UBA2 and plasma cell myeloma: mRNA profiling of myeloma patient cohort GSE5900 showed that SUMO E1 (Ubiquitin Like Modifier Activating Enzyme 2(UBA2)/SUMO activating enzyme 2 (SAE2)) gene expression was significantly upregulated at the premalignant myeloma stage (MGUS) and in the asymptomatic myeloma phase (smoldering MM) compared to healthy plasma cells (Supplemental Fig. S1A).