RUNX1/ETO tetramers, but not dimmers, trigger apoptosis and block cytokine-induced myeloid differentiation. (A) Expression of RUNX1/ETO (RE) and mutants thereof in stably transduced U937 cells using anti-ETO and antiactin antibodies. (B) Survival kinetics of RE/eGFP-expressing U937 cells. (C) Apoptosis induction in U937 cells, expressing the indicated forms of RE. (D) Cell-cycle distribution of U937 cells at day 4 after transduction as measured by Draq5 staining. (E) Cell-cycle distribution of stably transduced K562 cells. Draq5 staining was performed 4 days after transduction. (F) Differentiation pattern of U937 cells expressing the indicated RE forms. Two days after transduction, U937 cells were stimulated with vitamin D3/TGF-β for 24 hours and subsequently analyzed for CD14 surface marker expression. (G). Vitamin D3/TGF-β– or ATRA-induced differentiation of U937 cells expressing the indicated RE forms. Statistically significant P values of RE, RE-m5, and RE-cm5 compared with each other are indicated for the vitamin D3 (VD3)/TGF-β–stimulated cells (t test): ***P < .001, **P = .001, *P = .73. Data represent averages of 3 independent experiments.
