TM4SF19 controls GABP-dependent YAP transcription in head and neck cancer under oxidative stress conditions.

Tobacco and alcohol are risk factors for human papillomavirus-negative head and neck squamous cell carcinoma (HPV- HNSCC), which arises from the mucosal epithelium of the upper aerodigestive tract. Notably, despite the mutagenic potential of smoking, HPV- HNSCC exhibits a low mutational load directly attributed to smoking, which implies an undefined role of smoking in HPV- HNSCC. Elevated YAP (Yes-associated protein) mRNA is prevalent in HPV- HNSCC, irrespective of the YAP gene amplification status, and the mechanism behind this upregulation remains elusive. Here, we report that oxidative stress, induced by major risk factors for HPV- HNSCC such as tobacco and alcohol, promotes YAP transcription via TM4SF19 (transmembrane 4 L six family member 19). TM4SF19 modulates YAP transcription by interacting with the GABP (Guanine and adenine-binding protein) transcription factor complex. Mechanistically, oxidative stress induces TM4SF19 dimerization and topology inversion in the endoplasmic reticulum membrane, which in turn protects the GABPß1 subunit from proteasomal degradation. Conversely, depletion of TM4SF19 impairs the survival, proliferation, and migration of HPV- HNSCC cells, highlighting the potential therapeutic relevance of targeting TM4SF19. Our findings reveal the roles of the key risk factors of HPV- HNSCC in tumor development via oxidative stress, offering implications for upcoming therapeutic approaches in HPV- HNSCC.

The competitive mechanism of EZH1 and EZH2 in promoting oral squamous cell carcinoma.

Enhancer of Zeste Homolog 1 (EZH1) and Enhancer of Zeste Homolog 2 (EZH2) are the key components of polycomb repressive complex 2 (PRC2); however, the roles of these proteins in oral squamous cell carcinoma (OSCC) have yet to be elucidated. In this study, we aimed to determine the respective roles of these proteins in OSCC by investigating the expression levels of EZH1 and EZH2 in OSCC tissues (N = 63) by immunohistochemistry. In addition, we used lentiviruses to construct stable OSCC cell lines that overexpressed EZH1 and EZH2. Then, we investigated these cell lines for cell viability, colony formation capacity, stemness, and epithelial-mesenchymal transition (EMT). Binding competition between EZH1 and EZH2 with PRC2 was further evaluated using Co-immunoprecipitation (Co-IP). Compared with normal tissues, the expression levels of EZH2 in OSCC tissues was up-regulated, while the expression of EZH1 was down-regulated. EZH2 enhanced cell viability, colony formation capacity, stemness, and EMT, while EZH1 did not. Furthermore, analysis indicated that EZH1 and EZH2 bound competitively to PRC2 and influenced the methylation status of H3K27. In conclusion, our findings verified that EZH1 and EZH2 play opposing roles in OSCC and that EZH1 and EZH2 compete as the key component of PRC2, thus affecting the characteristics of OSCC via the methylation of H3K27.

CLSPN actives Wnt/ß-catenin signaling to facilitate glycolysis and cell proliferation in oral squamous cell carcinoma.

OBJECTIVE: Oral squamous cell carcinoma (OSCC) is a common malignancy with a poor prognosis. This study aimed to determine the influence and underlying mechanisms of CLSPN on OSCC. METHODS: CLSPN expression was tested using quantitative real-time polymerase chain reaction, immunohistochemistry, and western blotting. Flow cytometry, cell counting kit, and colony formation assays were performed to determine OSCC cell apoptosis, viability, and proliferation, respectively. In OSCC cells, the extracellular acidification rate (ECAR), oxygen consumption rate (OCR), glucose uptake, and lactate production were determined using the corresponding kits. Changes in the protein levels of HK2, PKM2, LDHA, Wnt3a, and ß-catenin were assessed using western blotting. RESULTS: CLSPN expression was increased in OSCC tissues. Overexpression of CLSPN in HSC-2 cells promoted cell proliferation, increased the levels of ECAR, glucose uptake, and lactate production, and increased the protein levels of HK2, PKM2, LDHA, Wnt3a, and ß-catenin, but inhibited OCR levels and apoptosis. The knockdown of CLSPN in CAL27 cells resulted in the opposite results. Moreover, the effects of CLSPN overexpression on glycolysis and OSCC cell proliferation were reversed by Wnt3a knockdown. In vivo, knockdown of CLSPN restrained tumor growth, glycolysis, and the activation of Wnt/ß-catenin signaling. CONCLUSION: CLSPN promoted glycolysis and OSCC cell proliferation, and reduced apoptosis, which was achieved by the activation of Wnt/ß-catenin signaling pathway.

