p60^src kinase activity in NIH-EGFR/ALK cells following EGF stimulation. Quiescent NIH-EGFR/ALK cells were either mock-treated or treated with 100 ng/mL EGF for the indicated time at 37°C. Cell lysates were immunoprecipitated with an anti-p60^src antibody. (A) An aliquot from each immunoprecipitate was directly analyzed by immunoblotting to evaluate p60^src content. (B) The remainder of each immunoprecipitate was subjected to in vitro kinase assay in the presence of [γ-³²P] ATP and acid-denaturated enolase. Samples were then analyzed by SDS-PAGE and autoradiography. (C) The ³²P content of bands corresponding to enolase shown in panel B was quantified by densitometric scanning of the autoradiograms and results are expressed as percent of control (signal obtained from medium-treated cells).