MLN8237 inhibits cell viability and proliferation in MM cells in the presence or absence of BM stroma cells. A panel of MM cell lines and tumor cells obtained from patients with MM were treated with DMSO or increasing doses of MLN8237 (0.0001-4μM) for 48 to 72 hours. (A) Inhibition of cell line viability was determined by MTT assay. Inhibition of cell proliferation was determined by 3[H]thymidine incorporation assay in MM cell lines (B) and in tumor cells obtained from MM patients (C). MM1.S and RPMI8226 cell lines and tumor cells from patients with MM were cocultured with either BM stroma cells from patients with MM or cytokines (IL-6, 10 ng/mL; IGF-1, 25 ng/mL), in the absence or presence of MLN8237 (0.001-4μM) for 24 to 48 hours. (D) MM cell proliferation was measured by 3[H]thymidine incorporation assay in the cocultures with BM stroma cells. (E) MM cell viability was also assessed by MTT assay, in the absence or presence of IL-6 or IGF-1. Data represent mean ± SD of triplicate cultures. Statistical significance indicated (t test, 1-tailed distribution, P < .05).