Effect of FTY720 analogs on the stability of the SET/PP2A complex. (A) Chemical structure of FTY720 analogs. (B) Freshly isolated CLL cells were cultured in the absence or presence of increasing concentrations of MP01-66, MP04-66, MP06-66, or MP07-66 for 8 hours. After such treatment, each sample was immunoprecipitated with anti-PP2Ac antibody, and the immunocomplexes were analyzed by western blot (Wb) analysis with anti-SET. Blots were then stripped and reprobed with anti-PP2Ac antibody. (C) Whole B-cell lysates were incubated with pAkt, obtained by immunoprecipitation from CLL cells, in the absence or presence of increasing concentrations of MP01-66, MP04-66, MP06-66, or MP07-66 for 10 minutes at 37°C. After such treatment, the samples were analyzed by Wb analysis with anti-pAkt and anti-Akt antibodies. Pooled densitometric analyses (arbitrary units) of the Wb bands of the immunoblots are shown. The figure is representative of experiments performed in triplicate on samples from each of 16 CLL patients.