Perineural invasion (PNI) by tumor cells is a key phenotype of highly-invasive oral squamous cell carcinoma (OSCC). Since Schwann cells (SCs) and fibroblasts maintain the physiological homeostasis of the peripheral nervous system, and we have focused on cancer-associated fibroblasts (CAFs) for decades, it's imperative to elucidate the impact of CAFs on SCs in PNI⁺ OSCCs. We describe a disease progression-driven shift of PNI^- towards PNI⁺ during the progression of early-stage OSCC (31%, n = 125) to late-stage OSCC (53%, n = 97), characterized by abundant CAFs and nerve demyelination. CAFs inhibited SC proliferation/migration and reduced neurotrophic factors and myelin in vitro, and this involved up-regulated ER stress and decreased MAPK signals. Moreover, CAFs also aggravated the paralysis of the hind limb and PNI in vivo. Unexpectedly, leukemia inhibitory factor (LIF) was exclusively expressed on CAFs and up-regulated in metastatic OSCC. The LIF inhibitor EC330 restored CAF-induced SC inactivation. Thus, OSCC-derived CAFs inactivate SCs to aggravate nerve injury and PNI development.
Schwann Cells/metabolism* ; Mouth Neoplasms/metabolism* ; Humans ; Cancer-Associated Fibroblasts/metabolism* ; Animals ; Carcinoma, Squamous Cell/metabolism* ; Neoplasm Invasiveness/pathology* ; Male ; Female ; Mice ; Cell Movement/physiology* ; Cell Proliferation/physiology* ; Cell Line, Tumor ; Leukemia Inhibitory Factor/metabolism* ; Middle Aged

Cancer stem cells (CSCs) are widely acknowledged as primary mediators to the initiation and progression of tumors. The association between microbial infection and cancer stemness has garnered considerable scholarly interest in recent years. Porphyromonas gingivalis (P. gingivalis) is increasingly considered to be closely related to the development of oral squamous cell carcinoma (OSCC). Nevertheless, the role of P. gingivalis in the stemness of OSCC cells remains uncertain. Herein, we showed that P. gingivalis was positively correlated with CSC markers expression in human OSCC specimens, promoted the stemness and tumorigenicity of OSCC cells, and enhanced tumor formation in nude mice. Mechanistically, P. gingivalis increased lipid synthesis in OSCC cells by upregulating the expression of stearoyl-CoA desaturase 1 (SCD1) expression, a key enzyme involved in lipid metabolism, which ultimately resulted in enhanced acquisition of stemness. Moreover, SCD1 suppression attenuated P. gingivalis-induced stemness of OSCC cells, including CSCs markers expression, sphere formation ability, chemoresistance, and tumor growth, in OSCC cells both in vitro and in vivo. Additionally, upregulation of SCD1 in P. gingivalis-infected OSCC cells was associated with the expression of KLF5, and that was modulated by P. gingivalis-activated NOD1 signaling. Taken together, these findings highlight the importance of SCD1-dependent lipid synthesis in P. gingivalis-induced stemness acquisition in OSCC cells, suggest that the NOD1/KLF5 axis may play a key role in regulating SCD1 expression and provide a molecular basis for targeting SCD1 as a new option for attenuating OSCC cells stemness.
Porphyromonas gingivalis/pathogenicity* ; Stearoyl-CoA Desaturase/metabolism* ; Humans ; Carcinoma, Squamous Cell/pathology* ; Mouth Neoplasms/metabolism* ; Animals ; Neoplastic Stem Cells/microbiology* ; Mice, Nude ; Mice ; Nod1 Signaling Adaptor Protein/metabolism* ; Kruppel-Like Transcription Factors/metabolism* ; Cell Line, Tumor

