Myelodysplastic syndromes (MDS) comprise a heterogeneous group of clonal stem-cell disorders characterized by ineffective hematopoiesis and risk of progression to acute myeloid leukemia. Increased apoptosis and suppressed functions of peripheral blood natural killer (NK) cells have been described in MDS patients, but only limited information is available on the phenotypic and functional integrity of NK cells in the bone marrow. In a cohort of 41 patients with distinct clinical subtypes of MDS, we here show that NK cells in the bone marrow show decreased surface expression of the activating receptors DNAM-1 and NKG2D. Notably, decreased receptor expression correlated with elevated bone marrow blast counts and was associated with impaired NK-cell responsiveness to stimulation with the K562 cell line, or co-activation by NKG2D or DNAM-1 in combination with the 2B4 receptor. Furthermore, antibodymasking experiments revealed a central role for DNAM-1 in NK cell-mediated killing of freshly isolated MDS blasts. Thus, given the emerging evidence for NK cell-mediated immune surveillance of neoplastic cells, we speculate that reduced expression of DNAM-1 on bone marrow NK cells may facilitate disease progression in patients with MDS.
Treatment with granulocyte colony-stimulating factor (G-CSF) plus erythropoietin may synergistically improve hemoglobin levels and reduce bone marrow apoptosis in patients with refractory anemia with ringed sideroblasts (RARS). Fasinduced caspase activity is increased in RARS bone marrow cells. We showed that G-CSF significantly reduced Fasmediated caspase-8 and caspase-3-like activity and the degree of nuclear apoptotic changes in bone marrow from nine RARS patients. A decrease in mitochondrial membrane potential and an increase in intracellular reactive oxygen species occurred in Fas-treated cells, but became significant only 24 h after changes in caspase activity and decrease in proliferation. G-CSF also reduced the magnitude of these late apoptotic changes. In CD34-selected normal cells, G-CSF induced myeloid colony growth, and an overall small decrease in the number of erythroid colonies. By contrast, G-CSF induced a 33-263% increase of erythroid colony formation in CD34 + cells from four of five RARS patients with severely reduced erythroid growth, while the normal or slightly reduced erythroid growth of three other patients was not influenced by G-CSF. This study suggests that G-CSF may reduce the pathologically increased caspase activity and concomitant apoptotic changes, and promote erythroid growth and differentiation of stem cells from RARS patients. Our data support the clinical benefit of G-CSF in this subgroup of myelodysplastic syndromes. Leukemia (2001) 15, 742-751.
Thirteen patients with acute myelocytic leukemia (AML) and with clonal aberrations involving chromosome 3 were studied. Three patients had monosomy 3, four had trisomy 3, and six had structural aberrations of chromosome 3. In the majority of cases chromosome 3 aberrations were parts of complex karyotypes, but in two patients, the abnormalities appeared as single aberrations, one as an interstitial deletion del(3)(p13p21) and the other as monosomy 3. All breakpoints of chromosome 3 were found in the fragile site regions 3p14.2, 3q21 and 3q26-27. All patients with monosomy 3 or structural aberrations of chromosome 3 and one of the four patients with trisomy 3 had been exposed to mutagens, such as occupational exposures to organic solvents and/or petroleum products or treatments with irradiation or antineoplastic agents. The association among mutagen exposure, structural chromosome 3 aberrations and fragile sites in AML may indicate that targeting of the mutagens to these sites is of importance for the etiology of the disease. Leukemia (2000) 14, 112-118.
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