Xiao Han

Background: Glioblastoma (GBM) depends on selenoproteins, yet the mechanisms underlying their dysregulation remain poorly understood. The tRNA-binding protein TRNAU1AP also remains largely uncharacterized, with its mechanistic functions in in vivo tumorigenesis undefined. Additionally, while IGF2BP3 is the most dysregulated N6-methyladenosine (m6A) reader in GBM, the pathways through which it promotes glioblastoma stem cell (GSC) self-renewal have yet to be elucidated. Methods: TRNAU1AP expression in human GBMs and public datasets was analyzed by Western blotting, immunohistochemistry, and gene expression profiling. Functions of TRNAU1AP in GSCs were evaluated through gain- and loss-of-function assays assessing proliferation, self-renewal, and tumorigenicity. Proteomics, spatial transcriptomics, RNA immunoprecipitation, and polysome profiling were employed to investigate TRNAU1AP-mediated regulation of selenoprotein synthesis. RNA immunoprecipitation and phase-separation assays were used to characterize the TRNAU1AP-EEFSEC interaction. Multiomics and RNA stability analyses were performed to elucidate IGF2BP3-dependent regulation of TRNAU1AP expression. Results: TRNAU1AP is essential for the proliferation, stemness, and tumorigenesis of GSCs and is associated with poor patient survival. TRNAU1AP interacts with EEFSEC to form a phase-separated complex that enhances EEFSEC binding to sec-tRNAsec, thereby promoting the translation of several selenoproteins. These selenoproteins act as key effectors mediating the oncogenic functions of TRNAU1AP. Furthermore, IGF2BP3 upregulates TRNAU1AP expression through m6A-dependent transcript stabilization, leading to increased selenoprotein synthesis and enhanced GSC stemness and tumorigenic potential. Conclusion: These findings establish novel oncogenic roles of TRNAU1AP, and reveal that IGF2BP3-TRNAU1AP coupling constitutes an important mechanism for the selenoprotein synthesis and for gliomagenesis, thereby advancing the understanding of RNA-binding proteins in cancer biology.

Expression of PD-1 and secretion of IL-2 by CD3+CD8+ cells

Expression of DC surface markers and P. gingivalis W83-induced PD-L1

Post-translational modifications (PTMs) are critical regulators of protein function and cellular signaling. While histone deacetylation by histone deacetylases (HDACs) is well established, the role of specific HDACs in modulating non-histone protein PTMs, particularly in an infectious context, is poorly understood. Here, we reveal a pivotal role for HDAC6 in orchestrating periodontal inflammation through its dual regulatory effects on FoxO1 acetylation and phosphorylation. Using Porphyromonas gingivalis , a key periodontal pathogen, as a model pathogen, we observed that infection induces HDAC6 activation, driving inflammatory responses via modulating FoxO1 activity. HDAC6 depletion increased FoxO1 acetylation and phosphorylation, leading to its cytoplasmic sequestration and subsequent suppression of FoxO1- mediated pro-inflammatory cytokine production in macrophages. Mechanistically, HDAC6 deficiency not only directly enhances the acetylation of FoxO1 but also upregulates the expression of Rictor, a critical component of the mTORC2 complex, thereby promoting Akt phosphorylation and subsequently FoxO1 phosphorylation. This results in its cytoplasmic retention and attenuated inflammatory transcriptional activity. Functional studies demonstrated that HDAC6 depletion suppressed the production of key inflammatory mediators, including TNFα, IL-6, IL-12p40, and MIP-2, while promoting macrophage polarization toward anti-inflammatory M2 phenotypes. In vivo , using oral gavage infection and ligature-induced mouse periodontitis models, HDAC6 deficiency significantly reduced inflammatory cell infiltration in gingival tissues and protected against alveolar bone loss. These findings establish HDAC6 as a central regulator of periodontal inflammation, acting through the coordinated modulation of FoxO1 acetylation and phosphorylation. Beyond its role in oral pathology, HDAC6 may serve as a promising therapeutic target for managing inflammatory diseases linked to immune dysregulation.

