Tyrosine phosphorylation of SHP2 in mutant cell lines. Cells were incubated in the absence or presence of 10 ng/mL GM-CSF for 15 minutes. Lysates from 10⁷ cells were immunoprecipitated with anti-SHP2 antibody and subjected to 6% to 12% gradient SDS-PAGE and immunoblot analysis with antiphosphotyrosine antibody. The same blot was stripped and reprobed with anti-SHP2 and anti-GRB2 antibody, as indicated.