CD34⁺ AML1-ETO-expressing cells retain telomerase activity and maintain telomere length. (A) Telomerase activity was assayed on cells selected for CD34 and CD61 expression by magnetic beads. Per lane, 2 × 10⁵ cells were used (2 × 10⁴ cells in the CD34⁺ sample). The neuroblastoma cell line served as a positive control (NB) and lysis buffer alone was used as the negative control. (B) To assess telomere length, 2 μg purified DNA was digested with restriction enzymes HinfI and RsaI, separated on 0.8% agarose gel, transferred to a nylon membrane, and probed with a digoxigenin-labeled probe specific for telomeric repeats. A digoxigenin-specific antibody, covalently coupled to alkaline phosphatase, was used for detection.