Pim2 is required for maintaining MM cell growth. (A) Significant knockdown of Pim2 protein by shRNAs in multiple MM cell lines, including KMS-11.luc, KMS-26, and KMS-34. (B) Pim2 knockdown inhibits MM cell growth. Pim2 levels were knocked down by shRNAs in KMS-11.luc, KMS-26, and KMS-34 cells as in (A). Cell growth was monitored by cell titer glow (CTG) assay at indicated time points. Relative proliferation was normalized to Day 2, which is 24 hours after puromycin selection. (C) Exogenous shRNA-1226–resistant Pim2 expression rescues the growth inhibition effect caused by Pim2 knockdown. Endogenous Pim2 level was reduced by shRNA-1226, which targets the 3′ untranslated region of Pim2 mRNA. WT-Pim2 and KD-Pim2, with empty vector as transfection control, were reintroduced into KMS-11.luc cells (top). Cell growth was monitored by CTG assay at indicated time points (bottom).