Unravelling the relevance of CLEC12A as a cancer stem cell marker in myelodysplastic syndrome

Acknowledgements The authors would like to thank Petter S. Woll, MSc, PhD, Karolinska Institutet, Stockholm, Sweden, for the kind and generous supervision of the LTC-IC experiments. We thank the FACS Core Facility at Aarhus University for access to the cell sorter and Pia S. Kristensen, Department of Haematology, Aarhus University Hospital for her excellent technical assistance conducting the FISH experiments. The Karen Elise Jensen Foundation, The Meyer Foundation, The Wellcome Trust and the Danish Cancer Society supported the study.Peer reviewedPublisher PD

The molecular and cellular origin of human prostate cancer

Prostate cancer is the most commonly diagnosed male malignancy. Despite compelling epidemiology, there are no definitive aetiological clues linking development to frequency. Pre-malignancies such as proliferative inflammatory atrophy (PIA) and prostatic intraepithelial neoplasia (PIN) yield insights into the initiating events of prostate cancer, as they supply a background "field" for further transformation. An inflammatory aetiology, linked to recurrent prostatitis, and heterologous signalling from reactive stroma and infiltrating immune cells may result in cytokine addiction of cancer cells, including a tumour-initiating population also known as cancer stem cells (CSCs). In prostate tumours, the background mutational rate is rarely exceeded, but genetic change via profound sporadic chromosomal rearrangements results in copy number variations and aberrant gene expression. In cancer, dysfunctional differentiation is imposed upon the normal epithelial lineage, with disruption/disappearance of the basement membrane, loss of the contiguous basal cell layer and expansion of the luminal population. An initiating role for androgen receptor (AR) is attractive, due to the luminal phenotype of the tumours, but alternatively a pool of CSCs, which express little or no AR, has also been demonstrated. Indolent and aggressive tumours may also arise from different stem or progenitor cells. Castrate resistant prostate cancer (CRPC) remains the inevitable final stage of disease following treatment. Time-limited effectiveness of second-generation anti-androgens, and the appearance of an AR-neuroendocrine phenotype imply that metastatic disease is reliant upon the plasticity of the CSC population, and indeed CSC gene expression profiles are most closely related to those identified in CRPCs

Single-cell analysis reveals the continuum of human lympho-myeloid progenitor cells.

The hierarchy of human hemopoietic progenitor cells that produce lymphoid and granulocytic-monocytic (myeloid) lineages is unclear. Multiple progenitor populations produce lymphoid and myeloid cells, but they remain incompletely characterized. Here we demonstrated that lympho-myeloid progenitor populations in cord blood - lymphoid-primed multi-potential progenitors (LMPPs), granulocyte-macrophage progenitors (GMPs) and multi-lymphoid progenitors (MLPs) - were functionally and transcriptionally distinct and heterogeneous at the clonal level, with progenitors of many different functional potentials present. Although most progenitors had the potential to develop into only one mature cell type ('uni-lineage potential'), bi- and rarer multi-lineage progenitors were present among LMPPs, GMPs and MLPs. Those findings, coupled with single-cell expression analyses, suggest that a continuum of progenitors execute lymphoid and myeloid differentiation, rather than only uni-lineage progenitors' being present downstream of stem cells

Screening for links between behaviour and acute hyperthermia and hypoxia resistance in rainbow trout using isogenic lines

In the context of adaptation to climate change, acute hyperthermia and hypoxia resistance are traits of growing interest in aquaculture. The feasibility of genetic improvement of these resistance traits through selection has been demonstrated in rainbow trout (Oncorhynchus mykiss). The present paper aims to test whether behaviour may be associated with acute hyperthermia and hypoxia resistance to better characterize these resistance phenotypes. For this, six rainbow trout isogenic lines were phenotyped for behaviour variables and for acute hyperthermia and hypoxia resistance, using different individuals for each phenotype. The behaviour variables of the fish were phenotyped using an individual test in a new environment. The experimental design used 150 fish phenotyped per isogenic line for each resistance trait and 18 fish per isogenic line for behavioural traits, distributed in triplicates. Relations between acute hyperthermia and hypoxia resistance phenotypes and behaviour phenotypes were tested at the level of isogenic lines.  Significant differences in behaviour between isogenic lines were found, with some behaviour variables being highly associated with hypoxia resistance and moderately associated with acute hyperthermia resistance. Travelling distance, frequency of change between a risky and a safe zone of the tank and the percentage of time in movement in the behaviour test were strongly positively associated with acute hypoxia resistance. Travelling distance and frequency of change between a risky and a safe zone of the tank in the behaviour test were slightly negatively associated with acute hyperthermia resistance. This previously unstudied link between behaviour and resistance phenotypes also suggests that some behaviour variables could be used as predictors for acute hyperthermia and hypoxia resistance in fish. This result could lead to more ethical acute hyperthermia and hypoxia resistance phenotyping protocols, as the current protocols in use are classified as severe by French ethics committees

Heterogeneous leukemia stem cells in myeloid blast phase chronic myeloid leukemia