Hellebrigenin induces oral cancer cell apoptosis by modulating MAPK signalling and XIAP expression.

Oral squamous cell carcinoma (OSCC), which accounts for 90% of all oral cancers, has become a public health crisis worldwide. despite advances in therapeutic interventions, the prognosis remains poor for advanced-stage OSCC. In this study, we investigate the anticancer activity and the mode of action of hellebrigenin in human OSCC. The findings demonstrated that hellebrigenin exerted cytotoxic effects in OSCC cells through cell cycle arrest at the G2/M phase and downregulation of cell cycle-related proteins (cyclins A2, B1 and D3, Cdc2, CDK4 and CDK6). Moreover, hellebrigenin caused activation of PARP and caspase 3, 8 and 9, followed by downregulation of antiapoptotic proteins (Bcl-2 and Bcl-xL) and upregulation of pro-apoptotic proteins (Bax and Bak). The hellebrigenin treatment also increased Fas, DR5, DcR2 and DcR3 expressions in oral cancer cells, indicating the compound causes oral cancer cell apoptosis through both intrinsic and extrinsic pathways. Regarding upstream signalling, hellebrigenin was found to reduce the phosphorylation of ERK, p38, and JNK, indicating that hellebrigenin triggers caspase-mediated apoptosis by downregulating MAPK signalling pathway. Finally, the human apoptosis array findings revealed that hellebrigenin specifically suppressed the expression of XIAP to execute its pro-apoptotic activities. Taken together, the study suggests that hellebrigenin can act as a potent anticancer compound in human OSCC.

Unravelling the heterogeneity of oral squamous cell carcinoma by integrative analysis of single-cell and bulk transcriptome data.

Oral squamous cell carcinoma (OSCC) is a prevalent malignancy of the head and neck with rising global incidence. Despite advances in treatment modalities, OSCC prognosis remains diverse due to the complex molecular and cellular heterogeneity within tumours, as well as the heterogeneity in tumour microenvironment (TME). In this study, we utilized single-cell RNA sequencing (scRNA-seq) analysis to explore distinct subpopulations of tumour cells in OSCC tissues and their interaction with components in TME. We identified four major tumour cell subpopulations (C0, C1, C2 and C3) with unique molecular characteristics and functional features. Pathway enrichment analysis revealed that C0 primarily expressed genes involved in extracellular matrix interactions and C1 showed higher proliferation levels, suggesting that the two cell subpopulations exhibited tumour aggressiveness. Conversely, C2 and C3 displayed features associated with keratinization and cornified envelope formation. Accordingly, C0 and C1 subpopulations were associated with shorter overall and disease-free survival times, while C2 and C3 were weakly correlated with longer survival. Genomic analysis showed that C1 demonstrated a positive correlation with tumour mutation burden. Furthermore, C0 exhibited resistant to cisplatin treatment, while C1 showed more sensitive to cisplatin treatment, indicating that C0 might exhibit more aggressive compared to C1. Additionally, C0 had a higher level of communication with fibroblasts and endothelial cells in TME via integrin-MAPK signalling, suggesting that the function of C0 was maintained by that pathway. In summary, this study provided critical insights into the molecular and cellular heterogeneity of OSCC, with potential implications for prognosis prediction and personalized therapeutic approaches.

