Patient-Derived Xenograft Models for Leukemias

Patient-derived xenograft (PDX) modeling is a valuable tool for the study of leukemia pathogenesis, progression, and therapy response. Engraftment of human leukemia cells occurs following injection into the tail vein (or retro-orbital vein) of preconditioned immunocompromised mice. Injected mice are maintained in a sterile and supportive housing environment until leukemia engraftment is observed, at which time studies such as drug treatments or leukemia sampling can occur. Here, we outline a method for generating PDXs from Acute Myeloid Leukemia (AML) patient samples using tail vein injection; however it can also be readily applied to T- and B- Acute Lymphoblastic Leukemia (ALL) samples.

An "unexpected" role for EMT transcription factors in hematological development and malignancy

The epithelial to mesenchymal transition (EMT) is a fundamental developmental process essential for normal embryonic development. It is also important during various pathogenic processes including fibrosis, wound healing and epithelial cancer cell metastasis and invasion. EMT is regulated by a variety of cell signalling pathways, cell-cell interactions and microenvironmental cues, however the key drivers of EMT are transcription factors of the ZEB, TWIST and SNAIL families. Recently, novel and unexpected roles for these EMT transcription factors (EMT-TFs) during normal blood cell development have emerged, which appear to be largely independent of classical EMT processes. Furthermore, EMT-TFs have also begun to be implicated in the development and pathogenesis of malignant hematological diseases such as leukemia and lymphoma, and now present themselves or the pathways they regulate as possible new therapeutic targets within these malignancies. In this review, we discuss the ZEB, TWIST and SNAIL families of EMT-TFs, focusing on what is known about their normal roles during hematopoiesis as well as the emerging and "unexpected" contribution they play during development and progression of blood cancers.

Human erythroleukemia genetics and transcriptomes identify master transcription factors as functional disease drivers

Acute erythroleukemia (AEL or acute myeloid leukemia [AML]-M6) is a rare but aggressive hematologic malignancy. Previous studies showed that AEL leukemic cells often carry complex karyotypes and mutations in known AML-associated oncogenes. To better define the underlying molecular mechanisms driving the erythroid phenotype, we studied a series of 33 AEL samples representing 3 genetic AEL subgroups including TP53-mutated, epigenetic regulator-mutated (eg, DNMT3A, TET2, or IDH2), and undefined cases with low mutational burden. We established an erythroid vs myeloid transcriptome-based space in which, independently of the molecular subgroup, the majority of the AEL samples exhibited a unique mapping different from both non-M6 AML and myelodysplastic syndrome samples. Notably, >25% of AEL patients, including in the genetically undefined subgroup, showed aberrant expression of key transcriptional regulators, including SKI, ERG, and ETO2. Ectopic expression of these factors in murine erythroid progenitors blocked in vitro erythroid differentiation and led to immortalization associated with decreased chromatin accessibility at GATA1-binding sites and functional interference with GATA1 activity. In vivo models showed development of lethal erythroid, mixed erythroid/myeloid, or other malignancies depending on the cell population in which AEL-associated alterations were expressed. Collectively, our data indicate that AEL is a molecularly heterogeneous disease with an erythroid identity that results in part from the aberrant activity of key erythroid transcription factors in hematopoietic stem or progenitor cells.

Genomic subtyping and therapeutic targeting of acute erythroleukemia

Acute erythroid leukemia (AEL) is a high-risk leukemia of poorly understood genetic basis, with controversy regarding diagnosis in the spectrum of myelodysplasia and myeloid leukemia. We compared genomic features of 159 childhood and adult AEL cases with non-AEL myeloid disorders and defined five age-related subgroups with distinct transcriptional profiles: adult, TP53 mutated; NPM1 mutated; KMT2A mutated/rearranged; adult, DDX41 mutated; and pediatric, NUP98 rearranged. Genomic features influenced outcome, with NPM1 mutations and HOXB9 overexpression being associated with a favorable prognosis and TP53, FLT3 or RB1 alterations associated with poor survival. Targetable signaling mutations were present in 45% of cases and included recurrent mutations of ALK and NTRK1, the latter of which drives erythroid leukemogenesis sensitive to TRK inhibition. This genomic landscape of AEL provides the framework for accurate diagnosis and risk stratification of this disease, and the rationale for testing targeted therapies in this high-risk leukemia.

ETO2-GLIS2 Hijacks Transcriptional Complexes to Drive Cellular Identity and Self-Renewal in Pediatric Acute Megakaryoblastic Leukemia

Chimeric transcription factors are a hallmark of human leukemia, but the molecular mechanisms by which they block differentiation and promote aberrant self-renewal remain unclear. Here, we demonstrate that the ETO2-GLIS2 fusion oncoprotein, which is found in aggressive acute megakaryoblastic leukemia, confers megakaryocytic identity via the GLIS2 moiety while both ETO2 and GLIS2 domains are required to drive increased self-renewal properties. ETO2-GLIS2 directly binds DNA to control transcription of associated genes by upregulation of expression and interaction with the ETS-related ERG protein at enhancer elements. Importantly, specific interference with ETO2-GLIS2 oligomerization reverses the transcriptional activation at enhancers and promotes megakaryocytic differentiation, providing a relevant interface to target in this poor-prognosis pediatric leukemia.

