RESUMEN
<p><b>OBJECTIVE</b>To investigate the changes of apoptosis and the activity of caspases 3 and 9 in bone marrow hematopoietic progenitor cells in myelodysplastic syndromes (MDS).</p><p><b>METHODS</b>Bone marrow hematopoietic progenitor cells (including both CD(34)(+) and CD(34)(-) cells) were collected by negative selection in 34 patients with MDS. Apoptosis was measured with Annexin V assay and activities of caspases 3 and 9 by spectrophotometer.</p><p><b>RESULTS</b>1. Apoptosis was significantly increased in MDS-RA (39.5%, P < 0.01) and MDS-RAEB (31.0%, P < 0.05), but was not different statistically in MDS-RAEBt/AML (18.8%) compared with that of control. 2. Activities of caspases 3 and 9 increased 45 and 20 fold in MDS-RA, increased 14 and 2 fold in MDS-RAEB, respectively and was not increased in MDS-RAEBt/AML compared with that of control. 3. Apoptosis and activities of caspases 3 and 9 reduced in 3 cases of MDS-RAEB group who progressed into AML.</p><p><b>CONCLUSION</b>Increased activities of caspases 3 and 9 may be one of causes of excessive apoptosis in MDS. With progress to AML, activities of caspases 3 and 9 and apoptosis reduced. Reduced activity of caspase 9 may result in apoptosis "escape" and progression into AML.</p>