p21-antisense increases primitive hematopoietic cells in transduced CD34⁺ human bone marrow cells. CD34⁺ human bone marrow cells were transduced with a lentiviral vector containing p21-antisense (p21-AS-V) or the control vector (GFP-V). At 4 days after transduction cells were analyzed by flow cytometric analysis and in vitro assays. (A) Transduced cells were stained for CD34 and CD38 and incubated with PI. Chart shows the mean ± SEM of total CD34⁺38^– PI^– cells after transduction. (B) Transduced cells were analyzed in a CFC assay for progenitor frequency. Chart shows mean ± SEM of CFU-mix representing primitive colony-forming cells per 500 transduced cells. (C) Transduced cells were analyzed in an LTC-IC assay for stem cell frequency. Chart shows the LTC-IC frequency per 100 000 transduced cells. Dashed line represents the average.