FGFR2 and Pfeiffer syndrome: The tyrosine kinase activities of FGFR2-IIIb carrying breast cancer mutations were compared to those of wt FGFR2-IIIb, of a dominant-negative kinase-defective (KD) FGFR2 mutant (p.K508A), and of a Pfeiffer syndrome gain-of-function FGFR2 mutant (p.K642R; previously named p.K641R according to another reference sequence) as controls.