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This study examined the expression of brain-derived neurotrophic factor (BDNF) in multiple myeloma (MM) and its role in bone marrow angiogenesis. The peripheral blood plasma was harvested from 71 MM patients and 63 patients without hematological malignancy. The BDNF level in the blood plasma was determined by ELISA. Human bone marrow endothelial cells (HBMECs) were cultured. The mRNA and protein expression levels of the BDNF receptor TrkB in HBMECs were detected by using RT-PCR and flow cytometry, respectively. The viability of HBMECs treated with recombinant human (rh) BDNF or not was measured by using MTT assay. The migration of HBMECs in the presence of rhBDNF or not was determined by modified Boyden chamber assay. In vitro tube formation assay was used to assess the effect of rhBDNF on HBMECs differentiation. The results of ELISA revealed that the BDNF level was significantly higher in peripheral blood plasma of MM patients than in that of control patients (4.39±0.67 vs. 1.96±0.39 ng/mL, P<0.05). The BDNF receptor TrkB was expressed in HBMECs at mRNA and protein level. MTT assay manifested that rhBDNF could significantly concentration-dependently promote the HBMECs proliferation. The number of HBMECs treated with 160 ng/mL rhBDNF for 48 h was 1.57±0.10 folds higher than that in control group (P<0.05). Moreover, rhBDNF could enhance HBMECs migration in a concentration-dependent manner and the maximal migration was reached in the presence of 100 ng/mL rhBDNF. The migration indexes were 1.40±0.11, 1.64±0.16, 2.06±0.25 and 2.18±0.21 in 25, 50, 100 ng/mL rhBDNF groups and 25 ng/mL rhVEGF group, respectively. In vitro tube formation assay demonstrated that the area of the formed tubular structure was increased with the rhBDNF concentration. In control group, there was no formation of intact tubular structure and the HBMECs on the matrigel were irregularly dispersed. HBMECs treated with 100 ng/mL rhBDNF could form intact tubular structure and the area and the diameter of tubes were significantly greater than those in control group (P<0.05). There was no significant difference in the formed tubular area between 25 ng/mL VEGF group and 100 ng/mL rhBDNF group. It was concluded that BDNF plays an important role in myeloma cell-induced angiogenesis, and it may become a new target of anti-angiogenesis treatment for MM.

Deregulated microRNAs (miRNAs) and their roles in cancer development have attracted much attention. Two miRNAs, miR-15a and miR-16, which act as putative tumor suppressor by targeting the oncogene BCL2, have been implicated in cell cycle, apoptosis and proliferation. In this study, we investigated the possible role of miR-15a/16 in the angiogenesis of multiple myeloma (MM). Using a stem-loop quantitative reverse transcription-PCR, we analyzed miR-15a/16 expressions in bone marrow samples from newly diagnosed MM patients and a panel of MM cell lines. miRNA transfection, western blotting analysis and assay of luciferase activity were used to examine whether vascular endothelial growth factor (VEGF) is the target of miR-15a/16. The functional roles of miR-15a/16 on tumorigenesis and angiogenesis were examined by in vitro angiogenesis models and in vivo tumor xenograft model. We showed that miR-15a and miR-16 were significantly underexpressed in primary MM cells as well as in MM cell lines. The aberrant expression of miR-15a/16 was detected especially in advanced stage MM. In human MM cell lines and normal plasma cells, expression of miR-15a/16 inversely correlated with the expression of VEGF-A. Western blotting combined with the luciferase reporter assay demonstrated that VEGF-A was a direct target of miR-15a/16. Ectopic overexpression of miR-15a/16 led to decreased pro-angiogenic activity of MM cells. Finally, infection of lentivirus-miR-15a or lentivirus-miR-16 resulted in significant inhibition of tumor growth and angiogenesis in nude mice. This study suggest that miR-15a/16 could play a role in the tumorigenesis of MM at least in part by modulation of angiogenesis through targeting VEGF-A.

Bone marrow (BM) neovascularization and vascular endothelial growth factor (VEGF) expression in multiple myeloma (MM) correlate with disease progression. Brain derived neurotrophic factor (BDNF) is highly expressed by malignant plasma cells isolated from the majority of MM patients. Recently, BDNF was identified as a potential proangiogenic factor for the promotion of endothelial cell survival, induction of neoangiogenesis in ischemic tissues, and increase of VEGF expression in neuroblastoma. Since tropomyosin receptor kinase B (TrkB), the receptor of BDNF, is expressed by stromal cells within the BM milieu, here we sought to evaluate the involvement of BDNF/TrkB in myeloma-marrow stroma interaction and its effects on BM angiogenesis. TrkB was abundantly expressed by bone marrow stromal cells (BMSCs) isolated from healthy donors. Stimulation of BMSCs with BDNF induced a time- and dose- dependent increase in VEGF secretion, which was completely abolished by K252alpha, an inhibitor of TrkB. BDNF triggered activation of signal transducer and activator of transcription 3 (STAT3) and activator protein-1 (AP-1), whereas STAT3 was involved in mediating VEGF expression. We further delineated the biological significance of BDNF in MM by using lentiviral short-interfering RNA (shRNA). When myeloma cells were cocultured with BMSCs in a noncontact Transwell system, VEGF levels in supernatants were significantly decreased when BDNF expression was knocked down. Furthermore, silencing of BDNF expression significantly inhibited xenograft tumor growth and angiogenesis, and prolonged survival in mouse model. Our studies demonstrate that BDNF, as a potential stimulator of angiogenesis, contributes to MM tumorgenesis; it mediates stromal-MM cell interactions via selective activation of specific receptor TrkB and downstream signal transducer STAT3, regulating VEGF secretion.

