RARα2 expression is associated with poor prognosis in MM. RT-PCR detected the expression of RARα1, RARα2, and GAPDH in MM cells from patients (P1-P4; A) and MM cell lines (B). Representative results are shown. (C) Kaplan-Meier analysis of OS of patients newly diagnosed with RARα2⁺ (n = 26) and RARα2⁻ (n = 54) MM in TT2 and TT3 trials. (D) RT-PCR was used to examine RARα2 expression in RARα2 knockdown MM cells (R2⁻). Wild-type (WT) and nontargeting scramble shRNA (SCR)–transfected cells were used as controls; RARα2 knockdown MM cells were cultured for 4 days, live cells were counted to calculate cell proliferation (E), and dead cells were determined by positive trypan blue staining, from which the dead-cell fraction was calculated (F). Results are expressed as means plus or minus SD of 3 independent experiments. *P < .05. (G) Western blot analysis of caspase-3, caspase-8, and caspase-9 (cleaved and uncleaved proteins) in WT, SCR, and R2− cells of ARK, KMS11, and OPM2 MM cells. Cells were collected at day 3 in the cultures. β-actin was used as loading control. Shown are the representative results of 3 independent experiments.