Introduction: It is well known that the Hedgehog (Hh) signaling pathway regulates cell differentiation and organ formation during embryonic development. Recent reports showed that activation of Hh signal pathway has been associated with gastrointestinal tract cancers including pancreatic cancer as well as Gorlin’s syndrome tumors, and activation of HH signaling might be important for early and late stage of tumorigenesis in pancreatic cancer. However, there is few data available about target molecules of Hh signal in pancreatic cancer. Therefore, we investigated Hh-related target molecules in Hh ligand expressing pancreatic cancer cells. Materials and Methods: Two human pancreatic cancer cell lines, MiaPaCa-2 and Panc-1 were treated with cyclopamine (5 μM, 10 μM, 20 μM, and 40 μM) for Hh signal inhibition and tomatidine (5 μM), as a control. After 72 hours, we performed Western blot analysis against Hh signal components and apoptosis were measured by FACS. In order to find out possible Hh-related target molecules in pancreatic cancer, gene expression patterns were analyzed by microarray in Panc-1 after cyclopamine administration. Of 3 folds or more downregulated genes resulted from microarray data, expression of cathepsin B (CATB) was measured by Western blot and real-time PCR after inhibition of Hh signal pathway. In order to investigate expression of Hh signal components and CATB in pancreatic cancer tissues, immunohistochemical study of these proteins was carried out. Results: Cyclopamine did increase apoptosis in Panc-1 cells which expressed Shh, not in MiaPaCa-2. When Panc-1 cells were cultured in cyclopamine containing media, a total of 138 genes were 2 folds or more downregulated and 32 genes were 3 folds or more downregulated (of 22,746 human oligo). Whereas cyclopamine did not change the expression of Hh signal components such as Shh, Ptch, and Gli1, expression of CATB decreased after treatment of cyclopamine (p<0.05). And also the expressions of CATB mRNA decreased by cyclopamine administrations (p<0.05). In immunohistochemical study, the rate of CATB expression in pancreatic cancer expressed Shh was higher than in those not expressed Shh (50%, 3/6 vs. 12%, 4/34), irrespective of not reaching statistical power (p=0.055). When cumulative survival rate in CATB (+) pancreatic cancer patients was compared to CATB (-) pancreatic cancer patients, patients with CATB expression had a poorer prognosis than those with CATB (-) expression (P = .04). Conclusion: CATB might be one of an important Hh signal-related target molecules in some pancreatic cancers, especially Shh expressing one. CATB expression in Hh signal activated pancreatic cancers is more common and those pancreatic cancer patients might have poorer prognosis, compared to the others.
98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA