Coculture with FN.

Coculture with FN prevents entry into S phase and is associated with elevated p27^KIP1 levels. G-CSF–mobilized PB CD34⁺ cells were analyzed fresh or after coculture with FN or PLL for 60 hours in the presence of serum-free medium supplemented with low concentrations of cytokines. Adherent and nonadherent cells were collected separately and labeled with propidium iodide (FACS analysis cell cycle status, n = 3) or subjected to Western blot (representative example of 2 experiments; levels of p27^KIP1) as described in “Materials and methods.” Quantitative differences in protein levels were evaluated by scanning images with the use of a GS-700 Imaging Densitometer, and the images were quantitated using Molecular Analyst software. Values under Western blot represent relative density of each band compared with day 0 levels of p27^KIP1.