Apoptosis and proliferation differences between CD34+ and CD34- leukemic subpopulations in childhood acute leukemia.

In view of the clinical and biological significance of leukemic heterogeneity we studied the efficacy of spontaneous apoptosis and cell cycle distribution in CD34+ and CD34 - leukemic subpopulations. Acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) leukemic samples with CD34 heterogeneous expression were separated into CD34+ and CD34 - fractions using fluorescence activated cell sorting. Cell cycle distribution, and apoptosis of the sorted subpopulations were estimated. CD34+ leukemic subpopulations had lower ability to apoptosis than that of CD34 - fractions in 6 out of 8 ALL samples and in 4 out of 5 AML samples. CD34+ fractions showed a higher percentage of proliferating cells compared to CD34 - cells in T-lineage ALL. These differences may lead to a more resistant phenotype of one of the subpopulations and reappearance this population in relapse.