Abstract. Pancreatic cancer is one of the most aggressive and devastating malignancies. The Hedgehog (Hh) pathway has been reported to play an important role in pancreatic cancer development and progression. The aim of this study was to examine the activation of the Hh pathway in human pancreatic cancer tissue samples and pancreatic cancer cell lines, and the molecular mechanisms involved in the Hh pathway mediated effects on pancreatic cancer cell proliferation and invasion. The expression levels of Hh molecules in human pancreatic cancer tissue samples and pancreatic cancer cell lines were evaluated using RT-PCR. The role of the Hh pathway in cell proliferation and invasion was evaluated using flow cytometry, MTT, colony formation assays and Transwell invasion assays, and the expression of cancer stem cell markers and epithelial-mesenchymal transition (EMT) were evaluated using flow cytometry and RT-PCR. Tumorigenicity assays were used to further investigate the role of the Hh pathway in vivo. Hh molecules were highly expressed in human pancreatic cancer tissue samples and pancreatic cancer cell lines. Inhibition of the Hh pathway notably decreased cell proliferation and induced apoptosis through inhibition of the PI3K/AKT pathway and cancer stem cells. Furthermore, inhibition of the Hh signaling pathway significantly inhibited EMT by suppressing the activation of transcription factors Snail and Slug, which are correlated with significantly reduced pancreatic cancer cell invasion, suggesting that the Hh signaling pathway is involved in early metastasis. These results indicate that activation of the Hh pathway is a common event. Inhibition of the Hh pathway may be a potential molecular target of new therapeutic strategies for pancreatic cancer.

IGF1R knockdown suppresses tumor growth and enhances chemosensitivity in pancreatic cancer via the inhibition of PI3K/AKT and NF-κB pathways, and is a promising approach to overcome the chemoresistance of pancreatic cancer.

In the present study, we established a new experimental model to investigate the effects of EGFR targeting by RNAi, and the synergistic actions between the hedgehog (Hh) and EGFR signaling pathways on the proliferation and apoptosis in pancreatic cancer cells. Three human pancreatic cancer cell lines expressing EGFR shRNA were established, and gene expression inhibition was assessed in these lines using RT-PCR and western blot analysis. The effects of EGFR RNAi and Hh inhibition on cell proliferation and apoptosis were explored in vitro and in vivo. We observed that EGFR RNAi notably inhibited cell proliferation and colony formation, induced apoptosis and markedly decreased xenograft tumor growth. Furthermore, EGFR RNAi significantly enhanced cyclopamine sensitivity both in vitro and in vivo, and a synergistic decrease of both AKT and ERK phosphorylation was observed. The present study demonstrates that combined inhibition of both EGFR and Hh signaling pathways could establish a more promising antitumor approach than inhibiting each singly, and that there is a possible synergistic effect for Hh and EGFR signaling pathways on ERK and AKT phosphorylation.