Project description:BACKGROUND: BCR-ABL1+ chronic myeloid leukemia (CML) is characterized by abnormal production of leukemic stem (LSC) and progenitor cells and their spread from the bone marrow into the blood resulting in extramedullary myeloproliferation. So far, little is known about specific markers and functions of LSC in CML. METHODS: We examined the phenotype and function of CD34+/CD38─/Lin─ CML LSC by a multi-parameter screen approach employing antibody-phenotyping, mRNA expression profiling, and functional studies, including LSC repopulation experiments in irradiated NOD-SCID-IL-2Rgamma-/- (NSG) mice, followed by marker-validation using diverse control-cohorts and follow-up samples of CML patients treated with imatinib. RESULTS: Of all LSC markers examined, dipeptidylpeptidase IV (DPPIV=CD26) was identified as specific and functionally relevant surface marker-enzyme on CD34+/CD38─ CML LSC. CD26 was not detected on normal CD34+/CD38─ stem cells or LSC in other hematopoietic malignancies. The percentage of CD26+ CML LSC decreased to undetectable levels during successful treatment with imatinib in all patients (p<0.001). Whereas the sorted CD26─ stem cells obtained from CML patients engrafted irradiated NSG mice with multilineage BCR-ABL1-negative hematopoiesis, CD26+ LSC engrafted NSG mice with BCR-ABL1+ cells. Functionally, CD26 was identified as target-enzyme disrupting the SDF-1alpha-CXCR4-axis by cleaving SDF-1alpha a chemotaxin for CXCR4+ stem cells. Whereas CD26 was found to inhibit SDF-1alpha-induced migration, CD26-targeting gliptins reverted this effect and blocked the mobilization of CML LSC in a stroma co-culture assay. CONCLUSIONS: CD26 is a robust biomarker of LSC and a useful tool for their quantification and isolation in patients with BCR/ABL1+ CML. Moreover, CD26 expression may explain the extramedullary spread of LSC in CML. To define specific mRNA expression patterns and to identify specific LSC markers in CML LSC, gene array analyses were performed. RNA was isolated from sorted CD34+/CD45+/CD38─ CML LSC, CD34+/CD45+/CD38+ CML progenitor cells, CML MNC, sorted CD34+/CD38─ cord blood (CB) SC, CB-derived CD34+/CD38+ progenitor cells, and CB MNC. Total RNA was extracted from sorted cells using RNeasy Micro-Kit (Qiagen) and used (100 ng total RNA) for Gene Chip analyses. Preparation of terminal-labeled cRNA, hybridization to genome-wide human PrimeView GeneChips (Affymetrix, Santa Clara, CA, USA) and scanning of arrays were carried out according to the manufacturer's protocols (https://www.affymetrix.com). Robust Multichip Average (RMA) signal extraction and normalization were performed according to http://www.bioconductor.org/ as described.18 Differences in mRNA expression levels (from multiple paired samples) were calculated as mRNA ratio of i) CML LSC versus CB SC, ii) CML LSC versus CD34+/CD38+ CML progenitors, and normal cord blood SC versus cord blood progenitors. To calculate differential gene expression between individual sample groups where appropriate, we performed a statistical comparison using the LIMMA package as described previously. Briefly, LIMMA estimates the fold change between predefined sample groups by fitting a linear model and using an empirical Bayes method to moderate the standard errors of the estimated log-fold changes for each probe set.

Project description:Epigenetic memory in induced pluripotent stem cells (iPSCs), with regards to their somatic cell type of origin, might lead to variations in their differentiation capacities. In this context, iPSCs from human CD34+ hematopoietic stem cells (HSCs) might be more suitable for hematopoietic differentiation than commonly used fibroblast-derived iPSCs. To investigate the influence of an epigenetic memory on the ex vivo expansion of iPSCs into erythroid cells, we compared iPSCs from human neural stem cells (NSCs) and human cord blood-derived CD34+ HSCs and evaluated their potential for differentiation into hematopoietic progenitor and mature red blood cells (RBCs). Although genome-wide DNA methylation profiling at all promoter regions demonstrates an epigenetic memory of iPSCs with regards to their somatic cell type of origin, we found a similar hematopoietic induction potential and erythroid differentiation pattern. All human iPSC lines showed terminal maturation into normoblasts and enucleated RBCs, producing predominantly fetal hemoglobin. Differences were only observed in the growth rate of erythroid cells, which was slightly higher in the CD34+ HSC-derived iPSCs. More detailed methylation analysis of the hematopoietic and erythrocyte promoters identified similar CpG methylation levels in the CD34+ iPSCs and NSC iPSCs, which confirms their comparable erythroid differentiation potential. To investigate the influence of an epigenetic memory on the ex vivo expansion of iPSCs into erythroid cells, we compared iPSCs from human neural stem cells (NSCs) and human cord blood-derived CD34+ HSCs and evaluated their potential for differentiation into hematopoietic progenitor and mature red blood cells (RBCs). RNA samples for microarray analysis were prepared using RNeasy columns (Qiagen, Germany) with on-column DNA digestion. 300ng of total RNA per sample was used as the input in the linear amplification protocol (Ambion), which involved the synthesis of T7-linked double-stranded cDNAs and 12hrs of in vitro transcription incorporating the biotin-labeled nucleotides. Purified and labeled cRNA was then hybridized for 18hrs onto HumanHT-12 v4 expression BeadChips (Illumina, USA) following the manufacturer's instructions. After the recommended washing, the chips were stained with streptavidin-Cy3 (GE Healthcare) and scanned using the iScan reader (Illumina) and the accompanying software. The samples were exclusively hybridized as biological replicates. 8 samples were analyzed: CD34 1, Human CD34+ Cord blood CD34+ Hematopoyetic Stem Cell(HSC) population 1, 1 replicate CD34 2, Human CD34+ Cord blood CD34+ Hematopoyetic Stem Cell(HSC) population 2, 1 replicate CD34 OSiPS 1, Human Human two factors (POU5F1, SOX2) induced Pluripotent Cell (iPSC) reprogrammed from CD34+ Cord blood CD34+ Hematopoyetic Stem Cell(HSC) induced Pluripotent Cell (iPSC) population 1, 1 replicate CD34 OSKMiPS 1, Human Human four factors (POU5F1, SOX2, KLF4, CMYC) induced Pluripotent Cell (iPSC) reprogrammed from CD34+ Cord blood CD34+ Hematopoyetic Stem Cell(HSC) induced Pluripotent Cell (iPSC) population 1, 1 replicate CD34 OSiPS 2, Human Human two factors (POU5F1, SOX2) induced Pluripotent Cell (iPSC) reprogrammed from CD34+ Cord blood CD34+ Hematopoyetic Stem Cell(HSC) induced Pluripotent Cell (iPSC) population 2, 1 replicate CD34 OSKMiPS 2, Human Human four factors (POU5F1, SOX2, KLF4, CMYC) induced Pluripotent Cell (iPSC) reprogrammed from CD34+ Cord blood CD34+ Hematopoyetic Stem Cell(HSC) induced Pluripotent Cell (iPSC) population 2, 1 replicate H1, Human H1 embryonic stem cell (ESC), 1 replicate H9, Human H9 embryonic stem cell (ESC), 1 replicate

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