CDDO-Im inhibits growth and induces apoptosis in human MM cells sensitive and resistant to conventional drugs. (A) MTT assays were performed after incubation of Dex-sensitive MM.1S (□), U266 (), Dex-resistant MM.1R (⋄), melphalan-resistant LR-5 (▪), RPMI 8226 (○), and doxorubicin-resistant Dox-40 (•) with indicated doses of CDDO-Im for 24 hours. Results are mean ± SD from 3 independent experiments (P < .0001 for all cell lines). (B) MM cell lines were treated with CDDO-Im (200 nM) and analyzed for apoptosis by annexin V staining. Results are mean ± SD from 3 independent experiments (P < .005 for all cell lines).