Par6 Enhances Glioma Invasion by Activating MEK/ERK Pathway Through a LIN28/let-7d Positive Feedback Loop

The invasion of glioblastoma usually results in the recurrence and poor prognosis in patients with glioma. However, the underlying mechanisms involved in glioma invasion remains undefined. In this study, immunohistochemistry analyses of glioma specimens demonstrated that high expression of Par6 was positively correlated with malignancy and poor prognosis of patients with glioma. Par6-overexpressing glioma cells showed much more fibroblast-like morphology, suggesting that regulation of Par6 expression might be associated with tumor invasion in glioma cells. Further study indicated that Par6 overexpression subsequently increased CD44 and N-cadherin expression to enhance glioma invasion through activating MEK/ERK/STAT3 pathway, in vivo and in vitro. Moreover, we found that LIN28/let-7d axis was involved in this process via a positive feedback loop, suggesting that MEK/ERK/LIN28/let-7d/STAT3 cascade might be essential for Par6-mediated glioma invasion. Therefore, these data highlight the roles of Par6 in glioma invasion, and Par6 may serve as a potential therapeutic target for patients with glioma.