Identification of p130Cas from silver-stained SDS-PAGE. The 293 T-Rex Tet-On cells were transfected with NPM-ALK and cultured for 24 hours in presence or absence of tetracycline. Thirty milligrams of total cell lysate was immunoprecipitated with a mixture of antiphosphotyrosine antibodies (4G10; Upstate Biotechnology; and PY20; Transduction Laboratories) and resolved on 8% SDS-PAGE. The gel was silver stained and the bands present only in the induced sample (+), as indicated by the arrows, were analyzed by mass spectrometry. Molecular marker is shown on the left. The p130Cas was identified from the circled band. See “Materials and methods” for details.