GGTI-298 reduces Mcl-1 protein levels. Plasma cell lines RPMI 8226 (A), L363 (B), XG-1 (C), and U266 (D) were treated for 2 days with solvent control, FTI-277 (20 μM), or GGTI-298 (20 μM). After protein isolation, Mcl-1, Bcl-XL, Bcl-2, and Bax expression levels were determined by Western blot analysis. Furthermore, the proapoptotic 23-kDa Bcl-2 form was detected after long exposure of the film. Data are representative of at least 3 independent experiments.