Quantitative assessment of preanalytic variables on clinical evaluation of PI3/AKT/mTOR signaling activity in diffuse glioma. (PubMed, Mod Pathol)
First, we determined the impact of delayed time-to-formalin fixation, or cold ischemia time (CIT), on the quantitative assessment of cellular expression of six phosphoproteins that are readouts of PI3K/AK/mTOR activity (phosphorylated -proline-rich Akt substrate of 40 kDa (p-PRAS40, T246), -mechanistic target of rapamycin (p-mTOR; S2448); -AKT (p-AKT, S473); -ribosomal protein S6 (p-RPS6, S240/244 and S235/236), and -eukaryotic initiation factor 4E-binding protein 1 (p-4EBP1, T37/46)...Quantification of p-RPS6 (240/244) expression in multiple regionally distinct human tumor samples from eight patients revealed significant intratumoral heterogeneity. Thus, the accurate assessment of PI3K/AKT/mTOR signaling in diffuse glioma must overcome intratumoral heterogeneity and multiple preanalytic factors, including time-to-formalin fixation, slide storage conditions, and phosphoprotein of interest.