Apoptosis in patients with myelodysplastic syndromes: differential involvement of marrow cells in ‘good’ versus ‘poor’ prognosis patients and correlation with apoptosis-related genes

Abstract

Apoptosis has been implicated in the pathogenesis of marrow failure in MDS and the coexistence of marrow hypercellularity along with blood cytopenias was seen as evidence of extreme cell death of mainly mature cells in the marrow (ineffective hematopoiesis). We investigated apoptosis in 53 patients with MDS, by using single-step DNA extraction and gel electrophoresis and then by separating fresh marrow mononuclear cells in CD34⁺ and CD34⁻ populations and in situ single cell evaluation of the process. We also studied the expression of apoptosis-related genes, in total and separated mononuclear marrow cells and correlated the findings with clinical and laboratory characteristics. Patients with apoptosis had increased marrow cellularity, longer overall survival and a longer period for transformation to AML. In ‘good’ prognosis MDS patients, total mononuclear marrow cells, as well as isolated populations of CD34⁺ and CD34⁻ cells showed significant degrees of apoptosis; in ‘poor’ prognosis cases, however, apoptosis was evident only in a large percentage of CD34⁺ marrow cells and not in total or CD34⁻ cells. Absence of expression of both c-myc and p53 in total marrow cells was associated with significant degrees of apoptosis and in isolated CD34⁺ and CD34⁻ marrow cells the phenomenon was inversely correlated with the level of bcl-2 expression. In conclusion, marrow apoptosis is detected in both CD34⁺ and CD34⁻ cells in early MDS and seems to be restricted to CD34⁺ cells in advanced MDS cases.