Objective: To evaluate the in vivo antitumor effect of anti-brain derived neurotrophic factor (BDNF) monoclonal antibody (MoAb) on a human myeloma xenograft animal model., Methods: The xenograft tumor model was established in the nonobese diabetic/severe combined immunodeficiency (NOD/ SCID) mice by subcutaneous injection of human myeloma cell line RPMI 8226. The antibodies were injected intraperitoneally at a dose of 20 microg/mouse at day 1, day 2, day 3 after tumor cell inoculation or at a dose of 100 microg/mouse once a week after tumors were developed. The histologic and cytologic examination were performed to confirm the development of plasmacytomas. The microvascular densities (MVD) in tumors were analyzed by immunohistochemistry. The effect of anti-BDNF MoAb on the proliferation of RPMI 8226 cells in vitro and on endothelial cell network formation in the co-culture system were determined by 3H-thymidine incorporation assay and Matrigel network formation assay, respectively., Results: The xenograft NOD/SCID animal model had high capacity for growth of RPMI 8226 subcutaneous tumors and presented pathologic features of plasmacytomas. After subcutaneous injection of RPMI 8226 cells, all mice developed localized tumors in (20 +/- 2) d. On 20 microg anti-BDNF MoAb 3 consecutive treatment, the mean tumor-free time was extended to (30 +/- 6) d and survival was significantly prolonged compared with IgG-treated group [(57 +/- 7) d vs (48 +/- 4) d, P < 0.05]. When mice died naturally, the tumors size in anti-BDNF MoAb treated ones was also reduced compared with control group [(157.9 +/- 21.6) mm3 vs (405.5 +/- 35.2) mm3, P < 0.05]. When the antibody treatment (100 microg/mouse) underwent from 27 th to 60 day once a week after tumor inoculation, the local tumor growth was inhibited partially and necrosis and infiltration were observed in the tumors. The median MVD in the antibody-treated mice (100 microg/mouse) was 11 vessels/0.216 mm2. The IgG treated mice had no decrease in MVD of subcutaneous tumors compared with untreated mice. In vitro, anti-BDNF MoAb (1.5 microg/ml) significantly but partially inhibited HUVEC network formation induced by RPMI 8226 (68.2% reduction) and significantly inhibited RPMI 8226 proliferation, too. The IgG (1.5 microg/ml) treated mice had no significant effect on both of two assays., Conclusions: Anti-BDNF monoclonal antibody could inhibit growth and angiogenesis in subcutaneous myeloma tumors. BDNF is a potential therapeutic target in MM.

Patients with multiple myeloma (MM) have increased bone marrow angiogenesis, but the angiogenic properties of myeloma cells and the mechanism of MM-induced angiogenesis have not been completely clarified. The brain-derived neurotrophic factor (BDNF) and its high-affinity receptor, TrkB, have been identified as critical factors in the regulation of vessel formation. In this study, we demonstrate that patients with MM had increased BDNF and vascular endothelial growth factor (VEGF) in their peripheral blood. We also found in particular that a decreased BDNF level was correlated with the remission of MM. BDNF was expressed by the human myeloma cell line RPMI8226 and primary myeloma cells, and TrkB was expressed by human umbilical vein endothelial cells (HUVEC) at the protein levels. In a coculture system, we observed that both RPMI8226 cells and primary myeloma cells induced the migration and formation of a net-like structure in HUVEC. The anti-BDNF monoclonal antibody significantly but partially restrained the angiogenesis effect of MM cells. Moreover, in an experimental model of angiogenesis in vivo, BDNF and VEGF significantly promoted vessel formation in Matrigel plug compared to the control. These effects were also blocked by anti-BDNF monoclonal antibody. Finally, our in vitro results were supported by the in vivo finding in human myeloma xenograft NOD/SCID models. Anti-BDNF mAb treatment resulted in inhibition of tumor growth, decreased vessel density, and tumor necrosis. Our study suggested that the BDNF/TrkB signaling pathway could be involved, at least in part, in MM-induced angiogenesis.

In order to explore the probability of curcumin treating multiple myeloma (MM) via the inhibition of angiogenesis, the expressions of brain derived neurotrophic factor (BDNF) and its specific receptor in human MM cells and endothelial cells were detected by reverse transcriptase-polymerase chain reaction (RT-PCR). The angiogenic activity was evaluated by endothelial cell migration assay and tubule formation assay in vitro. The results showed that exogenous BDNF significantly induced endothelial cell tubule formation and endothelial cell migration, these two effects were inhibited by curcumin. Furthermore, BDNF was detected in the MM cell and TrkB was detected in the endothelial cell and curcumin depressed the mRNA expression of BDNF and TrkB in the dose- and time-dependent manners. It is concluded that BDNF is a novel angiogenesis protein. Curcumin interrupts the interaction between multiple myeloma cells and endothelial cells by reducing TrkB expression in endothelial cells and inhibiting BDNF production in multiple myeloma cells, eventually, resulting in inhibition of angiogenesis. This is probably one part of the mechanism of the curcumin treating MM via the inhibition of angiogenesis.