Expression of p110 isoforms in leukemic blasts from patients with AML. Expression of class IA (p110α,-β and -δ) and class IB (p110γ) catalytic subunits of PI3K was tested in leukemic blasts of 21 patients showing a constitutive activation of PI3K. Results from the 10 patients described in Table 1 are presented. Blast analysis of the other patients gave similar results. Proteins from 10⁶ cells were separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) and analyzed by Western blot using antibodies specific for the various isoforms of p110. p110α and p110β antibodies were from Cell Signaling Technology (Beverly, MA). p110δ antibodies have been described previously¹⁸  and p110γ antibodies were provided by Dr R. Wetzker.¹⁹  Purified recombinant p110 proteins and cell lysates from 10⁶ OPM2 cells were used as controls. Western blot using antiactin antibodies (Sigma, St Louis, MO; cat number A5441) was used to assess equal loading of the samples.