Abstract 1672: PKC-ι and 14-3-3 are crucial regulators of c-Raf and the Erk pathway in human medulloblastoma

Abstract Medulloblastoma is the second most common childhood cancer, behind leukemia, and the most common pediatric brain tumor, comprising 20% of all childhood brain cancers. Current treatment options are limited to radiation therapy, surgical resection, and chemotherapy, which are extremely invasive. This underscores the need for more targeted and effective therapeutic treatments to improve patient outcomes. The following study will focus on exploring the PKC-ι specific inhibitor 5-amino-1- ( (1R, 2S, 3S, 4R) -2, 3-dihydroxy-4-methylcyclopentyl) -1H-imidazole-4-carboxamide (ICA-1S) and its effects on medulloblastoma cell lines Daoy and ONS-76. Our in-vitro treatments showed that PKC-ι functions an oncogenic protein that is necessary for Daoy and ONS-76 cell proliferation and that ICA-1S was found to be cytostatic to both Daoy and ONS-76 cells. The inhibition of PKC-ι in both cell lines resulted in a decreased phosphorylation of PKC-ι as well as downregulation of 14-3-3 and crucial components of the c-Raf/Erk pathway including total and phosphorylated levels of c-Raf, Mek1/2, and Erk1/2. This comes as a result of ICA-1S blocking the association of PKC-ι with 14-3-3 while PKC-ι and c-Raf were not found to directly associate with each other, indicating indirect modulation of c-Raf by PKC-ι. Additionally, PKC-ι inhibition decreased its association with Stat3. Expression levels of Stat1, Stat3, c-Fos, and c-Myc transcription factors were significantly downregulated, which is likely the result of reduced transcriptional activation due to upstream inhibition of PKC-ι and Erk signaling. Treatment with ICA-1S was also shown to substantially decrease cellular invasion of Daoy and ONS-76 cells and induce apoptosis. Taken together, these data suggest that PKC-ι likely plays a critical role in the regulation of the c-Raf/Erk pathway, which controls the proliferation and invasion of human medulloblastoma. Citation Format: Luke Lajmi, Wishrawana S. Ratnayake, Joseph Palathinkal, Sloan Breedy, Aaron Todman, Mildred Acevedo-Duncan. PKC-ι and 14-3-3 are crucial regulators of c-Raf and the Erk pathway in human medulloblastoma 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 1672.