p21 upregulation during myeloid differentiation of CD34⁺ cells. CD34⁺ cells were expanded in 100 ng/mL IL-3 and 100 ng/mL KL in 10% IMDM for 3 days and then G-CSF was added at 10 ng/mL. Similar results are seen if G-CSF is added at day 0. At day 0 and at 3-day intervals after the addition of G-CSF, nonadherent cells were harvested for morphologic analysis and RNA preparation. (Right) (bottom) Morphologic analysis of 86-107 cells on cytospins shown as percentages; myelocytes (not shown) peaked at 6%. (Top) Normalized p21 message as determined on a phosphoimager is plotted. (Left) RNA was blotted and sequentially probed with radiolabeled p21, G-CSF receptor, and actin cDNAs.