All-trans Retinoic Acid Induction Research Articles

Improving Clinical Outcomes in APL: Weight Maintenance Strategies to Reduce Complications during Induction Therapy

Introduction: The combination of all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO) has revolutionized the treatment of acute promyelocytic leukemia (APL). However, despite a remission rate exceeding 96% and 5-year disease-free and overall survival rates reaching 96% and 88%, respectively, death during induction in clinical trials occurs in 4% of patients. Differentiation syndrome (DS) is a significant complication during ATRA and/or ATO induction therapy. The signs and symptoms of DS include dyspnea, unexplained fever, weight gain greater than 5 kg, unexplained hypotension, acute renal failure, and the presence of infiltrates and/or pleural/pericardial effusions on chest radiographs. The occurrence of 4 or more of these findings is considered diagnostic. In APL, patients are at risk for fluid overload secondary to multiple blood product transfusions and intravenous hydration. Acute hypoxic respiratory failure (AHRF) and septic shock are common indications for ICU admission in this patient population. At our institution, we monitored patients' daily weights intending to maintain the admission weights with diuresis or intravenous fluids as needed. We assessed the impact of maintaining euvolemia and daily weight monitoring to reduce the incidence of DS and ICU admissions among the APL patients treated at our institution. Methods: A retrospective chart review was conducted on 60 patients with APL who received treatment at our institution between 2016 and 2021. A total of 17 patients who were either not induced at our institution or did not have daily weight monitoring were omitted. Patient demographics, median age at diagnosis, hospitalization complications, ICU admission, and DS were analyzed. Patients were grouped based on if their daily weights were maintained at their admission level, plus or minus 3 kilograms. Only standing weights and weights before ICU transfer were considered. Results: Of the 43 patients who underwent induction therapy at our institution, 25.6% (n=11) had their weight maintained via diuresis and intravenous fluids, and none required ICU admission. Of the remaining 32 patients, 34.4% (n=11) were transferred to the ICU. Of the 11 patients transferred to the ICU, 6 were for AHRF, 2 were for septic shock, 1 was for adrenal insufficiency with vasopressor requirements, 1 was for subdural and epidural hemorrhage, and 1 was for intracranial hemorrhage. Maintaining euvolemia and weight within 3 kilograms of admission level correlated with fewer ICU admissions (OR = 0.085, 95% CI = 0.0046-1.5761) (p=0.0980). Of the 11 patients whose weights were followed and maintained, 9% (n=1) developed DS. Of the 32 patients who did not have their weights followed and maintained, 28% (n=9) met the criteria for DS (OR = 0.256, 95% CI = 0.028-2.296) (p=0.223). Conclusion: Volume overload is a significant concern in APL and its treatment. Our findings suggest that maintaining euvolemia and daily weight monitoring can lead to effective management of patients on the floor and may prevent unnecessary ICU transfers. Although there are limitations to the study due to its retrospective nature and low sample size, the cost-effectiveness and noninvasive methods of maintaining euvolemia support its potential addition to the standard treatment protocols. While maintaining euvolemia and monitoring daily weights is a simple intervention, it represents a promising strategy to improve the management of APL patients during induction therapy by decreasing the incidence of DS and ICU admissions. Further prospective studies are warranted to validate and expand upon these findings.

All-Trans-Retinoic Acid Induction Overcomes Immune Evasion through Downregulating Immune Checkpoint Molecules and Inducing a Cytokine Storm Triggered By Overexpression of S100A8/A9 Signaling

