PBX3 enhances colony-forming/immortalization capacity of mouse normal bone marrow progenitor cells induced by HOXA9. Colony-forming and replating assays of mouse normal BM progenitor (ie, lineage negative) cells transduced with MSCV-PIG⁺MSCVneo (ie, control), MSCV-PIG-PBX3⁺MSCVneo (ie, PBX3), MSCV-PIG⁺MSCVneo-HOXA9 (ie, HOXA9), MSCV-PIG-PBX3⁺MSCVneo-HOXA9 (ie, PBX3⁺HOXA9), or MSCV-PIG⁺MSCVneo-MLL-AF9 (ie, MA9). Cells were plated for each transduction with 1 × 10⁴ cells per dish duplicates, and every 7 days the cells were replated for up to 4 passages. Mean ± SD values from 2 independent experiments are shown. (A) Numbers of colonies per dish in each passage are shown. (B) Cell numbers per dish are shown. (C) Morphology of cells of secondary passage. Cells were stained with Wright-Giemsa. Scale bars represent 10 μm. (D) Flow cytometric analysis of colony-forming cells (secondary passage) with APC-labeled anti-CD117 (ie, c-Kit) antibody and eFluor 450–labeled anti-CD11b (ie, Mac-1) antibody.