Expression of DC surface markers and P. gingivalis W83-induced PD-L1

Expression of PD-1 and secretion of IL-2 by CD3+CD8+ cells

Expression of DC surface markers and P. gingivalis W83-induced PD-L1

Accumulating evidence shows that PD-L1 expression on dendritic cells (DC) is critical for cancer immunotherapy and that Porphyromonas gingivalis (Pg) colonization aggravates the progression of upper gastrointestinal cancers. However, the effects of Pg infection on PD-L1 expression on DCs and related immune consequences in the infection milieu of oral cancer remain unexplored. Here, we found that Pg infection robustly enhanced PD-L1 expression on DCs in a gingipain-dependent manner in cultured cell and systemic infection assays. Pg infection suppressed antigen-specific CD8+ T cells through upregulation of PD-L1 expression on ovalbumin (OVA)-pulsed DCs. This suppression was manifested by decreased IFNγ, perforin, granzyme B, and CD107a. Further analysis showed that Pg drastically reduced CD8+ T cells’ ability to lyse OVA-pulsed target cells. Additionally, Pg infection increased the phosphorylation of Akt and STAT3, leading to a significant increase in PD-L1 expression. This was substantiated by using siRNA, overexpression plasmids, and pharmacologic inhibitors. Consistent with the in vitro observations, in a syngeneic mouse oral cancer model, Pg infection significantly enhanced PD-L1 expression on DCs from intratumoral tissues and cervical lymph nodes and exacerbated oral cancer progression, whereas a Pg lysine-specific, gingipain-defective mutant failed to do so. These influences of Pg were largely diminished when tumor cells were pretreated with antibiotics or a STAT3 inhibitor. Therefore, we demonstrated that Pg infection upregulates PD-L1 expression on DCs through Akt-STAT3 signaling, suppresses CD8+ T-cell cytotoxicity, and aggravates oral cancer growth, suggesting targeting Pg, and/or its mediated signaling, could be a therapeutic strategy to improve the efficacy of checkpoint blockade immunotherapy.

Accumulating evidence shows that PD-L1 expression on dendritic cells (DC) is critical for cancer immunotherapy and that Porphyromonas gingivalis (Pg) colonization aggravates the progression of upper gastrointestinal cancers. However, the effects of Pg infection on PD-L1 expression on DCs and related immune consequences in the infection milieu of oral cancer remain unexplored. Here, we found that Pg infection robustly enhanced PD-L1 expression on DCs in a gingipain-dependent manner in cultured cell and systemic infection assays. Pg infection suppressed antigen-specific CD8+ T cells through upregulation of PD-L1 expression on ovalbumin (OVA)-pulsed DCs. This suppression was manifested by decreased IFNγ, perforin, granzyme B, and CD107a. Further analysis showed that Pg drastically reduced CD8+ T cells’ ability to lyse OVA-pulsed target cells. Additionally, Pg infection increased the phosphorylation of Akt and STAT3, leading to a significant increase in PD-L1 expression. This was substantiated by using siRNA, overexpression plasmids, and pharmacologic inhibitors. Consistent with the in vitro observations, in a syngeneic mouse oral cancer model, Pg infection significantly enhanced PD-L1 expression on DCs from intratumoral tissues and cervical lymph nodes and exacerbated oral cancer progression, whereas a Pg lysine-specific, gingipain-defective mutant failed to do so. These influences of Pg were largely diminished when tumor cells were pretreated with antibiotics or a STAT3 inhibitor. Therefore, we demonstrated that Pg infection upregulates PD-L1 expression on DCs through Akt-STAT3 signaling, suppresses CD8+ T-cell cytotoxicity, and aggravates oral cancer growth, suggesting targeting Pg, and/or its mediated signaling, could be a therapeutic strategy to improve the efficacy of checkpoint blockade immunotherapy.

Expression of PD-1 and secretion of IL-2 by CD3+CD8+ cells