Gene expression profiling of normal, MGUS, smoldering, and myeloma patient plasma cells and generation of a sumoylation pathway signature. (A) Gene expression profiles of sumoylation pathway components from normal, MGUS, SMM (GEO dataset GSE5900), and MM (GEO dataset GSE4204). Samples were median centered and ordered according to average expression of the sumoylation pathway genes. B indicates normal B cells; PC, normal plasma cells; and PCL, plasma cell leukemia. (B) Sumo-pathway signature in the 7 sub-branches of MM, SMM, MGUS, and normal PCs. The sub-branches were classified by expression of MMSET (MS), MAF/MAFB (MF), and proliferation (PR) signatures that constituted high-risk disease, whereas hyperdiploidy (HY), low bone disease (LB), and CCND1/CCND3 translocations (CD1 and CD2) represented low-risk MM. (C) RT-PCR of UBE2I in MGUS and MM patient samples. GAPDH (glyceraldehyde phosphate dehydrogenase) served as a loading control. UBE2I refers to the gene that encodes the SUMO-conjugating enzyme UBE2I; Neg, PCR reaction with no plasma cell cDNA and primers added. Normal plasma cells were purchased from AllCells.