Up-regulation of TNF-alpha/NFkB/SIRT1 axis drives aggressiveness and cancer stem cells accumulation in chemoresistant oral squamous cell carcinoma.

Tumor resistance remains an obstacle to successfully treating oral squamous cell carcinoma (OSCC). Cisplatin is widely used as a cytotoxic drug to treat solid tumors, including advanced OSCC, but with low efficacy due to chemoresistance. Therefore, identifying the pathways that contribute to chemoresistance may show new possibilities for improving the treatment. This work explored the role of the tumor necrosis factor-alpha (TNF-alpha)/NFkB signaling in driving the cisplatin resistance of OSCC and its potential as a pharmacological target to overcome chemoresistance. Differential accessibility analysis demonstrated the enrichment of opened chromatin regions in members of the TNF-alpha/NFkB signaling pathway, and RNA-Seq confirmed the upregulation of TNF-alpha/NFkB signaling in cisplatin-resistant cell lines. NFkB was accumulated in cisplatin-resistant cell lines and in cancer stem cells (CSC), and the administration of TNF-alpha increased the CSC, suggesting that TNF-alpha/NFkB signaling is involved in the accumulation of CSC. TNF-alpha stimulation also increased the histone deacetylases HDAC1 and SIRT1. Cisplatin-resistant cell lines were sensitive to the pharmacological inhibition of NFkB, and low doses of the NFkB inhibitors, CBL0137, and emetine, efficiently reduced the CSC and the levels of SIRT1, increasing histone acetylation. The NFkB inhibitors decreased stemness potential, clonogenicity, migration, and invasion of cisplatin-resistant cell lines. The administration of the emetine significantly reduced the tumor growth of cisplatin-resistant xenograft models, decreasing NFkB and SIRT1, increasing histone acetylation, and decreasing CSC. TNF-alpha/NFkB/SIRT1 signaling regulates the epigenetic machinery by modulating histone acetylation, CSC, and aggressiveness of cisplatin-resistant OSCC and the NFkB inhibition is a potential strategy to treat chemoresistant OSCC.

2α, 3α, 24-Thrihydroxyurs-12-en-24-ursolic acid enhances the cytotoxic effect of cisplatin on oral cancer cells by down-regulating autophagy.

This study aimed to investigate the effect and mechanism of 2α, 3α, 24-thrihydroxyurs-12-en-24-ursolic acid (TEOA) alone or in combination with cisplatin on oral cancer. TEOA, a pentacyclic triterpenoid compound isolated from the roots of Actinidia eriantha, has demonstrated antitumor activity in preclinical experiments. However, its role in oral cancer remains poorly understood. Our findings revealed that a low concentration of TEOA did not exhibit significant cytotoxicity against oral squamous cell carcinoma cells. However, when combined with cisplatin, TEOA showed a significant therapeutic effect. The combined treatments resulted in a significant inhibition of proliferation and migration and a significant increase in apoptosis of squamous cell carcinoma cells. Cisplatin exposure increased autophagy levels, which may contribute to chemoresistance. Of note, the presence of TEOA significantly inhibited cisplatin-induced autophagy, leading to improved chemotherapy efficacy. Our findings indicate that a mild low dosage of TEOA may enhance the cytotoxic effect of cisplatin by downregulating autophagy in oral cancer cells.

DNMT1-targeting remodeling global DNA hypomethylation for enhanced tumor suppression and circumvented toxicity in oral squamous cell carcinoma.