Abnormal accumulation of collagen fibrils is a hallmark feature of oral submucous fibrosis (OSF). However, the precise characteristics and underlying mechanisms remain unclear, impeding the advancement of potential therapeutic approaches. Here, we observed that collagen I, the main component of the extracellular matrix, first accumulated in the lamina propria and subsequently in the submucosa of OSF specimens as the disease progressed. Using RNA-seq and Immunofluorescence in OSF specimens, we screened the cartilage oligomeric matrix protein (COMP) responsible for the abnormal collagen accumulation. Genetic COMP deficiency reduced arecoline-stimulated collagen I deposition significantly in vivo. In comparison, both COMP and collagen I were upregulated under arecoline stimulation in wild-type mice. Human oral buccal mucosal fibroblasts (hBMFs) also exhibited increased secretion of COMP and collagen I after stimulation in vitro. COMP knockdown in hBMFs downregulates arecoline-stimulated collagen I secretion. We further demonstrated that hBMFs present heterogeneous responses to arecoline stimulation, of which COMP-positive fibroblasts secrete more collagen I. Since COMP is a molecular bridge with Fibril-associated collagens with Interrupted Triple helices (FACIT) in the collagen network, we further screened and identified collagen XIV, a FACIT member, co-localizing with both COMP and collagen I. Collagen XIV expression increased under arecoline stimulation in wild-type mice, whereas it was hardly expressed in the Comp^-/- mice, even with under stimulation. In summary, we found that COMP may mediates abnormal collagen I deposition by functions with collagen XIV during the progression of OSF, suggesting its potential to be targeted in treating OSF.
Oral Submucous Fibrosis/pathology* ; Cartilage Oligomeric Matrix Protein/genetics* ; Animals ; Mice ; Humans ; Fibroblasts/metabolism* ; Collagen Type I/metabolism* ; Arecoline/pharmacology* ; Mouth Mucosa/metabolism* ; Cells, Cultured ; Fluorescent Antibody Technique

Hypoxemia is a common pathological state characterized by low oxygen saturation in the blood. This condition compromises mucosal barrier integrity particularly in the gut and oral cavity. However, the mechanisms underlying this association remain unclear. This study used periodontitis as a model to investigate the role of platelet activation in oral mucosal immunopathology under hypoxic conditions. Hypoxia upregulated methyltransferase-like protein 4 (METTL4) expression in platelets, resulting in N⁶-methyladenine modification of mitochondrial DNA (mtDNA). This modification impaired mitochondrial transcriptional factor A-dependent cytosolic mtDNA degradation, leading to cytosolic mtDNA accumulation. Excess cytosolic mt-DNA aberrantly activated the cGAS-STING pathway in platelets. This resulted in excessive platelet activation and neutrophil extracellular trap formation that ultimately exacerbated periodontitis. Targeting platelet METTL4 and its downstream pathways offers a potential strategy for managing oral mucosa immunopathology. Further research is needed to examine its broader implications for mucosal inflammation under hypoxic conditions.
DNA, Mitochondrial/metabolism* ; Mouth Mucosa/pathology* ; Hypoxia/immunology* ; Methyltransferases/metabolism* ; Blood Platelets/metabolism* ; Animals ; Periodontitis/immunology* ; Humans ; Platelet Activation ; Mice

Hypoxia and aberrant activation of epidermal growth factor receptor (EGFR) are considered important features of various malignancies. However, whether hypoxia can directly trigger EGFR activation and its clinical implications remain unclear. In this study, we demonstrated that in oral cancer, a typical hypoxic tumor, hypoxia can induce chronic but constitutive phosphorylation of wild-type EGFR in the absence of ligands. Oral cancer cell lines exhibit different EGFR phosphorylation responses to hypoxia. In hypoxic HN4 and HN6 cells, ubiquitination-mediated endocytosis, lysosomal sorting, and degradation lead to low levels of EGFR phosphorylation. However, in CAL-27 and HN30 cells, a novel HIF-1α-induced long noncoding RNA (lncRNA), EUDAL, can compete with the E3 ligase/adaptor complex c-Cbl/Grb2 for binding to EGFR, stabilizing phosphorylated EGFR (pEGFR) and resulting in sustained activation of EGFR and its downstream STAT3/BNIP3 signaling. STAT3/BNIP3-mediated autophagy leads to antitumor drug resistance. A high EUDAL/EGFR/STAT3/autophagy pathway activation predicts poor response to chemotherapy in oral cancer patients. Collectively, hypoxia can induce noncanonical ligand-independent EGFR phosphorylation. High EUDAL expression facilitates sustained EGFR phosphorylation in hypoxic tumor cells and leads to autophagy-related drug resistance.
Humans ; ErbB Receptors/metabolism* ; Mouth Neoplasms/pathology* ; RNA, Long Noncoding/genetics* ; Drug Resistance, Neoplasm/genetics* ; Cell Line, Tumor ; Phosphorylation ; Signal Transduction ; STAT3 Transcription Factor/metabolism* ; Cell Hypoxia ; Autophagy ; Proto-Oncogene Proteins c-cbl/metabolism*