The Snail Family in Normal and Malignant Haematopoiesis

Snail family proteins are key inducers of the epithelial-mesenchymal transition (EMT), a critical process required for normal embryonic development. They have also been strongly implicated in regulating the EMT-like processes required for tumour cell invasion, migration, and metastasis. Whether these proteins also contribute to normal blood cell development, however, remains to be clearly defined. Increasing evidence supports a role for the Snail family in regulating cell survival, migration, and differentiation within the haematopoietic system, as well as potentially an oncogenic role in the malignant transformation of haematopoietic stem cells. This review will provide a broad overview of the Snail family, including key aspects of their involvement in the regulation and development of solid organ cancer, as well as a discussion on our current understanding of Snail family function during normal and malignant haematopoiesis.

Variability of inducible expression across the hematopoietic system of tetracycline transactivator transgenic mice

The tetracycline (tet)-regulated expression system allows for the inducible overexpression of protein-coding genes, or inducible gene knockdown based on expression of short hairpin RNAs (shRNAs). The system is widely used in mice, however it requires robust expression of a tet transactivator protein (tTA or rtTA) in the cell type of interest. Here we used an in vivo tet-regulated fluorescent reporter approach to characterise inducible gene/shRNA expression across a range of hematopoietic cell types of several commonly used transgenic tet transactivator mouse strains. We find that even in strains where the tet transactivator is expressed from a nominally ubiquitous promoter, the efficiency of tet-regulated expression can be highly variable between hematopoietic lineages and between differentiation stages within a lineage. In some cases tet-regulated reporter expression differs markedly between cells within a discrete, immunophenotypically defined population, suggesting mosaic transactivator expression. A recently developed CAG-rtTA3 transgenic mouse displays intense and efficient reporter expression in most blood cell types, establishing this strain as a highly effective tool for probing hematopoietic development and disease. These findings have important implications for interpreting tet-regulated hematopoietic phenotypes in mice, and identify mouse strains that provide optimal tet-regulated expression in particular hematopoietic progenitor cell types and mature blood lineages.

Heritable GATA2 mutations associated with familial myelodysplastic syndrome and acute myeloid leukemia

We report the discovery of the GATA2 gene as a new myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML) predisposition gene. We found the same, novel heterozygous c.1061C>T (p.Thr354Met) missense mutation in the GATA2 transcription factor gene segregating with the multigenerational transmission of MDS/AML in three families, and a GATA2 c.1063_1065delACA (p.Thr355del) mutation at an adjacent codon in a fourth MDS/AML family. The mutations reside within the second zinc finger of GATA2 which mediates DNA-binding and protein-protein interactions. We show differential effects of the mutants on transactivation of target genes, cellular differentiation, apoptosis and global gene expression. Identification of such predisposing genes to familial forms of MDS and AML is critical for more effective diagnosis and prognosis, counselling, selection of related bone marrow transplant donors, and development of therapies.

Transgenic, inducible RNAi in megakaryocytes and platelets in mice

BACKGROUND

RNA interference (RNAi) is a powerful tool for suppressing gene function. The tetracycline (tet)-regulated expression system has recently been adapted to allow inducible RNAi in mice, however its efficiency in a particular cell type in vivo depends on a transgenic tet transactivator expression pattern and is often highly variable.

OBJECTIVE

We aimed to establish a transgenic strategy that allows efficient and inducible gene knockdown in particular hematopoietic lineages in mice.

METHODS AND RESULTS

Using a tet-regulated reporter gene strategy, we found that transgenic mice expressing the rtTA (tet-on) transactivator under control of the cytomegalovirus (CMV) promoter (CMV-rtTA mice) display inducible reporter gene expression with unusual and near-complete efficiency in megakaryocytes and platelets. To test whether the CMV-rtTA transgene can drive inducible and efficient gene knockdown within this lineage, we generated a novel mouse strain harboring a tet-regulated short hairpin RNA (shRNA) targeting Bcl-x(L) , a pro-survival Bcl-2 family member known to be essential for maintaining platelet survival. Doxycycline treatment of adult mice carrying both transgenes induces shRNA expression, depletes Bcl-x(L) in megakaryocytes and triggers severe thrombocytopenia, whereas doxycycline withdrawal shuts off shRNA expression, normalizes Bcl-x(L) levels and restores platelet numbers. These effects are akin to those observed with drugs that target Bcl-x(L) , clearly demonstrating that this transgenic system allows efficient and inducible inhibition of genes in megakaryocytes and platelets.

CONCLUSIONS

We have established a novel transgenic strategy for inducible gene knockdown in megakaryocytes and platelets that will be useful for characterizing genes involved in platelet production and function in adult mice.