Background: More than 95% of acute promyelocytic leukemia (APL) patients can achieve complete remission by dual induction of all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO). However, early death is a treatment obstacle of APL. The main causes of early death in APL include hemorrhage, differentiation syndrome (DS) related to induction therapy, and infection. Currently, the mechanism of DS in APL largely remains unclear. This study aims to investigate the pathogenetic mechanism and treatment pattern for APL DS and find a suitable biomarker for DS using multiomics approaches. Methods: Eighty newly diagnosed APL patients were recruited through Jan 2019 to Jan 2021 from a clinical trial (NCT04446806). Matched RNA and plasma samples of APL at presentation and DS were studied by RNA-seq and Human Cytokine Array. Two matched peripheral blood samples at presentation and DS from 2 severe DS patients were selected for 10×scRNA-seq analysis, compared with 3 peripheral blood and 2 bone marrow controls. Results: The incidence of DS was 35.3% (29/80), including 21.3% (17/80) moderate DS and 15% (12/80) severe DS. Bulk RNA-seq suggested immune response and cytokines interaction might play important roles in the development of DS ( Figure 1A and B). Significant downregulation of immune checkpoint molecules was shown in the DS period, such as GAL-9, which plays a crucial role in regulating the immune response ( Figure 1C). The activated CD4 +T and CD8 +T cells were amplification at diagnosis period compared with the corresponding CR/CRi period, then declined dramatically at DS period ( Figure 1 D). 10×scRNA-seq analysis revealed the activation of neutrophils and monocytes through innate immune response and inflammatory response ( Figure 1 E). Consistent with bulk RNA-seq results, apparent elevated expression of multiple inflammatory storm-related cytokines/receptors are shown in the DS period in monocytes and neutrophils, which indicates they contribute to the inflammatory cytokine storm ( Figure 1 F). These results indicated that ATRA induction overcomes immune evasion and induces highly activated immune response through downregulating immune checkpoint molecules. Based on 10×scRNA-seq data, differentiated promyelocytic leukemic cell, neutrophils and monocytes are major cell populations and expressed significantly higher cytokine and chemokine in DS stage, indicating that these cells might be major sources of the cytokine storm ( data not shown). We found S100A8 and S100A9, which function as danger-associated molecular pattern (DAMP) molecules and activate innate immune responses via binding to PRRs, significantly upregulated among all known alarmins ( Figure 1G). S100A8/A9 can be induced by ATRA induction, and also activate ERK, JAK-STAT and NF-κB signaling pathways ( Figure 1H). S100A8/A9 expression can be repressed by ERK inhibitor ( Figure 1I). Knockdown of S100A9 induced lower phosphorylation level of STAT1 and P65 ( Figure 1J). These results indicated S100A8/A9 were regulated by the ERK signaling and controlled the JAK-STAT and NF-κB signaling pathway. As a result, JAK-STAT related cytokines could be regulated by S100A8/A9 signaling. Importantly, ROC analysis showed that S100A8/A9 displayed both high sensitivity and specificity as a biomarker for predicting APL DS ( Figure 1K). According to clinical and cytokine storm characteristics of APL DS patients, Dexamethasone (DEX) and Ruxolitinib (RUX) were applied in the treatment of APL DS patients. The percentage of severe DS reduced remarkably after DEX prevention ( Figure 1L, P<0.05). The early death rate of APL declined under the DEX prevention and RUX treatment, and no patient died due to DS ( Figure 1M). The expression of a series of inflammatory cytokines dramatically decreased, indicating that the cytokine storm was effectively suppressed by the treatment of DEX and/or RUX ( Figure 1N). Conclusion s : Our data indicate that ATRA induction could overcome immune evasion through downregulating immune checkpoint molecules. ATRA-induced upregulation of S100A8/A9 may contribute to the cytokine storm observed in the DS stage of APL patients by activating the JAK-STAT and NF-κB signaling pathway. S100A8/A9 is recommended as a biomarker for predicting APL DS. Dexamethasone and Ruxolitinib are appropriate prevention and treatment pattern for APL DS patients.

Anti-Fibrotic Potential of All Trans Retinoic Acid in Inflammatory Bowel Disease.

Inflammatory bowel disease (IBD) embraces Crohn’s disease (CD), ulcerative colitis (UC) and the less common indeterminate colitis, all chronic inflammatory processes of the gastrointestinal (GI) tract. Together, they cause significant morbidity for a million and a half Americans [1]. Symptoms include diarrhea, nausea, abdominal pain, weight loss, which can occasionally prove fatal (i.e., toxic megacolon, perforated bowel) [2]. Patients are also at increased risk for colorectal cancer [3]. First line treatments, including various anti-inflammatory agents and antibiotics, are variably effective against active disease [4]. Remissions can be short-lived and uncontrolled activity is associated with significant side-effects [3]. Gut fibrosis will require most patients (80% and 45% of CD and UC patients, respectively) to undergo surgery [4]. Over the last decade, the so-called biological response modifiers or ‘biologics’, macromolecules that target inflammatory lymphocytes or the cytokines they produce, have emerged as effective therapeutic agents [5]. For example, infliximab, a chimeric anti-human tumor necrosis factor (TNF)-α antibody earned FDA approval almost 20 years ago, based on a high response rate, significant mucosal and fistula healing and long-term remissions in both CD and UC. Additional targets of biologics, either marketed or in various stages of development, include anti-p40, anti-p19, anti-interleukin (IL)-12/23, and anti-alpha 4/beta 7 integrin antibodies [5, 6]. However, an estimated 30% of patients will not respond to such treatments, and of those who initially respond, 50% will relapse within a year risking significant, often serious side effects including infections and increased risk of cancer. So far, biologics have had only a modest impact on surgery rates [7]. The need for novel therapies remains acute. Literature reports indicate that All trans retinoic acid (ATRA) provides benefit in various rodent models of IBD, including potential anti-fibrotic activity [8, 9]. Retinoic acid can exist in the body as any of five different chemical isomers (all-trans-RA, 9-cisRA, 13-cisRA, 11-cisRA and 9, 13-dicisRA). ATRA is the biologically active isomer and the primary enzymatic product of retinaldehyde oxidation. The retinoic acid family regulates a wide range of biological processes, including embryonic development, reproduction, vision, cell growth and differentiation, as well as, apoptosis and inflammation [10]. Topical ATRA is known as tretinoin, and is currently marketed under several trade names such as Retin-A®, Retin-A Micro®, Atralin®, Renova®, and Avita® as FDA approved topical treatment for acne and skin wrinkles. Oral formulations, called isotretinoin (Accutane®, Claravis®, Sotret® and Amnesteem® and Vesanoid®) can cure severe acne and treat acute promyelocytic leukemia (APL), but oral dosing induces more severe side effects. Isotretinoin has not been tested in IBD clinical trials, perhaps due to the serious side effects associated with oral administration, including teratogenicity, suicidality, headache, dizziness, fever, weakness, tiredness, dry mouth, dry skin, other skin changes, thinning hair, nausea, vomiting, itching, bone pain, mouth sores, increased sweating, earaches, and perhaps even colitis. Black-box warnings for oral formulations have been issued by the FDA because of these serious side effects, including retinoic acid syndrome in APL patients. Retinoic acid syndrome may manifest as life threatening upper respiratory tract disturbances (dyspnea, respiratory insufficiency, pleural effusion, expiratory wheezing and increased susceptibility to pneumonia). Its frequency, mechanism and treatment have recently been reviewed [11]. Efforts to circumvent toxicities by tissue targeted administration have included encapsulation in liposomes and aerosolization, although none of these have progressed further in development or resulted in marketed products [12,13]. This review begins with an analysis of published studies bearing on the efficacy of ATRA as an anti-inflammatory treatment for IBD, including in vitro and in vivo work in rodents, as well as ex vivo studies using human tissues. Clinical reports about ATRA attenuation or induction of IBD will also be reviewed. Efforts to deliver ATRA directly to gut tissue to improve activity and reduce side effects will then be discussed. Finally, the potential of ATRA to treat fibrosis will be considered. If successful, oral delivery of ATRA directly to the immune structures of the gut could represent a novel IBD therapy with a potential to reduce fibrosis and the subsequent need for surgery.

