Comparison of gene expression in CD34+ cells from bone marrow and G-CSF-mobilized peripheral blood by high-density oligonucleotide array analysis

Abstract

A prospective randomized trial has shown that there is a survival advantage for allogeneic transplant recipients who received granulocyte colony-stimulating factor (G-CSF)-stimulated peripheral blood mononuclear cells (GPBMC) versus those who received bone marrow (BM) as a source of stem cells. The biological basis for this advantage is not clear and may be attributable to qualitative as well as quantitative differences in the CD34 cells, T cells, and/or the monocytes transplanted. To begin to address this issue, gene expression patterns in CD34 cells isolated from these 2 stem cell sources were compared to identify functional pathways that may distinguish these 2 populations. CD34 cells were isolated to purity from the BM and peripheral blood stem cells of multiple healthy donors. (The complete data set will be available at http://parma.fhcrc.org/lgraf upon publication.) Two separate RNA preparations from pooled samples from both sources were analyzed by Affymetrix Oligonucleotide Array chips for expression of over 6400 human genes. Comparative analyses among the samples showed that a small set of 28 sequences increased and 38 sequences decreased in expression more than 3-fold in both of the GPBMC samples compared to those in BM samples. More highly expressed genes include several for nuclear proteins and transcriptional factors. Functional categorization of the genes decreased in expression indicated sequences influential in cell cycle progression, in agreement with the recognized quiescence of circulating CD34 cells. Multiple transcriptional regulators and chemokines were also found to be decreased. These data emphasize that in addition to increased numbers of CD34 cells, G-CSF mobilization also results in significant qualitative changes. Whether they impact engraftment remains to be determined.

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.…”

Hematopoietic Progenitor Cells (HPC) from Mobilized Peripheral Blood Display Enhanced Migration and Marrow Homing Compared to Steady-State Bone Marrow HPC

“…[15] The mechanism of CD26 downregulation is unclear but does not seem to occur at gene expression level. (data not shown and [57,58]) If G-CSF directly induces increased motility of ssBM, then mobilized BM may be expected to also have enhanced homing compared to ssBM. However, BM cells from G-CSF treated mice neither display the same enhanced motility shown by MPB, nor the enhanced marrow homing, at least when tested on day 5, at the peak of mobilization (data not shown).…”

Bone marrow transplantation: how important is CD34 cell dose in HLA-identical stem cell transplantation?

“…G-CSF mobilization and apheresis collection does result in significant changes in gene expression within the CD34 compartment when compared with bone marrow. 15 Other changes also occur in dendritic cell subsets after G-CSF mobilization. 16 In conclusion, we have examined the dose-response relationship of CD34 + cells in related and unrelated donor bone marrow or G-PBMC in terms of clinical outcomes such as engraftment, chronic GVHD and overall survival.…”