The relationship between caries, fluoridation and material deprivation in five-year-old children in Country Durham

An investigation to assess the impact of fluoridation on the caries experience of young children at high and low levels of material deprivation measured by the Townsend Index was undertaken in County Durham. Electoral wards were ranked for deprivation from 1991 Census data. Dental caries data for 2,751 five-year-old children resident in electoral wards in the upper and lower quartiles of material deprivation in the County were obtained from a dental survey conducted in 1991-92. Wards were stratified for fluoridated and non-fluoridated water supply and the dental data for the resultant four populations, defined by high and low material deprivation and the presence or absence of fluoridation, were analysed. The mean dmft values in the four groups were 0.8 in the fluoridated low deprivation group, 1.2 in the non-fluoridated low deprivation group, 1.2 in the fluoridated high deprivation wards and 2.1 in the non-fluoridated high deprivation wards. Thus, with fluoridation the variation in caries between high and low deprivation groups was significantly reduced but not eliminated, leaving the level significantly lower in the least deprived group, to the continuing disadvantage of that deprived group.

The use of an index of material deprivation to identify groups of children at risk to dental caries in County Durham

An investigation of the potential for an index of material deprivation to indicate groups of young children at risk to dental caries and to assess caries experience in their age group at three levels of deprivation, measured by the Townsend Index, was undertaken in County Durham. Electoral wards were ranked on an index of material deprivation derived from 1991 Census data. Dental caries data for the upper quartile, inter-quartile range and lower quartile of material deprivation in the County were obtained from a dental survey of 6052 five-year-old children in 1991-92. The number of children in each group ranged from 1145 to 3058. Significant differences in dental caries experience between high, middle and low ranges of material deprivation existed. The index of material deprivation can indicate groups of children in the community at high and low risk of dental caries.

Dental disease and current treatment needs in a group of physically handicapped children

One hundred and twenty-nine physically handicapped children (89 males, 40 females) were dentally examined in a local authority residential special school taking pupils from a wide geographical area in the Northern Region, for caries, periodontal disease, malocclusions and treatment need using World Health Organization criteria. The children were aged between 3 and 17 years with a mean age of 10.7 years. Mean deciduous caries experience (dft) was 0.9 and the mean permanent caries experience (DMFT) was 2.0. The mean dfs/DMFS values were 2.5 and 3.4 respectively. A higher experience of deciduous caries was found in girls, dft = 1.3, than in boys who had a mean dft value of 0.8 and in the permanent dentition girls had a mean DMFT value of 2.8 compared with 1.6 for boys. Each component of the index was also higher for girls in both dentitions. The gender difference identified in caries experience extended to treatment need for the permanent dentition, where more girls were recorded as requiring treatment than boys. Of the 129 children, 126 were assessed for treatment co-operation. Only 18 (14.3 per cent) were assessed as being amenable to routine dental care, 66 (52.4 per cent) were thought likely to present some management problems and the remaining 42 (33.3 per cent) were thought to require all their treatment under a general anaesthetic.

A 10-year comparison of General Dental Service care in the Northern Region 1979-1989

The 1979/1989 patterns of General Dental Service provision in the Northern Region and its nine FPC/FHSA areas have been examined in relation to intraregional variations and assessed against the national average and other regions. Attention is drawn to the Northern Region's failure to reach national averages in a number of key measures of dental care, owing to the low numbers of practitioners working within the Region. It is clear that redistribution of dental manpower will not be generated under the present system. Alternatives are required if dentistry is to continue to be an essential part of a comprehensive health service for all.

The relationship between fluoridation, social class and caries experience in 5-year-old children in Newcastle and Northumberland in 1987

The dental health of 457 5-year-old children who have lived continuously in fluoridated (at 1.0 mg F/litre) Newcastle and 370 children of the same age in non-fluoridated (less than 0.1 mg F/litre) South Northumberland has been reported. This paper examines in detail the caries prevalence in social class groups I + II, III, IV + V, and the social class/fluoridation relationship in 1987. The prevalence of dental caries in the three social class groupings I + II, III, and IV + V (and the mean dmft), respectively, was 35% (1.1), 46% (1.7) and 67% (2.4) in the fluoridated area, and 59% (2.2), 67% (3.7) and 77% (5.0) in the non-fluoridated area. Fluoridation was effective in all social class groupings and, because caries levels were higher in social classes IV + V, fluoridation brought about greater savings for these children than for those in social classes I + II. Fluoridation reduces but does not eliminate social inequalities, leaving social disadvantage/social background/social class as the major factors in caries prevalence for this age group. Further research into the fluoridation/social class relationship is required, particularly since the understanding of occupational class, now considered an imperfect representation of social class, is being superseded by other criteria which have stronger associations with measures of poor health.

Dental health and the application of geographical methodology

Reorganisation of dental services in Britain gives new opportunities for planning. Geographical methodology provides new techniques. An elementary spatial analysis of variations in dental health in Newcastle Area Health Authority (Teaching) shows that dental health varies with availability and access to treatment facilities. Opposite types of geographical distribution of community (School) and general dental services are illustrated showing location biases for each type of service. The evaluation of the spatial distribution of dental services is shown to be basic to planning and a key to improved dental health.