Decrease in MIP-1 α in response to FGFR3 inhibition. (A) An MTT assay performed at 72 hours following drug exposure shows inhibition of cell proliferation in CHIR258-treated cells. H929 cells harboring a t(4;14) and a RAS mutation are resistant to treatment. The error bars show standard deviation in replicate of 3 experiments. indicates the DMSO control; ▪, cells treated with CHIR258. (B) Flow cytometry shows down-regulation of intracellular MIP-1α in CHIR258-sensitive KMS11 but not-resistant H929 MM cells. Cells were examined at 48 hours after drug exposure. The dotted line indicates isotype control; black line, vehicle-treated cells; and gray line, CHIR258-treated cells. Experiments were repeated twice with similar results. (C) Flow cytometry confirms down-regulation of intracellular MIP-1α in PD173074-sensitive KMS11. Cells were examined at 48 hours after drug exposure. The dotted line indicates isotype control; black line, vehicle-treated cells; and gray line, PD173074-treated cells. Experiments were repeated twice with similar results.