Oncogenic K-Ras down-regulates Rac1 and RhoA activity and enhances migration and invasion of pancreatic carcinoma cells through activation of p38.
Activating mutations in the K-ras gene are genetic alterations frequently found in human carcinomas, particularly in pancreatic adenocarcinomas. Mutation of the K-ras gene is thought to be an early and important event in pancreatic tumor initiation, but the precise role of the mutant K-Ras proteins in neoplastic progression is still unknown. In the present study, we have characterized the influence of oncogenic K-Ras on the phenotype and on the signal transduction of epitheloid PANC-1 pancreatic carcinoma cells by generating PANC-1 cell clones, which stably express EGFP(enhanced green fluorescent protein)-K-Ras (V12). EGFP-K-Ras (V12)-expressing cells exhibited a more fibroblastoid cellular phenotype with irregular cell shape and disorganized cytokeratin filaments. Moreover, these cells showed a marked enhancement of their migratory and invasive properties. Stable expression of EGFP-K-Ras (V12) down-regulated the activity of Rac1 and RhoA, resulting in reduced subcortical actin filaments and stress fibers, which might contribute to the epithelial dedifferentiation. Characterization of the activity of mitogen-activated protein kinases revealed that EGFP-K-Ras (V12) enhanced the activity of p38, but did not affect the activities of the Raf/MEK/ERK cascade and JNK. While inhibition of either MEK or JNK activity had no effect on EGFP-K-Ras (V12)-induced migration, inhibition of p38 activity markedly reduced EGFP-K-Ras (V12)-induced migration. Collectively, the results suggest that oncogenic K-Ras enhances the malignant phenotype and identify the mitogen-activated protein kinase p38 as a target to inhibit oncogenic K-Ras-induced pancreatic tumor cell migration.
Dreissigacker
Ute
U
Department of Pharmacology and Toxicology, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
Mueller
Meike S
MS
Unger
Monika
M
Siegert
Patrizia
P
Genze
Felicitas
F
Gierschik
Peter
P
Giehl
Klaudia
K
D000818:Animals; D002465:Cell Movement; D002645:Chickens; D003599:Cytoskeleton / Q000473:pathology; D015536:Down-Regulation / Q000235:genetics*; D004789:Enzyme Activation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000473:pathology*; D021381:Protein Transport; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D015689:Oncogene Protein p21(ras); D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein