SDC1 and monoclonal gammopathy: To investigate the latter possibility, HGF mRNA expression levels were measured by whole genome cDNA microarray in CD138+ cells isolated from bone marrow aspirates of healthy individuals (NPC; n = 22) and patients diagnosed with monoclonal gammopathy of undetermined significance (MGUS; n = 14), smouldering MM (SMM; n = 34), and MM (MM; n = 344).