Wen-Li et al. Journal of Experimental & Clinical Cancer Research 2012, 31:92 http://www.jeccr.com/content/31/1/92 Page 4 of 9 subunit of F1F0 ATPase was detected in 11 leukemia cell lines (two ALL cell lines 697 and Jurkat; three lymphoma cell lines CCRF, Raji and MOLT4; six mye- loid leukemia cell lines MV4-11, SHI-1,DAMI, K562, HL-60 and U937). MV4-11, HL-60 and Jurkat are the top three cells (Figure 1). The β subunit of F1F0 ATPase was also detected in the positive control HUVEC cell line (Figure 1). The number of cells expressing ecto-ATPase β subunit on the cell mem- brane ranged from 0.1% to 56%. The percentage of cells expressing ecto-ATPase β subunit on the cell membrane in the K562 cell line (17.2%), derived from a 53 year old female CML patient, and the monocytic cell line U937 (18.6%), were similar to the previous re- port of Scotet E et al. [11]. Production and characterization of McAb7E10 In order to generate a monoclonal antibody (McAb) against the natural epitopes of the ATPase catalytic subunit, we immunized BALB/c mice with both natural Figure 1 Expression of ecto-ATPase β subunit in cell lines from hematological malignancies. Cells were collected, incubated with an ATP synthase subunit β monoclonal antibody or mouse IgG control antibody, then with fluorescein-isothiocyanate (FITC)-labeled goat anti-mouse IgG and membrane ATP synthase subunit β expression was analyzed using fluorescence activated cell sorting (FACS). FACS results of 11 leukemia cells and HUVEC cells incubated with control IgG and ATP synthase subunit β monoclonal antibody.