Figure 6.

Induction of macrophage differentiation in U937T cells. Wright–Giemsa-stained Cytospin preparation of U937T clones cultured for 72 hr in the presence (Left) or absence (Right) of tetracycline. (×400.) The morphology of the parental cell line U937T (Top) is unaffected by tetracycline withdrawal. Induction of MLL-AF9 expression in representative clone B37 results in differentiation into macrophages accompanied by apoptotic cell death. Similar results were seen with MLLΔT. Induction of expression of the amino-terminal portion of MLL containing 2 AT hook motifs (MLL2AT; Bottom) results in partial differentiation into macrophages as evidenced by increased amount of cytoplasm and less conspicuous nucleoli (clone C15).