OBJECTIVETo investigate the expression of amyloid precursor protein (APP) gene in acute myeloid leukemia (AML) and its biological behaviour in AML cells.

METHODSThe expressions of APP mRNA in 85 AML and 20 nonmalignant hematological diseases patients (as control) were measured by real-time PCR. The expression of APP in AML cell lines was also examined by real-time PCR and Western blot and the results were compared with those in their original subtypes. Small interfering RNAs (siRNAs) targeting APP gene were synthesized and transfected into HL-60 cell by lipofectamine 2000 for 24 h, 48h and 72 h. Cell growth was measured by trypan blue dye exclusion and MTT, differentiation by Wright-Giemsa staining, cell cycle by PI/RNase staining, apoptosis by Annexin V/PI and Hoechst33342 staining. Apoptosis-related protein NF-κB, bcl-2 and Caspase-3 were detected by Western blot after siRNAs transfection for 48 h. Sensitivity to adriamycin was measured by MTT.

RESULTSThe expression of APP mRNA among AML subtypes differed significantly (P = 0.019), the highest expression subtype was M(2) with t(8;21) (median 0.1080), followed in order by AML-undefined (0.0467), M(3) (0.0266), M(2a) (0.0221), M(4a) (0.0167), M(5b) (0.0151), and M(4b) (0.0025). APP expression had no significant effect on AML clinical characteristics excepting for subtypes. The expression of APP in Kasumi-1 cells was significantly higher than that of U937 cells (P < 0.05), which was in agreement with APP expression in their original AML subtypes. After siRNAs transfection for 24 h, 48 h, and 72 h, no significant difference in proliferation, differentiation, apoptosis, cell cycle and sensitivity to adriamycin was detected between interfering group and control groups (P > 0.05).

CONCLUSIONSThe APP mRNA expression was highest in M(2) with t(8;21) and lowest in M(5b). Down-regulation of APP expression has no significant effects on biological behaviour of HL-60 cells.