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Malignant-like transformation of normal stem and progenitor cells by myeloid leukemia

ABSTRACT: It has long been known that leukemic cells disrupt normal patterns of blood cell formation, but little is understood about mechanisms. It has generally been assumed that normal hematopoietic stem and progenitor cells (HSPC) are simply out-competed for space by malignant cells. We designed a strategy to determine if leukemic cells alter intrinsic properties and functions of normal HSPCs. Chimeric mice were generated by transplantation of normal marrow and marrow from an inducible transgenic model of chronic myelogenous leukemia (CML). With induction of CML, the composition of the marrow changed dramatically, and normal HSPCs divided more readily and lost their ability to produce lymphocytes. In contrast, only modest changes were recorded in numbers of normal hematopoietic stem cells (HSCs). However, these stem cells were not unscathed, and had reduced reconstitution and self-renewal potential upon transplantation. Interestingly, the normal bystander cells acquired gene expression patterns resembling their neighboring malignant counterparts. This suggested that much of the leukemia signature is mediated by extrinsic factors in the environment.

ORGANISM(S): Mus musculus

PROVIDER: GSE59337 | GEO | 2014/12/01

SECONDARY ACCESSION(S): PRJNA255100

REPOSITORIES: GEO

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Project description:Purpose: We designed this study to evaluate the feasibility of using only one factor to respecify human induced pluripotent stem cells (iPSCs)-derived blood cells into long-term engraftable hematopoietic stem and progenitor cells (HSPCs). We also parallelly compared iPSC-derived HSPCs (iHSPCs) with primary HSPCs under the same induction and transplantation condition in order to examine the functional equivalency between iHSPCs and bona fide HSPCs. Methods: In vitro derived human iPSC-HSPCs are induced with or without (w/o) doxycycline for the expression of MLL-AF4. In vivo derived bone marrow cells are harvested and FACS-sorted for human populations from primary transplants over nine to sixteen weeks after transplantation. Either iPSC-HSPCs or primary HSPCs, both of which are induced by MLL-AF4, is used for the transplantation experiments. iPSCs are either derived from peripheral blood mobilized CD34+ HSPCs (CD34-iPSC) or mononuclear cells (MN-iPSCs). Normal human CD34+ HSPCs and mononuclear cells are set as control groups. Results: MLL-AF4 can impart HSC and lymphoid potential to iPSC-derived blood cells in vitro, and induction of MLL-AF4 leads to the cellular identity transition from common myeloid progenitors to hematopoietic stem and progenitor cells. MLL-AF4 alone is sufficient to realize the potent engraftment of induced HSPCs (iHSPCs) from iPSCs, and multilineage and long-term hematopoiesis could be observed. Primary HSPCs with the induction of MLL-AF4 could gain significantly enhanced engraftability. During the long-term engraftment period, leukemic mutations with a bias to B-cell leukemia could be found in the iHSPCs and their derivatives. By contrast, MLL-AF4 induced primary HSPCs maintain the normal hematopoiesis without leukemic transformation. Conclusions: Our study has demonstrated for the first time, to our knowledge, that the pluripotency-dependent conversion of somatic cells to long-term engraftable HSPCs can be achieved by using a single factor in a non-integrative way. This study also suggests that iPSC-derived HSPCs are more prone to leukemic mutations during the long-term engraftment period, which provides a necessary caveat of using them in the actual therapies.

Project description:Comparison of gene expression profiles of CD34+ hematopoietic stem and progenitor cells from bone marrow of patients with untreated chronic myelogenous leukemia (CML) in chronic phase with those from bone marrow of healthy volunteers. Chronic myelogenous leukaemia (CML) is a malignant disorder of the hematopoietic stem cell, which is characterized by the reciprocal translocation between chromosomes 9 and 22 (t(9;22)(q34;q11)) The translocation results in the formation of the BCR-ABL fusion oncogene encoding a protein with constitutive activated tyrosine kinase activity which plays a central role in the pathogenesis of the disease. There are still several open questions with respect to BCR-ABL-induced malignant transformation. A large limitation of the existing data about BCR-ABL effects is that they are derived to a great proportion from human hematopoietic cell lines, BCR-ABL-transformed murine cell lines or fibroblasts and mouse models, which might not be representative for chronic phase CML. A suitable cell population for studies on CML biology are primary hematopoietic stem and progenitor cells from patients with CML. Therefore, we provide in this study a genome-wide expression signature of highly enriched CD34+ cells from bone marrow (BM) of untreated patients with CML in chronic phase. Gene expression profiles of immunomagnetically enriched BM CML CD34+ cells (n=9) were compared with those of normal BM CD34+ cells (n=8) using microarrays covering 8.746 genes. Total RNA was extracted, reversely transcribed, in vitro transcribed and labelled and hybridized to Affymetrix HG Focus Arrays. Following quality control and normalization differentially expressed genes were identified by significance analysis of microarrays (SAM). Comparing both groups 918 genes were significantly differentially expressed (q value <0.1%; fold change > 1.3). Several of the BCR-ABL-induced effects described in cell lines and BCR-ABL-transduced cells could also be found in primary CML progenitor cells as for example the transcriptional activation of the classical MAPK pathway and the PI3 kinase/AKT pathway and the down-regulation of the pro-apoptotic gene IRF8. Moreover, novel transcriptional changes in comparison with normal CD34+ cells were identified. These include an up-regulation of components of the TGFb signalling pathway and the non-canonical Wnt/Ca2+ pathway, a transcriptional activation of fetal haemoglobin genes and genes associated with early hematopoietic stem cells (HSC) such as HoxA9 and MEIS1 and up-regulation of genes involved in fatty acid metabolism, of the thrombin receptor PAR1 and the neuroepithelial cell transforming gene 1. Differential expression of differentiation-associated genes suggested an alteration of the composition of the CD34+ cell population in CML. This was confirmed by immunophenotypical subset analyses of chronic phase CML CD34+ cells showing an increase of erythroid progenitors and a decrease of granulocyte-macrophage progenitor cells while the proportion of HSC was similar in normal and CML CD34+ cells. In conclusion, our results give novel insights into the biology of CML hematopoietic stem and progenitor cells and could be the basis for identification of new targets for therapy.

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Malignant-like transformation of normal stem and progenitor cells by myeloid leukemia

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