Alterations of specific chromatin conformation affect ATRA-induced leukemia cell differentiation

Chromatin conformation plays a key role in regulating gene expression and controlling cell differentiation. However, the whole-genome chromatin conformation changes that occur during leukemia cell differentiation are poorly understood. Here, we characterized the changes in chromatin conformation, histone states, chromatin accessibility, and gene expression using an all-trans retinoic acid (ATRA)-induced HL-60 cell differentiation model. The results showed that the boundaries of topological associated domains (TADs) were stable during differentiation; however, the chromatin conformations within several specific TADs were obviously changed. By combining H3K4me3, H3K27ac, and Hi-C signals, we annotated the differential gene-regulatory chromatin interactions upon ATRA induction. The gains and losses of the gene-regulatory chromatin interactions are significantly correlated with gene expression and chromatin accessibility. Finally, we found that the loss of GATA2 expression and DNA binding are crucial for the differentiation process, and changes in the chromatin structure around the GATA2 regulate its expression upon ATRA induction. This study provided both statistical insights and experimental details regarding the relationship between chromatin conformation changes and transcription regulation during leukemia cell differentiation, and the results suggested that the chromatin conformation is a new type of potential drug target for cancer therapy.

The association and significance of H3K27me3 and a folate metabolic gene ACat2 in neural tube defects.

AimTo study the association between the expression of H3K27me3 and ACat2 (a folate metabolic protein), in order to elucidate the protective mechanism of folic acid (FA) in neural tube defects (NTDs).MethodsEighteen female SD rats were randomly divided into normal, NTD and FA group. NTD group was induced by all-trans retinoic acid (ATRA) at E10d. FA group was fed with FA supplementation since 2 weeks before pregnancy, followed by ATRA induction. At E15d, FA level in the embryonic neural tube was determined by ELISA. Neural stem cells (NSCs) were isolated. Cell proliferation was compared by CCK-8 assay. The differentiation potency was assessed by immunocytochemical staining. H3K27me3 expression was measured by immunofluorescence method and Western blot. ACat2 mRNA expression was detected by qRT-PCR.ResultsCultured NSCs formed numerous Nestin-positive neurospheres. After 5 days, they differentiated into NSE-positive neurons and GFAP-positive astrocytes. When compared with controls, the FA level in NTD group was significantly lower, the ability of cell proliferation and differentiation was significantly reduced, H3K27me3 expression was increased, and ACat2 mRNA expression was decreased (P <0.05). The intervention of FA notably reversed these changes (P <0.05). H3K27me3 expression was negatively correlated with the FA level (rs = −0.908, P <0.01) and ACat2 level (rs = −0.879, P <0.01) in the neural tube.ConclusionThe increased H3K27me3 expression might cause a disorder of folate metabolic pathway by silencing ACat2 expression, leading to reduced proliferation and differentiation of NSCs, and ultimately the occurrence of NTD. FA supplementation may reverse this process.

Selection of the Inducer for the Differentiation of Chicken Embryonic Stem Cells into Male Germ Cells In Vitro.

Several inducers have been used to differentiate embryonic stem cells (ESCs) into male germ cells but the induction process has been inefficient. To solve the problem of low efficiency of inducer for ESCs differentiation into male germ cells, all-trans retinoic acid (ATRA), Am80(the retinoic acid receptor agonist), and estradiol (E2) was used to induce ESCs to differentiate into male germ cells in vitro. ESCs were cultured in media containing ATRA, Am80, or E2 respectively which can differentiate ESCs into a germ cell lineage. In process of ATRA and Am80 induction Group, germ cell-like cells can be observed in 10 days; but have no in E2 induction Group. The marker genes of germ cell: Dazl, Stra8, C-kit, Cvh, integrinα6, and integrinβ1 all showed a significant up-regulation in the expression level. The ATRA-induction group showed high expression of C-kit and Cvh around 4 days, and integrinα6 and integrinβ1 were activated on day 10, respectively, while the E2-,Am80- induction group showed a high expression of C-kit as early as 4 days immunocytochemistry results shown that, integrinα6 and integrinβ1 could be detected in the ATRA-, Am80-, and E2-induction group, Positive clones in the ATRA group were greater in number than those in the other two groups. we conclued that ATRA, Am80, and E2 can promote the expression of the corresponding genes of germ cells, and had different effect on the differentiation of ESCs into male germ cells. ATRA was the most effective inducer of germ cell differentiation.

