PSME1 and monoclonal gammopathy: We next evaluated the expression of PSME1 (which encodes PA28α) in plasma cells from healthy donors, monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), newly diagnosed multiple myeloma (NDMM), and relapsed/refractory multiple myeloma (RRMM) using data from Chng et al.26.