BACKGROUND: The faithful maintenance of DNA methylation homeostasis indispensably requires DNA methyltransferase 1 (DNMT1) in cancer progression. We previously identified DNMT1 as a potential candidate target for oral squamous cell carcinoma (OSCC). However, how the DNMT1- associated global DNA methylation is exploited to regulate OSCC remains unclear. METHODS: The shRNA-specific DNMT1 knockdown was employed to target DNMT1 on oral cancer cells in vitro, as was the use of DNMT1 inhibitors. A xenografted OSCC mouse model was established to determine the effect on tumor suppression. High-throughput microarrays of DNA methylation, bulk and single-cell RNA sequencing analysis, multiplex immunohistochemistry, functional sphere formation and protein immunoblotting were utilized to explore the molecular mechanism involved. Analysis of human samples revealed associations between DNMT1 expression, global DNA methylation and collaborative molecular signaling with oral malignant transformation. RESULTS: We investigated DNMT1 expression boosted steadily during oral malignant transformation in human samples, and its inhibition considerably minimized the tumorigenicity in vitro and in a xenografted OSCC model. DNMT1 overexpression was accompanied by the accumulation of cancer-specific DNA hypomethylation during oral carcinogenesis; conversely, DNMT1 knockdown caused atypically extensive genome-wide DNA hypomethylation in cancer cells and xenografted tumors. This novel DNMT1-remodeled DNA hypomethylation pattern hampered the dual activation of PI3K-AKT and CDK2-Rb and inactivated GSK3ß collaboratively. When treating OSCC mice, targeting DNMT1 achieved greater anticancer efficacy than the PI3K inhibitor, and reduced the toxicity of blood glucose changes caused by the PI3K inhibitor or combination of PI3K and CDK inhibitors as well as adverse insulin feedback. CONCLUSIONS: Targeting DNMT1 remodels a novel global DNA hypomethylation pattern to facilitate anticancer efficacy and minimize potential toxic effects via balanced signaling synergia. Our study suggests DNMT1 is a crucial gatekeeper regarding OSCC destiny and treatment outcome.

Isocorydine Exerts Anticancer Activity by Disrupting the Energy Metabolism and Filamentous Actin Structures of Oral Squamous Carcinoma Cells.

Isocorydine (ICD) exhibits strong antitumor effects on numerous human cell lines. However, the anticancer activity of ICD against oral squamous cell carcinoma (OSCC) has not been reported. The anticancer activity, migration and invasion ability, and changes in the cytoskeleton morphology and mechanical properties of ICD in OSCC were determined. Changes in the contents of reactive oxygen species (ROS), the mitochondrial membrane potential (MMP), ATP, and mitochondrial respiratory chain complex enzymes Ⅰ-Ⅳ in cancer cells were studied. ICD significantly inhibited the proliferation of oral tongue squamous cells (Cal-27), with an IC50 of 0.61 mM after 24 h of treatment. The invasion, migration, and adhesion of cancer cells were decreased, and cytoskeletal actin was deformed and depolymerized. In comparison to an untreated group, the activities of mitochondrial respiratory chain complex enzymes I-IV were significantly decreased by 50.72%, 27.39%, 77.27%, and 73.89%, respectively. The ROS production increased, the MMP decreased by 43.65%, and the ATP content decreased to 17.1 ± 0.001 (mmol/mL); ultimately, the apoptosis rate of cancer cells increased up to 10.57% after 24 h of action. These findings suggest that ICD exerted an obvious anticancer activity against OSCC and may inhibit Cal-27 proliferation and growth by causing mitochondrial dysfunction and interrupting cellular energy.

Investigating Cox-2 and EGFR as Biomarkers in Canine Oral Squamous Cell Carcinoma: Implications for Diagnosis and Therapy.

Oral squamous cell carcinoma (OSCC) is a common and highly aggressive dog tumor known for its local invasiveness and metastatic potential. Understanding the molecular mechanisms driving the development and progression of OSCC is crucial for improving diagnostic and therapeutic strategies. Additionally, spontaneous oral squamous cell carcinomas in dogs are an excellent model for studying human counterparts. In this study, we aimed to investigate the significance of two key molecular components, Cox-2 and EGFR, in canine OSCC. We examined 34 tumor sections from various dog breeds to assess the immunoexpression of Cox-2 and EGFR. Our findings revealed that Cox-2 was highly expressed in 70.6% of cases, while EGFR overexpression was observed in 44.1%. Cox-2 overexpression showed association with histological grade of malignancy (HGM) (p = 0.006) and EGFR with vascular invasion (p = 0.006). COX-2 and EGFR concurrent expression was associated with HGM (p = 0.002), as well as with the presence of vascular invasion (p = 0.002). These data suggest that Cox-2 and EGFR could be promising biomarkers and potential therapeutic targets, opening avenues for developing novel treatment strategies for dogs affected by OSCC. Further studies are warranted to delve deeper into these findings and translate them into clinical practice.

