Quantitative multiplex quantum dot in-situ hybridisation based gene expression profiling in tissue microarrays identifies prognostic genes in acute myeloid leukaemia

Aberrant stem cell and developmental programs in pediatric leukemia

Hematopoiesis is a finely orchestrated process, whereby hematopoietic stem cells give rise to all mature blood cells. Crucially, they maintain the ability to self-renew and/or differentiate to replenish downstream progeny. This process starts at an embryonic stage and continues throughout the human lifespan. Blood cancers such as leukemia occur when normal hematopoiesis is disrupted, leading to uncontrolled proliferation and a block in differentiation of progenitors of a particular lineage (myeloid or lymphoid). Although normal stem cell programs are crucial for tissue homeostasis, these can be co-opted in many cancers, including leukemia. Myeloid or lymphoid leukemias often display stem cell-like properties that not only allow proliferation and survival of leukemic blasts but also enable them to escape treatments currently employed to treat patients. In addition, some leukemias, especially in children, have a fetal stem cell profile, which may reflect the developmental origins of the disease. Aberrant fetal stem cell programs necessary for leukemia maintenance are particularly attractive therapeutic targets. Understanding how hijacked stem cell programs lead to aberrant gene expression in place and time, and drive the biology of leukemia, will help us develop the best treatment strategies for patients.

Methyltransferase DNMT3B in leukemia

DNA methyltransferases (DNMTs) are highly conserved DNA-modifying enzymes that play important roles in epigenetic regulation and they are involved in cell proliferation, differentiation, and apoptosis. In mammalian cells, three active DNMTs have been identified: DNMT1 acts as a maintenance methyltransferase to replicate preexisting methylation patterns, whereas DNMT3A and DNMT3B primarily act as de novo methyltransferases that are responsible for establishing DNA methylation patterns by adding a methyl group to cytosine bases. The expression of DNMT3B is widespread in a variety of hematological cells and it is altered in each type of leukemia, which is associated with its pathogenesis, progression, treatment, and prognosis. Here, we review current information on DNMT3B in leukemia, including its expression, single-nucleotide polymorphisms, mutations, regulation, function, and clinical value for anti-leukemic therapy and prognosis.

Phenotyping Multiple Subsets of Immune Cells In Situ in FFPE Tissue Sections: An Overview of Methodologies

The recent clinical success of new cancer immunotherapy agents and methods is driving the need to understand the role of immune cells in solid tissues, especially tumors. Immune cell phenotyping via flow cytometry, while a cornerstone of immunology, is not spatially resolved and cannot analyze immune cell subsets in situ in clinical biopsy sections or to determine their interrelationships. To address this problem, a number of methodologies have been developed in attempts to phenotype immune and other cells in images acquired from tissue sections and to assess their organization in the tumor and its microenvironment. This chapter review the staining and multiplex image analysis methods that have been developed for phenotyping immune and other cells in formalin-fixed, paraffin-embedded (FFPE) tissue sections.

Fatty acid-binding protein FABP4 mechanistically links obesity with aggressive AML by enhancing aberrant DNA methylation in AML cells

Obesity is becoming more prevalent worldwide and is a major risk factor for cancer development. Acute myeloid leukemia (AML), the most common acute leukemia in adults, remains a frequently fatal disease. Here we investigated the molecular mechanisms by which obesity favors AML growth and uncovered the fatty acid-binding protein 4 (FABP4) and DNA methyltransferase 1 (DNMT1) regulatory axis that mediates aggressive AML in obesity. We showed that leukemia burden was much higher in high-fat diet-induced obese mice, which had higher levels of FABP4 and interleukin (IL)-6 in the sera. Upregulation of environmental and cellular FABP4 accelerated AML cell growth in both a cell-autonomous and cell-non-autonomous manner. Genetic disruption of FABP4 in AML cells or in mice blocked cell proliferation in vitro and induced leukemia regression in vivo. Mechanistic investigations showed that FABP4 upregulation increased IL-6 expression and signal transducer and activator of transcription factor 3 phosphorylation leading to DNMT1 overexpression and further silencing of the p15^INK4B tumor-suppressor gene in AML cells. Conversely, FABP4 ablation reduced DNMT1-dependent DNA methylation and restored p15^INK4B expression, thus conferring substantial protection against AML growth. Our findings reveal the FABP4/DNMT1 axis in the control of AML cell fate in obesity and suggest that interference with the FABP4/DNMT1 axis might be a new strategy to treat leukemia.

Higher expression levels of the HOXA9 gene, closely associated with MLL-PTD and EZH2 mutations, predict inferior outcome in acute myeloid leukemia

BACKGROUND

Although the biological insight of acute myeloid leukemia (AML) has increased in the past few years, the discovery of novel discriminative biomarkers remains of utmost value for improving outcome predictions. Systematical studies concerning the clinical implications and genetic correlations of HOXA9 aberrations in patients with AML are relatively promising.

