Inhibition of colony growth by the addition of U0126, FPT-3, and FTI-277.

Purified human CD34⁺ cells and myeloid leukemia cell lines were incubated in liquid suspension cultures with increasing concentrations of the MEK inhibitor U0126, the FPP-based FTI FPT-3, and the CAAX-based FTase inhibitor FTI-277. After 4 days, viability of the cells was determined by trypan blue dye assays. Aliquots of the samples were incubated in methylcellulose for an additional 7 to 14 days in the presence of freshly added inhibitors. Representative experiments are shown. Results are expressed in percentage inhibition of maximal spontaneous colony growth or cell density. Error bars indicate the SE of margin.