We also observed that the expression of PU.1 driven by a conditional estrogen-activated element led to cell growth arrest and apoptosis, in agreement with earlier findings of MEL, K562 leukemia and myeloma cell lines (Aoyama et al. 2012; Tatetsu et al. 2007; Yamada et al. 1997). The gene discussed is SPI1; the disease is plasma cell myeloma.