Cytotoxicity profile of CEP-18870 against normal human cells. (A,B) BMMCs and PBMCs were treated with control diluent, CEP-18770 (20 nM) or BOR (10 nM) for 48 hours. PBMCs were derived from 5 nonmyelomatous donors; BMMCs from 2 nonmyelomatous donors and from 7 patients with MM; cell viability was measured by MTT assay. Cells were incubated in triplicate for each condition. Histograms represent means (± SD, error bars) of data derived from different patients, as indicated above in this paragraph. (C) BMMCs derived from 5 nonmyelomatous donors and from 7 patients with MM were used to establish long-term BMSC cultures. BMSCs were treated with control diluent, CEP-18770 (20 nM), or BOR (10 nM) for 6 days. Apoptosis was measured by flow cytometry after TMRM staining. Histograms represent the means (± SD, error bars). (D) CEP-18870 inhibits the expression of inflammatory cytokines and adhesion molecules in BMSCs. BMSC cultures, obtained as described above, were expanded for 4 to 6 passages and treated with control diluent, CEP-18870 (20 nM), or bortezomib (BOR) (10 nM) for 60 hours. Levels of VCAM1, ICAM1, IL6, IL1β, VEGF isoforms, and β2-microglobulin mRNA were analyzed by semiquantitative RT-PCR. Fragment length is indicated; 275 base pairs (bp) and 407 bp amplification fragments correspond to the known VEGF isoforms of 121 and of 165 amino acids, respectively. BMSCs were derived from 1 patient with MM (BMSC 1) and from 2 nonmyelomatous donors (BMSC 2 and 3). (E,F) Hematotoxicity of CEP-18770 and BOR on bone marrow progenitors. BMMC derived from 16 patients with MM (PC < 10%) were pretreated with control diluent, CEP-18870 (20 nM), or BOR (10 nM) for 48 hours. Cells were washed and cultured in cytokine-containing methylcellulose medium for granulocyte-macrophages (CFU-GM) or erythroid (BFU-E) colony formation. (E) Early CFU-GM and (F) BFU-E-derived colonies were scored after 14 days of incubation. Histograms represent the means (± SD; error bars). *P < .05; **P < .01 as analyzed by Student t test.