We attempted to identify upstream signaling mechanisms for alcohol activating PAK1 phosphorylation of Snail and Snail mRNA expression. We have previously shown oxidative stress activates EGFR signaling in Caco-2 cells (Forsyth et al., 2007). EGFR signaling can regulate EMT and cancer as well as PAK1 mediated phosphorylation of Snail and stimulation of Snail mRNA expression via ERK1/2 signaling (Barbera et al., 2004, Yang et al., 2005). In Figure 6 the data show alcohol (0.2%, 43 mM) stimulates phosphorylation 5–10 fold of the EGFR and downstream ERK1/2 in both colon cancer (6A) and breast cancer (6B) cells. Alcohol-induced EGFR and ERK1/2 activation was significantly blocked by an EGFR inhibitor, AG1478 (500nM, 85% inhibition), or inhibition of the metalloprotease tumor necrosis factor converting enzyme-TACE (ADAM17) (TAPI-2, 20μM;85% inhibition). This supports the requirement for TACE-EGFR transactivation by alcohol for EGFR and ERK1/2 activation as we have shown for oxidative stress (Forsyth et al., 2007).
