CLDN1 and gastrointestinal stromal tumor: We found that culturing these cells in the presence of FGF-2 (100 ng/mL) increased CLDN1 expression in a time-dependent manner, which reached its maximal level after 1 week and retained on its high level until the end period of the experiment (14 days), thereby suggesting the potential crosstalk between the activated FGFR-pathway and CLDN1 in GIST (Figure 5A).