As the field of oral pathology has evolved, the nomenclature and classification of oral mucosal diseases with a remarkable risk of malignant transformation have undergone several modifications. In 2005, the World Health Organization (WHO) introduced the concept of oral potentially malignant disorders (OPMDs) as an alternative to the terms for oral precancerous lesions and precancerous conditions. In the consensus report by the WHO Collaborating Center for Oral Cancer of 2021, OPMD is defined as "any oral mucosal abnormality that is associated with a statistically increased risk of developing oral cancer."This definition encompasses a range of conditions, in-cluding oral leukoplakia, oral submucous fibrosis, proliferative verrucous leukoplakia, oral lichen planus, and other lesions. In light of the complex etiology, unclear pathogenesis, and carcinogenesis of OPMDs, early and precise diagnosis and treatment can contribute to the secondary prevention of oral cancer. For this reason, this review, which aims to provide a basis for the precise clinical diagnosis of OPMDs, was performed. Its aim was achieved by reviewing the historical evolution and research progress of the nomenclature, classification, and histopathological diagnostic criteria of OPMDs.
Humans ; Mouth Neoplasms/diagnosis* ; Precancerous Conditions/diagnosis* ; Leukoplakia, Oral/diagnosis* ; Lichen Planus, Oral/pathology* ; Oral Submucous Fibrosis/pathology* ; Mouth Mucosa/pathology* ; World Health Organization

OBJECTIVES: The aim of this study is to determine the effect of cannabinoid receptor (CB) 2 inhibitor on desmoglein 3 (DSG3) expression in HaCaT cells co-cultured with pemphigus serum. METHODS: Immunohistochemical staining was used to compare CB expression in pemphigus patients and normal individuals. Enzyme-linked immunosorbent assay (ELISA) was employed to quantify the concentration of CB2 in the serum of pemphigus patients and normal individuals. A correlation analysis was performed to examine the relationship between the serum CB2 and DSG of pemphigus patients. The CCK-8 assay was used to evaluate the inhibitory effect of AM630 on HaCaT cells, and the half-maximal inhibitory concentration (IC₅₀) value was utilized to determine the experimental concentration. Serum from normal individuals (negative control group) and pemphigus patients (pemphigus group) was co-cultured with HaCaT cells at a 1∶1 ratio. HaCaT cells cultured in complete medium were used as the control group. HaCaT cells in the pemphigus group treated with AM630 were employed as the AM630 group. Real-time polymerase chain reaction (PCR) and Western blot were conducted to assess the expression levels of CB2, DSG3, and β-catenin. Cell dissociation experiments were conducted to evaluate the effect of AM630 on the adhesion of HaCaT cells. RESULTS: Immunohistochemistry revealed significant differences in CB2 expression between pemphigus and normal mucosa (P<0.000 1), but no difference was found in CB1 expression. ELISA analysis revealed a statistically significant difference in the expression levels of CB2 in the serum between normal individuals and pemphigus patients (P<0.001). The expression of CB2 in the serum of pemphigus patients exhibited a significant positive correlation with that of DSG3 (r=0.831, P=0.003). The CCK-8 assay indicated that the IC₅₀ of AM630 on HaCaT cells was 0.55 μmol/L. Real-time PCR and Western blot showed that the expression levels of CB2 and DSG3 increased in the pemphigus group, while the expression level of β-catenin decreased compared with that in the AM630 groups (P<0.05). CONCLUSIONS CB2 is highly expressed in oral mucosal pemphigus. AM630 inhibits overexpression of CB2 and DSG3 and underexpression of β-catenin levels, which can provide new therapeutic targets for pemphigus.
Humans ; Pemphigus/pathology* ; Receptor, Cannabinoid, CB2/metabolism* ; Desmoglein 3/metabolism* ; Acantholysis/metabolism* ; Mouth Mucosa/pathology* ; HaCaT Cells ; Coculture Techniques ; beta Catenin/metabolism*