Enhanced lipid biosynthesis in oral squamous cell carcinoma cancer-associated fibroblasts contributes to tumor progression: Role of IL8/AKT/p-ACLY axis.

Lipid metabolic reprogramming of tumor cells has been proven to play a critical role in tumor initiation and development. However, lipid metabolism in cancer-associated fibroblasts (CAFs) has rarely been studied, particularly in CAFs of oral squamous cell carcinoma (OSCC). Additionally, the molecular mechanism by which tumor cells regulate lipid metabolism in fibroblasts is unclear. In this study, we found that phosphorylated ATP citrate lyase (p-ACLY), a key lipid metabolic enzyme, was upregulated in OSCC CAFs. Compared to paracancerous normal fibroblasts, CAFs showed enhanced lipid synthesis, such as elevated cytosolic acetyl-CoA level and accumulation of lipid droplets. Conversely, reduction of p-ACLY level blocked this biological process. In addition, blocking lipid synthesis in CAFs or inhibiting fatty acid uptake by OSCC cells reduced the promotive effects of CAFs on OSCC cell proliferation, invasion, and migration. These findings suggested that CAFs are one of lipid sources required for OSCC progression. Mechanistically, AKT signaling activation was involved in the upregulation of p-ACLY level and lipid synthesis in CAFs. Interleukin-8 (IL8), an exocrine cytokine of OSCC cells, could activate AKT and then phosphorylate ACLY in fibroblasts. This study suggested that the IL8/AKT/p-ACLY axis could be considered as a potential target for OSCC treatment.

CD271 mRNA/hnRNPA2B1 complex promotes proliferation and stemness in oral and head and neck squamous cell carcinoma.

RNAs, such as noncoding RNA, microRNA, and recently mRNA, have been recognized as signal transduction molecules. CD271, also known as nerve growth factor receptor, has a critical role in cancer, although the precise mechanism is still unclear. Here, we show that CD271 mRNA, but not CD271 protein, facilitates spheroid cell proliferation. We established CD271-/- cells lacking both mRNA and protein of CD271, as well as CD271 protein knockout cells lacking only CD271 protein, from hypopharyngeal and oral squamous cell carcinoma lines. Sphere formation was reduced in CD271-/- cells but not in CD271 protein knockout cells. Mutated CD271 mRNA, which is not translated to a protein, promoted sphere formation. CD271 mRNA bound to hnRNPA2B1 protein at the 3'-UTR region, and the inhibition of this interaction reduced sphere formation. In surgical specimens, the CD271 mRNA/protein expression ratio was higher in the cancerous area than in the noncancerous area. These data suggest CD271 mRNA has dual functions, encompassing protein-coding and noncoding roles, with its noncoding RNA function being predominant in oral and head and neck squamous cell carcinoma.

Guanylate binding protein 5 triggers NF-κB activation to foster radioresistance, metastatic progression and PD-L1 expression in oral squamous cell carcinoma.

Radioresistance and metastasis are critical issues in managing oral squamous cell carcinoma (OSCC). Although immune checkpoint inhibitors (ICIs) has been recommended to treat OSCC, lacking useful biomarkers limited their anti-cancer effectiveness. We found that guanylate binding protein 5 (GBP5) is upregulated in primary tumors and associates with radioresistance in OSCC. GBP5 expression causally associated with cellular radioresistance and migration ability in the OSCC cell variants. GBP5 upregulation was examined to be correlated with NF-κB activation and programmed cell death-ligand 1 (PD-L1) elevation in OSCC samples. GBP5 knockdown was mitigated, but overexpression enhanced, NF-κB activity and PD-L1 expression in the OSCC cells. NF-κB inhibition by SN50 dramatically suppressed the GBP5-forested irradiation resistance, cellular migration ability and PD-L1 expression in OSCC cells. Importantly, GBP5 upregulation predicted a favorable outcome in cancer patients received ICI treatment. Our findings provide GBP5 as a useful biomarker to predict the anti-OSCC effectiveness of irradiation and ICIs.

