Figure 3. EPZ004777 Selectively Inhibits Proliferation of MLL-Rearranged Cell Lines and MLL-AF9-Transformed Murine Hematopoietic Cells.

(A) Growth of MV4-11 (MLL-AF4), MOLM-13 (MLL-AF9), and Jurkat (non-MLL-rearranged) cells during several days incubation with 3 μM EPZ004777. Viable cells were counted every 3 to 4 days in the presence of EPZ004777 (+) or DMSO vehicle control (−) and results plotted on a logarithmic scale. See also Figure S1. Error bars represent standard deviation.

(B) Effect of EPZ004777 on the proliferation of leukemia cell lines bearing MLL-AF4, MLL-AF9, and MLL-ENL fusions, or cell lines lacking an MLL rearrangement. Cell lines were maintained in the presence of increasing concentrations of EPZ004777 up to 50 μM. Viable cells counts were used to derive IC₅₀ values after 14 days of treatment for all cell lines apart from THP-1 cells, which were treated for 18 days. Fifty percent inhibition of growth was not achieved in HL60, Jurkat and U937 cells even at the highest EPZ004777 concentration and so IC₅₀ values are given as >50 μM.

(C) Effect of EPZ004777 on the proliferation of primary murine hematopoietic progenitors transformed by retroviral expression of MLL-AF9, or coexpression of HoxA9 and Meis1a. Retrovirally transformed cells were maintained in the presence of increasing concentrations of EPZ004777 up to 30 μM for 10 days, then plated in 96-well plates for MTT assay at day 12. Following the MTT assay, plate ODs were read at 570 nM and plotted on the y axis. Results from two independent transductions are shown for each retroviral construct. Error bars represent standard deviation.

(D) Inhibition of cellular H3K79me2 levels in MLL-AF9 or Hoxa9-Meis1a transformed hematopoietic progenitors following 10 days of treatment with the indicated concentrations of EPZ004777 as measured by immunoblot analysis of extracted histones with an anti-H3K79me2 antibody.