Ras induces NBT-II epithelial cell scattering through the coordinate activities of Rac and MAPK pathways

Area of Science:

• Cell Biology
• Molecular Biology
• Cancer Research

Background:

• Epithelial-mesenchymal transition (EMT) involves cell dissociation and migration.
• Ras signaling is crucial for EGF-induced EMT in NBT-II rat carcinoma cells.

Purpose of the Study:

• To identify Ras downstream targets responsible for cell dissociation and migration during EMT.
• To elucidate the specific roles of Raf/MAPK and Rac pathways in Ras-mediated EMT.

Main Methods:

• Overexpression of activated Ras pathway components (c-Raf, MEK1, PI3K, RalA/B).
• Use of specific inhibitors (PD098059, LY294002) and Ras mutants (RasV12S35, RasV12E38).
• Assessment of cell dissociation via desmosome loss and cell migration using dominant-negative Rac1 (Rac1N17).

Main Results:

• Activated c-Raf and MEK1 induced cell dissociation by disrupting desmosomes.
• MEK1 inhibition blocked EGF- and Ras-induced cell dispersion; PI3K inhibition had no effect.
• Specific Ras mutants targeting Raf induced dissociation, while PI3K/RalGDS mutants did not.
• MEK1 alone did not promote motility, but Ras mutants and Rac activation did.
• Rac1 is essential for EGF-induced cell migration, and its activation correlates with motility.

Conclusions:

• Ras mediates NBT-II cell scattering through coordinated activation of Rac and the Raf/MAPK pathway.
• Distinct Ras effectors regulate cell dissociation (Raf/MAPK) and cell migration (Rac).
• Understanding these pathways is key for targeting EMT in cancer progression.