Clinically, a gene array assay using plasma cells from healthy donors, patients with monoclonal gammopathy of undetermined significance (MGUS), and patients with smoldering MM (SMM) revealed no obvious difference in HRP2 expression between healthy donors and patients with MGUS, but significantly lower expression was detected in plasma cells of patients whose disease had progressed to SMM (Figure 1E). The gene discussed is HDGFL2; the disease is monoclonal gammopathy.