Pharmacogenomic analysis of acute promyelocytic leukemia cells highlights CYP26 cytochrome metabolism in differential all-trans retinoic acid sensitivity

Abstract

Disease relapse sometimes occurs after acute promyelocytic leukemia (APL) therapy with all-trans retinoic acid (ATRA). Among the diagnostic parameters predicting relapse, heterogeneity in the in vitro differentiation rate of blasts is an independent factor. To identify biologic networks involved in resistance, we conducted pharmacogenomic studies in APL blasts displaying distinct ATRA sensitivities. Although the expression profiles of genes invested in differentiation were similarly modulated in low-and high-sensitive blasts, low-sensitive cells showed higher levels of transcription of ATRA-target genes, transcriptional regulators, chromatin remodelers, and transcription factors. In opposition, only high-sensitive blasts expressed the CYP26A1 gene, encoding the p450 cytochrome which is known to be involved in retinoic acid catabolism. In NB4 cells, ATRA treatment activates a novel signaling pathway, whereby interleukin-8 stimulates the expression of the homeobox transcription factor HOXA10v2, an effective enhancer of CYP26A1 transcription. These data were corroborated in primary APL cells, as maturation levels correlated with CYP26A1 expression. IntroductionHematopoiesis can be described as a balance between proliferation and differentiation. In 90% of acute promyelocytic leukemia (APL) cases, the t(15;17) translocation and consequent expression of the PML (promyelocytic leukemia protein)/RAR␣ (retinoic acid receptor ␣) fusion protein blocks differentiation at the promyelocytic stage. RAR␣ belongs to the nuclear receptor superfamily and functions as a ligand-dependent transcription factor, acting to establish the granulocytic lineage. Under normal conditions, binding of the ligand (all-trans retinoic acid, or ATRA) to the receptor provokes a conformational change in the receptor resulting in the disruption of a co-repression complex, recruitment of coactivators, binding to the retinoic acid response element (RARE), and finally the transcription of ATRA-dependent genes. 1 The PML portion of the PML/RAR␣ fusion protein has a high affinity for the corepression complex, preventing RAR␣ transcriptional activity. To induce complete remission in a high proportion of patients, a pharmacologic dose of ATRA is required to destabilize this interaction and reestablish the differentiation program. Combining ATRA with chemotherapy results in a significant prolongation of disease-free and overall survival. [2][3][4][5][6] Despite the general efficacy of ATRA-based therapy, 10% to 20% of patients with APL still relapse. Several mechanisms have been proposed to explain the involved retinoid resistance arising during cancer therapy. With the exception of primary resistance, which is extremely rare in PML/RAR␣ cells, 7,8 APL relapse has been suggested to be related to various processes observed in cell lines. These include variations in nuclear ATRA concentrations due to, for example, cytoplasm retinoid sequestration, 9,10 increased intracellular metabolism, 11 alterations in ATRA transcriptional efficiency via mutations in the P...

Differentiation Therapy Exerts Antitumor Effects on Stem-like Glioma Cells

“…It is thus tempting to speculate that patients, which underwent first-line therapy and feature low tumor burden could profit from ATRA therapy (41). In addition, it cannot be excluded that some tumor cells might be endowed with an ATRA-resistant phenotype caused by ATRA-metabolizing enzymes, which are culprits of ATRA resistance in other tumor entities (42,43). Further, loss of RARs in a fraction of tumor cells, which occurs as a common event in several extracranial cancers (44)(45)(46), could render cells irresponsive to ATRA effects and require long-term, supraphysiologic ATRA doses.…”

Transcriptional repression of microRNA genes by PML-RARA increases expression of key cancer proteins in acute promyelocytic leukemia

“…RA is known to induce a temporal program of HOX gene expression and this expression is often perturbed in leukemias. 25,[41][42][43][44] Of note, the miR-10b, which is potentially repressed by PML-RARA (Table 1 and Figure 1D), also regulates HOXD10. 45 The up-regulation of HOX genes in AML due to the downregulation of miRNAs has already been suspected 26,46,47 but we revealed here a potential link with oncogene-mediated transcriptional repression at least in the case of APL.…”

“…The blast cells were treated with 100 nM ATRA for 6 days and RNA extraction was performed each day from day 0 to day 4 of treatment. 24,25 Cell viability and maturation of APL cells was assessed by trypan blue ( Figure 4A) and NitroBlueTetrazolium (NBT) dye reduction assays ( Figure 4B), respectively, at days 0, 3, and 6 of ATRA treament. We also controlled the induction of the prototypic RARB by ATRA ( Figure 4C).…”

“…31 Overall, our microarray analyses were consistent with those previously published. 25,32 The lists of the up-and down-regulated genes were then compared with the list of miRNAs bioinformatically predicted to be repressed by PML-RARA using the miRBase targets (http://microrna.sanger.ac.uk/targets/v5/). Among the first hundred genes analyzed in each case, we observed that 77% of the down-regulated genes and 79% of the up-regulated genes could potentially be targeted by at least one miRNA predicted to be repressed by PML-RARA ( Figure 6A).…”

All-trans-retinoic acid inhibits tumour growth of malignant pleural mesothelioma in mice

“…By TUNEL assay, the increase of apoptosis was not observed in ATRA-treated MPM tumour cells in mice compared with untreated mice (data not shown). Next, we examined the mRNA expression of CYP26A1 [32], a retinoic acid regulated gene, by real-time RT-PCR, and found that mRNA levels of CYP26A1 were decreased in ATRAtreated MPM tumour cells in mice compared with untreated mice, which suggested an increased amount of active retinoic acid, namely, an autoregulation feedback loop (data not shown). However, it is not clear whether the observed effect is specific to retinoic acid signalling.…”