ATRA transcriptionally induces nSMase2 through CBP/p300-mediated histone acetylation

Neutral sphingomyelinase-2 (nSMase2) is a key ceramide-producing enzyme in cellular stress responses. While many posttranslational regulators of nSMase2 are known, emerging evidence suggests a more protracted regulation of nSMase2 at the transcriptional level. Previously, we reported that nSMase2 is induced by all-trans retinoic acid (ATRA) in MCF7 cells and implicated nSMase2 in ATRA-induced growth arrest. Here, we further investigated how ATRA regulates nSMase2. We find that ATRA regulates nSMase2 transcriptionally through the retinoic acid receptor-α, but this is independent of previously identified transcriptional regulators of nSMase2 (Sp1, Sp3, Runx2) and is not through increased promoter activity. Epigenetically, the nSMase2 gene is not repressively methylated in MCF7 cells. However, inhibition of histone deacetylases (HDACs) with trichostatin A (TSA) induced nSMase2 comparably to ATRA; furthermore, combined ATRA and TSA treatment was not additive, suggesting ATRA regulates nSMase2 through direct modulation of histone acetylation. Confirming this, the histone acetyltransferases CREB-binding protein and p300 were required for ATRA induction of nSMase2. Finally, use of class-specific HDAC inhibitors suggested that HDAC4 and/or HDAC5 are negative regulators of nSMase2 expression. Collectively, these results identify a novel pathway of nSMase2 regulation and suggest that physiological or pharmacological modulation of histone acetylation can directly affect nSMase2 levels.

All-trans retinoic acid inhibits proliferation, migration, invasion and induces differentiation of hepa1-6 cells through reversing EMT in vitro.

Hepatocellular carcinoma (HCC) has the characristics of tumor invasiveness, frequent intrahepatic spread and extra hepatic metastases, which affects the therapy efficiency and prognosis. Epithelial-mesenchymal transition (EMT) is now recognized as a key process in tumor invasion, metastasis and the generation of cancer initiating cells. All-trans retinoic acid (ATRA) is currently used as a potential chemo-therapeutic or chemo-preventive agent because of its anti-proliferative, pro-apoptotic and antioxidant properties. This study investigated the effects of ATRA at different concentrations on the proliferation, migration, invasion, differentiation and functions of the mouse hepa1-6 hepatocarcinoma cell line and explored whether ATRA regulates EMT in the antitumor process. Trypan blue staining and colony formation assay were used to detect cell proliferation. Wound-healing assay and Transwell Matrigel assay were performed to examine migration. Invasion was assessed by using Transwell invasion assay. In the present study, ATRA significantly inhibited the cell growth, colony formation, migration, and invasion capability of hepa1-6 cells in a dose-dependent manner. Furthermore, ATRA at low concentration (0.1µmol/l) could generate these influences. After treated in the ATRA medium, the expression of mature hepatic markers ALB (albumin), CK18 (cytokeratin 18), TAT (tyrosine aminotransferase), ApoB (apolipoprotein B) decreased and that of hepatocarcinoma marker AFP (α fetoprotein) increased. At day 7 after ATRA induction, hepa1-6 cells showed comparable indocyanine green (ICG) uptake and glycogen storage function to the blank control. The mRNA expression of mesenchymal markers N-cadherin, vimentin, snail and twist decreased, while expression of epithelial marker E-cadherin increased in hepa1-6 cells after treated with ATRA. Therefore, this study demonstrates that ATRA remarkably suppressed the proliferation, migration, invasion of hepa1-6 hepatocarcinoma cell line and effectively induced its differentiation and liver functions in vitro through the reversal of EMT. HCC may be more sensitive to ATRA than other cancers, suggesting the prospective usefulness of ATRA in the treatment of HCC.

IRF1 Is Crucial for ATRA-Induced Differentiation By Regulating Its Multiple Functional Targets

AbstractAcute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia (AML), characterized by the accumulation of the blasts arrest at the promyelocyte stage and cytogenetically defined by the PML-RARa oncofusion gene generated by the t(15;17) translocation. All-trans retinoic acid (ATRA), as a front-line agent in the treatment of APL, can reactivate PML-RARα targets by transcriptional switch and degradation of PML-RARα fusion protein, finally induce promyelocytic blasts to terminal differentiation and elicit complete remission of APL. However, a significant amount of evidence has demonstrated that the effect of ATRA treatment is not simply a direct consequence of the reversion of pathological processes caused by PML-RARα. Furthermore, the removal of PML-RARa only has been illustrated to stimulate cell apoptosis and demonstrated to be insufficient for ATRA-mediated differentiation. There must be other important signaling pathways synergizing with ATRA to induce differentiation. And several lines of studies have indicated early ATRA-responsive genes are more important in the ATRA-induced transcriptional regulatory cascades by mediating crosstalk among various ATRA downstream pathways. Our previous studies, together with others, indicate that interferon regulator factor 1 (IRF1) is upregulated rapidly at a very early stage after ATRA treatment. It’s not only a direct target of ATRA, but also a central transducer of IFN signaling. IFN and ATRA can potentiate each other to induce gene expression and various biological responses. Gene set enrichment analysis (GSEA) showed that IRF1 was the major transcriptional factor participating in the regulation of ATRA-upregulated genes, especially at the early stage after ATRA treatment. Thus, IRF1 may play an important role in ATRA-induced transcriptional regulatory cascades by regulating its targets. To understand molecular mechanisms of IRF1 after ATRA induction, we performed ChIP-seq to identify the genome-wide binding sites of IRF1 at 4 hours after ATRA treatment. ChIP-QPCR and luciferase assays were conducted to validate the ChIP-seq enriched target genes of IRF1 and further demonstrated that IRF1 can directly transactivated its targets in 293T cells. Furthermore, the binding sites of IRF1 mainly located near the transcription start sites (TSS), especially at the proximal promoter region, and conserved. Motif analysis showed that there were two binding motifs, classical IRF1 motif (short motif) and long motif. And these differential motifs appeared at different stages during ATRA-induced differentiation and involved in different sets of biological processes. After gene ontology analysis, IRF1 targets were identified to be involved in a variety of important biological processes, such as hematopoiesis, cell cycle, apoptosis, JAK-STAT cascade, immune response, etc. Furthermore, knockdown of IRF1 with siRNA led to a significantly repression of ATRA-induced differentiation, degradation of PML-RARα, cell cycle arrest and proliferation inhibition in APL cells. These results collectively demonstrate that IRF1 plays a crucial role in ATRA-induced differentiation and mediates multiple signaling pathways by regulating its various functional targets. Thus, our results will provide a better understanding of treatment mechanisms in APL and extend the application of ATRA to the treatment of other cancers. DisclosuresNo relevant conflicts of interest to declare.

