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. 2001 Aug;21(16):5447–5458. doi: 10.1128/MCB.21.16.5447-5458.2001

FIG. 7.

FIG. 7

A dominant negative mutant of Stat3 inhibits IGF-I-mediated differentiation and causes transformation of 32D IGF-IR cells. 32D cells were transduced with the appropriate retroviral vectors, and mixed populations were selected. (A) IGF-IR cells and 32D IGF-IR/DN Stat3 cells were grown in medium supplemented with 10% serum and either IL-3 or IGF-I. The percentage of differentiated cells is indicated on the ordinate. In this experiment, the cells were fixed and stained after 4 days in the indicated medium. The percentage of differentiated cells was determined by standard methods (60). (B) After withdrawal of IL-3, the cells were grown in medium supplemented with 10% serum and either IGF-I or insulin at a concentration of 50 ng/ml. The cells were counted 48 h after IL-3 withdrawal. The cell lines are indicated on the left of the figure. 32D, parental cells; 32D IR, cells overexpressing the insulin receptor; 32D IGF-IR, cells expressing increased levels of IGF-IR. DN/STAT3 indicates the same cell lines stably transduced with the dominant negative mutant of Stat3. The inset shows levels of expression of DN/Stat3, after immunoprecipitation with a FLAG antibody and blotting with an anti-Stat3 antibody. Lanes of inset: 1, 32D/DN Stat3; 2, 32D IR/DN Stat3; 3, 32D IGF-IR/DN Stat3; 4, parental 32D cells.