CLDN1 and gastrointestinal stromal tumor: Given that the activation of the FGFR-signaling pathway was previously shown by our group as a potent mechanism of secondary resistance to IM in GIST [12] and taking into account our present data illustrating a tight cross-talk between CLDN1 and FGFR-signaling (Figure 8), we conclude that CLDN1 regulates FGFR expression and signaling in IM-resistant GIST.