Acute promyelocytic leukemia: a paradigm for differentiation therapy

The Intersection of Epigenetic Alterations and Developmental State in Pediatric Ependymomas

BACKGROUND

Ependymomas are the third most common brain cancer in children and have no targeted therapies. They are divided into at least 9 major subtypes based on molecular characteristics and major drivers and have few genetic mutations compared to the adult form of this disease, leading to investigation of other mechanisms.

SUMMARY

Epigenetic alterations such as transcriptional programs activated by oncofusion proteins and alterations in histone modifications play an important role in development of this disease. Evidence suggests these alterations interact with the developmental epigenetic programs in the cell of origin to initiate neoplastic transformation and later disease progression, perhaps by keeping a portion of tumor cells in a developmental, proliferative state.

KEY MESSAGES

To better understand this disease, research on its developmental origins and associated epigenetic states needs to be further pursued. This could lead to better treatments, which are currently lacking due to the difficult-to-drug nature of known drivers such as fusion proteins. Epigenetic and developmental states characteristic of these tumors may not just be potential therapeutic targets, but used as a tool to find new avenues of treatment.

Nanozymes: a new approach for leukemia therapy

Leukemia is a type of clonal disorder of hematopoietic stem and progenitor cells characterized by bone marrow failure, differentiation arrest, and lineage skewing. Despite leukemia being a complex disease and it being difficult to identify a single driving force, redox homeostasis, the balance between reactive oxygen species (ROS) producers and cellular antioxidant systems, is normally impaired during leukemogenesis. In this context, the modulation of ROS in leukemia cells can be harnessed for therapeutic purposes. Nanozymes are functional nanomaterials with enzyme-like characteristics, which address the intrinsic limitations of natural enzymes and exhibit great potential in synergistic antitumor therapy. Nanozymes possess catalytic activities (e.g., peroxidase-like activity, catalase-like activity, superoxide dismutase-like activity, and oxidase-like activity) to regulate ROS levels in vitro and in vivo, making them promising for leukemia therapy. On account of the rapid development of nanozymes recently, their application potentials in leukemia therapy are gradually being explored. To highlight the achievements of nanozymes in the leukemia field, this review summarizes the recent studies of nanozymes with anti-leukemia efficacy and the underlying mechanism. In addition, the challenges and prospects of nanozyme research in leukemia therapy are discussed.

Retinoic Acid Signaling in Fatty Liver Disease

Retinoic acid (RA) is a metabolite of vitamin A and is essential for development and growth as well as cellular metabolism. Through genomic and nongenomic actions, RA regulates a variety of physiological functions. Dysregulation of RA signaling is associated with many diseases. Targeting RA signaling has been proven valuable to human health. All-trans retinoic acid (AtRA) and anthracycline-based chemotherapy are the standard treatment of acute promyelocytic leukemia (APL). Both human and animal studies have shown a significant relationship between RA signaling and the development and progression of nonalcoholic fatty liver disease (NAFLD). In this review article, we will first summarize vitamin A metabolism and then focus on the role of RA signaling in NAFLD. AtRA inhibits the development and progression of NAFLD via regulating lipid metabolism, inflammation, thermogenesis, etc.

Treating low- and intermediate-risk acute promyelocytic leukemia with and without chemotherapy: A comparison in a tertiary care center

Background

Acute promyelocytic leukemia (APL) comprises approximately 10% of acute myeloid leukemia (AML) cases.

Material and Methods

Both options of treatment (ATRA-ATO and ATRA-chemotherapy) were discussed with patients with low- and intermediate-risk APL, pros and cons explained in details, and treatment regimen selected after getting informed written consent.

Results

Total 71 patients were included in the study; among these patients, 3 were negative for both FISH for t (15,17) and RT-PCR for promyelocytic leukemia retinoic acid receptor alpha, and 36 patients with APL had white blood cell count at diagnosis >10 × 109/l. Total 30 patients with newly diagnosed as low- and intermediate-risk-APL fulfilled all inclusion criteria, treated and followed for a minimum period of 2 years up to June, 2016. Fifteen patients liked to be treated with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), while rest of the 15 patients preferred treatment with ATRA and chemotherapy.

Conclusion

Combination of ATRA and ATO is equally effective, less toxic, and more feasible in comparison to ATRA and chemotherapy for patients with low- and intermediate-risk APL and is a viable option for this subset of patients, especially in countries with limited resources.

Nuclear factor I-C overexpression promotes monocytic development and cell survival in acute myeloid leukemia

Nuclear factor I-C (NFIC) belongs to a family of NFI transcription factors that binds to DNA through CAATT-boxes and are involved in cellular differentiation and stem cell maintenance. Here we show NFIC protein is significantly overexpressed in 69% of acute myeloid leukemia patients. Examination of the functional consequences of NFIC overexpression in HSPCs showed that this protein promoted monocytic differentiation. Single-cell RNA sequencing analysis further demonstrated that NFIC overexpressing monocytes had increased expression of growth and survival genes. In contrast, depletion of NFIC through shRNA decreased cell growth, increased cell cycle arrest and apoptosis in AML cell lines and AML patient blasts. Further, in AML cell lines (THP-1), bulk RNA sequencing of NFIC knockdown led to downregulation of genes involved in cell survival and oncogenic signaling pathways including mixed lineage leukemia-1 (MLL-1). Lastly, we show that NFIC knockdown in an ex vivo mouse MLL::AF9 pre-leukemic stem cell model, decreased their growth and colony formation and increased expression of myeloid differentiation markers Gr1 and Mac1. Collectively, our results suggest that NFIC is an important transcription factor in myeloid differentiation as well as AML cell survival and is a potential therapeutic target in AML.

ATRA treatment slowed P-selectin-mediated rolling of flowing HL60 cells in a mechano-chemical-dependent manner

All-trans retinoic acid (ATRA)-induced differentiation of acute promyelocytic leukemia (APL) toward granulocytes may trigger APL differentiation syndrome (DS), but there is less knowledge about the mechano-chemical regulation mechanism of APL DS under the mechano-microenvironment. We found that ATRA-induced changes in proliferation, morphology, and adhesive molecule expression levels were either dose or stimulus time dependent. An optimal ATRA stimulus condition for differentiating HL60 cells toward neutrophils consisted of 1 × 10^-6 M dose and 120 h of stimulus time. Under wall shear stresses, catch-slip bond transition governs P-selectin-mediated rolling for neutrophils and untreated or ATRA-treated (1 × 10^-6 M, 120 h) HL60 cells. The ATRA stimuli slowed down the rolling of HL60 cells on immobilized P-selectin no matter whether ICAM-1 was engaged. The β2 integrin near the PSGL-1/P-selectin axis would be activated within sub-seconds for each cell group mentioned above, thus contributing to slow rolling. A faster β2 integrin activation rate and the higher expression levels of PSGL-1 and LFA-1 were assigned to induce the over-enhancement of ATRA-treated HL60 adhesion in flow, causing APL DS development. These findings provided an insight into the mechanical-chemical regulation for APL DS development via ATRA treatment of leukemia and a novel therapeutic strategy for APL DS through targeting the relevant adhesion molecules.