OBJECTIVES: To investigate the mechanism of PHPS1 for promoting apoptosis of oral squamous cell carcinoma cells and the role of AMPK in regulating tumor angiogenesis under hypoxic conditions. METHODS: Human oral squamous cell carcinoma Ca9-22 cells cultured in hypoxic conditions (1% O₂) were inoculated subcutaneously in 16 nude mice, which were divided into control group and PHPS1 group (n=8) for treatment with 10% DMSO and 10% PHPS1 respectively. Tumor growth in the mice was monitored till 14 days after the treatment, and the xenografts were examined pathologically using HE staining. In Ca9-22 cells cultured in 1% O₂, the effect of PHPS1, compound C (an AMPK inhibitor), and their combination on expressions of SHP-2, AMPK, HIF-1α, PD-L1, caspase-8, caspase-3 and BAX were evaluated using Western blotting. RESULTS: In the tumor-bearing nude mice, PHPS1 treatment significantly inhibited tumor growth and neovascularization. HE staining showed significantly reduced tumor angiogenesis in PHPS1-treated mice. In Ca9-22 cells in hypoxic cultures, PHPS1 treatment significantly decreased the expression levels of SHP-2, HIF-1α, PD-L1, ERK2, STAT3 and VEGF and increased the expression of AMPK. The inhibitory effects of PHPS1 on HIF-1α and PD-L1 were obviously attenuated by the addition of compound C. PHPS1 also enhanced the expressions of caspase-3, caspase-8 and Bax proteins and increased the phosphorylation levels of PD-L1 and S195 in Ca9-22 cells, and these effects were effectively attenuated by compound C. CONCLUSIONS PHPS1 can enhance PD-L1 serine phosphorylation by regulating SHP-2/AMPK activity to promote apoptosis of oral squamous cell carcinoma cells under hypoxic conditions.
Animals ; B7-H1 Antigen/metabolism* ; Apoptosis/drug effects* ; Mice ; Carcinoma, Squamous Cell/pathology* ; Cell Line, Tumor ; Mouth Neoplasms/pathology* ; Mice, Nude ; Humans ; AMP-Activated Protein Kinases/metabolism* ; Phosphorylation ; Protein Tyrosine Phosphatase, Non-Receptor Type 11/metabolism* ; Reactive Oxygen Species/metabolism* ; Neovascularization, Pathologic/metabolism* ; Hypoxia-Inducible Factor 1, alpha Subunit/metabolism*

Oral squamous cell carcinoma (OSCC) escape from the immune system is mediated through several immunosuppressive phenotypes that are critical to the initiation and progression of tumors. As a hallmark of cancer, DNA damage repair is closely related to changes in the immunophenotypes of tumor cells. Although flap endonuclease-1 (FEN1), a pivotal DNA-related enzyme is involved in DNA base excision repair to maintain the stability of the cell genome, the correlation between FEN1 and tumor immunity has been unexplored. In the current study, by analyzing the clinicopathological characteristics of FEN1, we demonstrated that FEN1 overexpressed and that an inhibitory immune microenvironment was established in OSCC. In addition, we found that downregulating FEN1 inhibited the growth of OSCC tumors. In vitro studies provided evidence that FEN1 knockdown inhibited the biological behaviors of OSCC and caused DNA damage. Performing multiplex immunohistochemistry (mIHC), we directly observed that the acquisition of critical immunosuppressive phenotypes was correlated with the expression of FEN1. More importantly, FEN1 directly or indirectly regulated two typical immunosuppressive phenotype-related proteins human leukocyte antigen (HLA-DR) and programmed death receptor ligand 1 (PD-L1), through the interferon-gamma (IFN-γ)/janus kinase (JAK)/signal transducer and activator transcription 1 (STAT1) pathway. Our study highlights a new perspective on FEN1 action for the first time, providing theoretical evidence that it may be a potential immunotherapy target for OSCC.
Humans ; Carcinoma, Squamous Cell/pathology* ; DNA ; Down-Regulation ; Flap Endonucleases/metabolism* ; Head and Neck Neoplasms ; Interferon-gamma/metabolism* ; Mouth Neoplasms/pathology* ; Phenotype ; Squamous Cell Carcinoma of Head and Neck ; Tumor Microenvironment ; Janus Kinases/metabolism*

Neuroendocrine carcinoma(NEC) is a malignant tumor derived from neuroendocrine cells, with distinct clinical, morphological and immunohistochemical characteristics. Neuroendocrine carcinoma of the head and neck is very rare in clinic. Larynx is the most common affected site, and the root of the tongue is extremely rare. The clinical manifestations are mainly eating pain, cauliflower like mass in the mouth, and ulcerative lesions that have not healed for a long time. Maxillofacial MRI and contrastenhanced CT are the most commonly used examination tools for such diseases, which can detect the spaceoccupying lesions of tumors. Neuroendocrine granules found in the cytoplasm under pathological light microscope can be diagnosed as neuroendocrine carcinoma. However, for most cases, it is difficult to make a diagnosis only under light microscope, and it is often necessary to make a diagnosis by means of immunohistochemistry and other technical means. This paper reports a case of neuroendocrine carcinoma of the root of the tongue, introduces its characteristics, diagnosis and treatment, and reviews the relevant literature of this case.
Humans ; Carcinoma, Neuroendocrine/pathology* ; Tongue ; Neck/pathology* ; Larynx/pathology* ; Mouth/pathology*