E-cadherin inhibits tumor cell growth by suppressing PI3K/Akt signaling via β-catenin-Egr1-mediated PTEN expression.

E-cadherin is a cell-cell adhesion protein and tumor suppressor that is silenced in many malignancies. E-cadherin is thought to suppress tumor cell growth by antagonizing β-catenin signaling. However, the role of E-cadherin in ovarian cancer progression is still controversial. In this study, we showed that loss of E-cadherin induced ovarian cancer cell growth and constitutive activation of phosphoinositide 3-kinase (PI3K)/Akt signaling by the inhibition of phosphatase and tensin homolog (PTEN) transcription through the downregulation of early growth response gene 1 (Egr1). In addition, immunofluorescence microscopy and T-cell factor promoter/luciferase reporter assays showed that E-cadherin loss was associated with enhanced nuclear β-catenin signaling. Constitutive activation of PI3K/Akt signaling reinforced nuclear β-catenin signaling by inactivating glycogen synthase kinase-3β indicating cross-talk between the PI3K/Akt and β-catenin signaling pathways. Finally, we found that E-cadherin negatively regulates tumor cell growth, in part, by positively regulating PTEN expression via β-catenin-mediated Egr1 regulation, thus influencing PI3K/Akt signaling. In summary, endogenous E-cadherin inhibits PI3K/Akt signaling by antagonizing β-catenin-Egr1-mediated repression of PTEN expression. Thus, the loss of E-cadherin itself may contribute to dysregulated PI3K/Akt signaling through its effects on PTEN, or it may exacerbate the frequent activation of PI3K/Akt signaling that occurs as a result of overexpression, mutation and/or amplification.