FGFR2 and gastrointestinal stromal tumor: Although we failed to confirm the possible interactions between the endogenous KIT and FGFR1/2 in IM-resistant GISTs by co-immunoprecipitation experiments (Figure S4, the whole western blot of Figure S4 is in Figure S9), we observed a strong co-localization pattern between c-KIT and FGFR2 in GIST T1-R (Figure 4A–E), thereby suggesting the active crosstalk between these RTKs in IM-resistant GISTs.