Akt activity is greatly induced in the 2 human MM lines (OPM2 and Δ47), but not in any mouse PCT lines.

(A) Cell lines were serum starved for 2 hours and either untreated or stimulated with either IGF-I (100 ng/mL) or PDGF-BB (100 ng/mL) for 10 minutes. Equivalent amounts of cell lysates from each sample were immunoprecipitated with anti-Akt serum. Washed immunoprecipitates were subjected to an Akt activity assay using Histone H2B as substrate. The kinase reaction was separated by 12% SDS-PAGE and transferred proteins on Immobilon P were detected by autoradiography. Phosphorylated Histone H2B is indicated. (B) Cell lines were similarly treated as in panel A. When wortmannin (100 nmol/L; abbreviated as wort in the figure) was used, it was added 20 minutes before IGF-I stimulation. Equivalent amounts of cell lysates were subjected to a SDS-PAGE. Transferred proteins were immunoblotted with anti–P-Akt (Ser473). (C) The same Immobilon P derived from panel B was reblotted with anti–Akt antibody.