Phosphospecificity: Whole cell extracts of control (co) or Ins ulin, IGF1, Pervanadate stim ulated MDA-MB-231 tumor cells were applied to SDS-PAGE (ca 20.000 cells per lane) and transferred to PVDF membranes. Immunoblots were probed with Monoclonal InsR antibody 21G12 (0.5 ug/ ml) for 1h at RT and developed by ECL (exp. time: 30 sec). Lane 1: untreated Lane 2: Ins ulin-treated Lane 3: IGF1-treated Lane 4: Pervanadate-treated