Three-day treatment of drugs targeting phosphatidylinositol 3-kinase pathway reduces active Akt level in basal-like xenografts. (A) Immunostaining of tissue sections from basal-like (BL; left) and luminal-like (LL; right) xenografts given vehicle control (upper panel), MK-2206 (middle panel) or BEZ253 (lower panel). pAktser473 (red) and total Akt (green) are stained as in Figure 1. All scale bars = 1 mm. (B) Quantification data from near-infrared (NIR) immunofluorescence imaging (n = 4). The signal intensity was significantly reduced after treatment with MK-2206 and BEZ235 in BL but not in LL xenografts. *P <0.05, **P <0.0005. (C) Immunoblot analysis of tumor lysates for the level of pAktser473 (upper panel) and β-actin loading control (lower panel). Lysates were prepared from tumors harvested 3 to 6 hours after the last administration of MK-2206 and BEZ235.