FIGURE 4.

Ectopic expression of VentX in CD34⁺ cells inhibits colony formation. A–C, human bone marrow CD34⁺ cells were transfected with either the GFP VentX or GFP VentX plasmid as described under “Experimental Procedures.” Positively transfected cells (2 × 10⁴) were sorted and cultured in triplicates in methylcellulose-based medium for CFC enumeration. The number of BFU-E/CFU-E colonies is shown in A, and the number of CFU-GM colonies in B. C, total progenitor cells from 2 × 10⁴ CD34⁺ cells after culturing for 2 weeks. The significant difference was determined by Student's t test (p < 0.05). D, representative images of the CFC assay showing erythroid colonies in GFP- or GFP-VentX-transfected CD34⁺ cells. E, human CD34⁺ cells were treated with 1 μm SR1 for 1 week or mock-treated (control (Ctr)). The treated cells were then harvested for analysis of VentX mRNA expression levels. F, GFP- or GFP-VentX-transfected CD34⁺ cells (2 × 10⁴) were sorted and treated with 1 μm SR1 for 1 week or mock-treated. The total cell numbers were then counted and plotted.