Bioinformatics analysis of the prognosis and biological significance of N6 methyladenine regulators in oral squamous cell carcinoma.

BACKGROUND: Oral squamous cell carcinoma (OSCC) is a common type of cancer. We performed the present study to explore the function and specific regulatory mechanism of m6A in OSCC and to find a new diagnosis and treatment strategy for OSCC. METHODS: Using bioinformatics, we examined the associations between 20 genes associated with methylation and the epidemiological data about OSCC tumor samples. RESULTS: We created two subgroup curves based on the gene expression levels related to m6A methylation. In total, 14 genes were found to be differentially expressed. Significant differences in terms of survival rates, Grade and gender were found among subgroups with different m6A expression levels. Nine genes had areas under the curves greater than 0.7. Therefore, these genes may be utilized for the clinical diagnosis and prognosis of OSCC. Because of their high individual predictive value, HNRNPC and IGF2BP2 were chosen as the two potential predictors. The two regulatory elements were used to create the prognostic signals for OSCC. The developed prognostic signals made it possible to discern between the samples with good and poor prognoses without potential confounding factors. Four genes (HNRNPC, METTL14, YTHDF2 and ALKBH5) combined well with compounds, which had an anti-cancer effect. CONCLUSIONS: Our findings suggested that OSCC-related genes with m6A methylation could be beneficial treatment targets or prognostic indicators.

Combination treatment with ferroptosis and autophagy inducers significantly inhibit the proliferation and migration of oral squamous cell carcinoma.

Oral squamous cell carcinoma (OSCC), a malignancy originating from mucosal epithelial cells. Currently, triggering apoptotic cell death with anticancer drugs is the main way to inhibit OSCC cells. However, the capability to trigger apoptosis in tumors is constrained by the intrinsic resistance of tumor cells to apoptosis, hampering its effectiveness. Thus, utilizing alternative modes of non-apoptotic cell death offers new therapeutic possibilities, such as using a drug combination strategy to simultaneously induce ferroptosis and autophagy has the potential to improve OSCC therapy. In this study, we found the ferroptosis inducer RSL3 has certain inhibitory effects on the proliferation and migration of OSCC cells. Interestingly, our studies showed that RSL3 is also associated with autophagy activation. Based on this finding, we tried to combine RSL3 with the autophagy inducer LYN-1604 to improve the therapeutic effect. The results demonstrated that simultaneous regulation of autophagy and ferroptosis significantly reduced the proliferation and migration of OSCC cells. Taken together, we demonstrated the therapeutic potential of RSL3 in OSCC cells and proposed that simultaneous activation of autophagy and ferroptosis have synergistic effects, which would provide valuable clues for further exploration of targeted therapy for OSCC.

Transforming growth factor-ß signals promote progression of squamous cell carcinoma by inducing epithelial-mesenchymal transition and angiogenesis.

At present, the molecular mechanisms driving the progression and metastasis of oral squamous cell carcinoma (OSCC) remain largely uncharacterized. The activation of transforming growth factor-ß (TGF-ß) signaling in the tumor microenvironment has been observed in various types of cancer and has been implicated their progression by enhancing the migration and invasion of epithelial cancer cells. However, its specific roles in the oral cancer progression remain unexplored. In this study, we examined the effects of TGF-ß signaling on the murine squamous cell carcinoma, SCCVII cells in vitro and in vivo. The incubation of SCCVII cells with TGF-ß induced the activation of TGF-ß signals and epithelial-mesenchymal transition (EMT). Notably, the motility of SCCVII cells was increased upon the activation of the TGF-ß signaling. RNA sequencing revealed upregulation of genes related to EMT and angiogenesis. Consistent with these in vitro results, the inhibition of TGF-ß signals in SCCVII cell-derived primary tumors resulted in suppressed angiogenesis. Furthermore, we identified six candidate factors (ANKRD1, CCBE1, FSTL3, uPA, TSP-1 and integrin ß3), whose expression was induced by TGF-ß in SCCVII cells, and associated with poor prognosis for patients with head and neck squamous cell carcinoma. These results highlight the role of TGF-ß signals in the progression of OSCC via multiple mechanisms, including EMT and angiogenesis, and suggest novel therapeutic targets for the treatment of OSCC.