Multilayer omics analysis reveals a non-classical retinoic acid signaling axis that regulates hematopoietic stem cell identity

Hematopoietic stem cells (HSCs) rely on complex regulatory networks to preserve stemness. Due to the scarcity of HSCs, technical challenges have limited our insights into the interplay between metabolites, transcription, and the epigenome. In this study, we generated low-input metabolomics, transcriptomics, chromatin accessibility, and chromatin immunoprecipitation data, revealing distinct metabolic hubs that are enriched in HSCs and their downstream multipotent progenitors. Mechanistically, we uncover a non-classical retinoic acid (RA) signaling axis that regulates HSC function. We show that HSCs rely on Cyp26b1, an enzyme conventionally considered to limit RA effects in the cell. In contrast to the traditional view, we demonstrate that Cyp26b1 is indispensable for production of the active metabolite 4-oxo-RA. Further, RA receptor beta (Rarb) is required for complete transmission of 4-oxo-RA-mediated signaling to maintain stem cells. Our findings emphasize that a single metabolite controls stem cell fate by instructing epigenetic and transcriptional attributes.

Differentiation therapy for myeloid malignancies: beyond cytotoxicity

Blocked cellular differentiation is a central pathologic feature of the myeloid malignancies, myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Treatment regimens promoting differentiation have resulted in incredible cure rates in certain AML subtypes, such as acute promyelocytic leukemia. Over the past several years, we have seen many new therapies for MDS/AML enter clinical practice, including epigenetic therapies (e.g., 5-azacitidine), isocitrate dehydrogenase (IDH) inhibitors, fms-like kinase 3 (FLT3) inhibitors, and lenalidomide for deletion 5q (del5q) MDS. Despite not being developed with the intent of manipulating differentiation, induction of differentiation is a major mechanism by which several of these novel agents function. In this review, we examine the new therapeutic landscape for these diseases, focusing on the role of hematopoietic differentiation and the impact of inflammation and aging. We review how current therapies in MDS/AML promote differentiation as a part of their therapeutic effect, and the cellular mechanisms by which this occurs. We then outline potential novel avenues to achieve differentiation in the myeloid malignancies for therapeutic purposes. This emerging body of knowledge about the importance of relieving differentiation blockade with anti-neoplastic therapies is important to understand how current novel agents function and may open avenues to developing new treatments that explicitly target cellular differentiation. Moving beyond cytotoxic agents has the potential to open new and unexpected avenues in the treatment of myeloid malignancies, hopefully providing more efficacy with reduced toxicity.

The RARγ Oncogene: An Achilles Heel for Some Cancers

Cancer "stem cells" (CSCs) sustain the hierarchies of dividing cells that characterize cancer. The main causes of cancer-related mortality are metastatic disease and relapse, both of which originate primarily from CSCs, so their eradication may provide a bona fide curative strategy, though there maybe also the need to kill the bulk cancer cells. While classic anti-cancer chemotherapy is effective against the dividing progeny of CSCs, non-dividing or quiescent CSCs are often spared. Improved anti-cancer therapies therefore require approaches that target non-dividing CSCs, which must be underpinned by a better understanding of factors that permit these cells to maintain a stem cell-like state. During hematopoiesis, retinoic acid receptor (RAR) γ is selectively expressed by stem cells and their immediate progeny. It is overexpressed in, and is an oncogene for, many cancers including colorectal, renal and hepatocellular carcinoma, cholangiocarcinomas and some cases of acute myeloid leukemia that harbor RARγ fusion proteins. In vitro studies suggest that RARγ-selective and pan-RAR antagonists provoke the death of CSCs by necroptosis and point to antagonism of RARγ as a potential strategy to treat metastatic disease and relapse, and perhaps provide a cure for some cancers.

L-Ascorbic Acid and α-Tocopherol Synergistically Triggers Apoptosis Inducing Antileukemic Effects of Arsenic Trioxide via Oxidative Stress in Human Acute Promyelocytic Leukemia Cells

Chemosensitization is an effective strategy to overcome the drawbacks of arsenic trioxide (As₂O₃) treatment, which may be possible through the use of dietary supplements in combination. The present investigation evaluates the synergistic mechanism of action of vitamins, such as L-ascorbic acid (L-AA) and α-tocopherol (α-TOC) in As₂O₃ chemotherapy using human leukemia (HL-60) cells. In vitro assays on the cytotoxicity of As₂O₃ and vitamins and cellular apoptotic evidences were done; a proteomic investigation with mass spectrometry was also performed. The combination of L-AA and α-TOC potentiates As₂O₃ cytotoxicity in HL-60 cells, substantiated by depletion in antioxidant status, mitochondrial transmembrane potential, and inhibition of nuclear factor erythroid 2-related factor 2 and B-cell lymphoma 2 transcription factors. Mass spectrometry results showed decreased expression of proteins regulating cell cycle and translation in cells treated with As₂O₃, L-AA, and α-TOC when compared with As₂O₃-treated sample. In addition, this combination treatment identified numerous proteins associated with apoptosis and cell stress. HL-60 cells became more prone to As₂O₃ on exposure to L-AA and α-TOC, indicating that this combination may be a promising approach to increase the outcome of As₂O₃ chemotherapy.

Strategies to generate functionally normal neutrophils to reduce infection and infection-related mortality in cancer chemotherapy

Neutrophils form an essential part of innate immunity against infection. Cancer chemotherapy-induced neutropenia (CCIN) is a condition in which the number of neutrophils in a patient's bloodstream is decreased, leading to increased susceptibility to infection. Granulocyte colony-stimulating factor (GCSF) has been the only approved treatment for CCIN over two decades. To date, CCIN-related infection and mortality remain a significant concern, as neutrophils generated in response to administered GCSF are functionally immature and cannot effectively fight infection. This review summarizes the molecular regulatory mechanisms of neutrophil granulocytic differentiation and innate immunity development, dissects the biology of GCSF in myeloid expansion, highlights the shortcomings of GCSF in CCIN treatment, updates the recent advance of a selective retinoid agonist that promotes neutrophil granulocytic differentiation, and evaluates the benefits of developing GCSF biosimilars to increase access to GCSF biologics versus seeking a new mode to fundamentally advance GCSF therapy for treatment of CCIN.

B7H3 regulates differentiation and serves as a potential biomarker and theranostic target for human glioblastoma

B7H3 (CD276), a co-stimulator molecule of the cell surface B7 protein superfamily, is expressed on glioblastomas (GBM). Recently, B7H3 functions beyond immune costimulation have been demonstrated. However, the mechanisms underlying B7H3 function are diverse and not well understood. GBM tumors contain undifferentiated self-renewing cells, which confound therapeutic attempts. We investigated the role of B7H3 in the regulation of GBM cell differentiation and the regulatory pathways involved. Analysis of public databases (TCGA, Rembrandt, and GEO NCBI) and RNA sequencing were performed to explore the role of B7H3 in GBM. Knockdown and overexpression of B7H3, were used to verify the downstream pathway in vitro. Further studies in vivo were performed to support the new finding. Bioinformatics analysis identified a correlation between the expression of B7H3, the expression of glioma self-renewing cell (GSC)-related genes, and MYC expression. These observations were verified by RNA-sequencing analyses in primary GBM cell lines. In vitro knockdown of B7H3-induced differentiation, associated with downregulation of SMAD6 (a TGF-β pathway inhibitor) and enhancement of SMAD1 phosphorylation-induced SMAD4 expression. Importantly, activation of the TGF-β pathway resulted in downregulation of MYC expression. In vivo assays conducted in a human GBM cell line xenograft mouse model demonstrated that B7H3 knockdown decreased MYC expression and inhibited tumor growth. B7H3 knockdown could regulate GBM differentiation by modulating MYC expression. So, B7H3 could serve as a potential theranostic target for the treatment of patients with GBM.

