Phosphospecificity: Whole cell extracts of control (co), EGF stim ulated (EGF) or pervanadate treated (VH) HEPG2 tumor cells were applied to SDS-PAGE (ca 20.000 cells per lane) and transferred to a PVDF membrane. The immunoblot was probed with mab STAT3-9E12 (0.5 ug/ ml) for 1h at RT and developed by ECL (exp. time: 30 sec).