High expression of PD-L1 on conventional dendritic cells in tumour-draining lymph nodes is associated with poor prognosis in oral cancer.

INTRODUCTION: Oral squamous cell carcinoma (OSCC), while common and with a favorable prognosis in early stages, presents a marked reduction in survival rate upon metastasis to lymph nodes. Early detection of lymph node metastasis via biomarkers could enhance the therapeutic strategy for OSCC. Here, we explored dendritic cells (DCs) and cytotoxic T-cells in tumour-draining lymph nodes (TDLNs) as potential biomarkers. METHOD: Dendritic cells and cytotoxic T-cells in 33 lymph nodes were analyzed with multi-parameter flow cytometry in TDLNs, regional non-TDLNs surgically excised from 12 OSCC patients, and compared to 9 lymph nodes from patients with benign conditions. RESULTS: Our results displayed a higher proportion of conventional cDC1s with immunosuppressive features in TDLN. Further, high PD-L1 expression on cDC1 in TDLNs was associated with metastasis and/or recurrent disease risk. Also, elevated levels of memory CD8+ T-cells and terminally exhausted PD-1+TCF-1-CD8+ T-cells were observed in TDLNs and non-TDLNs compared to healthy lymph nodes. CONCLUSIONS: We conclude that TDLNs contain cells that could trigger an anti-tumor adaptive response, as evidenced by activated cDC1s and progenitor-like TCF-1+ T-cells. The detection of high PDL1 expression on cDC1s was indicative of TDLN metastasis and an adverse prognosis, proposing that PD-L1 on dendritic cells in TDLN could serve as a predictive biomarker of OSCC patients with a worse prognosis.

Extracellular N6 -isopentenyladenosine (i6A) addition induces cotranscriptional i6A incorporation into ribosomal RNAs.

N6 -isopentenyladenosine (i6A), a modified adenosine monomer, is known to induce cell death upon its addition to the culture medium. However, the molecular fate of extracellularly added i6A has yet to be identified. Here we show that i6A addition to cell culture medium results in i6A incorporation into cellular RNA in several cell lines, including the 5-fluorouracil (5-FU)-resistant human oral squamous cell carcinoma cell line FR2-SAS and its parental 5-FU-sensitive cell line SAS. i6A was predominantly incorporated into 18S and 28S rRNAs, and i6A incorporation into total RNA was mostly suppressed by treating these cell lines with an RNA polymerase I (Pol I) inhibitor. i6A was incorporated into RNA even upon inactivation of TRIT1, the only cellular i6A-modifying enzyme. These results indicate that upon cellular uptake of i6A, it is anabolized to be used for Pol I transcription. Interestingly, at lower i6A concentrations, the cytotoxic effect of i6A was substantially more pronounced in FR2-SAS cells than in SAS cells. Moreover, in FR2-SAS cells, i6A treatment decreased the rate of cellular protein synthesis and increased intracellular protein aggregation, and these effects were more pronounced than in SAS cells. Our work provides insights into the molecular fate of extracellularly applied i6A in the context of intracellular nucleic acid anabolism and suggests investigation of i6A as a candidate for a chemotherapy agent against 5-FU-resistant cancer cells.

AIM2 promotes irradiation resistance, migration ability and PD-L1 expression through STAT1/NF-κB activation in oral squamous cell carcinoma.

