CLDN1 and gastrointestinal stromal tumor: Given that GIST T-1R cells exhibit the signs of activation of the FGFR-signaling pathway, which was previously shown as a potent mechanism of secondary resistance to IM named receptor tyrosine kinase switch [12], and taking into account increased expression of CLDN1 in these particular GIST cells, we examined the potential interplay between these molecular events.