Differential gene expression in hematopoietic progenitors from paroxysmal nocturnal hemoglobinuria patients reveals an apoptosis/immune response in ‘normal’ phenotype cells

Abstract

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired stem cell disorder characterized clinically by intravascular hemolysis, venous thrombosis, and bone marrow failure. Despite elucidation of the biochemical and molecular defects in PNH, the pathophysiology of clonal expansion of glycosylphosphatidylinositol-anchored protein (GPI-AP)-deficient cells remains unexplained. In pursuit of evidence of differences between GPI-AP-normal and -deficient CD34 cells, we determined gene expression profiles of isolated marrow CD34 cells of each phenotype from PNH patients and healthy donors, using DNA microarrays. Pooled and individual patient samples revealed consistent gene expression patterns relative to normal controls. GPI-AP-normal cells from PNH patients showed upregulation of genes involved in apoptosis and the immune response. Conversely, genes associated with antiapoptotic function and hematopoietic cell proliferation and differentiation were downregulated in these cells. In contrast, the PNH clone of GPI-AP-deficient cells appeared more similar to CD34 cells of healthy individuals. Gene chip data were confirmed by other methods. Similar gene expression patterns were present in PNH that was predominantly hemolytic as in PNH associated with aplastic anemia. Our results implicate an environmental influence on hematopoietic cell proliferation, in which the PNH clone evades immune attack and destruction, while normal cells suffer a stress response followed by programmed cell death.

A systematic analysis of bone marrow cells by flow cytometry defines a specific phenotypic profile beyond GPI deficiency in paroxysmal nocturnal hemoglobinuria

“…The antigenic profile of CD34þ cells did not show relevant abnormalities; the increased expression of CD7 was probably related to B precursors reduction, since CD7 is normally expressed by a fraction of myeloid CD34þ cells. These data parallel the lack of significant differences in gene expression profiles between CD34þ cells from PNH patients and healthy individuals described by Chen et al [26]. As for morphology, several abnormalities on maturing cell compartments emerged.…”

The GOD of Hematopoietic Stem Cells: A Clonal Diversity Model of the Stem Cell Compartment

“…However, changes in the HSC compartment can be induced-for example through diseases, chemotherapy, transplantation, cytokine treatment, and aging. 43,34,[44][45][46][47][48][49][50][51][52][53] After such events the HSC compartment can become pauciclonal.…”

Paroxysmal nocturnal hemoglobinuria and myelodysplastic sydromes: clonal expansion of PIG-A-mutant hematopoietic cells in bone marrow failure

“…In contrast, the normal phenotype cells (expressing GPI-anchored proteins) from the PNH patients showed activation of apoptosis, cell death, and immune response pathways, as in bone marrow form patients with aplastic anemia (the same patterns were seen in classic and aplastic PNH, suggesting a common pathophysiology). 4 Nevertheless, no satisfying molecular mechanism has been well supported by results of in vitro experiments, and immune escape does not have good clinical correlates. In tissue culture, PNH cells have generally been equivalent to normal cells in immunological assays that test their ability to stimulate an immune response and their adequacy as targets of immune-mediated cytotoxicity.…”

“…These entities share some clinical features such as a high risk of developing thrombosis, 3 evolution into secondary myelofibrosis (for PV and ET) and transformation into leukemia. 4 The most intriguing question that arose after the discovery of the mutation is how a single mutation might give rise to at least three different diseases. This question remains unanswered, but clinical, biological and pathological data have led to three potential hypotheses.…”