RNF8 is responsible for ATRA resistance in variant acute promyelocytic leukemia with GTF2I/RARA fusion, and inhibition of the ubiquitin-proteasome pathway contributes to the reversion of ATRA resistance

Background

GTF2I-RARA is a newly identified RARA fusion gene in variant acute promyelocytic leukemia (APL) patients with t(7;17)(q11;q21). Clinical manifestation in the patient showed that it is a sort of ATRA-insensitive oncogene and is different from the classic PML-RARA in terms of therapeutic reaction.

Methods

To reveal the functional characteristics and regulating mechanism of the GTF2I-RARA fusion gene, we established a GTF2I-RARA-transfected HL60 cell model and examined its sensitivity to ATRA by western blot, MTT assay, flow cytometry, and Wright-Giemsa staining. Coimmunoprecipitation and confocal microscopy were used to examine the binding of GTF2I-RARA and transcriptional corepressors. We also performed ChIP-seq to search for potential target genes. Immunoprecipitation, ubiquitination assay, western blot, luciferase assay, and real-time PCR were used to analyze the effects of RNF8 on RARA. Flow cytometry and Wright-Giemsa staining were used to study the effect of MG132 and ATRA on the GTF2I-RARA-transfected HL60 cell model.

Result

We confirmed resistance of GTF2I-RARA to ATRA. Compared with PML-RARA, GTF2I-RARA has a higher affinity to HDAC3 under ATRA treatment. Using the ChIP-sequencing approach, we identified 221 GTF2I-RARA binding sites in model cells and found that the RING finger protein 8 (RNF8) is a target gene of GTF2I-RARA. RNF8 participates in disease progression and therapy resistance in APL with the GTF2I-RARA transcript. Elevated RNF8 expression promotes the interaction between RARA and RNF8 and induces RARA Lys-48 linkage ubiquitylation and degradation, resulting in attenuated transcriptional activation of RARA.

Conclusion

Our results suggest that RNF8 is a key GTF2I-RARA downstream event. Using the combination of MG132 and ATRA to treat GTF2I-RARA-HL60 cells, a synergistic effect leading to GTF2I-RARA-HL60 cell differentiation was confirmed. Taken together, the targeting of RNF8 may be an alternative choice for treatment in variant APL with GTF2I-RARA fusion.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0803-4) contains supplementary material, which is available to authorized users.

Targeting Transcription Factors for Cancer Treatment

Transcription factors are involved in a large number of human diseases such as cancers for which they account for about 20% of all oncogenes identified so far. For long time, with the exception of ligand-inducible nuclear receptors, transcription factors were considered as “undruggable” targets. Advances knowledge of these transcription factors, in terms of structure, function (expression, degradation, interaction with co-factors and other proteins) and the dynamics of their mode of binding to DNA has changed this postulate and paved the way for new therapies targeted against transcription factors. Here, we discuss various ways to target transcription factors in cancer models: by modulating their expression or degradation, by blocking protein/protein interactions, by targeting the transcription factor itself to prevent its DNA binding either through a binding pocket or at the DNA-interacting site, some of these inhibitors being currently used or evaluated for cancer treatment. Such different targeting of transcription factors by small molecules is facilitated by modern chemistry developing a wide variety of original molecules designed to specifically abort transcription factor and by an increased knowledge of their pathological implication through the use of new technologies in order to make it possible to improve therapeutic control of transcription factor oncogenic functions.

Molecular Heterogeneity in Acute Promyelocytic Leukemia - a Single Center Experience from India

Atypical breakpoints and variant APL cases involving alternative chromosomal aberrations are seen in a small subset of acute promyelocytic leukemia (APL) patients. Over seven different partner genes for RARA have been described. Although rare, these variants prove to be a diagnostic challenge and require a combination of advanced cytogenetic and molecular techniques for accurate characterization. Heterogeneity occurs not only at the molecular level but also at clinico-pathological level influencing treatment response and outcome. In this case series, we describe the molecular heterogeneity of APL with a focus on seven variant APL cases from a single tertiary cancer center in India over a period of two and a half years.

We discuss five cases with ZBTB16-RARA fusion and two novel PML-RARA variants, including a Bcr3 variant involving fusion of PML exon4 and RARA exon3 with an additional 40 nucleotides originating from RARA intron2, another involving exon 6 of PML and exon 3 of RARA with addition of 126 nucleotides, which mapped to the central portion of RARA intron 2. To the best of our knowledge, this is the first case series of this kind from India.

CD70/CD27 signaling promotes blast stemness and is a viable therapeutic target in acute myeloid leukemia

Riether et al. show that CD70/CD27 signaling activates stem cell gene expression programs in acute myeloid leukemia (AML). Blocking the CD70/CD27 interaction inhibits self-renewal and induces differentiation of AML blasts and stem/progenitor cells.

Aberrant proliferation, symmetric self-renewal, increased survival, and defective differentiation of malignant blasts are key oncogenic drivers in acute myeloid leukemia (AML). Stem cell gene signatures predict poor prognosis in AML patients; however, with few exceptions, these deregulated molecular pathways cannot be targeted therapeutically. In this study, we demonstrate that the TNF superfamily ligand–receptor pair CD70/CD27 is expressed on AML blasts and AML stem/progenitor cells. CD70/CD27 signaling in AML cells activates stem cell gene expression programs, including the Wnt pathway, and promotes symmetric cell divisions and proliferation. Soluble CD27, reflecting the extent of CD70/CD27 interactions in vivo, was significantly elevated in the sera of newly diagnosed AML patients and is a strong independent negative prognostic biomarker for overall survival. Blocking the CD70/CD27 interaction by mAb induced asymmetric cell divisions and differentiation in AML blasts and AML stem/progenitor cells, inhibited cell growth and colony formation, and significantly prolonged survival in murine AML xenografts. Importantly, hematopoietic stem/progenitor cells from healthy BM donors express neither CD70 nor CD27 and were unaffected by blocking mAb treatment. Therefore, targeting CD70/CD27 signaling represents a promising therapeutic strategy for AML.