BACKGROUND: Radioresistance and lymph node metastasis are common phenotypes of refractory oral squamous cell carcinoma (OSCC). As a result, understanding the mechanism for radioresistance and metastatic progression is urgently needed for the precise management of refractory OSCC. Recently, immunotherapies, e.g. immune checkpoint inhibitors (ICIs), were employed to treat refractory OSCC; however, the lack of predictive biomarkers still limited their therapeutic effectiveness. METHODS: The Cancer Genome Atlas (TCGA)/Gene Expression Omnibus (GEO) databases and RT-PCR analysis were used to determine absent in melanoma 2 (AIM2) expression in OSCC samples. Colony-forming assay and trans-well cultivation was established for estimating AIM2 function in modulating the irradiation resistance and migration ability of OSCC cells, respectively. RT-PCR, Western blot and flow-cytometric analyses were performed to examine AIM2 effects on the expression of programmed death-ligand 1 (PD-L1) expression. Luciferase-based reporter assay and site-directed mutagenesis were employed to determine the transcriptional regulatory activity of Signal Transducer and Activator of Transcription 1 (STAT1) and NF-κB towards the AIM2-triggered PD-L1 expression. RESULTS: Here, we found that AIM2 is extensively upregulated in primary tumors compared to the normal adjacent tissues and acts as a poor prognostic marker in OSCC. AIM2 knockdown mitigated, but overexpression promoted, radioresistance, migration and PD-L1 expression via modulating the activity of STAT1/NF-κB in OSCC cell variants. AIM2 upregulation significantly predicted a favorable response in patients receiving ICI treatments. CONCLUSIONS: Our data unveil AIM2 as a critical factor for promoting radioresistance, metastasis and PD-L1 expression and as a potential biomarker for predicting ICI effectiveness on the refractory OSCC.

TIMELESS promotes reprogramming of glucose metabolism in oral squamous cell carcinoma.

BACKGROUND: Oral squamous cell carcinoma (OSCC), the predominant malignancy of the oral cavity, is characterized by high incidence and low survival rates. Emerging evidence suggests a link between circadian rhythm disruptions and cancer development. The circadian gene TIMELESS, known for its specific expression in various tumors, has not been extensively studied in the context of OSCC. This study aims to explore the influence of TIMELESS on OSCC, focusing on cell growth and metabolic alterations. METHODS: We analyzed TIMELESS expression in OSCC using western blot, immunohistochemistry, qRT-PCR, and data from The Cancer Genome Atlas (TCGA) and the Cancer Cell Line Encyclopedia (CCLE). The role of TIMELESS in OSCC was examined through clone formation, MTS, cell cycle, and EdU assays, alongside subcutaneous tumor growth experiments in nude mice. We also assessed the metabolic impact of TIMELESS by measuring glucose uptake, lactate production, oxygen consumption, and medium pH, and investigated its effect on key metabolic proteins including silent information regulator 1 (SIRT1), hexokinase 2 (HK2), pyruvate kinase isozyme type M2 (PKM2), recombinant lactate dehydrogenase A (LDHA) and glucose transporter-1 (GLUT1). RESULTS: Elevated TIMELESS expression in OSCC tissues and cell lines was observed, correlating with reduced patient survival. TIMELESS overexpression enhanced OSCC cell proliferation, increased glycolytic activity (glucose uptake and lactate production), and suppressed oxidative phosphorylation (evidenced by reduced oxygen consumption and altered pH levels). Conversely, TIMELESS knockdown inhibited these cellular and metabolic processes, an effect mirrored by manipulating SIRT1 levels. Additionally, SIRT1 was positively associated with TIMELESS expression. The expression of SIRT1, HK2, PKM2, LDHA and GLUT1 increased with the overexpression of TIMELESS levels and decreased with the knockdown of TIMELESS. CONCLUSION: TIMELESS exacerbates OSCC progression by modulating cellular proliferation and metabolic pathways, specifically by enhancing glycolysis and reducing oxidative phosphorylation, largely mediated through the SIRT1 pathway. This highlights TIMELESS as a potential target for OSCC therapeutic strategies.