Chronic myeloid leukemia (CML) is an excellent model of the multistep processes in cancer. Initiating BCR-ABL mutations are required for the initial phase of the disease (chronic phase, CP-CML). Some CP-CML patients acquire additional mutation(s) that transforms CP-CML to poor prognosis, hard to treat, acute myeloid or lymphoid leukemia or blast phase CML (BP-CML). It is unclear where in the hemopoietic hierarchy additional mutations are acquired in BP-CML, how the hemopoietic hierarchy is altered as a consequence, and the cellular identity of the resulting leukemia-propagating stem cell (LSC) populations. Here, we show that myeloid BP-CML is associated with expanded populations that have the immunophenotype of normal progenitor populations that vary between patients. Serial transplantation in immunodeficient mice demonstrated functional LSCs reside in multiple populations with the immunophenotype of normal progenitor as well as stem cells. Multicolor fluorescence in situ hybridization detected serial acquisition of cytogenetic abnormalities of chromosome 17, associated with transformation to BP-CML, that is detected with equal frequency in all functional LSC compartments. New effective myeloid BP-CML therapies will likely have to target all these LSC populations

NKX3.1 is a direct TAL1 target gene that mediates proliferation of TAL1-expressing human T cell acute lymphoblastic leukemia

TAL1 (also known as SCL) is expressed in >40% of human T cell acute lymphoblastic leukemias (T-ALLs). TAL1 encodes a basic helix-loop-helix transcription factor that can interfere with the transcriptional activity of E2A and HEB during T cell leukemogenesis; however, the oncogenic pathways directly activated by TAL1 are not characterized. In this study, we show that, in human TAL1–expressing T-ALL cell lines, TAL1 directly activates NKX3.1, a tumor suppressor gene required for prostate stem cell maintenance. In human T-ALL cell lines, NKX3.1 gene activation is mediated by a TAL1–LMO–Ldb1 complex that is recruited by GATA-3 bound to an NKX3.1 gene promoter regulatory sequence. TAL1-induced NKX3.1 activation is associated with suppression of HP1-α (heterochromatin protein 1 α) binding and opening of chromatin on the NKX3.1 gene promoter. NKX3.1 is necessary for T-ALL proliferation, can partially restore proliferation in TAL1 knockdown cells, and directly regulates miR-17-92. In primary human TAL1-expressing leukemic cells, the NKX3.1 gene is expressed independently of the Notch pathway, and its inactivation impairs proliferation. Finally, TAL1 or NKX3.1 knockdown abrogates the ability of human T-ALL cells to efficiently induce leukemia development in mice. These results suggest that tumor suppressor or oncogenic activity of NKX3.1 depends on tissue expression

Contribution of an Aged Microenvironment to Aging-Associated Myeloproliferative Disease

The molecular and cellular mechanisms of the age-associated increase in the incidence of acute myeloid leukemia (AML) remain poorly understood. Multiple studies support that the bone marrow (BM) microenvironment has an important influence on leukemia progression. Given that the BM niche itself undergoes extensive functional changes during lifetime, we hypothesized that one mechanism for the age-associated increase in leukemia incidence might be that an aged niche promotes leukemia progression. The most frequent genetic alteration in AML is the t(8;21) translocation, resulting in the expression of the AML1-ETO fusion protein. Expression of the fusion protein in hematopoietic cells results in mice in a myeloproliferative disorder. Testing the role of the age of the niche on leukemia progression, we performed both transplantation and in vitro co-culture experiments. Aged animals transplanted with AML1-ETO positive HSCs presented with a significant increase in the frequency of AML-ETO positive early progenitor cells in BM as well as an increased immature myeloid cell load in blood compared to young recipients. These findings suggest that an aged BM microenvironment allows a relative better expansion of pre-leukemic stem and immature myeloid cells and thus imply that the aged microenvironment plays a role in the elevated incidence of age-associated leukemia

The transcriptional architecture of early human hematopoiesis identifies multilevel control of lymphoid commitment.

Understanding how differentiation programs originate from the gene-expression 'landscape' of hematopoietic stem cells (HSCs) is crucial for the development of new clinical therapies. We mapped the transcriptional dynamics underlying the first steps of commitment by tracking transcriptome changes in human HSCs and eight early progenitor populations. We found that transcriptional programs were extensively shared, extended across lineage-potential boundaries and were not strictly lineage affiliated. Elements of stem, lymphoid and myeloid programs were retained in multilymphoid progenitors (MLPs), which reflected a hybrid transcriptional state. By functional single cell analysis, we found that the transcription factors Bcl-11A, Sox4 and TEAD1 (TEF1) governed transcriptional networks in MLPs, which led to B cell specification. Overall, we found that integrated transcriptome approaches can be used to identify previously unknown regulators of multipotency and show additional complexity in lymphoid commitment

Genetically distinct leukemic stem cells in human CD34- acute myeloid leukemia are arrested at a hemopoietic precursor-like stage

Our understanding of the perturbation of normal cellular differentiation hierarchies to create tumor-propagating stem cell populations is incomplete. In human acute myeloid leukemia (AML), current models suggest transformation creates leukemic stem cell (LSC) populations arrested at a progenitor-like stage expressing cell surface CD34. We show that in ∼25% of AML, with a distinct genetic mutation pattern where &gt;98% of cells are CD34(-), there are multiple, nonhierarchically arranged CD34(+) and CD34(-) LSC populations. Within CD34(-) and CD34(+) LSC-containing populations, LSC frequencies are similar; there are shared clonal structures and near-identical transcriptional signatures. CD34(-) LSCs have disordered global transcription profiles, but these profiles are enriched for transcriptional signatures of normal CD34(-) mature granulocyte-macrophage precursors, downstream of progenitors. But unlike mature precursors, LSCs express multiple normal stem cell transcriptional regulators previously implicated in LSC function. This suggests a new refined model of the relationship between LSCs and normal hemopoiesis in which the nature of genetic/epigenetic changes determines the disordered transcriptional program, resulting in LSC differentiation arrest at stages that are most like either progenitor or precursor stages of hemopoiesis.</p