Evolution of a FLT3-TKD mutated subclone at meningeal relapse in acute promyelocytic leukemia

Here, we report the case of an acute promyelocytic leukemia (APL) patient who—although negative for FLT3 mutations at diagnosis—developed isolated FLT3 tyrosine kinase II domain (FLT3-TKD)-positive meningeal relapse, which, in retrospect, could be traced back to a minute bone marrow subclone present at first diagnosis. Initially, the 48-yr-old female diagnosed with high-risk APL had achieved complete molecular remission after standard treatment with all-trans retinoic acid (ATRA) and chemotherapy according to the AIDA (ATRA plus idarubicin) protocol. Thirteen months after the start of ATRA maintenance, the patient suffered clinically overt meningeal relapse along with minute molecular traces of PML/RARA (promyelocytic leukemia/retinoic acid receptor alpha) in the bone marrow. Following treatment with arsenic trioxide and ATRA in combination with intrathecal cytarabine and methotrexate, the patient achieved a complete molecular remission in both cerebrospinal fluid (CSF) and bone marrow, which currently lasts for 2 yr after completion of therapy. Whole-exome sequencing and subsequent ultradeep targeted resequencing revealed a heterozygous FLT3-TKD mutation in CSF leukemic cells (p.D835Y, c.2503G>T, 1000/1961 reads [51%]), which was undetectable in the concurrent bone marrow sample. Interestingly, the FLT3-TKD mutated meningeal clone originated from a small bone marrow subclone present in a variant allele frequency of 0.4% (6/1553 reads) at initial diagnosis. This case highlights the concept of clonal evolution with a subclone harboring an additional mutation being selected as the “fittest” and leading to meningeal relapse. It also further supports earlier suggestions that FLT3 mutations may play a role for migration and clonal expansion in the CSF sanctuary site.

Cholinergic activation enhances retinoic acid-induced differentiation in the human NB-4 acute promyelocytic leukemia cell line

The non-neuronal cholinergic system (NNCS) has been shown to play a role in regulating hematopoietic differentiation. We determined the expression of cholinergic components in leukemic cell lines by Western blotting and in normal leukocyte subsets by flow cytometry and found a heterogeneous expression of choline acetyltransferase (ChAT), acetylcholinesterase (AChE), choline transporter (CHT), M3 muscarinic acetylcholine receptor (M3-mAChR) and α7 nicotinic acetylcholine receptor (α7-nAChR). We then evaluated NNCS role in differentiation of human NB-4 acute promyelocytic leukemia cell line and discovered a dramatic induction of M3-mAChR after all-trans retinoic acid (ATRA) treatment (p<0.0001). Adding carbachol which is a cholinergic agonist to the ATRA treatment resulted in an increase of a granulocytic differentiation marker (CD11b) as compared with ATRA treatment alone (p<0.05), indicating that cholinergic activation enhanced ATRA in inducing NB-4 maturation. The combination of carbachol and ATRA treatment for 72h also resulted in decreased viability and increased cleaved caspase-3 expression when compared with ATRA treatment alone (p<0.05). However, this combination did not cause poly (ADP-ribose) polymerase (PARP) cleavage. Overall, we have shown that NB-4 cells expressed M3-mAChR in a differentiation-dependent manner and cholinergic stimulation induced maturation and death of ATRA-induced differentiated NB-4 cells.

Molecular Characteristics and Clinical Significance of 12 Fusion Genes in Acute Promyelocytic Leukemia: A Systematic Review

Acute promyelocytic leukemia (APL) is characterized by the generation of the promyelocytic leukemia-retinoic acid (RA) receptor α (PML-RARα) fusion gene. PML-RARα is the central leukemia-initiating event in APL and is directly targeted by all-trans-RA (ATRA) as well as arsenic. In classic APL harboring PML-RARα transcripts, more than 90% of patients can achieve complete remission when treated with ATRA combined with arsenic trioxide chemotherapy. In the last 20 years, more than 10 variant fusion genes have been found and identified in APL patients. These variant APL cases present different clinical phenotypes and treatment outcomes. All variant APL cases show a similar breakpoint within the RARα gene, whereas its partner genes are variable. These fusion proteins have the ability to repress rather than activate retinoic targets. These chimeric proteins also possess different molecular characteristics, thereby resulting in variable sensitivities to ATRA and clinical outcomes. In this review, we comprehensively analyze various rearrangements in variant APL cases that have been reported in the literature as well as the molecular characteristics and functions of the fusion proteins derived from different RARα partner genes and their clinical implications.

[Relapse of acute promyelocytic leukemia in the central nervous system revealed by isolated dementia]

INTRODUCTION

Approximately 1.5% of dementia is due to curable aetiology. We report an isolated dementia syndrome due to a meningeal relapse of acute promyelocytic leukaemia with favourable outcome after appropriate treatment.

CASE REPORT

A 72-year-old woman, in remission of an acute promyelocytic leukaemia, presented a loss of autonomy for several months due to corticosubcortical dementia. Lumbar puncture showed blast cells indicating meningeal relapse of leukaemia. Intrathecal chemotherapy and arsenic trioxide obtained biological and molecular remission as well as restoration of normal cognitive functions.

CONCLUSION

In patients with hematologic past history such as acute promyelocytic leukaemia, an isolated cognitive impairment should alert physicians to search for an isolated neuromeningeal relapse.

Process Pharmacology: A Pharmacological Data Science Approach to Drug Development and Therapy

A novel functional‐genomics based concept of pharmacology that uses artificial intelligence techniques for mining and knowledge discovery in “big data” providing comprehensive information about the drugs’ targets and their functional genomics is proposed. In “process pharmacology”, drugs are associated with biological processes. This puts the disease, regarded as alterations in the activity in one or several cellular processes, in the focus of drug therapy. In this setting, the molecular drug targets are merely intermediates. The identification of drugs for therapeutic or repurposing is based on similarities in the high‐dimensional space of the biological processes that a drug influences. Applying this principle to data associated with lymphoblastic leukemia identified a short list of candidate drugs, including one that was recently proposed as novel rescue medication for lymphocytic leukemia. The pharmacological data science approach provides successful selections of drug candidates within development and repurposing tasks.

Targeting Calcium Signaling Induces Epigenetic Reactivation of Tumor Suppressor Genes in Cancer

Targeting epigenetic pathways is a promising approach for cancer therapy. Here, we report on the unexpected finding that targeting calcium signaling can reverse epigenetic silencing of tumor suppressor genes (TSG). In a screen for drugs that reactivate silenced gene expression in colon cancer cells, we found three classical epigenetic targeted drugs (DNA methylation and histone deacetylase inhibitors) and 11 other drugs that induced methylated and silenced CpG island promoters driving a reporter gene (GFP) as well as endogenous TSGs in multiple cancer cell lines. These newly identified drugs, most prominently cardiac glycosides, did not change DNA methylation locally or histone modifications globally. Instead, all 11 drugs altered calcium signaling and triggered calcium-calmodulin kinase (CamK) activity, leading to MeCP2 nuclear exclusion. Blocking CamK activity abolished gene reactivation and cancer cell killing by these drugs, showing that triggering calcium fluxes is an essential component of their epigenetic mechanism of action. Our data identify calcium signaling as a new pathway that can be targeted to reactivate TSGs in cancer.

