Abstract 6963: The impact of aPKC inhibitors on PKC-ι/ζ; and connexin 43 in glioblastoma multiforme

Abstract Glioblastoma multiforme (GBM) is the most aggressive brain cancer in adults, arising from astrocytes. Its treatment is complicated by the blood-brain barrier, tumor infiltration, and genetic diversity, highlighting the urgent need for novel therapies. Our research group focuses on understanding the impact of ICA-S((-Amino-1-[(1R, 2S, 3R, 4R)-2, 3-dihydroxy-4-[(phosphonooxy)methyl]cyclopentyl]-1H-imidazole-4-carboxamide), an atypical inhibitor of PKC-ι, and ζ ;-Stat (8-hydroxy-1, 3, 6-naphthalenetrisulfonic acid) inhibitor of PKC- ζ ; on GBM proliferation and invasion, as well as their effects on Connexin 43 (Cx43). PKC-ι / ζ ; plays a crucial role in GBM tumorigenesis by regulating cell proliferation and invasion. Its overexpression is directly influenced by phosphoinositide 3-kinase (PI3K). PKC-ι/ ζ ; and its upstream regulator, Src tyrosine kinase, regulate Cx 43, a gap junction protein that facilitates communication between astrocytic cancer cells and surrounding normal cells, thereby promoting cancer progression. The effects of aPKC inhibitors were assessed through proliferation assays on glioblastoma cell lines T98G and U87MG, revealing the impressive efficacy of both ICA-1S and ζ ;-Stat. ICA-1S achieved a statistically significant 50% reduction in T98G cell proliferation (p <0.001), while ζ ;-Stat resulted in a decrease of approximately 40% in proliferation within T98G cells (p< 0.001). Furthermore, ICA-1S also achieved around 40% reduction in proliferation in the U87 cell line (p< 0.001). Co-immunoprecipitation experiments provided evidence of the association between PKC-ι and Cx 43, as well as between PKC-ζ and Cx 43, in both cell lines. This suggests a direct interaction between these proteins, demonstrating their potential role in mediating cellular signaling and communication in GBM. Western blot analysis showed that ICA-1S downregulated PKC-ι and Cx43, while ζ ;-Stat downregulated PKC-ζ and its phosphorylation of Cx43, impacting the PI3K/AKT pathway. Immunofluorescence Analysis of T98G cells showed decreased Cx43 distribution following treatment, suggesting potential disruption of cell communication. Further analysis will investigate the effects of ICA-1S and ζ-Stat on the U87MG cell line, specifically examining the PI3K/AKT pathway using western blotting and immunofluorescence. Moreover, High-Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS) will be essential for identifying phosphorylation sites directly impacted by aPKCs and Src in Cx 43. These innovative therapeutic strategies hold promise for overcoming chemical resistance challenges and may enhance patient survival outcomes. Citation Format: Grazielly Caroline Teodoro, Mildred Acevedo-Duncan. The impact of aPKC inhibitors on PKC-ι/ ζ ; and connexin 43 in glioblastoma multiforme [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6963.