Expansion of SALL4-transduced HSCs. (A) HSCs transduced with SALL4A and SALL4B are able to survive and expand rapidly 7 days after lentiviral infection (10×). (B) CD34⁺ cells isolated from peripheral blood stem cells of 3 different patients. CD34⁺ cells were isolated from the stem cell pool using magnetic anti-CD34⁺ human microbeads. The CD34⁺-enriched cells were transduced with SALL4A and imaged under bright field and fluorescent microscopy (40×). All 3 samples from the various patients were successfully transduced with SALL4A and expanded rapidly in culture. In addition, SALL4-induced HSCs are able to expand when growth factor concentrations are decreased. When SALL4-transduced HSCs were cultured in growth media containing 50% less cytokines (C), they were still able to survive and expand 6 days after lentiviral infection (40×). Furthermore, when growth factor concentrations were decreased to 25% of original values (D), the SALL4-transduced HSCs continued to proliferate (40×). In contrast, control cells had undergone cell death by day 6.