erbB4 activation Serum starved MDA-MB468 cells were incubated with 10 ng/ml EGF for the indicated times. Whole cell lysates were prepared with lysis buffer V19 and separated by SDS-PAGE (ca 20.000 cells/lane). The immunoblot was probed with mab erbB4 - 4C6 (0.5 ug/ ml) for 1h at RT and developed by ECL (exp. time: 30 sec). Lane 1: control; lane 2: 5 min EGF; lane 3: 15 min EGF; lane 4: 30 min EGF; lane 5: 1h EGF; lane 6: 2h EGF lane 7: 4h EGF; lane 8: 8h EGF