. "Activation of Erk1/2 downstream of FGFR mutants suggests that, as is the case for WT FGFR, FGFR mutant-associated SOS1 activates RAS nucleotide exchange from the inactive GDP-bound to the active GTP-bound state (see for instance, Weiss, 2010; Dutt, 2011; Raffioni, 1998; Cha, 2009; Hart, 2000; Turner, 2010; Kunii, 2008; Byron, 2008; Roidl, 2010; Chesi, 2001; Ronchetti, 2001; reviewed in Wesche, 2011)."^^ . . . . . . . . . . . . . .