Effect of MG-132. (A) MG-132 reversed the decrease of NPM-ALK and pJAK3 induced by SHP1. SU-DHL1 cells were transfected with pIRES2-EGFP-SHP1 and sorted based on GFP expression by flow cytometry. MG132 was then added 24 hours after gene transfection. The reduction in the levels of JAK3 and NPM-ALK induced by SHP1 was completely reversed by MG132 at 3 to 5 hours after the addition of MG132 to the cell culture. Cells transfected with pIRES2-EGFP (sorted based on GFP expression) served as negative controls. (B) MG132 did not induce up-regulation of JAK3, pSTAT3, and NPM-ALK in nontransfected SU-DHL cells. In contrast with the SHP1-transfected SU-DHL-1 cells, nontransfected SU-DHL-1 cells treated with MG132 for 3 to 5 hours showed no increase in the protein levels of NPM-ALK, pSTAT3, and JAK3.