Abstract 4382: PKC-ι/ζ signaling is crucial for apoptosis/pyroptosis inhibition and invasiveness of glioblastoma cells through upregulation of β-catenin, PDK1/Akt1 and Smad cascades via 14-3-3

Abstract Glioblastoma (GB) is an aggressive form of brain cancer derived from astrocytes. Poor predictability of patient outcomes has limited the development of current therapeutic treatments of GB mainly due to the development of drug resistance. Comparative over-expression of atypical protein kinase C-iota and zeta (aPKC-ι/ζ) in GB cells and tissue samples were previously reported. This study establishes the downstream effects of PKC-ι/ζ attenuation on key cellular signaling which governs apoptosis, pyroptosis, survival, proliferation and epithelial-mesenchymal transition (EMT). Our data suggested that aPKC knockdown of expression induces apoptosis and works as an antecedent of pyroptosis. Data also suggested that involvement of Akt1 and PDK1 in aPKC maturation process weakened due to aPKC attenuation. aPKC attenuation downregulated Ras/Erk1 and canonical β-catenin pathways which resulted in reduced transcriptional activities of Stat3, c-Myc, c-Jun and β-catenin. In addition SNAIL1, SLUG, and PRRX1 were diminished that have been known to stimulate EMT. Proteins 14-3-3 and Smad2/3 acted as molecular adaptors between these pathways. A PKC-ι specific inhibitor 5-amino-1- (2, 3-dihydroxy-4- (hydroxymethyl) cyclopentyl) -1H-imidazole-4-carboxamide (ICA-1S) and a PKC-ζ specific inhibitor 8-hydroxy-1, 3, 6-naphthalenetrisulfonic acid (ζ-Stat) were used to conduct in-vivo experiments using mouse models. Intravenous and oral administration of ICA-1S resulted in the reduction of tumor growth by approximately 30% in athymic nude mice for U-87 xenografts. Taken together, these results suggest that not only do aPKCs play a central role in GB progression, invasiveness, and cell survival, but that effective therapeutics can be developed to specifically target oncogenic aPKCs. Citation Format: Luke Lajmi, Wishrawana S. Ratnayake, Khandker M. Khalid, Sloan Breedy, Aaron Todman, Tracess Smalley, Christopher A. Apostolatos, Robert Hill, Mildred Acevedo-Duncan. PKC-ι/ζ signaling is crucial for apoptosis/pyroptosis inhibition and invasiveness of glioblastoma cells through upregulation of β-catenin, PDK1/Akt1 and Smad cascades via 14-3-3 abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 4382.