Tyrosine phosphorylation of cellular proteins in Dami/HEL and Mo7e cells. Cell lysates from Dami/HEL cells (A) and Mo7e cells (B) were cultured in medium without cytokines (CTL), or with 400 ng/mL TPO or 40 ng/mL GM-CSF (GM). The cellular proteins were lysed in SDS buffer, separated on SDS-PAGE, transferred onto PVDF membrane, and probed with antiphosphotyrosine antibodies. The arrowheads indicate cytokine-induced tyrosine-phosphorylated protein bands in Mo7e cells, which are constitutively expressed in unstimulated control Dami/HEL cells.