The Combination of Three Natural Compounds Effectively Prevented Lung Carcinogenesis by Optimal Wound Healing

The tumor stroma has been described as "normal wound healing gone awry". We explored whether the restoration of a wound healing-like microenvironment may facilitate tumor healing. Firstly, we screened three natural compounds (shikonin, notoginsenoside R1 and aconitine) from wound healing agents and evaluated the efficacies of wound healing microenvironment for limiting single agent-elicited carcinogenesis and two-stage carcinogenesis. The results showed that three compounds used alone could promote wound healing but had unfavorable efficacy to exert wound healing, and that the combination of three compounds made up treatment disadvantage of a single compound in wound healing and led to optimal wound healing. Although individual treatment with these agents may prevent cancer, they were not effective for the treatment of established tumors. However, combination treatment with these three compounds almost completely prevented urethane-induced lung carcinogenesis and reduced tumor burden. Different from previous studies, we found that urethane-induced lung carcinogenesis was associated with lung injury independent of pulmonary inflammation. LPS-induced pulmonary inflammation did not increase lung carcinogenesis, whereas decreased pulmonary inflammation by macrophage depletion promoted lung carcinogenesis. In addition, urethane damaged wound healing in skin excision wound model, reversed lung carcinogenic efficacy by the combination of three compounds was consistent with skin wound healing. Further, the combination of these three agents reduced the number of lung cancer stem cells (CSCs) by inducing cell differentiation, restoration of gap junction intercellular communication (GJIC) and blockade of the epithelial-to-mesenchymal transition (EMT). Our results suggest that restoration of a wound healing microenvironment represents an effective strategy for cancer prevention.

Directly targeting transcriptional dysregulation in cancer

Drugs that target intracellular signalling pathways have markedly improved progression-free survival of patients with cancers who were previously regarded as untreatable. However, the rapid emergence of therapeutic resistance, as a result of bypass signalling or downstream mutation within kinase-mediated signalling cascades, has curtailed the benefit gained from these therapies. Such resistance mechanisms are facilitated by the linearity and redundancy of kinase signalling pathways. We argue that, in each cancer, the dysregulation of key transcriptional regulators not only defines the cancer phenotype but is essential for its development and maintenance. Furthermore, we propose that, as therapeutic targets, these transcriptional regulators are less prone to bypass by alternative mutational events or clonal heterogeneity, and therefore we must rekindle our efforts to directly target transcriptional regulation across a broad range of cancers.

Functional-genetic dissection of HDAC dependencies in mouse lymphoid and myeloid malignancies

Histone deacetylase (HDAC) inhibitors (HDACis) have demonstrated activity in hematological and solid malignancies. Vorinostat, romidepsin, belinostat, and panobinostat are Food and Drug Administration-approved for hematological malignancies and inhibit class II and/or class I HDACs, including HDAC1, 2, 3, and 6. We combined genetic and pharmacological approaches to investigate whether suppression of individual or multiple Hdacs phenocopied broad-acting HDACis in 3 genetically distinct leukemias and lymphomas. Individual Hdacs were depleted in murine acute myeloid leukemias (MLL-AF9;Nras(G12D); PML-RARα acute promyelocytic leukemia [APL] cells) and Eµ-Myc lymphoma in vitro and in vivo. Strikingly, Hdac3-depleted cells were selected against in competitive assays for all 3 tumor types. Decreased proliferation following Hdac3 knockdown was not prevented by BCL-2 overexpression, caspase inhibition, or knockout of Cdkn1a in Eµ-Myc lymphoma, and depletion of Hdac3 in vivo significantly reduced tumor burden. Interestingly, APL cells depleted of Hdac3 demonstrated a more differentiated phenotype. Consistent with these genetic studies, the HDAC3 inhibitor RGFP966 reduced proliferation of Eµ-Myc lymphoma and induced differentiation in APL. Genetic codepletion of Hdac1 with Hdac2 was pro-apoptotic in Eµ-Myc lymphoma in vitro and in vivo and was phenocopied by the HDAC1/2-specific agent RGFP233. This study demonstrates the importance of HDAC3 for the proliferation of leukemia and lymphoma cells, suggesting that HDAC3-selective inhibitors could prove useful for the treatment of hematological malignancies. Moreover, our results demonstrate that codepletion of Hdac1 with Hdac2 mediates a robust pro-apoptotic response. Our integrated genetic and pharmacological approach provides important insights into the individual or combinations of HDACs that could be prioritized for targeting in a range of hematological malignancies.

Retinoids and rexinoids in cancer prevention: from laboratory to clinic

Early in the age of modern medicine the consequences of vitamin A deficiency drew attention to the fundamental link between retinoid-dependent homeostatic regulation and malignant hyperproliferative diseases. The term "retinoid" includes a handful of endogenous and a large group of synthetic derivatives of vitamin A. These multifunctional lipid-soluble compounds directly regulate target genes of specific biological functions and critical signaling pathways to orchestrate complex functions from vision to development, metabolism, and inflammation. Many of the retinoid activities on the cellular level have been well characterized and translated to the regulation of processes like differentiation and cell death, which play critical roles in the outcome of malignant transformation of tissues. In fact, retinoid-based differentiation therapy of acute promyelocytic leukemia was one of the first successful examples of molecularly targeted treatment strategies. The selectivity, high receptor binding affinity and the ability of retinoids to directly modulate gene expression programs present a distinct pharmacological opportunity for cancer treatment and prevention. However, to fully exploit their potential, the adverse effects of retinoids must be averted. In this review we provide an overview of the biology of retinoid (activated by nuclear retinoic acid receptors [RARs]) and rexinoid (engaged by nuclear retinoid X receptors [RXRs]) action concluded from a long line of preclinical studies, in relation to normal and transformed states of cells. We will also discuss the past and current uses of retinoids in the treatment of malignancies, the potential of rexinoids in the cancer prevention setting, both as single agents and in combinations.

RARRES3 suppresses breast cancer lung metastasis by regulating adhesion and differentiation

In estrogen receptor-negative breast cancer patients, metastatic relapse usually occurs in the lung and is responsible for the fatal outcome of the disease. Thus, a better understanding of the biology of metastasis is needed. In particular, biomarkers to identify patients that are at risk of lung metastasis could open the avenue for new therapeutic opportunities. Here we characterize the biological activity of RARRES3, a new metastasis suppressor gene whose reduced expression in the primary breast tumors identifies a subgroup of patients more likely to develop lung metastasis. We show that RARRES3 downregulation engages metastasis-initiating capabilities by facilitating adhesion of the tumor cells to the lung parenchyma. In addition, impaired tumor cell differentiation due to the loss of RARRES3 phospholipase A1/A2 activity also contributes to lung metastasis. Our results establish RARRES3 downregulation as a potential biomarker to identify patients at high risk of lung metastasis who might benefit from a differentiation treatment in the adjuvant programme.

De-differentiation confers multidrug resistance via noncanonical PERK-Nrf2 signaling

Upregulation of PERK-Nrf2 signaling is a key mechanism by which de-differentiated cancer cells gain multi-drug resistance.

