GLI1 and pancreatic ductal adenocarcinoma: Shh produced by pancreatic ductal epithelium can also upregulate GLI1 mRNA in fibroblasts of the stromal compartment in a paracrine manner [71], and activation of canonical Hh-GLI signaling in stromal cells leads to paracrine feedbacks to the epithelial compartment, which, in turn, promotes pancreatic ductal adenocarcinoma (PDAC) progression and chemoresistance [72,73].