Par6/SOX2 interact to modulate stemness maintenance in glioma by regulating the EGFR/PI3K/AKT signaling cascade

Glioma stem cells (GSCs) are a primary factor contributing to the failure of glioma treatment and lead to a poor prognosis for patients with glioma. However, the biological functions and mechanisms involved in regulating stemness maintenance in GSCs are not well understood. Here, we investigated the potential regulatory effects of Par6 on stemness maintenance in GSCs. Our data revealed high expression of Par6 in glioma specimens is usually accompanied by a poor prognosis. Further study indicated Par6 expression might be involved in stemness maintenance of GSCs by directly binding to SOX2 in glioma cells. In contrast, the blockade of Par6/SOX2 interaction with a specific inhibitory peptide (Par6i-P1) significantly suppressed the stemness maintenance of GSCs. Gene manipulation results showed the combination of Par6 and SOX2 promoted stemness maintenance in a complementary manner. Mechanistically, we identified PI3K/AKT signaling pathway as a downstream target of EGFR, which is also transcriptionally regulated by SOX2 in glioma cells. Moreover, a clinical study indicated the coexpression of Par6 and SOX2 predicted poor outcomes for glioma patients, suggesting the Par6/SOX2 interaction might trigger the regulation of stemness maintenance through activating EGFR/PI3K/AKT signaling pathway in glioma. Furthermore, comparing with the scrambled peptide control, the tumorigenicity assay and immunohistochemistry indicated that targeting the Par6/SOX2 interaction might effectively mitigate GSC-mediated chemotherapy resistance in temozolomide (TMZ) treatment, and improve the malignancy and prognosis in mice orthotopically transplanted with GBM. Together, these findings reveal a novel mechanism by which the Par6/SOX2 interaction contributes to the maintenance of stemness in GSCs and may serve as a promising therapeutic target for improving the prognosis of glioma patients.