IK6 enhances basophil production from both normal and CP-CML progenitors. (A) Numbers of different mature cell types in the nonadherent fraction of 3-week cultures initiated with IK6- or control-transduced CD34⁺ cells from CP-CML or normal BM samples (as assessed in Wright-Giemsa–stained cytospin preparations). Values shown are the mean ± SEM from 3 replicate cultures from 5 CML and 2 normal BM samples; P values: IK6 vs control. (B) Representative flow cytometric analyses of nonadherent cells from 3-week cultures initiated with IK6- or control-transduced CD34⁺ cells from 5 CP-CML and 2 normal BM samples. Basophils and eosinophils were defined by a CD33⁺14⁻15⁻HLA⁻DR⁻25⁺9^+/− phenotype. (C) Lineage-specific transcripts in the nonadherent cells shown in panel A; mean ± SEM of results from 3 replicate cultures from 5 CP-CML and 2 normal BM samples, P values: IK6 vs control. (D-E) Types of colonies obtained in assays of IK6- and control-transduced CP-CML cells harvested from 6-week cultures. The differentiated cell content of the colonies was confirmed in Wright-Giemsa–stained cytospin preparations of harvested colonies. P values: IK6 vs control. (F) Representative cytospin preparation of the cells in colonies generated in CFC assays from plating of nonadherent cells present in the tertiary cultures generated from CP-CML #1 and CP-CML #4. *P < .05; **P < .01; ***P < .001. EPX, eosinophil peroxidase (eosinophil specific); HDC, histidine decarboxylase (basophil specific); MPO, myeloperoxidase (neutrophil specific); NBM: normal bone marrow; PRG2, proteoglycan 2 (basophil/eosinophil).