Epidermal growth factor induces FoxO1 nuclear exclusion to activate MMP7-mediated metastasis of larynx carcinoma

Abstract

The molecular mechanism underlying cancer invasiveness and metastasis of larynx carcinoma remains elusive. Here we reported a strong correlation between phosphorylated epidermal growth factor receptor (EGFR) and matrix metalloproteinase-7 (MMP7) levels in larynx carcinoma patients. To examine whether a causal link exists, we used a human larynx carcinoma line, Hep-2, to study the molecular basis of EGFR signaling and MMP7 activation. We found that EGF-induced EGFR phosphorylation in Hep-2 cells resulted in activation of MMP7 and, consequently, an increase in cancer invasiveness. An EGFR inhibitor efficiently blocked this EGF-induced activation of MMP7. Moreover, an inhibitor for PI3 kinase (PI3K)/Akt, but not an inhibitor for mitogen-activated protein kinase (MAPK) or an inhibitor for c-Jun N-terminal kinase (JNK), significantly inhibited the EGF-induced activation of MMP7, suggesting that PI3K/Akt signaling cascades may be responsible for EGF-activated MMP7. Further dissection of the pathway revealed that nuclear exclusion of Akt downstream target, FoxO1, was induced by EGF-induced Akt activation and could be inhibited by either the EGFR inhibitor or by the PI3K/Akt inhibitor. Expression of a constitutive nuclear form of FoxO1 significantly inhibited MMP7 activation induced by EGF. Taken together, these findings suggest that EGF/EGFR signaling activates downstream PI3K/Akt to induce FoxO1 nuclear exclusion, which activates MMP7 to promote larynx carcinoma metastasis. Thus, Akt and FoxO1 appear to be promising therapeutic targets for preventing the metastasis of larynx carcinoma.