Cerebral venous and sinus thrombosis in a patient with acute promyelocytic leukemia during all-trans retinoic acid induction treatment

Cerebral venous and sinus thrombosis is a rare cerebrovascular disorder, which seldom represents a complication of acute promyelocytic leukemia (APL). As a part of the coagulopathy of APL, thrombosis is a less recognized and underestimated life-threatening manifestation and is overshadowed by the more obvious bleeding complications. Here, we described a 28-year-old woman with APL who developed massive thrombosis of the cerebral sinuses while on induction treatment with all-trans retinoic acid. On the basis of this report, the potential pathogenic mechanisms and the diagnosis based on magnetic resonance imaging (MRI) combined with magnetic resonance venogram (MRV) are discussed. Early anticoagulant therapy contributed to the progressive dissolution of the thrombosis, as documented by MRI, with the complete disappearance of neurological signs without sequelae. Given the increasing recognition of thromboembolic events in APL, the use of prophylactic anticoagulation during induction therapy may need to be redefined.

The oncogene EVI1 enhances transcriptional and biological responses of human myeloid cells to all-trans retinoic acid

The product of the ecotropic virus integration site 1 (EVI1) gene, whose overexpression is associated with a poor prognosis in myeloid leukemias and some epithelial tumors, regulates gene transcription both through direct DNA binding and through modulation of the activity of other sequence specific transcription factors. Previous results from our laboratory have shown that EVI1 influenced transcription regulation in response to the myeloid differentiation inducing agent, all-trans retinoic acid (ATRA), in a dual manner: it enhanced ATRA induced transcription of the RARβ gene, but repressed the ATRA induction of the EVI1 gene itself. In the present study, we asked whether EVI1 would modulate the ATRA regulation of a larger number of genes, as well as biological responses to this agent, in human myeloid cells. U937 and HL-60 cells ectopically expressing EVI1 through retroviral transduction were subjected to microarray based gene expression analysis, and to assays measuring cellular proliferation, differentiation, and apoptosis. These experiments showed that EVI1 modulated the ATRA response of several dozens of genes, and in fact reinforced it in the vast majority of cases. A particularly strong synergy between EVI1 and ATRA was observed for GDF15, which codes for a member of the TGF-β superfamily of cytokines. In line with the gene expression results, EVI1 enhanced cell cycle arrest, differentiation, and apoptosis in response to ATRA, and knockdown of GDF15 counteracted some of these effects. The potential clinical implications of these findings are discussed.

HOX antisense lincRNA HOXA-AS2 is an apoptosis repressor in allTransretinoic acid treated NB4 promyelocytic leukemia cells

HOXA cluster antisense RNA 2 (HOXA-AS2) is a long non-coding RNA located between the HOXA3 and HOXA4 genes in the HOXA cluster. Its transcript is expressed in NB4 promyelocytic leukemia cells and human peripheral blood neutrophils, and expression is increased in NB4 cells treated with all trans retinoic acid (ATRA). Knockdown of HOXA-AS2 expression by transduced shRNA decreases the number of viable cells and increases the proportion of apoptotic cells, measured by annexin V binding and by activity and cleavage of caspases-3, -8, and -9. The increase in death of HOXA-AS2 knockdown cells was accompanied by an elevated TNF-related apoptosis-inducing ligand (TRAIL) levels, but ATRA-induced NB4 cells treated with TRAIL did show an increase in HOXA-AS2 expression. These results demonstrate that ATRA induction of HOXA-AS2 suppresses ATRA-induced apoptosis, possibly through a TRAIL-mediated pathway. HOXA-AS2-mediated negative regulation thus contributes to the fine-tuning of apoptosis during ATRA-induced myeloid differentiation in NB4 cells.

