PML-RARα mRNA induction in U937/PR9 cells and expression levels in primary APL cells. (A) TaqMan RT-PCR analysis showing the induction of PML-RARα mRNA expression in U937/PR9 cells treated with 200 μM ZnSO4 for 24 hours and the levels of PML-RARα mRNA in primary APL cells. PML-RARα mRNA expression of each sample was normalized to β2-microglobulin. PR9 cells without ZnSO4 were used as calibrators (PML-RARα mRNA level in PR9 cells without ZnSO4 = 1). APL cell line NB4 was used as a reference. (B) Amplification plot of PML-RARα cDNA expression in PR9 cells following ZnSO4 treatment in NB4 and primary APL cells. Blue lines indicate PR9; magenta lines, NB4; and red lines, primary APL cells. (C) Western blot showing the induction of PML-RARα protein expression in U937/PR9 cells treated with 100 μM or 200 μM ZnSO4 and in NB4 cells. (D) PR9 cells exposed to ZnSO4 (200 μM) were cultured in medium with or without 1 μM ATRA, and growth curves were constructed. Live cells were counted daily using the trypan blue exclusion method. Graphs represent the mean ± SD of the results obtained from 3 independent experiments. In the absence of ZnSO4, PR9 cells were cultured without ATRA (□) or with ATRA (▪). In the presence of ZnSO4, PR9 cells were cultured without ATRA (○) or with ATRA (•).
