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Spontaneous intramedullary apoptosis is present in disorders other than myelodysplasia
A E Irvine1, M K Magill, L E Somerville
1Department of Haematology, The Queen's University of Belfast, N. Ireland, UK.
Abstract:
Myelodysplastic syndrome (MDS) is a group of hematopoietic disorders characterized by peripheral cytopenias in the presence of normo- or hypercellular dysplastic marrow. It has been suggested that premature intramedullary apoptosis may contribute to this phenomenon. We used terminal dUTP nick-end labeling (TUNEL) of bone marrow biopsy specimens and cytocentrifuge preparations from patients with MDS and a variety of other hematopoietic disorders to determine whether there is increased intramedullary apoptosis in MDS and whether any such effect is specific to MDS. TUNEL labeling of bone marrow from 24 patients with MDS revealed significant positivity in 10 of 11 patients with refractory anemia (RA), five of seven with RA and excess of blasts (RAEB), all three patients with RAEB in transformation (RAEB-t), and all three patients with RA with ring sideroblasts (RARS). The percent of positive cells ranged from 5 to 50% but showed no apparent correlation with morphological subtype. In a series of 29 patients with acute leukemia, 17 showed significant positivity (13 of 13 with myeloid disease: three M1, seven M2, one M3, two M4; four of 16 patients with lymphoid disease: one Burkitt-type lymphoma, two null acute leukemia, and one common acute lymphoid leukemia). Intramedullary apoptosis was associated with myeloid or early committed progenitor cells and was highest in secondary acute myeloid leukemia (AML). Normal bone marrow samples from 12 individuals showed no evidence of apoptosis. Our results suggest that an increased level of intramedullary apoptosis is apparent in both patients with MDS and those with AML; those with secondary AML have the highest levels. The relative absence of such findings in lymphoid malignancy suggests that the apoptotic pathways are different in this lineage.
Insights
Increased intramedullary apoptosis, or programmed cell death in the bone marrow, is a key feature in myelodysplastic syndromes (MDS). This programmed cell death is also observed in acute myeloid leukemia (AML), particularly secondary AML.
Area of Science:
- Hematology
- Cell Biology
- Oncology
Background:
- Myelodysplastic syndromes (MDS) are characterized by ineffective blood cell production and dysplasia in the bone marrow.
- Premature apoptosis (programmed cell death) within the bone marrow is a proposed mechanism contributing to MDS.
- The specificity of increased intramedullary apoptosis in MDS requires further investigation.
Purpose of the Study:
- To investigate the presence and extent of intramedullary apoptosis in patients with myelodysplastic syndromes.
- To determine if increased intramedullary apoptosis is specific to MDS or also present in other hematopoietic disorders.
- To correlate apoptosis levels with specific MDS subtypes and other hematologic malignancies.
Main Methods:
- Terminal dUTP nick-end labeling (TUNEL) assay was performed on bone marrow biopsy specimens and cytocentrifuge preparations.
- TUNEL staining was used to detect and quantify apoptotic cells in patients with MDS, acute leukemia, and healthy controls.
- Apoptosis levels were analyzed in relation to morphological subtypes and disease categories.
Main Results:
- Significant intramedullary apoptosis was detected in a majority of myelodysplastic syndrome patients across various subtypes (RA, RAEB, RAEB-t, RARS).
- Increased apoptosis was also observed in acute myeloid leukemia (AML), with the highest levels in secondary AML.
- Apoptosis was primarily associated with myeloid or early progenitor cells, and was largely absent in normal bone marrow and lymphoid malignancies.
Conclusions:
- An elevated level of intramedullary apoptosis is a characteristic feature of myelodysplastic syndromes.
- Increased apoptosis is also evident in acute myeloid leukemia, suggesting a shared or related pathogenetic mechanism.
- The findings indicate distinct apoptotic pathway involvement in myeloid versus lymphoid malignancies.