K-Ras promotes growth transformation and invasion of immortalized human pancreatic cells by Raf and phosphatidylinositol 3-kinase signaling.
Mutational activation of the K-Ras oncogene is well established as a key genetic step in the development and growth of pancreatic adenocarcinomas. However, the mechanism by which aberrant Ras signaling promotes uncontrolled pancreatic tumor cell growth remains to be fully elucidated. The recent use of primary human cells to study Ras-mediated oncogenesis provides important model cell systems to dissect this mechanism. We have used a model of telomerase-immortalized human pancreatic duct-derived cells (E6/E7/st) to study mechanisms of Ras growth transformation. First, we found that human papillomavirus E6 and E7 oncogenes, which block the function of the p53 and Rb tumor suppressors, respectively, and SV40 small t antigen were required to allow mutant K-Ras(12D) growth transformation. Second, K-Ras(12D) caused growth transformation in vitro, including enhanced growth rate and loss of density dependency for growth, anchorage independence, and invasion through reconstituted basement membrane proteins, and tumorigenic transformation in vivo. Third, we determined that the Raf, phosphatidylinositol 3-kinase (PI3K), and Ral guanine nucleotide exchange factor effector pathways were activated, although extracellular signal-regulated kinase (ERK) activity was not up-regulated persistently. Finally, pharmacologic inhibition of Raf/mitogen-activated protein kinase/ERK and PI3K signaling impaired K-Ras-induced anchorage-independent growth and invasion. In summary, our studies established, characterized, and validated E6/E7/st cells for the study of Ras-induced oncogenesis.
Campbell
Paul M
PM
Lineberger Comprehensive Cancer Center and Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Groehler
Angela L
AL
Lee
Kwang M
KM
Ouellette
Michel M
MM
Khazak
Vladimir
V
Der
Channing J
CJ
D021441:Carcinoma, Pancreatic Ductal / Q000235:genetics / Q000473:pathology*; D002461:Cell Line, Transformed; D002465:Cell Movement / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D011905:Genes, ras / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D009361:Neoplasm Invasiveness; D009856:Oncogene Proteins, Viral / Q000235:genetics; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000473:pathology*; D050725:Papillomavirus E7 Proteins; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012097:Repressor Proteins / Q000235:genetics; D015398:Signal Transduction; D048490:raf Kinases / Q000502:physiology*
D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D012097:Repressor Proteins; D048490:raf Kinases; C068651:E6 protein, Human papillomavirus type 16; C059731:oncogene protein E7, Human papillomavirus type 16