Significant induction of BIRC6 mRNA levels upon neutrophil differentiation of AML cells. (A) BIRC6 qPCR analysis of NB4 APL cells treated with 1 μM ATRA for 4 and 6 days. Raw Ct values were normalized to HMBS and to the untreated control of day 4. Results from four independent experiments in duplicates are shown. (B) BIRC6 qPCR analysis of ATRA-resistant NB4-R2 APL cells treated as in A. (C) CD11b surface expression of NB4 and NB4-R APL cells upon six days of ATRA-induced neutrophil differentiation. CD11b was measured by FACS analysis. (D) Neutrophil differentiation of HL60 AML cells with 1 μM ATRA for 4 and 6 days, respectively. BIRC6 mRNA expression was assessed by qPCR as in A. (E) BIRC6 qPCR analysis of ATRA-resistant HL60-R cells treated as in A. (F) The differentiation levels of HL60 and HL60-R were assessed by CD11b surface expression upon 6 days of ATRA-induced neutrophil differentiation. Mann–Whitney U test *p < 0.05, **p < 0.01, ***p < 0.001, ns not significant.