Nontranscriptional, mitochondrial STAT3 supports factor-independent colony formation. Control, Mx:K-Ras:F/+, Mx:K-Ras:F/F, or Mx:K-Ras:F/SA mice were injected with poly(I:C) and allowed to recover for 1 week. Bone marrow was harvested and lineage depleted. Cells (103) were plated in methylcellulose supplemented with 50 ng/mL SCF, 10 ng/mL IL-6, 10 ng/mL IL-3, 3 units/mL EPO, and 20 ng/mL GM-CSF (A) or without growth factors (B). Colonies were counted and identified after 10 days in culture. (C-D) Mx:K-Ras:F/F mice were injected with poly(I:C) and allowed to recover for 1 week. Bone marrow was harvested and transduced with pMIG retroviruses expressing WT, YF, MTS, or EV. Lineage-negative, GFP-positive cells were sorted and 103 cells per plate were cultured in methylcellulose supplemented with 50 ng/mL SCF, 10 ng/mL IL-6, 10 ng/mL IL-3, 3 units/mL EPO, and 20 ng/mL GM-CSF (C) or without growth factors (D). Colony numbers and cell types were enumerated after 10 days. Histograms represent the mean of triplicate experiments and error bars are 1 standard deviation from the mean of the total number of colonies. *P < .05 and **P < .001 of differences between groups calculated by the 1-way ANOVA and the Tukey multiple comparison test. EV, empty vector control; MTS, mitochondrially restricted STAT3 mutant; NS, not significant; WT, wild-type STAT3; YF, STAT3 Y705F mutant.