Malignant carcinomas that recur following therapy are typically de-differentiated and multidrug resistant (MDR). De-differentiated cancer cells acquire MDR by up-regulating reactive oxygen species (ROS)–scavenging enzymes and drug efflux pumps, but how these genes are up-regulated in response to de-differentiation is not known. Here, we examine this question by using global transcriptional profiling to identify ROS-induced genes that are already up-regulated in de-differentiated cells, even in the absence of oxidative damage. Using this approach, we found that the Nrf2 transcription factor, which is the master regulator of cellular responses to oxidative stress, is preactivated in de-differentiated cells. In de-differentiated cells, Nrf2 is not activated by oxidation but rather through a noncanonical mechanism involving its phosphorylation by the ER membrane kinase PERK. In contrast, differentiated cells require oxidative damage to activate Nrf2. Constitutive PERK-Nrf2 signaling protects de-differentiated cells from chemotherapy by reducing ROS levels and increasing drug efflux. These findings are validated in therapy-resistant basal breast cancer cell lines and animal models, where inhibition of the PERK-Nrf2 signaling axis reversed the MDR of de-differentiated cancer cells. Additionally, analysis of patient tumor datasets showed that a PERK pathway signature correlates strongly with chemotherapy resistance, tumor grade, and overall survival. Collectively, these results indicate that de-differentiated cells up-regulate MDR genes via PERK-Nrf2 signaling and suggest that targeting this pathway could sensitize drug-resistant cells to chemotherapy.

The development of multidrug resistance is the primary obstacle to treating cancers. High-grade tumors that are less differentiated typically respond poorly to therapy and carry a much worse prognosis than well-differentiated low-grade tumors. Therapy-resistant cancer cells often overexpress antioxidants or efflux proteins that pump drugs out of the cell, but how the differentiation state of cancer cells influences these resistance mechanisms is not well understood. Here we used genome-scale approaches and found that the PERK kinase and its downstream target, Nrf2—a master transcriptional regulator of the cellular antioxidant response—are key mediators of therapy resistance in poorly differentiated breast cancer cells. We show that Nrf2 is activated when cancer cells de-differentiate and that this activation requires PERK. We further show that blocking PERK-Nrf2 signaling with a small-molecule inhibitor sensitizes drug-resistant cancer cells to chemotherapy. Our results identify a novel role for PERK-Nrf2 signaling in multidrug resistance and suggest that targeting this pathway could improve the responsiveness of otherwise resistant tumors to chemotherapy.

Celastrol inhibits lung infiltration in differential syndrome animal models by reducing TNF-α and ICAM-1 levels while preserving differentiation in ATRA-induced acute promyelocytic leukemia cells

All-trans retinoic acid (ATRA) is a revolutionary agent for acute promyelocytic leukemia (APL) treatment via differentiation induction. However, ATRA treatment also increases cytokine, chemokine, and adhesive molecule (mainly ICAM-1) expression, which can cause clinical complications, including a severe situation known as differentiation syndrome (DS) which can cause death. Therefore, it is of clinical significance to find a strategy to specifically blunt inflammatory effects while preserving differentiation. Here we report that the natural compound, celastrol, could effectively block lung infiltrations in DS animal models created by loading ATRA-induced APL cell line NB4. In ATRA-treated NB4 cells, celastrol could potently inhibit ICAM-1 elevation and partially reduce TNF-α and IL-1β secretion, though treatment showed no effects on IL-8 and MCP-1 levels. Celastrol’s effect on ICAM-1 in ATRA-treated NB4 was related to reducing MEK1/ERK1 activation. Strikingly and encouragingly, celastrol showed no obvious effects on ATRA-induced NB4 differentiation, as determined by morphology, enzymes, and surface markers. Our results show that celastrol is a promising and unique agent for managing the side effects of ATRA application on APL, and suggest that hyper-inflammatory ability is accompanied by, but not necessary for, APL differentiation. Thus we offered an encouraging novel strategy to further improve differentiation therapy.

The PML domain of PML-RARα blocks senescence to promote leukemia

In most acute promyelocytic leukemia (APL) cases, translocons produce a promyelocytic leukemia protein-retinoic acid receptor α (PML-RARα) fusion gene. Although expression of the human PML fusion in mice promotes leukemia, its efficiency is rather low. Unexpectedly, we find that simply replacing the human PML fusion with its mouse counterpart results in a murine PML-RARα (mPR) hybrid protein that is transformed into a significantly more leukemogenic oncoprotein. Using this more potent isoform, we show that mPR promotes immortalization by preventing cellular senescence, impeding up-regulation of both the p21 and p19(ARF) cell-cycle regulators. This induction coincides with a loss of the cancer-associated ATRX/Daxx-histone H3.3 predisposition complex and suggests inhibition of senescence as a targetable mechanism in APL therapy.

HOX antisense lincRNA HOXA-AS2 is an apoptosis repressor in all trans retinoic 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.

CD99 drives terminal differentiation of osteosarcoma cells by acting as a spatial regulator of ERK 1/2

Differentiation therapy is an attractive treatment for osteosarcoma (OS). CD99 is a cell surface molecule expressed in mesenchymal stem cells and osteoblasts that is maintained during osteoblast differentiation while lost in OS. Herein, we show that whenever OS cells regain CD99, they become prone to reactivate the terminal differentiation program. In differentiating conditions, CD99-transfected OS cells express osteocyte markers, halt proliferation, and largely die by apoptosis, resembling the fate of mature osteoblasts. CD99 induces ERK activation, increasing its membrane-bound/cytoplasmic form rather than affecting its nuclear localization. Through cytoplasmic ERK, CD99 promotes activity of the main osteogenic transcriptional factors AP1 and RUNX2, which in turn enhance osteocalcin and p21(WAF1/CIP1) , leading to G0 /G1 arrest. These data underscore the alternative positions of active ERK into distinct subcellular compartments as key events for determining OS fate.

A calibrated agent-based computer model of stochastic cell dynamics in normal human colon crypts useful for in silico experiments

BACKGROUND

Normal colon crypts consist of stem cells, proliferating cells, and differentiated cells. Abnormal rates of proliferation and differentiation can initiate colon cancer. We have measured the variation in the number of each of these cell types in multiple crypts in normal human biopsy specimens. This has provided the opportunity to produce a calibrated computational model that simulates cell dynamics in normal human crypts, and by changing model parameter values, to simulate the initiation and treatment of colon cancer.

RESULTS

An agent-based model of stochastic cell dynamics in human colon crypts was developed in the multi-platform open-source application NetLogo. It was assumed that each cell's probability of proliferation and probability of death is determined by its position in two gradients along the crypt axis, a divide gradient and in a die gradient. A cell's type is not intrinsic, but rather is determined by its position in the divide gradient. Cell types are dynamic, plastic, and inter-convertible. Parameter values were determined for the shape of each of the gradients, and for a cell's response to the gradients. This was done by parameter sweeps that indicated the values that reproduced the measured number and variation of each cell type, and produced quasi-stationary stochastic dynamics. The behavior of the model was verified by its ability to reproduce the experimentally observed monocolonal conversion by neutral drift, the formation of adenomas resulting from mutations either at the top or bottom of the crypt, and by the robust ability of crypts to recover from perturbation by cytotoxic agents. One use of the virtual crypt model was demonstrated by evaluating different cancer chemotherapy and radiation scheduling protocols.