All-Trans-Retinoic Acid Modulates ICAM-1 N-Glycan Composition by Influencing GnT-III Levels and Inhibits Cell Adhesion and Trans-Endothelial Migration

Changes in the expression of glycosyltransferases directly influence the oligosaccharide structures and conformations of cell surface glycoproteins and consequently cellular phenotype transitions and biological behaviors. In the present study, we show that all-trans-retinoic acid (ATRA) modulates the N-glycan composition of intercellular adhesion molecule-1 (ICAM-1) by manipulating the expression of two N-acetylglucosaminyltransferases, GnT-III and GnT-V, via the ERK signaling pathway. Exposure of various cells to ATRA caused a remarkable gel mobility down-shift of ICAM-1. Treatment with PNGase F confirmed that the reduction of the ICAM-1 molecular mass is attributed to the decreased complexity of N-glycans. We noticed that the expression of the mRNA encoding GnT-III, which stops branching, was significantly enhanced following ATRA exposure. In contrast, the level of the mRNA encoding GnT-V, which promotes branching, was reduced following ATRA exposure. Silencing of GnT-III prevented the molecular mass shift of ICAM-1. Moreover, ATRA induction greatly inhibited the adhesion of SW480 and U937 cells to the HUVEC monolayer, whereas knock-down of GnT-III expression effectively restored cell adhesion function. Treatment with ATRA also dramatically reduced the trans-endothelial migration of U937 cells. These data indicate that the alteration of ICAM-1 N-glycan composition by ATRA-induced GnT-III activities hindered cell adhesion and cell migration functions simultaneously, pinpointing a unique regulatory role of specific glycosyltransferases in the biological behaviors of tumor cells and a novel function of ATRA in the modulation of ICAM-1 N-glycan composition.

Inferior Outcome in Patients with Acute Promyelocytic Leukemia and High Expression of the Ets Related Gene: Role in Leukemogenesis and Potential Implications for Future Therapeutic Approaches?,

Abstract 3531▪▪This icon denotes a clinically relevant abstract Introduction:In acute promyelocytic leukemia (APL) the translocation t(15;17) leading to the fusion transcript PML-RARα is necessary but not sufficient to generate leukemia. However, additional molecular alterations leading to overt APL remain elusive. The introduction of all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO) in the treatment of APL has resulted in long term survival in about 75% of patients with de novo APL, but still, relapse occurs in about 15% of cases. However, markers identifying patients at high risk for relapse are not well established yet. The ets related gene (ERG) is a downstream effector of mitogenic signaling transduction. It is involved in key steps regulating cell proliferation, differentiation and apoptosis. High expression of ERG has been shown to be associated with inferior overall survival (OS) and disease free survival (DFS) in different types of hematologic malignancies such as acute myeloid leukemia and T cell acute lymphoblastic leukemia. The aim of this study was to evaluate the role of ERG expression in APL development and to elucidate its value as a prognostic molecular marker in APL patients. Methods:Bone marrow (BM) mononuclear cells were obtained from 86 APL patients (50 female, 36 male) after informed consent. Median age of patients was 47 years with a range from 19 to 82 years. All patients were diagnosed and treated in the German AML Cooperative Group (AMLCG) study. The treatment consisted of simultaneous ATRA and double induction (TAD/HAM) chemotherapy including high-dose ara-C, one cycle of consolidation chemotherapy (TAD) and 3 years monthly maintenance chemotherapy. BM cells were analyzed in triplicates by multiplex reverse transcriptase quantitative real-time PCR (qRT-PCR) on a LightCycler 480 (Roche, Mannheim, Germany). Glucose-6-phosphat isomerase (GPI) served as a housekeeping gene. The comparative cycle threshold (CT) method was used to determine relative ERG expression levels and the cycle number difference (ΔCT=GPI-ERG) was calculated using the mean of ΔCT from the replicates, that is μ(ΔCT) and expressed as 2μ(ΔCT). cDNA from KG1a cells served as a calibrator in each run. Statistical analyses were performed using SAS version 9.2. ERG expression groups were defined as follows: ERG expression higher than the 75th percentile (ERGhigh) and ERG expression lower than the 75th percentile (ERGlow). Time to complete remission (CR), disease free survival (DFS) and overall survival (OS) were calculated using the Kaplan-Meier method and a log-rank test was used to compare differences between the curves. Significance was set at p < 0.05. Results:For patients who achieved CR high ERG expression was significantly associated with an inferior OS as compared to lower ERG expression (49% vs. 80% at 10 years, p=0.02). The effect on DFS was even stronger: only 28% of patients in the ERGhigh group survived without relapse after a follow-up of 10 years as compared to 75% of patients in the ERGlow group (p=0.001). However, the expression of ERG did not have an influence on whether patients achieved CR, neither on how fast they achieved CR. Conclusion:In univariate analysis high ERG expression was significantly associated with inferior outcome concerning overall survival and disease free survival. Therefore, ERG expression might serve as a molecular marker for risk stratification. It might identify patients who could benefit from intensified treatment regimens such as maintenance therapy or allogeneic stem cell transplantation. However, multivariate analyses and validation of these data in an independent patient cohort is warranted. Disclosures:No relevant conflicts of interest to declare.

