IRF4 and plasma cell myeloma: Recently, Phoebe et al. described the role of interferon regulatory factor 4 (IRF4) in the regeneration of myeloma progenitor cells in cell stem cell and found that the overexpression of IRF4 increased the proportion of myeloma progenitor cells, among which CD138− is used as an important screening marker for myeloma progenitor cells [60].