TY - JOUR AU - A van Stijn, AU - MA van der Pol, AU - A Kok, AU - PM Bontje, AU - GM Roemen, AU - RH Beelen, AU - GJ Ossenkoppele, AU - GJ Schuurhuis, PY - 2003/05/01 Y2 - 2024/03/29 TI - Differences between the CD34+ and CD34- blast compartments in apoptosis resistance in acute myeloid leukemia JF - Haematologica JA - haematol VL - 88 IS - 5 SE - Articles DO - 10.3324/%x UR - https://haematologica.org/article/view/2728 SP - 497-508 AB - BACKGROUND AND OBJECTIVES: Altered expression of members of the Bcl-2 family might account for the observed apoptosis resistance to chemotherapy in acute myeloid leukemia (AML). Given the poor prognosis associated with CD34+ expression in AML, we studied the role of spontaneous apoptosis and apoptosis regulatory proteins in sorted CD34+ and CD34- primary AML fractions. DESIGN AND METHODS: The expression levels of apoptosis regulatory proteins and spontaneous apoptosis were measured in primary AML samples by Western blot analysis and flow cytometry. To determine the role of CD34+ cells in apoptosis resistance, spontaneous apoptosis in serum-free conditions and apoptosis regulatory protein levels were measured in CD34+ and CD34- sorted cells from CD34+ primary AML samples. RESULTS: We show that CD34+ AML fractions are more resistant to apoptosis than are corresponding CD34- AML fractions, and that this is paralleled by higher Bcl-2, Bcl-xL, Mcl-1, Pgp and lower Bax expression levels. Interestingly, as the percentage of CD34 cells increased in the primary AML sample, so too did the apoptosis resistance in the corresponding CD34- fraction, which was reflected by an increasing anti-apoptosis protein profile. INTERPRETATION AND CONCLUSIONS: The data show that the CD34+ fraction is more resistant to apoptosis than is the corresponding CD34- fraction and secondly that the AML as a whole is more apoptosis resistant with increasing CD34 percentage. ER -