Abstract 7031: The role of atypical protein kinase C (aPKC) in the cellular invasion mechanism of diffuse intrinsic pontine glioma (DIPG) and diffuse midline glioma (DMG) and its regulation by ICA-1S and temozolomide (TMZ) inhibitors

Abstract The DIPG develops in the human brainstem area (pons) and the DMG develops in the region covering the pons, midbrain, and thalamus. Due to their locations, surgical resection is not available and sample collection through biopsy is also limited. Moreover, the lack of knowledge of cell signaling regulations is one of the major challenges in treating these lethal pediatric gliomas. To understand the cellular characteristics like migration and invasion of these gliomas our research focuses on the atypical PKC-ι, which plays a major role in tumorigenesis due to its overexpression directly impacted by phosphoinositide 3-kinase (PI3K), phosphatase and tensin homolog (PTEN) and other pathways. In this ongoing research, we are investigating the role of the aPKC-ι/ζ expression levels in correlation with the malignancy of two incurable pediatric gliomas DIPG (SU-DIPG-IV) and DMG (CNMC-D-1008). The study sheds light on a regulatory connection between the isoenzyme-specific signaling pathway for invasion [PKC-ι /Focal Adhesion Kinase (FAK) / Paxillin] and its inhibition by a potent aPKC inhibitor, ICA-1S (5-Amino-1-[(1R, 2S, 3R, 4R)-2, 3-dihydroxy-4-[(phosphonooxy)methyl]cyclopentyl]-1H-imidazole-4-carboxamide), alone or in combination with Temozolomide (TMZ) in-vitro. In a previous study, we demonstrated that ICA-1S in combination with TMZ decreased the invasion of glioma cell lines by lowering the FAK and paxillin phosphorylation in the PKC-ι/ FAK/ Paxillin pathway. In our current study, we have observed the presence of an immunoprecipitation (IP) complex formation between PKC-ι and FAK indicating the presence of a direct phosphorylation event in SU-DIPG-IV cells during the invasion mechanism. Unlike SU-DIPG-IV, the CNMC-D-1008 cells have shown no such phosphorylation events in the IP experiments. Moreover, the study of the PKC-ι expression level with cellular overgrowth, cell cycle progression, cell migration, apoptosis, and toxicity study of the drugs will also be reported based on different experiments such as western blot, scratch assay, flow cytometry, WST-1 assay, etc. These studies bring insights into cellular processes like invasion and proliferation after the mono/combination therapy of ICA-1S and TMZ in these cell lines. The results presented here shed light on two prospects: that PKC-ι expression level may be established as a biomarker to perform anti-PKC therapy and as an inhibitor of PKC-ι the prospect of ICA-1S as a form of novel personalized treatment for these pediatric gliomas. Citation Format: Radwan Ebna Noor, Nuzhat Nowshin Oishee, Mahfuza Marzan, Javad Nazarian, Mildred Acevedo-Duncan. The role of atypical protein kinase C (aPKC) in the cellular invasion mechanism of diffuse intrinsic pontine glioma (DIPG) and diffuse midline glioma (DMG) and its regulation by ICA-1S and temozolomide (TMZ) inhibitors [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 7031.