[Establishment of multiple myeloma mouse models expressing brain derived neurotrophic factor]

Previous studies have demonstrated the effects of brain-derived neurotrophic factor (BDNF) on promoting proliferation of multiple myeloma (MM) cells and inducing angiogenesis in MM in vitro. This study was aimed to further explore whether BDNF/TrkB pathway is a potential therapeutic target in MM, and to elucidate the advantages and disadvantages of two ways developed for human myeloma xenograft in animal models. The models of xenograft tumors were established in the non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice by subcutaneous or intravenous injection of human myeloma cell line RPMI8226. Mice were monitored daily for life state, and the volume of subcutaneous tumors were measured after inoculation. 3 weeks after inoculation, red blood cell counts, BDNF level in plasma, human lambda light chain and calcium level in serum of NOD/SCID were detected every two weeks. The histological and cytological examinations were performed to observe pathological features of tumors. Using flow cytometry to observe the expression of human CD38+ cell in murine blood and bone marrow. The changes of bone density and skeletal lesions were detected by computer radiography. The results showed that the subcutaneously injected animal model showed a high growth efficiency of RPMI8226 subcutaneous tumors (5/5) and several pathological features of plasmacytomas. There were neither obvious increase in lambda light chain and calcium levels, nor spread of human MM cells to murine bone marrow and no radiological evidence of skeletal lesions. The intravenously injected animal model had relative low efficiency for growth of tumors (4/7) but MM cells could engraft and proliferate in murine bone marrow. The human lambda light chain could be detected in serum as early as 3 weeks after inoculation. Myeloma-bearing mice had high level of lambda light chain and high calcium in serum and resorption of the murine bone. Furthermore, the concentrations of BDNF were increased with the tumor growth in both models with (73 +/- 11) pg/ml and (105 +/- 18) pg/ml in plasma respectively at 9 weeks after inoculation. It is concluded that two appropriate MM xenograft NOD/SCID animal models were established, both of which show high BDNF levels in the plasma. Therefore, two valuable in vivo systems to explore novel therapeutic target (BDNF/TrkB) in MM have been set up successfully.