CONCLUSIONS

A virtual crypt has been developed that simulates the quasi-stationary stochastic cell dynamics of normal human colon crypts. It is unique in that it has been calibrated with measurements of human biopsy specimens, and it can simulate the variation of cell types in addition to the average number of each cell type. The utility of the model was demonstrated with in silico experiments that evaluated cancer therapy protocols. The model is available for others to conduct additional experiments.

Retinoic acid and arsenic trioxide for acute promyelocytic leukemia

BACKGROUND

All-trans retinoic acid (ATRA) with chemotherapy is the standard of care for acute promyelocytic leukemia (APL), resulting in cure rates exceeding 80%. Pilot studies of treatment with arsenic trioxide with or without ATRA have shown high efficacy and reduced hematologic toxicity.

METHODS

We conducted a phase 3, multicenter trial comparing ATRA plus chemotherapy with ATRA plus arsenic trioxide in patients with APL classified as low-to-intermediate risk (white-cell count, ≤10×10(9) per liter). Patients were randomly assigned to receive either ATRA plus arsenic trioxide for induction and consolidation therapy or standard ATRA-idarubicin induction therapy followed by three cycles of consolidation therapy with ATRA plus chemotherapy and maintenance therapy with low-dose chemotherapy and ATRA. The study was designed as a noninferiority trial to show that the difference between the rates of event-free survival at 2 years in the two groups was not greater than 5%.

RESULTS

Complete remission was achieved in all 77 patients in the ATRA-arsenic trioxide group who could be evaluated (100%) and in 75 of 79 patients in the ATRA-chemotherapy group (95%) (P=0.12). The median follow-up was 34.4 months. Two-year event-free survival rates were 97% in the ATRA-arsenic trioxide group and 86% in the ATRA-chemotherapy group (95% confidence interval for the difference, 2 to 22 percentage points; P<0.001 for noninferiority and P=0.02 for superiority of ATRA-arsenic trioxide). Overall survival was also better with ATRA-arsenic trioxide (P=0.02). As compared with ATRA-chemotherapy, ATRA-arsenic trioxide was associated with less hematologic toxicity and fewer infections but with more hepatic toxicity.

CONCLUSIONS

ATRA plus arsenic trioxide is at least not inferior and may be superior to ATRA plus chemotherapy in the treatment of patients with low-to-intermediate-risk APL. (Funded by Associazione Italiana contro le Leucemie and others; ClinicalTrials.gov number, NCT00482833.).

JARID2 is a direct target of the PAX3-FOXO1 fusion protein and inhibits myogenic differentiation of rhabdomyosarcoma cells

Rhabdomyosarcomas (RMS) are the most frequent soft-tissue sarcoma in children and characteristically show features of developing skeletal muscle. The alveolar subtype is frequently associated with a PAX3-FOXO1 fusion protein that is known to contribute to the undifferentiated myogenic phenotype of RMS cells. Histone methylation of lysine residues controls developmental processes in both normal and malignant cell contexts. Here we show that JARID2, which encodes a protein known to recruit various complexes with histone-methylating activity to their target genes, is significantly overexpressed in RMS with PAX3-FOXO1 compared with the fusion gene-negative RMS (t-test; P < 0.0001). Multivariate analyses showed that higher JARID2 levels are also associated with metastases at diagnosis, independent of fusion gene status and RMS subtype (n = 120; P = 0.039). JARID2 levels were altered by silencing or overexpressing PAX3-FOXO1 in RMS cell lines with and without the fusion gene, respectively. Consistent with this, we demonstrated that JARID2 is a direct transcriptional target of the PAX3-FOXO1 fusion protein. Silencing JARID2 resulted in reduced cell proliferation coupled with myogenic differentiation, including increased expression of Myogenin (MYOG) and Myosin Light Chain (MYL1) in RMS cell lines representative of both the alveolar and embryonal subtypes. Induced myogenic differentiation was associated with a decrease in JARID2 levels and this phenotype could be rescued by overexpressing JARID2. Furthermore, we that showed JARID2 binds to and alters the methylation status of histone H3 lysine 27 in the promoter regions of MYOG and MYL1 and that the interaction of JARID2 at these promoters is dependent on EED, a core component of the polycomb repressive complex 2 (PRC2). Therefore, JARID2 is a downstream effector of PAX3-FOXO1 that maintains an undifferentiated myogenic phenotype that is characteristic of RMS. JARID2 and other components of PRC2 may represent novel therapeutic targets for treating RMS patients.

Retinoid differentiation therapy for common types of acute myeloid leukemia

Many cancers arise in a tissue stem cell, and cell differentiation is impaired resulting in an accumulation of immature cells. The introduction of all-trans retinoic acid (ATRA) in 1987 to treat acute promyelocytic leukemia (APL), a rare subtype of acute myeloid leukemia (AML), pioneered a new approach to obtain remission in malignancies by restoring the terminal maturation of leukemia cells resulting in these cells having a limited lifespan. Differentiation therapy also offers the prospect of a less aggressive treatment by virtue of attenuated growth of leukemia cells coupled to limited damage to normal cells. The success of ATRA in differentiation therapy of APL is well known. However, ATRA does not work in non-APL AML. Here we examine some of the molecular pathways towards new retinoid-based differentiation therapy of non-APL AML. Prospects include modulation of the epigenetic status of ATRA-insensitive AML cells, agents that influence intracellular signalling events that are provoked by ATRA, and the use of novel synthetic retinoids.

All-trans retinoic acid preconditioning protects against liver ischemia/reperfusion injury by inhibiting the nuclear factor kappa B signaling pathway

BACKGROUND

Inflammatory response plays a pathogenic role in liver ischemia/reperfusion (I/R) injury. All-trans retinoic acid (ATRA) is an active metabolite of vitamin A with anti-inflammatory effects. However, there are few reports on the anti-inflammatory effects of ATRA on liver I/R injury. The purpose of this study was to investigate the effects of ATRA on liver I/R injury and related mechanisms.

METHODS

A total of 54 male Sprague-Dawley rats were randomly divided into three groups (18 rats each), namely, sham, I/R, and I/R+ATRA groups. ATRA was intraperitoneally administered at a dose of 15mg/kg/d 14d before ischemia surgery. The segmental (70%) hepatic ischemia model was used by clamping the portal vein, hepatic artery, and bile duct of the left and median for 1h. The rats were sacrificed 3, 6, and 24h after reperfusion, and blood and liver tissue samples were obtained. Liver injury was evaluated by biochemical and histopathologic examinations. Myeloperoxidase activity was spectrophotometrically measured. The expression of pro-inflammatory cytokines, such as tumor necrosis factor-α and interleukin-6 was measured by enzyme-linked immunosorbent assay and real-time polymerase chain reaction. Liver nuclear factor kappa B (NF-κB) was detected by immunohistochemistry. The expression of NF-κB p65 and inhibitor NF-κB-α (IκBα) was determined by Western blot analysis.

RESULTS

The serum alanine aminotransferase level, Suzuki scores of hepatic histology, and hepatic myeloperoxidase activity, as indices of hepatic injury, were increased after reperfusion. The increase was attenuated by preadministration with ATRA. Compared with the I/R group, ATRA treatment increased IκBα expression and suppressed NF-κB p65 expression. Subsequently, the levels of tumor necrosis factor-α and interleukin-6 after liver I/R were effectively downregulated.

