Molecular and karyotypic characterization and engraftment potential of Lin⁻CD34⁺ and Lin⁻CD34⁻ CML cells. Characterization of CML Lin⁺CD34⁺, Lin⁻CD34⁺, and Lin⁻CD34⁻ cell populations purified from the PB of chronic-phase patients at diagnosis. (A) FISH analysis and RQ-PCR for BCR-ABL transcript demonstrating higher numbers of residual normal progenitors in Lin⁻CD34⁻ cell populations. The results are expressed as mean ± SD of 3 experiments. (B) Study design (number of experiments = 9 with a total of 37 and 22 NOD/SCID/β₂M and NOD/SCID/IL-2Rγ^null mice, respectively). (C-G) Flow cytometric and molecular evaluation of human cell engraftment in the marrow and blood of NOD/SCID/β₂M (F) and NOD/SCID/IL-2Rγ^null mice (G) engrafted with 100 000 human cells. Immunodeficient mice were evaluated up to 120 days after transplant. (C) The gate used to exclude platelets, debris, and dead cells in a representative case of xenotransplantation; (D) the negative control; (E) the gates used to identify hematopoietic (human CD45⁺) and endothelial (human CD45⁻/CD31⁺) cells. (Fi) The frequency of human hematopoietic and endothelial cell engraftment in NOD/SCID/β₂M mice transplanted with CML Lin⁻CD34⁺ and Lin⁻CD34⁻ cells. (Fii) The number of human VE-Cadherin RNA copies in the blood and marrow of transplanted mice. (Gi-Gii) Human hematopoietic and endothelial cell engraftment in NOD/SCID/IL-2Rγ^null mice. RQ-PCR of BCR-ABL mRNA transcript was used to confirm the leukemic origin of engrafted cells in both mice strains. Our results showed a mean of 176 ± 87 BCR-ABL/β2 microglobulin copies in NOD/SCID/β₂M mice (mean of 85 ± 32 β2 microglobulin copies) and a mean of 188 ± 62 copies in in NOD/SCID/IL-2Rγ^null mice (85 ± 32 β2 microglobulin copies); *P < .05.