MATERIALS AND METHODS

Here, we investigated mutational status and the mRNA levels of the HOXA9 gene in 258 patients with AML. Furthermore, hematological characteristics, chromosome abnormalities, and genetic mutations associated with AML were analyzed, followed by the assessment of clinical survival. Besides, the expression level and mutational status of MEIS1, a cofactor of HOXA9, were also detected in patients with AML with the aim of a deeper understanding about the homeodomain-containing transcription factors associated with hematological characteristics.

RESULTS

HOXA9 and MEIS1 mutations were detected in 4.26% and 3.49% AML cases, respectively. No correlations were detected between mutation status and clinical characteristics, cytogenetic and genetic aberrations, and clinical survival. Higher HOXA9 expression levels were correlated with white blood cell count and closely associated with unfavorable karyotype as well as MLL-PTD and EZH2 mutations, whereas, there was an inverse correlation with the French-American-British M3 subtype. Compared with patients with lower HOXA9 expression levels, those with higher HOXA9 expression levels had a lower complete remission rate and inferior survivals in both AML and cytogenetically normal AML.

CONCLUSION

HOXA9 expression may serve as a promising biomarker to ameliorate a prognostic model for predicting clinical outcome and consummating individualized treatment in patients with AML.

Role of HOXA9 in leukemia: dysregulation, cofactors and essential targets

HOXA9 is a homeodomain-containing transcription factor that has an important role in hematopoietic stem cell expansion and is commonly deregulated in acute leukemias. A variety of upstream genetic alterations in acute myeloid leukemia lead to overexpression of HOXA9, which is a strong predictor of poor prognosis. In many cases, HOXA9 has been shown to be necessary for maintaining leukemic transformation; however, the molecular mechanisms through which it promotes leukemogenesis remain elusive. Recent work has established that HOXA9 regulates downstream gene expression through binding at promoter distal enhancers along with a subset of cell-specific cofactor and collaborator proteins. Increasing efforts are being made to identify both the critical cofactors and target genes required for maintaining transformation in HOXA9-overexpressing leukemias. With continued advances in understanding HOXA9-mediated transformation, there is a wealth of opportunity for developing novel therapeutics that would be applicable for greater than 50% of AML with overexpression of HOXA9.

Promoter DNA methylation and expression levels of HOXA4, HOXA5 and MEIS1 in acute myeloid leukemia

HOXA genes encode transcription factors, which are crucial for embryogenesis and tissue differentiation and are involved in the early stages of hematopoiesis. Aberrations in HOXA genes and their cofactor MEIS1 are found in human neoplasms, including acute myeloid leukemia (AML). The present study investigated the role of HOXA4, HOXA5 and MEIS1 promoter DNA methylation and mRNA expression in AML. Samples from 78 AML patients and 12 normal bone marrow (BM) samples were included. The levels of promoter DNA methylation were determined using quantitative methylation‑specific polymerase chain reaction (PCR; qMSP) and the relative expression levels were measured using reverse transcription quantitative PCR in Ficoll‑separated BM mononuclear cells and in fluorescent activated cell sorting‑sorted populations of normal hematopoietic progenitors. In total, 38.1 and 28.9% of the patients exhibited high methylation levels of HOXA4 and HOXA5, respectively, compared with the control samples, and MEIS1 methylation was almost absent. An inverse correlation between HOXA4 methylation and expression was identified in a group of patients with a normal karyotype (NK AML). An association between the genes was observed and correlation between the DNA methylation and expression levels of the HOXA gene promoter with the expression of MEIS1 was observed. Patients with favorable chromosomal aberrations revealed a low level of HOXA4 methylation and decreased expression levels of HOXA5 and MEIS1 compared with the NK AML and the adverse cytogenetic risk patients. The NK AML patients with NPM1 mutations exhibited elevated HOXA4 methylation and expression levels of HOXA5 and MEIS1 compared with the NPM1 wild‑type patients. Comparison of the undifferentiated BM‑derived hematopoietic CD34+CD38low, CD34+CD38+ and CD15+ cells revealed a gradual decrease in the expression levels of these three genes and an increase in HOXA4 promoter methylation. This differentiation‑associated variability was not observed in AML, which was classified according to the French‑American‑British system.

Multispectral Imaging

The field of anatomic pathology has changed significantly over the last decades and, as a result of the technological developments in molecular pathology and genetics, has had increasing pressures put on it to become quantitative and to provide more information about protein expression on a cellular level in tissue sections. Multispectral imaging (MSI) has a long history as an advanced imaging modality and has been used for over a decade now in pathology to improve quantitative accuracy, enable the analysis of multicolor immunohistochemistry, and drastically reduce the impact of contrast-robbing tissue autofluorescence common in formalin-fixed, paraffin-embedded tissues. When combined with advanced software for the automated segmentation of different tissue morphologies (eg, tumor vs stroma) and cellular and subcellular segmentation, MSI can enable the per-cell quantitation of many markers simultaneously. This article covers the role that MSI has played in anatomic pathology in the analysis of formalin-fixed, paraffin-embedded tissue sections, discusses the technological aspects of why MSI has been adopted, and provides a review of the literature of the application of MSI in anatomic pathology.