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.[1]References
- Oncogenic K-Ras down-regulates Rac1 and RhoA activity and enhances migration and invasion of pancreatic carcinoma cells through activation of p38. Dreissigacker, U., Mueller, M.S., Unger, M., Siegert, P., Genze, F., Gierschik, P., Giehl, K. Cell. Signal. (2006) [Pubmed]
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