Fig. 1
BBR-induced inhibition of cell growth in vitro translated to anti-MM activity in vivo. a Chemical structure of BBR. Chemical name: 1,3-benzodioxolo[5,6-a] benzo[g] quinolizinium, 5,6-dihydro-9,10-dimethoxy-, hydrochloride (1:1). Molecular formula: C20H18ClNO4. Molecular weight: 371.81. CAS number: 633-65-8. b BBR induced cytotoxicity in MM cell lines. Mice BM, BaF3, SP2/0, and MM cell lines were treated with BBR (0–100 μM), and viability was determined at 48 h using MTT assay. The IC50 of BBR in MM cells ranged between 15 and 25 μM at 48 h. The data were presented as the mean ± SD obtained from three independent experiments. c BBR activity on normal human peripheral blood mononuclear cells (hPBMCs). Normal hPBMCs were separated using Ficoll-paque density sedimentation and treated with BBR (0–100 μM) for 48 h. Cell viability was determined at 48 h using MTT assay. The data were presented as the mean ± SD obtained from three independent experiments. d BBR induced cytotoxicity in primary tumor cells from MM patients. Purified patient MM cells were cultured with BBR (0–100 μM), and cell viability was determined at 48 h using MTT assay. The data were presented as the mean ± SD obtained from three independent experiments. e, f BBR inhibited the colony formation ability of RPMI-8266 and MM.1S cell lines. Histogram and statistics indicated the relative number of colonies per 1000 plated cells. The data were presented as the mean ± SD obtained from three independent experiments. Significance was determined by Student’s t test, *p < 0.05 versus control. g–i The anti-MM activity of BBR in vivo. 2 × 107 RPMI-8266 cells were subcutaneously injected into sub-lethally irradiated (3 Gy) BALB/c mice. Tumor-bearing mice were randomly assigned into 2 cohorts receiving either vehicle or BBR (50 mg/kg) every other day for 2 consecutive weeks. BBR treatment resulted in tumor growth inhibition. The average and SD of tumor volume (mm3) are shown from mice (n = 7/group) versus the time when the tumor was measured (p = 0.0252). Prolonged survival was observed in BBR treatment groups (p < 0.01)