Figure 2.

Effects of PTEN loss and PIK3CA mutation on AKT activation in human breast tumors. PTEN and the two AKT phosphorylation sites (AKTp308 and AKTp473) were quantified using reverse-phase protein lysate array. The quantification data were then log transformed (base 2), mean centered, ordered by increasing PTEN expression level from above down, and plotted in the heat map shown. In the mean centering schema used, red indicates a relatively high level of (phospho)protein expression and green indicates a relatively low level of (phospho)protein expression. The level of PTEN expression is shown in lane 1 and the levels of AKT phosphorylation at Thr³⁰⁸ and Ser⁴⁷³ are shown in lanes 2 and 3, respectively. AKT phosphorylation was expressed as a ratio to total AKT expression for presentation in this figure. Clearly, AKT phosphorylation is strongly inversely correlated with PTEN protein expression. However, there is no clear association between PIK3CA mutation and AKT phosphorylation at either amino acid site. Further, there was no significant difference (P = 0.41) in the frequency of tumors with PIK3CA mutations among those tumors with the highest and lowest quartiles of PTEN expression [17 of 77 (22.1%) and 12 of 77 (15.6%), respectively]. Tumors from one institution batch (i.e., from Clinic Hospital) were used for this analysis.