CLDN1 and gastrointestinal stromal tumor: In contrast, selective inhibition of FGFR1 or FGFR4 signaling pathways by corresponding inhibitors (e.g., PD 170374 and H3B-6527, respectively) failed to decrease CLDN1 levels in IM-resistant GIST (Figure 5B), thereby suggesting the potential crosstalk between CLDN1 and FGFR1 or FGFR2.