OPN protein expression by IHC and survival. OPN expression in control BM (A) and AML (FAB AML M5; B) obtained at presentation. IHC localization was performed using the respective specific Abs and the alkaline phosphatase/antialkaline phosphatase technique. Note the expression of OPN in the BM sections of AML patients (B arrowhead) compared with the controls (A arrow). Original magnification, 200×. Images were captured with Axiocam (Zeiss) using Axiovision (Zeiss) and Image-Pro Plus (Media Cybernetics). Kaplan-Meier curves of OS and relapse-free survival for AML patients stratified for BM OPN expression are shown. OS of patients expressing high levels of OPN (≥ 9.662 AUs) in the BM was significantly lower than of patients with low OPN expression (< 9.662 AUs; P = .025; C). Although a visible trend, the difference found for relapse-free survival was not significant (P = .279; D).