The positive regulatory loop of TCF4N/p65 promotes glioblastoma tumourigenesis and chemosensitivity

Abstract

Background NF‐κB signaling is widely linked to the pathogenesis and treatment resistance in cancers. Increasing attention has been paid to its anti‐oncogenic roles, due to its key functions in cellular senescence and the senescence‐associated secretory phenotype (SASP). Therefore, thoroughly understanding the function and regulation of NF‐κB in cancers is necessary prior to the application of NF‐κB inhibitors. Methods We established glioblastoma (GBM) cell lines expressing ectopic TCF4N, an isoform of the β‐catenin interacting transcription factor TCF7L2, and evaluated its functions in GBM tumorigenesis and chemotherapy in vitro and in vivo. In p65 knock‐out or phosphorylation mimic (S536D) cell lines, the dual role and correlation of TCF4N and NF‐κB signaling in promoting tumorigenesis and chemosensitivity was investigated by in vitro and in vivo functional experiments. RNA‐seq and computational analysis, immunoprecipitation and ubiquitination assay, minigene splicing assay and luciferase reporter assay were performed to identify the underlying mechanism of positive feedback regulation loop between TCF4N and the p65 subunit of NF‐κB. A eukaryotic cell‐penetrating peptide targeting TCF4N, 4N, was used to confirm the therapeutic significance. Results Our results indicated that p65 subunit phosphorylation at Ser 536 (S536) and nuclear accumulation was a promising prognostic marker for GBM, and endowed the dual functions of NF‐κB in promoting tumorigenesis and chemosensitivity. p65 S536 phosphorylation and nuclear stability in GBM was regulated by TCF4N. TCF4N bound p65, induced p65 phosphorylation and nuclear translocation, inhibited its ubiquitination/degradation, and subsequently promoted NF‐κB activity. p65 S536 phosphorylation was essential for TCF4N‐led senescence‐independent SASP, GBM tumorigenesis, tumor stem‐like cell differentiation and chemosensitivity. Activation of p65 was closely connected to alterative splicing of TCF4N, a likely positive feedback regulation loop between TCF4N and p65 in GBM. 4N increased chemosensitivity, highlighting a novel anti‐cancer strategy. Conclusion Our study defined key roles of TCF4N as a novel regulator of NF‐κB through mutual regulation with p65 and provided a new avenue for GBM inhibition.

Suppression of ITPKB degradation by Trim25 confers TMZ resistance in glioblastoma through ROS homeostasis

“…TMZ serves as the primary chemotherapeutic agent for GBM treatment; however, intrinsic or acquired resistance to TMZ significantly limits the efficacy of the drug. 38 Numerous combinations of TMZ with various chemotherapy, immunotherapy, and radiotherapy methods have been investigated to overcome the challenges in GBM treatment. 39 , 40 Despite these efforts, clinically significant benefits from such combinations have yet to be realized, underscoring the need for more understanding of TMZ resistance mechanisms to achieve successful GBM treatment.…”

The Recent Research Progress of NF-κB Signaling on the Proliferation, Migration, Invasion, Immune Escape and Drug Resistance of Glioblastoma

“…Some of the studies here indirectly indicate that the gene regulates GBM cell proliferation through phosphorylation, nuclear translocation, and the stability of p65. For example, TCF4N, an isoform of the β-catenin interacting transcription factor TCF7L2, binds and promotes s536 phosphorylation, nuclear translocation, and the stability of p65, ultimately upregulating the NF-κB target gene in GBM cells [ 63 ]. G protein inhibitory α subunit 2 (Gαi2) increases the expression of the NF-κB target gene Sp1 (a transcription factor) through dephosphorylation of the p65 subunit, and at the same time, Sp1 has been confirmed to bind to the Gαi2 promoter region, mediating Gαi2 overexpression [ 64 ].…”