Aberrant expression of annexin A2-S100A10 heterotetramer (AIIt) associated with PML/RARα fusion protein causes lethal hyperfibrinolysis in acute promyelocytic leukemia (APL),but the mechanism is unclear.To facilitate the investigation of regulatory association between ANXA2 and promyelocytic leukemia/retinoic acid receptor α (PML/RARα) fusion protein,this work was performed to determine the transcription start site of ANXA2 promoter with rapid amplification of S’-cDNA ends analysis.Zinc-induced U937/PR9 cells expressed PML/RARα fusion protein,and resultant increases in ANXA2 transcripts and translational expressions of both ANXA2 and S100A10,while S100A10 transcripts remained constitutive.The transactivation of ANXA2 promoter by PML/RARα fusion protein was 3.29 ± 0.13 fold higher than that by control pSG5 vector or wild-type RARα.The overexpression of ANXA2 in U937 transfected with full-length ANXA2 eDNA was associated with increased S100A10 subunit,although S100A10 transcripts remained constitutive.The tPA-dependent initial rate of plasmin generation (IRPG) in zinc-treated U937/PR9 increased by 2.13-fold,and cell invasiveness increased by 27.6％.Antibodies against ANXA2,S100A10,or combination of both all remarkably inhibited the IRPG and invasiveness in U937/PR9 and NB4.Treatment of zinc-induced U937/PR9 or circulating APL blasts with all-trans retinoic acid (ATRA) significantly reduced cell surface ANXA2 and S100A10 and associated reductions in IRPG and invasiveness.Thus,PML/RARα fusion protein transactivated the ANXA2 promoter to upregulate ANXA2 and accumulate S100A10.Increased AIIt promoted IRPG and invasiveness,both of which were partly abolished by antibodies against ANXA2 and S100A10 or by ATRA.