Stable drug-resistant phenotype of B-1R cells is not caused by inactivation of the FT. (A) B-1 cells were treated with SCH66336 as indicated. Viability is expressed as the percentage of trypan blue-excluding cells of the total number of cells present. The error bars indicate the standard deviation. (B) B-1R or B-1S cells were cultured for 6 weeks without SCH66336, then treated de novo with 16 μM SCH66336 or with vehicle DMSO for 48 hours and viability was determined. One of 2 experiments with similar results is shown. The error bars in panels A and B indicate standard deviation. (C) Western blot analysis with an anti-HDJ-2 antibody, diagnostic for FT activity. B-1R or B-1S cells not treated with SCH66336 show only the farnesylated form of HDJ-2 (left), indicating that the FT is active. After 24 hours of treatment with 1 μM SCH66336, the original B-1 cells, the FTI-resistant B-1R cells, and the drug-sensitive B-1S cells all exhibit the appearance of the more slowly migrating, nonfarnesylated HDJ-2 protein (middle), showing that all 3 contain an FT that is inhibited by the FTI. Treatment of B-1R cells with 16 μM SCH66336 (right) caused the appearance of very large amounts of nonfarnesylated HDJ-2 protein.