Molecular signature of retinoic acid treatment in acute promyelocytic leukemia

Abstract

Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia characterized by a block of differentiation at the promyelocytic stage. APL patients respond to pharmacological concentrations of all-trans retinoic acid ( RA) and disease remission correlates with terminal differentiation of leukemic blasts. The PML/RAR oncogenic transcription factor is responsible for both the pathogenesis of APL and for its sensitivity to RA. In order to identify physiological targets of RA therapy, we analysed gene expression profiles of RA-treated APL blasts and found 1056 common target genes. Comparing these results to those obtained in RA-treated U937 cell lines revealed that transcriptional response to RA is largely dependent on the expression of PML/RAR. Several genes involved in the control of differentiation and stem cell renewal are early targets of RA regulation, and may be important effectors of RA response. Modulation of chromatin modifying genes was also observed, suggesting that specific structural changes in local chromatin domains may be required to promote RA-mediated differentiation. Computational analysis of upstream genomic regions in RA target genes revealed nonrandom distribution of transcription factor binding sites, indicating that specific transcriptional regulatory complexes may be involved in determining RA response

MicroRNA gene expression during retinoic acid-induced differentiation of human acute promyelocytic leukemia

“…Previous studies have shown the activation of NF-kB upon ATRA-induced maturation of APL (Mathieu et al, 2005) and enrichment for NFkB binding sites in RA target genes has been described (Meani et al, 2005). To investigate whether ATRAinduced NF-kB activation regulates miRNAs, we cotransfected NB4 cells with a potent NF-kB inhibitor expression plasmid (IkBa-SR) or empty vector and treated the cells with ATRA or dimethylsulphoxide (DMSO) (control).…”

Pirin downregulation is a feature of AML and leads to impairment of terminal myeloid differentiation

“…Total RNA was extracted from U937 cells transduced with shPIR 7 or with the empty pSICO-R vector and hybridized to Affymetrix GeneChip HG-U133 Plus 2.0 arrays as described in Materials and methods. Results were analyzed as previously Pirin downregulation in AML S Licciulli et al described, 3,18 and regulated genes (more than twofold) were annotated and classified using the Ingenuity pathways analysis software. A total of 492 regulated genes were identified, 305 induced and 187 repressed, after knockdown of PIR protein (Supplementary Table 2).…”

Pro-proliferative function of the long isoform of PML-RARα involved in acute promyelocytic leukemia

“…PML-RARa is a potent and specific activator of c-fos promoter By gene array, PML-RARa upregulates 1569 and downregulates another 1726 genes (Alcalay et al, 2003;Park et al, 2003;Nouzova et al, 2004;Meani et al, 2005). Examples of repressed genes are RARb2 and C/EBPb (Di Croce et al, 2002;Duprez et al, 2003), while examples of induced genes are Cyclin A1, p21 and c-fos (Casini and Pelicci, 1999;Mu¨ller et al, 2000;Alcalay et al, 2003;Meani et al, 2005).…”

“…Examples of repressed genes are RARb2 and C/EBPb (Di Croce et al, 2002;Duprez et al, 2003), while examples of induced genes are Cyclin A1, p21 and c-fos (Casini and Pelicci, 1999;Mu¨ller et al, 2000;Alcalay et al, 2003;Meani et al, 2005). Given that c-fos gene is involved in proliferation, we hypothesized that part of the function of PML-RARa may be to directly promote cellular growth via transcriptional regulation of c-fos.…”

“…PML-RARa induces DNA hypermethylation and heterochromatin formation through aberrant recruitment of different chromatin modifying enzymes to specific promoters, leading to its transcriptional silencing. But PML-RARa also has been shown to upregulate a number of genes on different microarray setups (Alcalay et al, 2003;Park et al, 2003;Nouzova et al, 2004;Meani et al, 2005). Either PMLRARa has acquired new DNA-binding properties different from those of the RARa (Hauksdottir and Privalsky, 2001) such that it does not only bind to RAREs, or it can also upregulate target genes through indirect mechanisms (Duprez et al, 2003;Duprez, 2004).…”