Effect of RUNX1 and CD56 expression on K562 acute myeloid leukemia cells. (A) Effect on K562 cell growth. The cells were transfected with either the RUNX1 isoforms or the CD56 (120 kDa and 140 kDa) isoforms. After 4 days, RUNX1 p48 and CD56-transfected cells showed less than a 2-fold increase in total cell number compared with vector control [VC] or untransfected (–) cells. p38a and p24 transfected cells revealed a less than 50% growth inhibition, whereas p30 had no significant effect. Data are means plus or minus SD. (B) Detection of phosphatidylserine [PS] on the cell surface of RUNX1-p48, -p38a, -p30, and -p24 transfected K562 cells by fluorescent-activated cell sorter analysis using Annexin-V. There was a decreased number of apoptotic cells among the RUNX1-p48-transfected K562 cells compared with K562 cells transfected with the vector control. By contrast, there was clearly increased apoptosis among RUNX1-p38a and -p24-transfected K562 cells. Compared with vector control, the transfection of RUNX1-p30 had no significant impact on apoptosis. (C) NF-κB and bcl2L12 expression examined by reverse transcriptase–polymerase chain reaction and nuclear translocation of NF-κB/p65 visualized by Western blot of cytoplasmic [C] and nuclear [N] protein extracts (see also Figure S8) after transfection of the K562 acute myeloid leukemia cell line with either RUNX1 isoforms or CD56 (120 kDa and 140 kDa) compared with levels in vector-control [VC] or untransfected [–] cells. Increased expression of NF-κB and bcl2L12 as well as nuclear translocation of p65 in RUNX1 p48 and CD56-transfected cell lines. By contrast, p38a and p24-transfected K562 cells showed clear down-regulation of NF-κB and bcl2L12 and no nuclear translocation of p65.