Abstract 5025: Reduced level of protein kinase C iota renders human glioblastoma less invasive and induces apoptosis via modulating Tak1/NF-κB pathway

Abstract

Abstract Glioblastoma (GBM) is characterized by poor therapeutic response and overall survival. It is the most aggressive form of primary brain tumor with a tendency to invade surrounding healthy brain tissues, rendering them largely incurable. In this study, small-interference RNA was used to knock down the expression of protein kinase C PKC-ι. The reduced PKC-ι expression impaired the phosphorylation of LIM kinase 1/2 (LIMK), which is a critical step in cofilin recycling and actin polymerization. Additionally, there was a down-regulation of matrix metalloprotease-9 expression in LN-229 and U87G cells, which coincided with decreased invasion. Therefore, PKC-ι regulates both cytoskeleton rearrangement and cell adhesion, which contributed to cell migration. Silencing of PKC-ι also dampened Transforming growth factor-β (TGF-β)-activated kinase 1 (Tak1) level. TAK1 is an essential component in genotoxic stresses-induced NF-κB-activation and mitogen-activated protein kinase (MAPK)-pathways in GBM. TAK1, when activated, forms a complex with TAB1-3 (Tak1 binding proteins). Our data reveal, reduced Tak1 level after silencing PKC-ι interferes with complex formation and reduces NF-κB-activation. Diminished PKC-ι level also reduces activation of Tak1/JNK axis. This deactivation exerts an anti-oncogenic effect on glioblastoma via suppression of Akt1, c-Myc, and STAT3. This implies PKC-ι may have a crucial role in the activation of Tak1. Reduced migration and invasion in glioblastoma cells upon inhibition of PKC-ι was further confirmed by Scratch assay and Boyden assay. These results indicate that PKC-ι is involved in the control of glioblastoma cell migration and invasion. PKC-ι is a central component of multiple converging and bifurcating pathways and is a potential therapeutic target against GBM survival and infiltration. Citation Format: Khandker Mohammad Khalid, Wishrawana S. Ratnayake, Avijit Dey, Nuzhat N. Oishee, Mahfuza Marzan, Mildred Acevedo-Duncan. Reduced level of protein kinase C iota renders human glioblastoma less invasive and induces apoptosis via modulating Tak1/NF-κB pathway. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5025.