CD33 expression and Pgp activity in responders and nonresponders. (A) CD33 expression on AML blasts of responders (CR+CRp) and nonresponders (NR) who survived beyond day 28 of study initiation, determined by flow cytometry after staining with the anti-CD33 antibody hP67.6. (B) Pgp activity of AML blasts of responders and nonresponders who survived beyond day 28 of study initiation, determined by flow cytometry using the fluorescent Pgp substrate DiOC2. (C) Correlation between CD33 expression and Pgp activity. Dot plot graph showing individual data on CD33 expression levels and Pgp activity in responders (CR+CRp; ○) as well as nonresponders (NR; •) who survived beyond day 28 of study initiation; n = 208. The same magnitude of correlation was seen when the patients who died before day 28 were not excluded from the analysis (r = −0.23; n = 230; P < .001).
