Activation of FGFR signaling in IM-resistant GIST T-1R cells was also evidenced by an increased expression of Tyr-phosphorylated FGF receptor (pFGFR Y653/654) and Tyr-phosphorylated FGFR substrate 2 (FRS2 Tyr196) which is a downstream substrate of FGFR signaling (Figure 1C). This evidence concerns the gene FRS2 and gastrointestinal stromal tumor.