CD34 cells from patients with trisomy 8 myelodysplastic syndrome (MDS) express early apoptotic markers but avoid programmed cell death by up-regulation of antiapoptotic proteins

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Abstract
CD34 cells from patients with trisomy 8 myelodysplastic syndrome (MDS) are distinguished from other MDS cells and from normal hematopoietic cells by their pronounced expression of apoptotic markers. Paradoxically, trisomy 8 clones can persist in patients with bone marrow failure and expand following immunosuppression. We previously demonstrated up-regulation of c-myc and CD1 by microarray analysis. Here, we confirmed these findings by real-time polymerase chain reaction (PCR), demonstrated up-regulation of survivin, c-myc, and CD1 protein expression, and documented comparable colony formation by annexin+ trisomy 8− CD34+ and annexin− CD34 cells. There were low levels of DNA degradation in annexin+ trisomy 8 CD34 cells, which were comparable with annexin− CD34 cells. Trisomy 8 cells were resistant to apoptosis induced by gamma irradiation. Knock-down of survivin by siRNA resulted in preferential loss of trisomy 8 cells. These results suggest that trisomy 8 cells undergo incomplete apoptosis and are nonetheless capable of colony formation and growth.