CONCLUSIONS

ATRA administration can significantly attenuate I/R injury in rat liver. The protective mechanism is related to its anti-inflammatory function of inhibiting NF-κB activation.

Diagnostic and prognostic value of cytogenetics in acute myeloid leukemia

The last 4 decades have seen major advances in understanding the genetic basis of acute myeloid leukemia (AML), and substantial improvements in survival of children and young adults with the disease. A key step forward was the discovery that AML cells harbor recurring cytogenetic abnormalities. The identification of the genes involved in chromosomal rearrangements has provided insights into the regulation of normal hematopoiesis and how disruption of key transcription factors and epigenetic modulators promote leukemic transformation. Cytogenetics has been widely adopted to provide the framework for development of risk-stratified treatment approaches to patient management.

Development of real-time quantitative polymerase chain reaction assays to track treatment response in retinoid resistant acute promyelocytic leukemia

Molecular detection of minimal residual disease (MRD) has become established to assess remission status and guide therapy in patients with ProMyelocytic Leukemia-RARA+ acute promyelocytic leukemia (APL). However, there are few data on tracking disease response in patients with rarer retinoid resistant subtypes of APL, characterized by PLZF-RARA and STAT5b-RARA. Despite their rarity (<1% of APL) we identified 6 cases (PLZF-RARA, n = 5; STAT5b-RARA, n = 1), established the respective breakpoint junction regions and designed reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) assays to detect leukemic transcripts. The relative level of fusion gene expression in diagnostic samples was comparable to that observed in t(15;17) - associated APL, affording assay sensitivities of ∼1 in 10(4)-10(5). Serial samples were available from two PLZF-RARA APL patients. One showed persistent polymerase chain reaction positivity, predicting subsequent relapse, and remains in CR2, ∼11 years post-autograft. The other, achieved molecular remission (CRm) with combination chemotherapy, remaining in CR1 at 6 years. The STAT5b-RARA patient failed to achieve CRm following frontline combination chemotherapy and ultimately proceeded to allogeneic transplant on the basis of a steadily rising fusion transcript level. These data highlight the potential of RT-qPCR detection of MRD to facilitate development of more individualized approaches to the management of rarer molecularly defined subsets of acute leukemia.

Differentiation syndrome in promyelocytic leukemia: clinical presentation, pathogenesis and treatment

Differentiation syndrome (DS) represents a life-threatening complication in patients with acute promyelocytic leukemia (APL) undergoing induction therapy with all-trans retinoic acid (ATRA) or arsenic trioxide (ATO). It affected about 20–25% of all patients and so far there are no definitive diagnostic criteria. Clinically, DS is characterized by weight gain, fever not attributable to infection, respiratory distress, cardiac involvement, hypotension, and/or acute renal failure. At the histological point of view, there is an extensive interstitial and intra-alveolar pulmonary infiltration by maturing myeloid cells, endothelial cell damage, intra-alveolar edema, inter-alveolar hemorrhage, and fibrinous exsudates. DS pathogenesis is not completely understood, but it is believed that an excessive inflammatory response is the main phenomenon involved, which results in increased production of chemokines and expression of adhesion molecules on APL cells. Due to the high morbidity and mortality associated with DS, its recognition and the prompt initiation of the treatment is of utmost importance. Dexamethasone is considered the mainstay of treatment of DS, and the recommended dose is 10 mg twice daily by intravenous route until resolution of DS. In severe cases (respiratory or acute renal failure) it is recommended the discontinuation of ATRA or ATO until recovery.

Characterisation of genome-wide PLZF/RARA target genes

The PLZF/RARA fusion protein generated by the t(11;17)(q23;q21) translocation in acute promyelocytic leukaemia (APL) is believed to act as an oncogenic transcriptional regulator recruiting epigenetic factors to genes important for its transforming potential. However, molecular mechanisms associated with PLZF/RARA-dependent leukaemogenesis still remain unclear.

We searched for specific PLZF/RARA target genes by ChIP-on-chip in the haematopoietic cell line U937 conditionally expressing PLZF/RARA. By comparing bound regions found in U937 cells expressing endogenous PLZF with PLZF/RARA-induced U937 cells, we isolated specific PLZF/RARA target gene promoters. We next analysed gene expression profiles of our identified target genes in PLZF/RARA APL patients and analysed DNA sequences and epigenetic modification at PLZF/RARA binding sites. We identify 413 specific PLZF/RARA target genes including a number encoding transcription factors involved in the regulation of haematopoiesis. Among these genes, 22 were significantly down regulated in primary PLZF/RARA APL cells. In addition, repressed PLZF/RARA target genes were associated with increased levels of H3K27me3 and decreased levels of H3K9K14ac. Finally, sequence analysis of PLZF/RARA bound sequences reveals the presence of both consensus and degenerated RAREs as well as enrichment for tissue-specific transcription factor motifs, highlighting the complexity of targeting fusion protein to chromatin. Our study suggests that PLZF/RARA directly targets genes important for haematopoietic development and supports the notion that PLZF/RARA acts mainly as an epigenetic regulator of its direct target genes.

Molecular tumor profiling for prediction of response to anticancer therapies

Personalized medicine in the treatment of cancer is based on the recognition that molecularly targeted therapies are most effective in patients whose tumors carry specific genetic or genomic alterations. These alterations, which often activate oncogenes that encode the components of signal transduction pathways, serve as predictive markers for sensitivity or resistance of individual tumors to drugs that target such pathways. In the recent past, individual mutations and other changes within tumors have been assayed to determine the likelihood of response or nonresponse to specific targeted therapies. However, with the development of increasing numbers of molecularly targeted drugs, attention has shifted to high-throughput testing of tumors for dozens of predictive markers. This approach to predictive testing has been termed molecular tumor profiling. This review describes the background to this field, the principal markers analyzed, and the methodologies that are being utilized or are under development for tumor profiling.

Gene expression profiling in MDS and AML: potential and future avenues

Today, the classification systems for myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) already incorporate cytogenetic and molecular genetic aberrations in an attempt to better reflect disease biology. However, in many MDS/AML patients no genetic aberrations have been identified yet, and even within some cytogenetically well-defined subclasses there is considerable clinical heterogeneity. Recent advances in genomics technologies such as gene expression profiling (GEP) provide powerful tools to further characterize myeloid malignancies at the molecular level, with the goal to refine the MDS/AML classification system, incorporating as yet unknown molecular genetic and epigenetic pathomechanisms, which are likely reflected by aberrant gene expression patterns. In this study, we provide a comprehensive review on how GEP has contributed to a refined molecular taxonomy of MDS and AML with regard to diagnosis, prediction of clinical outcome, discovery of novel subclasses and identification of novel therapeutic targets and novel drugs. As many challenges remain ahead, we discuss the pitfalls of this technology and its potential including future integrative studies with other genomics technologies, which will continue to improve our understanding of malignant transformation in myeloid malignancies and thereby contribute to individualized risk-adapted treatment strategies for MDS and AML patients.