Effect of SHP1 activity on the proliferation of NPM-ALK–positive cells. (A) Karpas 299 cells were transfected with SHP1 siRNA or control siRNA and cultivated overnight in IMDM containing 10% FCS. Cells were then diluted in IMDM containing 5% FCS and seeded in triplicate at 2 × 103 cells per well in 96-well plates. Cell proliferation was determined each day for 3 days using an MTS proliferation assay and the OD (490 nm) was measured. (B) NPM-ALK–positive NIH3T3 fibroblasts were transfected with pcDNA3 or pcDNA3-SHP1 plasmids. After overnight culture in DMEM containing 10% FCS, fibroblasts (4 × 103 cells/well) were seeded in triplicate in 96-well plates. Cell proliferation was measured each day for 4 days as described in panel A. The histogram (inset) represents the effect of SHP1 expression on the proliferation of NIH3T3 stably transfected with NPM-ALK (□) or NIH3T3 transfected with empty vector (▪). Each value is expressed as percentage of control cells that did not express SHP1. Results are mean ± SD; Student t test, *P < .05, **P < .01, ***P < .005 of 3 (Karpas) or 4 (NIH3T3) independent experiments performed in triplicate.
