Otub1 is overexpressed in MM and confers poor prognosis to patients with MM. (A) Otub1 cDNA expression (exp.) was analyzed from HDs (n = 23), monoclonal gammopathy of undetermined significance (MGUS) (n = 44), and smoldering MM (SMM) (n = 12) based on the Zhan Myeloma 3 data set.¹³  (B) Otub1 cDNA was analyzed from HD (n = 5), MGUS (n = 11), MM (n = 133), and plasma cell leukemia (PCL) (n = 9) based on the Agnelli Myeloma 3 data set.¹⁴  (C) qRT-PCR analysis of Otub1 in bone marrow cells from HDs (n = 10) and patients with MM (n = 30). (D-E) Otub1 expression and clinical outcomes were evaluated based on the GSE2658 GEP data set²  on the PROGgeneV2 platform.¹⁵  Otub1 predicted an inferior prognosis for patients with MM in the myloid (MY) (D) and the proliferation (E) subgroups. (F-G) RPMI-8226 (F) with high c-Maf and KMS11 (G) with low c-Maf were stably infected with lentiviral GFP or GFP-Otub1. Cells were injected into nude mice via the tail vein. Mice survival was then monitored. (H) RPMI-8226 and MM1.S cells were stably infected with lentiviral Otub1, followed by cell viability assay with MTT. (I-J) MM cells were transfected with siOtub1 for 48 hours, followed by IB (I) and apoptotic assays on a flow cytometer (J). **P < .01; ***P < .001. NS, not significant; Scr, scramble.