MiR-125b, a Target of CDX2, Regulates Cell Differentiation through Repression of the Core Binding Factor in Hematopoietic Malignancies

MicroRNA-125b (miR-125b), a small noncoding RNA molecule, has been found to be deregulated and functions as an oncogene in many cancers including hematopoietic malignancies. However, the mechanisms accounting for miR-125b dysregulation remain to be elucidated. The present study aims to identify the factors that might contribute to up-regulation of miR-125b in human hematopoietic malignancies and its downstream targets for lineage-specific differentiation. We at first reported that CDX2, a homeobox transcription factor, binds to promoter regions of the miR-125b gene and activates transcriptional regulation of miR-125b in malignant myeloid cells. We further revealed that increasing levels of CDX2 in malignant myeloid cells activate miR-125b expression, which in turn inhibits core binding factor β (CBFβ) translation, thereby counteracting myeloid cell differentiation, at least for granulocytic lineage, and promoting leukemogenesis. Interestingly, we found that this novel pathway including CDX2, miR-125b, and CBFβ was mediated by undergoing all-trans-retinoic acid induction. Once differentiation ensues with all-trans-retinoic acid treatment, CDX2 activity decreases, leading to a reduction in miR-125b transcription and up-regulation of CBFβ in myeloid cells and in patients. The study provides a new mechanism that contributes to hematopoietic malignancies, which could involve deregulation of miR-125b and its up- and downstream factors. As altered expression of miRNAs has been reported in a wide range of malignancies, delineating the underlying molecular mechanisms of aberrant miRNA expression and characterizing the upstream and downstream factors will help to understand important steps in the pathogenesis of these afflictions.

Advances in therapies for acute promyelocytic leukemia

Acute promyelocytic leukemia (APL), a distinct subtype of acute myelogenous leukemia (AML), results from the arrest of the maturation of hematopoietic progenitors at the promyelocyte stage. It has been shown that APL is associated with a reciprocal chromosomal translocation, involving chromosomes 15 and 17, which fuses the gene encoding the retinoic acid receptor α (RARα) and the promyelocytic leukemia (PML) gene. The resultant PML-RARα fusion protein plays a critical role in the pathogenesis of APL. Although there are many subtypes of AML, all are typically managed using a standard chemotherapy regimen of an anthracycline plus cytarabine arabinoside (CA). Despite high rates of complete remission following standard chemotherapy, most patients relapse and long-term disease-free survival is only 30-40%. The introduction of drugs such as all-trans retinoic acid (ATRA) that promote progenitor differentiation by directly inhibiting the PML-RARα fusion protein has changed the treatment paradigm for APL and markedly improved patient survival. The purposes of the present review are to provide the latest results and future directions of clinical research into APL and to illustrate how new therapies, such as ATRA plus anthracycline-based induction and consolidation therapy, risk-adapted therapy, salvage therapy containing arsenic trioxide-based regimens, and hematopoietic stem cell transplantation, have improved the treatment outcomes for APL patients.

Olfactomedin 4 is a novel target gene of retinoic acids and 5-aza-2′-deoxycytidine involved in human myeloid leukemia cell growth, differentiation, and apoptosis

AbstractClinical application of retinoic acids (RAs) and demethylation agents has proven to be effective in treating certain myeloid leukemia patients. However, the target genes that mediate these antileukemia activities are still poorly understood. In this study, we identified olfactomedin 4 (OLFM4), a myeloid-lineage–specific gene from the olfactomedin family, as a novel target gene for RAs and the demethylation agent, 5-aza-2′-deoxycytidine. We demonstrated that the retinoic acid receptor alpha/retinoic X receptor alpha heterodimer binds to a retinoic acid response-element (DR5) site in the OLFM4 promoter and mediates all-trans-retinoic acid (ATRA)–induced transactivation of the OLFM4 gene. OLFM4 overexpression in HL-60 cells led to growth inhibition, differentiation, and apoptosis, and potentiated ATRA induction of these effects. Conversely, down-regulation of endogenous OLFM4 in acute myeloid leukemia-193 cells compromised ATRA-induced growth inhibition, differentiation, and apoptosis. Overexpression of OLFM4 in HL-60 cells inhibited constitutive and ATRA-induced phosphorylation of the eukaryote initiation factor 4E-binding protein 1 (4E-BP1), whereas down-regulation of OLFM4 protein in acute myeloid leukemia-193 cells increased 4E-BP1 phosphorylation, suggesting that OLFM4 is a potent upstream inhibitor of 4E-BP1 phosphorylation/deactivation. Thus, our study demonstrates that OLFM4 plays an important role in myeloid leukemia cellular functions and induction of OLFM4-mediated effects may contribute to the therapeutic value of ATRA.

High WT1 Expression Is Associated with a Shorter Time to Complete Remission After ATRA Based Induction Therapy In Acute Promyelocytic Leukemia

