investigate the expression of brain-derived neurotrophic factor (BDNF) and its receptors in multiple myeloma (MM) cells and the biological effects of BDNF on MM cells.

Methods: Transcription and protein expression of BDNF and its receptors (TrkB and P75(NTR)) in human myeloma cell lines (HMCLs) was determined with RT-PCR and Western blotting. BDNF levels in culture supernatant was determined with enzyme-linked immunosorbent assay. The expression of BDNF and TrkB by myeloma cells was studied with immunohistochemistry in bone marrow biopsy samples from 15 patients with MM. The effect of BDNF on the in vitro proliferation of HMCLs (RPMI 8226, U266, KM3) was examined with 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. The effect of BDNF on HMCLs migration was studied with modified Boyden chamber assay.

Results: BDNF was expressed and secreted by HMCLs in high concentrations up to 14.7 microg/L. Furthermore, expression of its high affinity receptor TrkB was observed in HMCLs. BDNF expression by myeloma cells was demonstrated in 12 of the 15 patients with MM (80%), TrkB expression was demonstrated in all the 15 patients (100%), whereas control bone marrow samples showed weaker expression of BDNF in 2 of 9 (22.2%) and TrkB in 4 of 9 (44.4%). Functional studies demonstrated that BDNF has strong proliferative effects on HMCLs and proliferation of RPMI 8226 was enhanced by BDNF in a time- and dose-dependent manner. Moreover, BDNF has chemotactic properties on HMCLs. The maximal responses were seen at 50 microg/L for RPMI 8266 (P < 0.05) and 25 microg/L for KM3 cells (P < 0.01) as compared with nonstimulated controls.

Conclusion: BDNF and its high affinity receptor TrkB are co-expressed by MM cells. BDNF appears to have a major contribution to the pathophysiology of MM leading to proliferation and migration of MM cells. These provide the framework for novel therapeutic strategies targeting BDNF/TrkB signaling in MM.