Gene expression profiling identifies significant differences between the molecular phenotypes of bone marrow–derived and circulating human CD34+ hematopoietic stem cells

Abstract

CD34 ؉ hematopoietic stem cells are used clinically to support cytotoxic therapy, and recent studies raised hope that they could even serve as a cellular source for nonhematopoietic tissue engineering. Here, we examined in 18 volunteers the gene expressions of 1185 genes in highly enriched bone marrow CD34 ؉ (BM-CD34 ؉ ) or granulocyte-colony-stimulating factormobilized peripheral blood CD34 ؉ (PB-CD34 ؉ ) cells by means of cDNA array technology to identify molecular causes underlying the functional differences between circulating and sedentary hematopoietic stem and progenitor cells. In total, 65 genes were significantly differentially expressed. Greater cell cycle and DNA synthesis activity of BM-CD34 ؉ than PB-CD34 ؉ cells were reflected by the 2-to 5-fold higher expression of 9 genes involved in cell cycle progression, 11 genes regulating DNA synthesis, and cell cycleinitiating transcription factor E2F-1. Conversely, 9 other transcription factors, including the differentiation blocking GATA2 and N-myc, were expressed 2 to 3 times higher in PB-CD34 ؉ cells than in BM-CD34 ؉ cells. Expression of 5 apoptosis driving genes was also 2 to 3 times greater in PB-CD34 ؉ cells, reflecting a higher apoptotic activity. In summary, our study provides a gene expression profile of primary human CD34 ؉ hematopoietic cells of the blood and marrow. Our data molecularly confirm and explain the finding that CD34 ؉ cells residing in the bone marrow cycle more rapidly, whereas circulating CD34 ؉ cells consist of a higher number of quiescent stem and progenitor cells. Moreover, our data provide novel molecular insight into stem cell physiology.

Tumorigenesis and neurodegeneration: two sides of the same coin?

“…APP, along with ETS2 and ERG, is part of the transcriptional signature of the hematopoietic stem cell, the cell of origin for most acute leukemias. (38) Consistent with this observation, APP is the most highly upregulated gene on chromosome 21 in a subset of AML patients with complex karyotypes. (39) APP is best-characterized as the precursor for Ab, whose secreted 42-amino acid form shows a strong tendency to form the extracellular amyloid plaques that accumulate preferentially in brain regions affected by AD.…”

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

“…CD34 þ cells (median: 5 Â 10 5 ; range 2 Â 10 5 -1.8 Â 10 6 ) were isolated immunomagnetically from bone marrow mononuclear cells of eight patients and six healthy volunteers with a purity 498% using the MACS system (Miltenyi Biotec, Bergisch Gladbach, Germany) as previously described. 6 As assessed by FISH analysis following immunomagnetic isolation using LSI BCR/ABL Dual Color, Dual Fusion Translocation Probes (Vysis, BergischGladbach, Germany) according to the manufacturer's instructions (threshold for false-positive colocalization: 5%), we found no evidence for the t(9;22) translocation in the CD34 þ cells from imatinib-treated patients examined in this study. Total RNA (median: 550 ng; range: 130-990 ng) from isolated CD34 þ cells was used to generate biotin-labelled cRNA (median: 7.5 mg; range: 2.6-12.3 mg) by means of Enzo BioArray HighYield RNA Transcript Labelling Kit (Affymetrix Ltd, UK).…”

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

“…Therefore, the reduced CXCR-4 expression in CML CD34 þ cells might contribute to the release of malignant progenitor cells from BM. Surprisingly, we were unable to detect differentially expressed genes when comparing CML CD34 þ cells from BM with those from PB, although we and others had observed distinct molecular phenotypes when examining normal CD34 þ cells from BM and PB (Graf et al, 2001;Steidl et al, 2002;Ng et al, 2004). In normal BM CD34 þ cells, a significantly higher expression of genes governing cell-cycle progression was found in comparison to PB CD34 þ cells.…”