HOXB4 overexpression down-regulates the lymphoid marker B220 in EML cells. (A) Western blot analysis of total cell lysates fractionated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and probed with the I12 monoclonal anti-HOXB4 antibody revealed the presence of HOXB4 only in the lysate of EML cells transduced with retrovirus expressing HOXB4 (EML-HOXB4) and not in control cells. (B) By immunophenotyping of cell surface markers, the percentage of cells that express B220 decreases when HOXB4 is overexpressed in EML cells. All other lineage markers and stem/progenitor cell markers are expressed at similar levels in EML, EML-GFP, and EML-HOXB4 cells.