AML1-ETO promotes the long-term in vitro expansion of human CD34⁺ cells. Human CD34⁺ cells were transduced with the MIGR1 or the MIGR1-AE retrovirus and expanded in culture using a mixture of human cytokines and 20% FBS or a serum substitute. Cells were counted by trypan blue dye exclusion weekly and replated at 4 × 10⁵ cells/mL. Dagger indicates death of culture.