Expression of a SHP2 gain-of-function mutant results in increased sensitivity to the knockdown of SHP2. (A) TF-1 cells were transduced with vectors carrying WT SHP2 cDNA (SHP2-WT; coexpressing GFP) and gain-of-function mutant SHP2 cDNA (SHP2-E76K) followed by transduction with sh-Ctrla and sh-Shp2-2 vectors, respectively (coexpressing DsRED). GFP⁺DsRED⁺ cells were selected by flow cytometry and cultured in the presence of GM-CSF (2 ng/mL). Apoptosis was analyzed by labeling with annexin V and DAPI, and data from sh-Shp2-2–transduced cells were normalized over the corresponding sh-Ctrla-transduced cells. Data are mean ± SEM of fold changes of apoptosis from 3 experiments. **P < .01, SHP2-WT compared with SHP2-E76K. (B) Dual-transduced TF-1 cells were cultured without GM-CSF overnight and then cultured in the presence of GM-CSF (0.3 ng/mL) for 3 days. Cell growth in response to the GM-CSF was evaluated by MTS assay. Data from sh-Shp2-2–transduced cells were normalized over sh-Ctrla–transduced cells, and the inhibition of cell growth relative to sh-Ctrla was calculated. Data are mean ± SEM from 3 replicates.