pAKT expression in paraffin-embedded xenograft tumors after fixation delays and human breast cancer by optimized immunohistochemistry.

10603 Background: With progress in targeting PI3K/AKT pathway in the treatment of a wide range of cancers, it is getting more important than ever for optimization of detection method of AKT kinase, a central effector of the pathway, in archived tissues. Recently, we found that pAKT-S473 (pAKT) significantly predicts paclitaxel benefit in breast cancer (JCO 28: 2974, 2010), in which a good analytical and clinical performance of quantitative pAKT immunohistochemistry (IHC) was demonstrated. The current study evaluates pAKT stability in human breast cancer xenograft tumors after delays in fixation, and assesses a detection window following fixation delays with an established cutoff [staining index (SI) > 2]. Methods: Xenograft tumors with high (MDA-MB-468) and intermediate levels (MDA-MB-231) of pAKT were fixed or snapped frozen in 10% neutral-buffered formalin or liquid nitrogen after delays post-excision. pAKT staining was performed in xenograft tumors and 96 cases of human surgical breast tumors by our op...