RARA and acute promyelocytic leukemia: This conclusion is supported by three lines of evidence: in fresh APL blasts, we observed a significant inverse correlation between HHEX and VEGF-A levels; HHEX silencing in PR9 cells mimics the stimulatory effect of PML-RARα on VEGF-A expression; HHEX overexpression in both NB4 and PR9 cells markedly inhibits PML-RARα-induced VEGF-A expression.