ζ-Stat inhibits glioblastoma multiforme progression by targeting PKC-ζ/Cx43 signaling and inducing senescence

Glioblastoma multiforme (GBM) is a grade IV astrocytic tumor and the most aggressive form of brain cancer, marked by poor prognosis, complex vascular networks, and genomic heterogeneity. PI3K/AKT (Phosphoinositide 3-kinase/Protein Kinase B) signaling and the atypical protein kinase C isoform PKC-ζ, play essential roles in GBM cell proliferation, migration, and resistance to therapy. In addition, PKC-ζ regulates Connexin 43 (Cx43), a gap junction protein that influences cell communication, cytoskeletal organization, and tumor cell motility. This study investigated the effects of ζ-Stat (8-hydroxy-1,3,6-naphthalenetrisulfonic acid), a selective PKC-ζ inhibitor, on GBM cell lines. Treatment with ζ-Stat significantly reduced proliferation by approximately 40% in T98G cells (80 μM) and 30% in U87MG cells (40 μM) (p ≤ 0.001). Co-immunoprecipitation confirmed a strong association between PKC-ζ and Cx43 in both cell lines. Western blot analysis demonstrated that treatment with ζ-Stat reduced the levels of PKC-ζ and Cx43. As a result of PKC-ζ/Cx43 inhibition, PI3K/AKT signaling was downregulated in T98G cells. In addition, ζ-Stat induced cell cycle arrest, with increased expression of p21, p27, and PTEN, while inducing cellular senescence, as indicated by elevated beta-galactosidase activity. Furthermore, ζ-Stat affected epithelial-mesenchymal transition (EMT), reducing the migratory potential of the cells through inhibition of vimentin expression. These findings highlight ζ-Stat as a promising therapeutic candidate for overcoming chemoresistance and improving treatment outcomes in glioblastoma.