Simone Bork

Molecular signature of CD34 + hematopoietic stem and progenitor cells of patients with CML in chronic phase

In this study, we provide a molecular signature of highly enriched CD34+ cells from bone marrow of untreated patients with chronic myelogenous leukemia (CML) in chronic phase in comparison with normal CD34+ cells using microarrays covering 8746 genes. Expression data reflected several BCR-ABL-induced effects in primary CML progenitors, such as transcriptional activation of the classical mitogen-activated protein kinase pathway and the phosphoinositide-3 kinase/AKT pathway as well as downregulation of the proapoptotic gene IRF8. Moreover, novel transcriptional changes in comparison with normal CD34+ cells were identified. These include upregulation of genes involved in the transforming growth factorβ pathway, fetal hemoglobin genes, leptin receptor, sorcin, tissue inhibitor of metalloproteinase 1, the neuroepithelial cell transforming gene 1 and downregulation of selenoprotein P. Additionally, genes associated with early hematopoietic stem cells (HSC) and leukemogenesis such as HoxA9 and MEIS1 were transcriptionally activated. Differential expression of differentiation-associated genes suggested an altered composition of the CD34+ cell population in CML. This was confirmed by subset analyses of chronic phase CML CD34+ cells showing an increase of the proportion of megakaryocyte-erythroid progenitors, whereas the proportion of HSC and granulocyte–macrophage progenitors was decreased in CML. In conclusion, our results give novel insights into the biology of CML and could provide the basis for identification of new therapeutic targets.

Successful transplantation of peripheral blood stem cells mobilized by chemotherapy and a single dose of pegylated G-CSF in patients with multiple myeloma

Summary:Following induction therapy and 4 g/m2 cyclophosphamide, a single dose of 12 mg polyethyleneglycol-conjugated G-CSF (pegfilgrastim; n=12) or daily doses of unconjugated G-CSF (8.5 μg/kg/day) (n=12) were administered to myeloma patients. Pegfilgrastim was associated with an earlier leukocyte recovery (12 vs 14 days) and peripheral blood CD34+ cell peak (12 vs 15 days). The peripheral blood CD34+ cell peak was lower in the pegfilgrastim group (78 vs 111/μl). Following high-dose melphalan (200 mg/m2) and autografting, leukocyte and platelet reconstitution was similar in both groups and stable blood counts were observed 100 days post transplant. In summary, a single dose of pegfilgrastim after chemotherapy is capable of mobilizing a sufficient number of CD34+ cells for successful autografting with early engraftment and sustained hematological reconstitution in patients with myeloma. These data provide the basis for randomized studies evaluating the optimal dose and time of pegfilgrastim as well as long-term outcome in larger cohorts of patients.

Distinct molecular phenotype of malignant CD34+ hematopoietic stem and progenitor cells in chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is a malignant disorder of the hematopoietic stem cell characterized by the BCR–ABL oncogene. We examined gene expression profiles of highly enriched CD34+ hematopoietic stem and progenitor cells from patients with CML in chronic phase using cDNA arrays covering 1.185 genes. Comparing CML CD34+ cells with normal CD34+ cells, we found 158 genes which were significantly differentially expressed. Gene expression patterns reflected BCR–ABL-induced functional alterations such as increased cell-cycle and proteasome activity. Detoxification enzymes and DNA repair proteins were downregulated in CML CD34+ cells, which might contribute to genetic instability. Decreased expression of junction plakoglobulin and CXC chemokine receptor 4 (CXCR-4) might facilitate the release of immature precursors from bone marrow in CML. GATA-2 was upregulated in CML CD34+ cells, suggesting an increased self-renewal in comparison with normal CD34+ cells. Moreover, we found upregulation of the proto-oncogene SKI and of receptors for neuromediators such as opioid μ1 receptor, GABA B receptor, adenosine A1 receptor, orexin 1 and 2 receptors and corticotropine-releasing hormone receptor. Treatment of CML progenitor cells with the selective adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) resulted in a dose-dependent significant inhibition of clonogenic growth by 40% at a concentration of 10−5 M, which could be reversed by the equimolar addition of the receptor agonist 2-chloro-N6-cyclopentyladenosine (P<0.05). The incubation of normal progenitor cells with DPCPX resulted in an inhibition of clonogenic growth to a significantly lesser extent in comparison with CML cells (P<0.05), suggesting that the adenosine A1 receptor is of functional relevance in CML hematopoietic progenitor cells.

Gene expression profiling of Philadelphia chromosome (Ph)-negative CD34+ hematopoietic stem and progenitor cells of patients with Ph-positive CML in major molecular remission during therapy with imatinib

Gene expression profiling of Philadelphia chromosome (Ph)-negative CD34+ hematopoietic stem and progenitor cells of patients with Ph-positive CML in major molecular remission during therapy with imatinib

Distinct gene expression pattern of malignant hematopoietic stem and progenitor cells in polycythemia vera

Abstract: Polycythemia vera (PV) is a chronic myeloproliferative disorder with an expansion of multipotent hematopoietic progenitor cells. Although it is known that hematopoietic progenitors in PV are erythropoietin independent and hypersensitive to several cytokines, the molecular oncogenic mechanisms in PV are largely unknown. In this study, we examined gene expression profiles of CD34+ cells from bone marrow of patients with de novo PV and from healthy volunteers to identify molecular changes associated with the malignant growth of hematopoietic stem and progenitor cells in this myeloproliferative disorder. Using cDNA arrays, we found significant differences (P < .01) in the expression of 107 genes. Proapoptotic genes (CASP2, CASP3, DAPK1, ALG2) were expressed at lower levels in PV‐CD34+ cells, reflecting a lower apoptotic activity. Fibrosis‐stimulating growth factors (transforming growth factor β1, transforming growth factor β2, bone morphogenetic protein 2, and endothelial growth factor) were expressed at significantly higher levels in PV‐CD34+ cells. Furthermore, PV‐CD34+ cells overexpressed several receptors, protein kinases, and proteasome subunits, which might be targets for directed therapeutic approaches. It is interesting that three retinoid receptors were overexpressed in PV‐CD34+ cells—retinoic acid receptor β (RARβ), retinoid X receptor β (RXRβ), and cellular retinoic acid binding protein 2 (CRABP2). Using methylcellulose colony‐forming assays, we found that the formation of erythroid colonies derived from PV hematopoietic progenitors was inhibited by all‐trans‐retinoic acid (ATRA), a natural ligand of those receptors, in a dose‐dependent manner, showing a maximum inhibition of 89% at 10 μM; the growth of myelomonocytic colonies was not significantly affected. These data suggest that the use of ATRA could be of therapeutic benefit for patients with PV.