AbstractAbstract 1694 Introduction:In acute promyelocytic leukemia (APL) the t(15;17) is detectable in the vast majority of cases and leads to the fusion transcript PML-RARα. The introduction of all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO) into therapeutic management of APL resulted in long term remissions in about 80% of patients. However, relapse occurs in about 10–15% of cases and remains a major cause of treatment failure. The Wilms Tumor 1 gene (WT1) encodes for a transcription factor that is involved in normal and malignant hematopoiesis. Aberrant expression of WT1 has been shown to be associated with an adverse outcome in different types of hematological malignancies such as acute myeloid leukemia, acute lymphoblastic leukemia and myelodysplastic syndromes. To date only small series exist on aberrant WT1 expression in APL. Therefore, the aim of this study was to further elucidate the incidence of aberrant WT1 expression in APL and its prognostic significance for clinical endpoints. Methods:Bone marrow (BM) mononuclear cells were retrospectively evaluated in 89 APL patients (53 female, 36 male) and 21 healthy controls (15 female, 6 male) after informed consent. The median age of APL patients and healthy controls was 46 (range: 19–82 years) and 60 years (range: 21–84 years), respectively. All patients were diagnosed and treated in the German AML Cooperative Group (AMLCG) study. The treatment consisted of simultaneous ATRA and double induction (TAD/HAM) chemotherapy including high-dose ara-C, one cycle of consolidation chemotherapy (TAD) and 3 years monthly maintenance chemotherapy. BM cells were analyzed by multiplex reverse transcriptase quantitative real-time PCR (qRT-PCR) in triplicates on a LightCycler 480 (Roche, Mannheim, Germany). Beta–glucuronidase (GUS) served as a housekeeping gene for normalization. For quantification of relative expression values a modified delta-delta CT calculation model according to Pfaffl was used (Pfaffl MW, Nucleic Acids Res, 2001) after determination of PCR efficiencies. WT1 expression groups were defined as follows: WT1 expression higher than the 75th percentile (WT1high) and WT1 expression lower than the 25th percentile (WT1low). Time to complete remission, disease free survival (DFS) and overall survival (OS) were calculated using the Kaplan-Meier method and a log-rank test was used to compare differences between the groups (p < 0.05). Results:Normalized WT1 expression was significantly higher in APL samples (median: 0.1129, range: 0.00001–1.414) as compared to normal controls (median: 0.00135, range: 0.00001–0.01105) (p=0.0011). WT1high was not significantly associated with high white blood cell counts (WBC). In univariate analysis time to complete remission was significantly shorter in patients showing high WT1 expression as compared to patients with low WT1 expression (47 days vs. 58 days, p=0.0051). However, this did not translate into a longer DFS or OS. In contrast, there was a trend toward an impaired DFS and OS in the WT1high group. Interestingly, analyzing deaths prior to complete remission WT1high was significantly associated with early death as compared to the WT1low group (median 6 days vs. 17 days, p=0.0197). Conclusion:WT1 is highly expressed in APL as compared to healthy controls but is not associated with increased WBC. WT1high was significantly associated with a shorter time to CR. Since WT1 plays a critical role in differentiation and survival in myeolopoiesis this finding might be due to a higher succeptibility of WT1high APL patients to ATRA induced differentiation as compared to the WT1low group. Moreover, in vitro studies have shown that in NB4 cells WT1 mRNA levels decrease upon treatment with ATRA, this provides further evidence that WT1 might be an additional target for ATRA in APL (Gu W, Haematologica, 2005). Interestingly, WT1high is significantly correlated with early death prior to CR achievement. We hypothezise that this might also be an effect of an increased toxicity of the ATRA based induction therapy in patients having high WT1 expression. Disclosures:Lengfelder:Cephalon: Research Funding.

C/EBPε participates in all-trans retinoic acid induction of PI3Kγ in U937 cells via an intronic matrix attachment region sequence

ATRA (all-trans retinoic acid) regulates gene expression by binding as a ligand to its specific receptors like C/EBPε which is directly induced. In the U937 cell line, PI3Kγ is selectively induced over other PI3Ks by ATRA, although the mechanism is still unclear. Here, we show that C/EBPε and PI3Kγ are induced in U937 cells by ATRA both in levels of mRNA and protein. Reporter gene assay revealed that C/EBPε is able to interact with a previously identified 2 kb MAR (matrix attachment region) sequence in the last intron of PI3Kγ gene, and increases its linked heterogeneous reporter gene expression. ChIP assay showed that induction of endogenous PI3Kγ is at least partially caused by enhanced, direct C/EBPε binding to a 15 bp sequence at nucleotides 1428-1442 within this MAR sequence, and EMSA analysis confirmed this binding in vitro. The results above collectively show that C/EBPε participates in ATRA induction of PI3Kγ.

Expression of RALDHs (ALDH1As) and CYP26s in human tissues and during the neural differentiation of P19 embryonal carcinoma stem cell

Retinoic acid (RA) plays a critical role in embryonic development and function maintenance of vital organs in adult. Subtle regulation of RA signaling is relied on spatio-temporal control of RA synthesis and catabolism. In this study, we investigated the expression patterns of RA synthetases RALDHs and metabolic enzymes CYP26s in multiple human tissues, and this study revealed unique expression pattern for every isoform from these two enzyme families. And it was worth noting that there were evident differences between fetal brain and adult brain in the expression of RALDHs and CYP26s. To investigate the dynamic expression of RALDH isoforms and CYP26 isoforms during neural differentiation, we applied a P19 embryonal carcinoma stem cell neural differentiation model. And during P19 cell neural differentiation induced by all trans-retinoic acid (ATRA) and cell aggregate formation, RALDH1, RALDH2, CYP26A1, and CYP26B1 could be notably upregulated by ATRA, and keeping the high-level expression of RALDH1 and RALDH2 was dependent on the further neural differentiation, but not continuous ATRA induction. RALDH3 transcription could not be directly induced by ATRA, and obvious upregulation of its transcription initiated at the late stage of ATRA induction or after the removement of ATRA implied its neural differentiation-dependent expression pattern. CYP26C1 transcription was significantly repressed by ATRA, and this downregulation also showed a neural differentiation-dependent pattern, in respect that CYP26C1 expression was kept in low-level even after the withdrawal of ATRA.