title: Loss of canonical Smad4 signaling promotes KRAS driven malignant transformation of human pancreatic duct epithelial cells and metastasis.
abstract: Pancreatic ductal adenocarcinoma (PDAC) is the fourth most common cause of cancer death in North America. Activating KRAS mutations and Smad4 loss occur in approximately 90% and 55% of PDAC, respectively. While their roles in the early stages of PDAC development have been confirmed in genetically modified mouse models, their roles in the multistep malignant transformation of human pancreatic duct cells have not been directly demonstrated. Here, we report that Smad4 represents a barrier in KRAS-mediated malignant transformation of the near normal immortalized human pancreatic duct epithelial (HPDE) cell line model. Marked Smad4 downregulation by shRNA in KRAS (G12V) expressing HPDE cells failed to cause tumorigenic transformation. However, KRAS-mediated malignant transformation occurred in a new HPDE-TGF-β resistant (TβR) cell line that completely lacks Smad4 protein expression and is resistant to the mito-inhibitory activity of TGF-β. This transformation resulted in tumor formation and development of metastatic phenotype when the cells were implanted orthotopically into the mouse pancreas. Smad4 restoration re-established TGF-β sensitivity, markedly increased tumor latency by promoting apoptosis, and decreased metastatic potential. These results directly establish the critical combination of the KRAS oncogene and complete Smad4 inactivation in the multi-stage malignant transformation and metastatic progression of normal human HPDE cells.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada ; Ontario Cancer Institute/Princess Margaret Hospital, and University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Lisa
authors.initials: L
authors.lastname: Leung
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada ; Ontario Cancer Institute/Princess Margaret Hospital, and University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Nikolina
authors.initials: N
authors.lastname: Radulovich
authors.affiliation: Ontario Cancer Institute/Princess Margaret Hospital, and University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Chang-Qi
authors.initials: CQ
authors.lastname: Zhu
authors.affiliation: Ontario Cancer Institute/Princess Margaret Hospital, and University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Dennis
authors.initials: D
authors.lastname: Wang
authors.affiliation: Ontario Cancer Institute/Princess Margaret Hospital, and University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Christine
authors.initials: C
authors.lastname: To
authors.affiliation: Ontario Cancer Institute/Princess Margaret Hospital, and University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Emin
authors.initials: E
authors.lastname: Ibrahimov
authors.affiliation: Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada ; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada ; Ontario Cancer Institute/Princess Margaret Hospital, and University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Ming-Sound
authors.initials: MS
authors.lastname: Tsao
mesh_terms: D000818:Animals; D021441:Carcinoma, Pancreatic Ductal / Q000473:pathology*; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000187:drug effects; D004847:Epithelial Cells / Q000473:pathology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D006801:Humans; D051379:Mice; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D010183:Pancreatic Ducts / Q000473:pathology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras); D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D051901:Smad4 Protein / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D016019:Survival Analysis; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D018631:ras Proteins / Q000378:metabolism*
chemical_list: C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; C497796:SMAD4 protein, human; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins