The behaviour of human oral squamous cell carcinoma in cell culture

Fusobacterium nucleatum induces invasive growth and angiogenic responses in malignant oral keratinocytes that are cell line- and bacterial strain-specific

Fusobacterium nucleatum is an anaerobic commensal of the oral cavity recently reported to be associated with cancers of the gastrointestinal tract and oral squamous cell carcinoma (OSCC). In this study, we investigate the impact on oral keratinocytes of infection with a genetically diverse set of strains of F. nucleatum subsp. polymorphum recovered from patients with oral dysplasia (n=6). We employed H357 oral keratinocytes derived from a stage 1 OSCC and H376 cells derived from a stage 3 OSCC. Adhesion phenotypes were strain specific, with 3/6 clinical isolates examined exhibiting higher adherence to the stage 3 H376 cell line. Conversely, intracellular invasion was greatest in the H357 cells and was associated with specific transcriptional responses including autophagy and keratinization. Infection of both H357 and H376 cell lines induced transcriptional and cytokine responses linked to cancer cell migration and angiogenesis. F. nucleatum infection induced greater levels of MMP9 secretion in the H376 cell line which was associated with enhanced motility and invasion phenotypes. Additionally, the degree of F. nucleatum induced invasive growth by H376 cells varied between different clinical isolates of F. nucleatum subsp. polymorphum. Blockage of CCL5 signalling using the inhibitor metCCL5 resulted in reduced keratinocyte invasion. F. nucleatum infection also induced expression of the pro-angiogenic chemokine MCP-1 and the angiogenic growth factor VEGF-A resulting in increased capillary-like tube formation in HUVEC cells, most significantly in H376 cells. Treatment of HUVEC cells with resveratrol, a VEGF-A signalling inhibitor, significantly attenuated F. nucleatum induced tube formation. Our data indicate that the outcomes of F. nucleatum-oral cell interactions can vary greatly depending on the bacterial genotype and the malignant phenotype of the host cell.

Expression of Epsin3 and its interaction with Notch signalling in oral epithelial dysplasia and oral squamous cell carcinoma

BACKGROUND

Most oral squamous cell carcinoma patients present with late-stage disease. Early detection of the disease is considered to be the most effective way of improving patient outcomes. Several biomarkers have been identified as indicators of oral cancer development and progression; however, none have been translated into clinical practice. In this study, we have investigated the role of Epsin3, an endocytic adaptor protein, and Notch1, a transmembrane signalling protein, in oral carcinogenesis with a view to explore their potential as biomarkers.

METHODS

Oral cancer cell lines and a normal oral keratinocyte cell line were used together with tissue samples of normal oral mucosa (n = 21), oral epithelial dysplasia (n = 74) and early stage (Stages I and II) oral squamous cell carcinoma (n = 31). Immunocytochemical staining, immunoblotting and real-time quantitative polymerase chain reaction (PCR) were performed to assess protein as well as gene expression levels.

RESULTS

The expression levels of Epsin3 and Notch1 mRNA and protein are variable across different oral squamous cell carcinoma derived cell lines. Epsin3 was upregulated in oral epithelial dysplasia and oral squamous cell carcinoma tissues compared with normal epithelium. Overexpression of Epsin3 resulted in a significant reduction of Notch1 expression in oral squamous cell carcinoma. Notch1 was generally downregulated in the dysplasia and oral squamous cell carcinoma samples.

CONCLUSION

Epsin3 is upregulated in oral epithelial dysplasia and oral squamous cell carcinoma and has the potential to be used as a biomarker for oral epithelial dysplasia. Notch signalling is downregulated in oral squamous cell carcinoma, possibly through an Epsin3-induced de-activation pathway.

TIMP-1 Protects Tight Junctions of Brain Endothelial Cells From MMP-Mediated Degradation

OBJECTIVE

The blood-brain barrier (BBB) plays a critical role in central nervous system homeostasis, and the integrity of BBB is disrupted in many neurodegenerative diseases. Matrix metalloproteinases (MMPs) degrade the tight junctions (TJs) of endothelial cells and basement membrane components essential to BBB integrity, which leads to increased BBB permeability and allows inflammatory cells and neurotoxic substances to enter the brain. Tissue inhibitors of metalloproteinases (TIMPs), endogenous inhibitors of MMPs, regulate MMP activity, thereby maintaining BBB integrity.

METHODS

The disruptive impacts of MMP-3 and MMP-9 on BBB and protective effect of TIMP-1 were investigated in a simplified in vitro model of the BBB, which was generated using rat brain microvascular endothelial cells (RBMEC). The main features of BBB formation, including permeability and the trans-endothelial electrical resistance (TEER), were monitored over time after the addition of MMP-3 and MMP-9 and their complexes with TIMP-1 inhibitor.

RESULTS

Our results indicated that MMP-3 and MMP-9 caused a dose-dependent disruption of the BBB, with 1.5 µM MMPs resulting in an over threefold increase in permeability, while TIMP-1 inhibition protected the integrity of the BBB model and recovered TEER and permeability of RBMECs. The disruption and recovery of tight junction proteins of RBMECs after MMP and TIMP treatment were also detected using fluorescent microscopy.

CONCLUSION

MMP-9 and MMP-3 disrupt the BBB by degrading tight junctions in endothelial cells, and TIMP-1 could inhibit the disruptive effect of MMP-3 and MMP-9 by showing potential as therapeutic protein against MMP-related diseases where BBB disruption plays a role.

Assessment of Oxidative Stress-Induced Oral Epithelial Toxicity

Reactive oxygen species (ROS) are highly reactive molecules generated in living organisms and an excessive production of ROS culminates in oxidative stress and cellular damage. Notably, oxidative stress plays a critical role in the pathogenesis of a number of oral mucosal diseases, including oral mucositis, which remains one of cancer treatments' most common side effects. We have shown previously that oral keratinocytes are remarkably sensitive to oxidative stress, and this may hinder the development and reproducibility of epithelial cell-based models of oral disease. Here, we examined the oxidative stress signatures that parallel oral toxicity by reproducing the initial events taking place during cancer treatment-induced oral mucositis. We used three oral epithelial cell lines (an immortalized normal human oral keratinocyte cell line, OKF6, and malignant oral keratinocytes, H357 and H400), as well as a mouse model of mucositis. The cells were subjected to increasing oxidative stress by incubation with hydrogen peroxide (H2O2) at concentrations of 100 μM up to 1200 μM, for up to 24 h, and ROS production and real-time kinetics of oxidative stress were investigated using fluorescent dye-based probes. Cell viability was assessed using a trypan blue exclusion assay, a fluorescence-based live-dead assay, and a fluorometric cytotoxicity assay (FCA), while morphological changes were analyzed by means of a phase-contrast inverted microscope. Static and dynamic real-time detection of the redox changes in keratinocytes showed a time-dependent increase of ROS production during oxidative stress-induced epithelial injury. The survival rates of oral epithelial cells were significantly affected after exposure to oxidative stress in a dose- and cell line-dependent manner. Values of TC50 of 800 μM, 800 μM, and 400 μM were reported for H400 cells (54.21 ± 9.04, p < 0.01), H357 cells (53.48 ± 4.01, p < 0.01), and OKF6 cells (48.64 ± 3.09, p < 0.01), respectively. Oxidative stress markers (MPO and MDA) were also significantly increased in oral tissues in our dual mouse model of chemotherapy-induced mucositis. In summary, we characterized and validated an oxidative stress model in human oral keratinocytes and identified optimal experimental conditions for the study of oxidative stress-induced oral epithelial toxicity.

The effect of matrices on the gene expression profile of patient-derived head and neck carcinoma cells for in vitro therapy testing

OBJECTIVE

Head and neck squamous cell carcinoma (HNSCC) is a highly aggressive tumor with a 5-year mortality rate of ~ 50%. New in vitro methods are needed for testing patients' cancer cell response to anti-cancer treatments. We aimed to investigate how the gene expression of fresh carcinoma tissue samples and freshly digested single cancer cells change after short-term cell culturing on plastic, Matrigel or Myogel. Additionally, we studied the effect of these changes on the cancer cells' response to anti-cancer treatments.

MATERIALS/METHODS

Fresh tissue samples from HNSCC patients were obtained perioperatively and single cells were enzymatically isolated and cultured on either plastic, Matrigel or Myogel. We treated the cultured cells with cisplatin, cetuximab, and irradiation; and performed cell viability measurement. RNA was isolated from fresh tissue samples, freshly isolated single cells and cultured cells, and RNA sequencing transcriptome profiling and gene set enrichment analysis were performed.

RESULTS

Cancer cells obtained from fresh tissue samples changed their gene expression regardless of the culturing conditions, which may be due to the enzymatic digestion of the tissue. Myogel was more effective than Matrigel at supporting the upregulation of pathways related to cancer cell proliferation and invasion. The impacts of anti-cancer treatments varied between culturing conditions.

CONCLUSIONS

Our study showed the challenge of in vitro cancer drug testing using enzymatic cell digestion. The upregulation of many targeted pathways in the cultured cells may partially explain the common clinical failure of the targeted cancer drugs that pass the in vitro testing.

Pre-conditioning of gingival epithelial cells with sub-apoptotic concentrations of curcumin prevents pro-inflammatory cytokine release

BACKGROUND AND OBJECTIVE

Plaque-induced gingival inflammation (gingivitis) is ubiquitous in humans. The epithelial barrier reacts to the presence of oral bacteria and induces inflammatory cascades. The objective of this study was to investigate the mechanism by which the small molecule micronutrient curcumin could decrease inflammatory response in vitro to oral bacterium heat-killed Fusobacterium nucleatum as curcumin could be a useful compound for combatting gingivitis already consumed by humans.

METHODS

H400 oral epithelial cell line was pre-conditioned with curcumin and the production of cytokines was measured by enzyme-linked immunosorbent assay (ELISA) and translocation of transcription factors was used to monitor inflammatory responses. Haem oxygenase (HO-1) expression and molecules that HO-1 releases were evaluated for their potential to reduce the quantity of cytokine production. Immunofluorescence microscopy and Western blotting were used to evaluate changes in transcription factor and enzyme location.

RESULTS

Pre-conditioning of H400 cells with a sub-apoptotic concentration of curcumin (20 μM) attenuated secretion of Granulocyte-Macrophage - Colony-Stimulating Factor (GM-CSF) and reduced NFkB nuclear translocation. This pre-conditioning caused an increase in nuclear Nrf2; an initial drop (at 8 h) followed by an adaptive increase (at 24 h) in glutathione; and an increase in haem oxygenase (HO-1) expression. Inhibition of HO-1 by SnPPIX prevented the curcumin-induced attenuation of GM-CSF production. HO-1 catalyses the breakdown of haem to carbon monoxide, free iron and biliverdin: the HO-1/CO anti-inflammatory pathway. Elevations in carbon monoxide, achieved using carbon monoxide releasing molecule-2 (CORM2) treatment alone abrogated F. nucleatum-induced cytokine production. Biliverdin is converted to bilirubin by biliverdin reductase (BVR). This pleiotropic protein was found to increase in cell membrane expression upon curcumin treatment.

CONCLUSION

Curcumin decreased inflammatory cytokine production induced by Fusobacterium nucleatum in H400 oral epithelial cells. The mechanism of action appears to be driven by the increase of haem oxygenase and the production of carbon monoxide.

Oral Epithelial Cell Culture Model for Studying the Pathogenesis of Chronic Inflammatory Disease

The interactions between bacteria, epithelium, and neutrophilic polymorphonuclear leukocytes (neutrophils) are the key to the initiation and progression of many chronic inflammatory-immune diseases. In addition, all can be influenced by external factors, such as micronutrients, thereby providing potentially novel approaches to therapy. This chapter will therefore provide detailed methods for core techniques involved in studying cellular and molecular epithelial responses to a bacterial challenge in relation to chronic inflammatory disease pathogenesis and therapy.

A 3D Printed Device for In Vitro Generation of Stratified Epithelia at the Air-Liquid Interface

Air-liquid interface (ALI) cultures are used to produce stratified epithelial tissues in vitro, notably for the production of oral mucosal equivalents. Currently, there are few purpose-built devices which aim to enhance the ease and reproducibility of generating such tissue. Most ALI cultures utilise stainless steel grids or cell culture inserts to elevate the matrix or scaffold to the surface of the culture media. Here, a novel buoyant epithelial culture device (BECD) was designed to both contain a fibroblast-seeded collagen hydrogel and float in culture media, thereby automatically maintaining the ALI without further user intervention. BECDs aim to mitigate several issues associated with ALI culture; reducing the chance of media flooding the epithelial layer from physical disturbance, reducing technique-sensitivity for less experienced users, and improving the reproducibility of the epithelia generated. H400 oral squamous cell carcinoma cells cultured in BECDs for 7, 14 and 21 days showed continuous increase in epithelial tissue thickness with expected localisation of epithelial differentiation markers: cytokeratin 5, involucrin and E-cadherin. Fused filament fabrication 3D printing with polypropylene used in BECD production allows for rapid turnover and design iteration, presenting a versatile, adaptable and useful tool for application in in vitro cell culture.

Identification of a Novel Cuproptosis-Related Gene Signature for Prognostic Implication in Head and Neck Squamous Carcinomas

Simple Summary

Head and neck squamous carcinoma (HNSC) is a common malignancy that requires novel therapeutic targets. Cuproptosis is an emerging research hotspot. The purpose of this study is to mine the cuproptosis-related genes to find prognosis-related genes. We successfully identified a 24-gene signature for predicting overall survival (OS) in HNSC patients and may expand the range of potential targets for treating HNSC.

Abstract

Head and neck squamous carcinoma (HNSC) is a frequent and deadly malignancy that is challenging to manage. The existing treatment options have considerable efficacy limitations. Hence, the identification of new therapeutic targets and the development of efficacious treatments are urgent needs. Cuproptosis, a non-apoptotic programmed cell death caused by excess copper, has only very recently been discovered. The present study investigated the prognostic importance of genes involved in cuproptosis through the mRNA expression data and related clinical information of HNSC patients downloaded from public databases. Our results revealed that many cuproptosis-related genes were differentially expressed between normal and HNSC tissues in the TCGA cohort. Moreover, 39 differentially expressed genes were associated with the prognosis of HNSC patients. Then, a 24-gene signature was identified in the TCGA cohort utilizing the LASSO Cox regression model. HNSC expression data used for validation were obtained from the GEO database. Consequently, we divided patients into high- and low-risk groups based on the 24-gene signature. Furthermore, we demonstrated that the high-risk group had a worse prognosis when compared to the low-risk group. Additionally, significant differences were found between the two groups in metabolic pathways, immune microenvironment, etc. In conclusion, we found a cuproptosis-related gene signature that can be used effectively to predict OS in HNSC patients. Thus, targeting cuproptosis might be an alternative and promising strategy for HNSC patients.

Extracellular Prostaglandins E1 and E2 and Inflammatory Cytokines Are Regulated by the Senescence Program in Potentially Premalignant Oral Keratinocytes

Simple Summary

The early treatment of oral cancer is a high priority, as improvements in this area could lead to greater cure rates and reduced disability due to extensive surgery. Oral cancer is very difficult to detect in over 70% of cases as it develops unseen until quite advanced, sometimes rapidly. It has become apparent that there are at least two types of epithelial cells (keratinocytes) found in oral tissue on the road to cancer (premalignant). One type secretes molecules called prostaglandins but the other does not and the former may stimulate the latter to progress to malignancy, either by stimulating their proliferation or encouraging the influx of blood vessels to feed them. Additionally, we have identified regulators of prostaglandin secretion in premalignant oral cells that could be targeted in future therapies, such as inducers of cellular senescence, drugs which kill senescent cells (senolytics), steroid metabolism, cyclo-oxygenase 2 (COX2) and p38 mitogen-activated protein kinase.

Abstract

Potentially pre-malignant oral lesions (PPOLs) are composed of keratinocytes that are either mortal (MPPOL) or immortal (IPPOL) in vitro. We report here that MPPOL, but not generally IPPOL, keratinocytes upregulate various extracellular tumor-promoting cytokines (interleukins 6 and 8) and prostaglandins E1 (ePGE1) and E2 (ePGE2) relative to normal oral keratinocytes (NOKs). ePGE upregulation in MPPOL was independent of PGE receptor status and was associated with some but not all markers of cellular senescence. Nevertheless, ePGE upregulation was dependent on the senescence program, cyclo-oxygenase 2 (COX2) and p38 mitogen-activated protein kinase and was partially regulated by hydrocortisone. Following senescence in the absence of p16^INK4A, ePGEs accumulated in parallel with a subset of tumor promoting cytokine and metalloproteinase (MMP) transcripts, all of which were ablated by ectopic telomerase. Surprisingly, ataxia telangiectasia mutated (ATM) function was not required for ePGE upregulation and was increased in expression in IPPOL keratinocytes in line with its recently reported role in telomerase function. Only ePGE1 was dependent on p53 function, suggesting that ePGEs 1 and 2 are regulated differently in oral keratinocytes. We show here that ePGE2 stimulates IPPOL keratinocyte proliferation in vitro. Therefore, we propose that MPPOL keratinocytes promote the progression of IPPOL to oral SCC in a pre-cancerous field by supplying PGEs, interleukins and MMPs in a paracrine manner. Our results suggest that the therapeutic targeting of COX-2 might be enhanced by strategies that target keratinocyte senescence.

Commonly Prescribed Anticoagulants Exert Anticancer Effects in Oral Squamous Cell Carcinoma Cells In Vitro

Simple Summary

Oral squamous cell carcinoma (OSCC) is the sixth most common cancer worldwide with 840,000 new cases and 420,000 deaths in 2020. Anticoagulants are widely prescribed medications routinely administered to help prevent blood clots. Despite the great relevance of these two topics, there is complete lack of knowledge regarding the potential effects that these drugs could exert on oral cancer patients. In this in vitro study, we comprehensively investigated the effect of anticoagulants on OSCC activity. This includes the effect of these drugs on cancer cell ability to survive, migrate to colonise distant sites, and resist treatment with conventional chemotherapy. We have demonstrated for the first time that various anticoagulants have anticancer effects on OSCC. Moreover, some of the anticoagulants tested were able to reduce the migratory ability of cancer cells. Finally, the great majority of anticoagulants studied reduced the effectiveness of the tested chemotherapeutic agent, allowing an increase in cancer cell proliferation. Our results highlight the need for urgent further research in the field, to improve the anticoagulant strategies in patients with oral cancer, and in turn their prognosis.

Abstract

Oral squamous cell carcinoma (OSCC) is the most common head and neck cancer. With anticoagulant usage on the rise, it is important to elucidate their potential effects on tumour biology and interactions with chemotherapeutics. The aim of the present study was to investigate the effects of anticoagulants on OSCC cell lines and their interactions with the drug 5-fluorouracil (5-FU). Cell proliferation was assessed using an MTS in vitro assay in two human OSCC cell lines (H357/H400) and in normal oral keratinocytes (OKF6) treated with the 5-FU (0.2/1/5/10 μg/mL), conventional anticoagulants warfarin (1/5/10/20 μM) and heparin (5/20/80 U), as well as four new oral anticoagulants, dabigatran (5/10/20 μM), rivaroxaban (5/10/20 μM), apixaban (0.1/1/5 μg/mL), and edoxaban (5/10/20 μM). Cell migration was assessed at 3 h intervals up to18 h using a wound healing assay. Our results clearly demonstrate, for the first time, that commonly prescribed anticoagulants exert in vitro antiproliferative effects on OSCC cells. Furthermore, treatment with some anticoagulants reduced the migration of OSCC cell lines. Nevertheless, most of the anticoagulants tested reduced the effectiveness of the chemotherapeutic agent tested, 5-FU, highlighting potential flaws in the current pharmacological management of these patients. Our findings showed the need for the immediate translation of this research to preclinical animal models.

Desmoglein-3 induces YAP phosphorylation and inactivation during collective migration of oral carcinoma cells

Alterations of the Hippo-YAP pathway are potential targets for oral squamous cell carcinoma (OSCC) therapy, but heterogeneity in this pathway could be responsible for therapeutic resistance. We analysed the Hippo-YAP signatures in a cohort of characterised keratinocyte cell lines derived from the mouth floor and buccal mucosa from different stages of OSCC tumour progression and focused on the specific role of YAP on invasive and metastatic potential. We confirmed heterogeneity in the Hippo-YAP pathway in OSCC lines, including overexpression of YAP1, WWTR1 (often referred to as TAZ) and the major Hippo signalling components, as well as the variations in the genes encoding the intercellular anchoring junctional proteins, which could potentially regulate the Hippo pathway. Specifically, desmoglein-3 (DSG3) exhibits a unique and mutually exclusive regulation of YAP via YAP phosphorylation during the collective migration of OSCC cells. Mechanistically, such regulation is associated with inhibition of phosphorylation of epidermal growth factor receptor (EGFR) (S695/Y1086) and its downstream effectors heat shock protein beta-1 (Hsp27) (S78/S82) and transcription factor AP-1 (c-Jun) (S63), leading to YAP phosphorylation coupled with its cytoplasmic translocation and inactivation. Additionally, OSCC lines display distinct phenotypes of YAP dependency or a mixed YAP and TAZ dependency for cell migration, and present distinct patterns in YAP abundance and activity, with the latter being associated with YAP nuclear localisation. In conclusion, this study has provided evidence for a newly identified paradigm in the Hippo-YAP pathway and suggests a new regulation mechanism involved in the control of collective migration in OSCC cells.

A pan-cancer analysis of the prognostic and immunological role of β-actin (ACTB) in human cancers

Beta-actin (ACTB), a highly conserved cytoskeleton structural protein, has been regarded as a common housekeep gene and used as a reference gene for years. However, accumulating evidence indicates that ACTB is abnormally expressed in multiple cancers and hence changes the cytoskeleton to affect the invasiveness and metastasis of tumors. This study aimed to investigate the function and clinical significance of ACTB in pan-cancer. The role of ACTB for prognosis and immune regulation across 33 tumors was explored based on the datasets of gene expression omnibus and the cancer genome atlas. Differential expression of ACTB was found between cancer and adjacent normal tissues, and significant associations was found between ACTB expression and prognosis of tumor patients. In most cancers, ACTB expression was associated with immune cells infiltration, immune checkpoints and other immune modulators. Relevance between ACTB and metastasis and invasion was identified in various types of cancers by CancerSEA. Moreover, focal adhesion and actin regulation-associated pathways were included in the functional mechanisms of ACTB. The expression of ACTB was verified by quantitative real-time polymerase chain reaction. Knockdown of ACTB inhibited head and neck squamous carcinoma cell migration and invasion by NF-κB and Wnt/β-catenin pathways. Our first pan-cancer study of ACTB offers insight into the prognostic and immunological roles of ACTB across different tumors, indicating ACTB may be a potential biomarker for poor prognosis and immune infiltration in cancers, and the role of ACTB as a reference gene in cancers was challenged.

Extracellular ATP Induced S-Phase Cell Cycle Arrest via P2Y Receptor-Activated ERK Signaling in Poorly Differentiated Oral Squamous Cell Carcinoma SAS Cells

Extracellular ATP in the tumor microenvironment exhibits either pro- or antitumor effect via interaction with P2Y receptors, but the intracellular signaling and functional roles of P2Y receptors in oral squamous cell carcinoma (OSCC) are unclear. We aimed to study the effect of ATP on OSCC cell lines and the potential mechanisms involved. Through GEPIA dataset analysis, high expression levels of mRNA encoding P2Y receptors, the ATP-induced G protein-coupled receptors, were associated with better overall patient survival in head and neck squamous cell carcinoma. qPCR analysis showed that the poorly differentiated OSCC SAS cell line, had higher P2RY1 expression level compared to the well-differentiated H103 and H376 cell lines. Western blotting and flow cytometry analyses revealed that ATP phosphorylated ERK and elevated intracellular calcium signaling in all tested cell lines. A significant S-phase cell cycle arrest was observed in SAS, and preincubation with the MEK inhibitor PD0325901 reversed the ATP-induced S-phase arrest. We further demonstrated that ATP induced a slight reduction in cell count and colony formation yet significant apoptosis in SAS. Overall, we postulate that the ATP-induced S-phase arrest effect in SAS cells may be regulated through P2Y receptor-mediated ERK signaling, thus suggesting a potential antitumor effect of ATP via interaction with its distinct profile of P2Y receptors.

Autophagy is deregulated in cancer-associated fibroblasts from oral cancer and is stimulated during the induction of fibroblast senescence by TGF-β1

Many of the characteristics ascribed to cancer-associated fibroblasts (CAFs) are shared by activated, autophagic and senescent fibroblasts. Whilst most oral squamous cell carcinomas (OSCCs) are genetically unstable (GU-OSCC), genetically stable variants (GS-OSCC) have been described and, notably, CAF activation (myofibroblast differentiation) and senescence are characteristics particularly associated with GU-OSCCs. However, it is not known whether autophagy is disrupted in these cells or whether autophagy regulates the development of the myofibroblast and senescent phenotypes. In this study, we show that senescent CAFs from GU-OSCCs contained more autophagosomes than normal human oral fibroblasts (NHOFs) and CAFs from GS-OSCCs possibly due to autophagic impairment. Further, we show that deregulation of autophagy in normal fibroblasts, either by inhibition with autophagy inhibitor, SAR405, or activation with TGF-β1, induced fibroblast activation and senescence: In response to TGF-β1, autophagy was induced prior to the development of the activated and senescent phenotypes. Lastly, we show that both SAR405- and TGF-β1-treated NHOFs enhance OSCC cell migration but only TGF-β1-treated cells increase OSCC invasion through Matrigel, indicating that TGF-β1 has additional effects that are independent of fibroblast activation/senescence. These results suggest a functional role for autophagy in the development of myofibroblast and CAF phenotypes.

Deregulation of lysophosphatidic acid metabolism in oral cancer promotes cell migration via the up-regulation of COX-2

Oral squamous cell carcinoma (OSCC) is the sixth most common cancer worldwide and accounts for 300,000 new cases yearly. The five-year survival rate is approximately 50% and the major challenges to improving patient prognosis include late presentation, treatment resistance, second primary tumours and the lack of targeted therapies. Therefore, there is a compelling need to develop novel therapeutic strategies. In this study, we have examined the effect of lysophosphatidic acid (LPA) on OSCC cell migration, invasion and response to radiation, and investigated the contribution of cyclooxygenase-2 (COX-2) in mediating the tumour promoting effects of LPA. Using the TCGA data set, we show that the expression of the lipid phosphate phosphatases (LPP), LPP1 and LPP3, was significantly down-regulated in OSCC tissues. There was no significant difference in the expression of the ENPP2 gene, which encodes for the enzyme autotaxin (ATX) that produces LPA, between OSCCs and control tissues but ENPP2 levels were elevated in a subgroup of OSCCs. To explore the phenotypic effects of LPA, we treated OSCC cell lines with LPA and showed that the lipid enhanced migration and invasion as well as suppressed the response of the cells to irradiation. We also show that LPA increased COX-2 mRNA and protein levels in OSCC cell lines and inhibition of COX-2 activity with the COX-2 inhibitor, NS398, attenuated LPA-induced OSCC cell migration. Collectively, our data show for the first time that COX-2 mediates some of the pro-tumorigenic effects of LPA in OSCC and identifies the ATX-LPP-LPA-COX-2 pathway as a potential therapeutic target for this disease.

CTEN Induces Tumour Cell Invasion and Survival and Is Prognostic in Radiotherapy-Treated Head and Neck Cancer

Head and neck squamous cell carcinoma (HNSCC) is a heterogenous disease treated with surgery and/or (chemo) radiotherapy, but up to 50% of patients with late-stage disease develop locoregional recurrence. Determining the mechanisms underpinning treatment resistance could identify new therapeutic targets and aid treatment selection. C-terminal tensin-like (CTEN) is a member of the tensin family, upregulated in several cancers, although its expression and function in HNSCC are unknown. We found that CTEN is commonly upregulated in HNSCC, particularly HPV-ve tumours. In vitro CTEN was upregulated in HPV-ve (n = 5) and HPV+ve (n = 2) HNSCC cell lines. Stable shRNA knockdown of CTEN in vivo significantly reduced tumour growth (SCC-25), and functional analyses in vitro showed that CTEN promoted tumour cell invasion, colony formation and growth in 3D-culture (SCC-25, Detroit 562). RNA sequencing of SCC-25 cells following CTEN siRNA knockdown identified 349 differentially expressed genes (logFC > 1, p < 0.05). Gene ontology analysis highlighted terms relating to cell locomotion and apoptosis, consistent with in vitro findings. A membrane-based antibody array confirmed that CTEN regulated multiple apoptosis-associated proteins, including HSP60 and cleaved caspase-3. Notably, in a mixed cohort of HPV+ve and HPV-ve HNSCC patients (n = 259), we found a significant, independent negative association of CTEN with prognosis, limited to those patients treated with (chemo)radiotherapy, not surgery, irrespective of human papillomavirus (HPV) status. These data show that CTEN is commonly upregulated in HNSCC and exerts several functional effects. Its potential role in modulating apoptotic response to therapy suggests utility as a predictive biomarker or radio-sensitising target.

Development of an in vitro model of the dentogingival junction using 3D organotypic constructs

OBJECTIVES

The overall aim was to propose a plausible model of the dentogingival junction (DGJ) to deepen our understanding of the extrinsic influences responsible for the development of the junctional epithelial phenotype. The specific objective was to test the hypothesis that epithelial migration and proliferation would be inhibited by periodontal ligament (PDL) fibroblasts in an in vitro model of the DGJ consisting of 3D organotypic cultures.

BACKGROUND

Previously, we showed that 3D organotypic cultures containing human gingival fibroblasts (HGF) supported the development of a multi-layered epithelium, while constructs containing human periodontal ligament fibroblasts (HPDLF) resulted in epithelial atrophy (Lu EMC, Hobbs C, Dyer CJ, Ghuman M, Hughes FJ. J Perio Res., 2020). However, changes in epithelial phenotype have not been studied within an in vitro model of the DGJ.

METHODS

The in vitro model of the DGJ comprised of a donor HGF construct (H400 epithelium overlying HGF-collagen matrix) supported by a dimensionally larger recipient collagen bed enriched with HPDLF. Samples were harvested, fixed and processed for immunohistochemistry. The changes in epithelial migration and proliferation following contact with HPDLF were assessed by measuring the horizontal extension of the epithelial outgrowth on the recipient collagen matrix.

RESULTS

Within our in vitro model of the DGJ, epithelial migration and proliferation were inhibited following contact with the recipient HPDLF. By contrast, the control set-up showed a relative increase in epithelial growth, where the epithelium came into contact with the recipient HGF. Overall, there were limited changes in the molecular expression of keratin markers.

CONCLUSION

This study has proposed a plausible in vitro model of the DGJ to illustrate the role of different fibroblasts in the regulation of dentogingival epithelia. Furthermore, it suggests that the anatomical positional stability of the JE and its apparent resistance to apical migration could be associated with its interaction with the PDL.

Kava constituents exert selective anticancer effects in oral squamous cell carcinoma cells in vitro

Kava is a beverage made from the ground roots of the plant Piper Methysticum. Active compounds of Kava have previously been demonstrated to exert an antiproliferative effect through cell cycle arrest and promotion of apoptosis. Our aim was to investigate the in vitro effects of the main constituents derived from Kava on oral squamous cell carcinoma (OSCC) activity. Gas chromatography mass spectrometry (GCMS) was used to characterise the main constituents of two Kava preparations. Cell proliferation was assessed in two human OSCC cell lines (H400 and BICR56) and in normal oral keratinocytes (OKF6) treated with the identified Kava constituents, namely Flavokawain A (FKA), Flavokawain B (FKB), yangonin, kavain and methysticin using an MTS in vitro assay. Cell migration at 16 h was assessed using a Transwell migration assay. Cell invasion was measured at 22 h using a Matrigel assay. Cell adhesion was assessed at 90 min with a Cytoselect Adhesion assay. The two Kava preparations contained substantially different concentrations of the main chemical constituents. Treatment of malignant and normal oral keratinocyte cell lines with three of the identified constituents, 10 μg/ml FKA, 2.5 μg/ml FKB and 10 μg/ml yangonin, showed a significant reduction in cell proliferation in both H400 and BICR56 cancer cell lines but not in normal OKF6 cells. Remarkably, the same Kava constituents induced a significant reduction of OSCC cell migration and invasion. We have demonstrated, for the first time, that Kava constituents, FKA, FKB and yangonin have potential anticancer effects on OSCC. This highlights an avenue for further research of Kava constituents in the development of future cancer therapies to prevent and treat OSCC.

Differential regulation of epithelial growth by gingival and periodontal fibroblasts in vitro

OBJECTIVES

To investigate the underlying molecular mechanisms by which gingival and periodontal ligament (PDL) fibroblasts regulate epithelial phenotype.

BACKGROUND

Fibroblast populations regulate the epithelial phenotype through epithelial-mesenchymal interactions (EMI). Previous studies have proposed that maintenance of the junctional epithelium (JE) is dependent on the differential effects from gingival and PDL tissues. However, these cell populations are undefined and the signalling mechanisms which may regulate JE are unknown.

METHODS

Immunohistochemical analyses were performed on formalin-fixed paraffin-embedded sections of dentogingival tissues to identify phenotypic differences in fibroblast populations. The effect of distinct fibroblasts on epithelial phenotype was studied via 3D organotypic cultures, consisting of an H400 epithelium supported by human gingival fibroblasts (HGF) or human periodontal ligament fibroblasts (HPDLF), embedded in collagen gel. To investigate the involvement of Wnt signalling in EMI, the Wnt antagonist rhDKK1 was added to HGF constructs. The gene expression of Wnt antagonists and agonists was tested via RNA extraction and qPCR. Specific gene silencing using RNA interference was performed on HPDLF/HGF constructs.

RESULTS

Gingival fibroblasts were characterized by Sca1 expression, and PDL fibroblasts, characterized by Periostin and Asporin expression. Through the construction of 3D organotypic cultures, we showed that HGF supported epithelial multilayering, whilst HPDLF failed to support epithelial cell growth. Furthermore, HGF constructs treated with rhDKK1 resulted in a profound reduction in epithelial thickness. We identified SFRP4 to be highly specifically expressed in HPDLF, at both the mRNA and protein levels. A knockdown of SFRP4 in HPDLF constructs led to an increase in epithelial growth.

CONCLUSION

The study demonstrates the presence of phenotypically distinct fibroblast populations within dentogingival tissues and that these specific populations have different influences on the epithelium. Our data suggest that a downregulation of Wnt signalling within PDL may be important in maintaining the integrity and anatomical position of the JE.

Effects of Porphyromonas gingivalis and Fusobacterium nucleatum on inflammasomes and their regulators in H400 cells

INTRODUCTION

Inflammasomes are multiprotein complexes that regulate immune processes in response to infections and tissue damage. They modulate Interleukin-1beta (IL-1β) expression, a major proinflammatory cytokine. The inflammasome/IL-1β pathway is involved in head and neck squamous cell carcinoma (HNSCC) progression and the periodontal pathogens Fusobacterium nucleatum (Fn) and Porphyromonas gingivalis (Pg) have been reported to cause chronic inflammation in HNSCC. The aim of this study was to characterise the role of these pathogens in regulating inflammasome activity and the IL-1β response in HNSCC in vitro.

METHODS

An HNSCC cell line (H400) was exposed to Fn and Pg individually or in combination for 24h, ± incubation for 30 min with 5 mM adenosine triphosphate (ATP). Transcript levels of inflammasomes, NLRP3 and AIM2; inflammasome-regulatory proteins, POP1, CARD16 and TRIM16; and inflammasome-component, ASC and caspase 1 and IL-1β, were assayed by RT-PCR. Expression of IL-1β was by immunocytochemistry and ELISA.

RESULTS

NLRP3 expression was significantly upregulated in response to Pg, Fn + Pg, Pg + ATP and Fn + Pg + ATP. AIM2 was significantly upregulated by Fn, Pg and Fn + Pg + ATP exposure. All conditions significantly upregulated IL-1β gene expression. POP1 expression was significantly downregulated by Pg or Fn exposure but not by Fn + Pg. Intracellular pro- and mature IL-1β were significantly higher following Fn and Pg + ATP exposure.

CONCLUSION

Pg alone increased IL-1β by upregulating AIM2, NLRP3 and downregulating POP1. Fn promoted IL-1β by increasing AIM2 and downregulating POP1. Pg + ATP with or without Fn upregulated NLRP3, IL-1β by downregulating POP1. Periodontal pathogens may contribute to HNSCC pathogenesis by increasing the IL-1β response due to inflammasome dysregulation.

Inhibition of matrix metalloproteinase-2 modulates malignant behaviour of oral squamous cell carcinoma cells

BACKGROUND

Matrix metalloproteinases (MMPs) play a crucial role in the malignant phenotype of cancer cells. In particular, active levels of MMP2 in cancer cells have been associated with invasion and metastasis through the degradation of basement membrane extracellular matrix proteins. However, little is known about the role of this potential biomarker in oral cancer. Our aim was to investigate the effect of MMP2 inhibition on OSCC activity in vitro, as well as to assess MMP2 dysregulation in oral cancer samples.

METHODS

Human OSCC cell lines H357 and H400 were tested with the selective MMP2 inhibitor ARP101 and the MMP2 neutralising monoclonal antibody MA5-13590 to assess cell proliferation in vitro using MTS assay. Cell migration at 12/24 h was assessed using a Transwell migration assay. Cell invasion was assessed at 24 h using a Corning Matrigel invasion assay. MMP2 expression was assessed in 208 tissue samples (related to 60 OSCC cases and nine normal control) using tissue microarray (TMA) and further analysed via TCGA.

RESULTS

Both ARP101 and MA5-13590 monoclonal antibody reduced cell proliferation in both the cell lines tested. Treatment with 4μg/mL of MMP2 monoclonal antibody showed a significant decrease in cell migration at 24 hours. The administration of ARP101 and monoclonal antibody to H357 and H400 cell lines induced a drastic reduction in cell invasion at 24 h compared to the control. In patients, TCGA analysis demonstrated that oral cancer tissues express significantly higher levels of MMP2 mRNA compared to normal oral tissues. Further, IHC analysis on TMA showed significant difference in MMP2 protein expression between low and high histopathological grade OSCC.

CONCLUSIONS

We have demonstrated, for the first time, that MMP2 inhibition affects oral cancer cells ability to survive, migrate and invade in vitro. Differences between MMP2 expression in normal and malignant tissues varied. Further research on the role of MMP2 in OSCC and novel mechanisms to inhibit MMP2-dependent pathways should be encouraged.

Cisplatin-Resistance in Oral Squamous Cell Carcinoma: Regulation by Tumor Cell-Derived Extracellular Vesicles

Drug resistance remains a severe problem in most chemotherapy regimes. Recently, it has been suggested that cancer cell-derived extracellular vesicles (EVs) could mediate drug resistance. In this study, the role of EVs in mediating the response of oral squamous cell carcinoma (OSCC) cells to cisplatin was investigated. We isolated and characterized EVs from OSCC cell lines showing differential sensitivities to cisplatin. Increased EV production was observed in both de novo (H314) and adaptive (H103/cisD2) resistant lines compared to sensitive H103 cells. The protein profiles of these EVs were then analyzed. Differences in the proteome of EVs secreted by H103 and H103/cisD2 indicated that adaptation to cisplatin treatment caused significant changes in the secreted nanovesicles. Intriguingly, both resistant H103/cisD2 and H314 cells shared a highly similar EV protein profile including downregulation of the metal ion transporter, ATP1B3, in the EVs implicating altered drug delivery. ICP-MS analysis revealed that less cisplatin accumulated in the resistant cells, but higher levels were detected in their EVs. Therefore, we inhibited EV secretion from the cells using a proton pump inhibitor and observed an increased drug sensitivity in cisplatin-resistant H314 cells. This finding suggests that control of EV secretion could be a potential strategy to enhance the efficacy of cancer treatment.

Targeted magnetic nanoparticle hyperthermia for the treatment of oral cancer

INTRODUCTION

Patients with oral squamous cell carcinoma currently experience a five-year survival rate of approximately 60% with conventional surgical, chemotherapy and radiotherapy treatments. Magnetic hyperthermia offers an alternative treatment method by utilising the heating properties of magnetic nanoparticles to produce thermal ablation of the tumour site when exposed to an alternating magnetic field. In this study, we investigate in vitro if targeted magnetic hyperthermia offers a potential treatment for oral squamous cell carcinoma.

MATERIALS AND METHODS

Magnetic iron oxide nanoparticles, with a biocompatible silica coating, were produced and conjugated with antibodies to target integrin αvβ6, a well-characterised oral squamous cell carcinoma biomarker. Utilising the heating properties of the magnetic nanoparticles, we exposed them to an alternating magnetic field to produce thermo ablation of tumour cells either negative for or overexpressing integrin αvβ6.

RESULTS

The cell surface biomarker, αvβ6 integrin, was upregulated in tissue biopsies from oral squamous cell carcinoma patients compared to normal tissue. Functionalisation of the silica coating with anti-αvβ6 antibodies enabled direct targeting of the nanoparticles to αvβ6 overexpressing cells and applying thermal therapy significantly increased killing of the targeted tumour cells compared to control cells.

CONCLUSION

Combining antibody-targeting magnetic nanoparticles with thermal ablation offers a promising therapy for the targeted treatment of oral squamous cell carcinoma.

Comprehensive mapping of the methylation landscape of 16 CpG-dense regions in oral and pharyngeal squamous cell carcinoma

Aim: The goal of this study was to comprehensively interrogate and map DNA methylation across 16 CpG-dense regions previously associated with oral and pharyngeal squamous cell carcinoma (OPSCC). Materials & methods: Targeted multiplex bisulfite amplicon sequencing was performed on four OPSCC cell lines and primary non-neoplastic oral epithelial cells. Real-time quantitative polymerase chain reaction (RT-qPCR) was performed for a subset of associated genes. Results: There was clear differential methylation between one or more OPSCC cell lines and control cells for the majority of CpG-dense regions. Conclusion: Targeted multiplex bisulfite amplicon sequencing allowed us to efficiently map methylation across the entire region of interest with a high degree of sensitivity and helps shed light on novel differentially methylated regions that may have value as biomarkers of OPSCC.

A miRNA-145/TGF-β1 negative feedback loop regulates the cancer-associated fibroblast phenotype

The dissemination of cancer cells to local and distant sites depends on a complex and poorly understood interplay between malignant cells and the cellular and non-cellular components surrounding them, collectively termed the tumour microenvironment. One of the most abundant cell types of the tumour microenvironment is the fibroblast, which becomes corrupted by locally derived cues such as TGF-β1 and acquires an altered, heterogeneous phenotype (cancer-associated fibroblasts, CAF) supportive of tumour cell invasion and metastasis. Efforts to develop new treatments targeting the tumour mesenchyme are hampered by a poor understanding of the mechanisms underlying the development of CAF. Here, we examine the contribution of microRNA to the development of experimentally-derived CAF and correlate this with changes observed in CAF derived from tumours. Exposure of primary normal human fibroblasts to TGF-β1 resulted in the acquisition of a myofibroblastic CAF-like phenotype. This was associated with increased expression of miR-145, a miRNA predicted in silico to target multiple components of the TGF-β signalling pathway. miR-145 was also overexpressed in CAF derived from oral cancers. Overexpression of miR-145 blocked TGF-β1-induced myofibroblastic differentiation and reverted CAF towards a normal fibroblast phenotype. We conclude that miR-145 is a key regulator of the CAF phenotype, acting in a negative feedback loop to dampen acquisition of myofibroblastic traits, a key feature of CAF associated with poor disease outcome.

Cell culture models of oral mucosal barriers: A review with a focus on applications, culture conditions and barrier properties

Understanding the function of oral mucosal epithelial barriers is essential for a plethora of research fields such as tumor biology, inflammation and infection diseases, microbiomics, pharmacology, drug delivery, dental and biomarker research. The barrier properties are comprised by a physical, a transport and a metabolic barrier, and all these barrier components play pivotal roles in the communication between saliva and blood. The sum of all epithelia of the oral cavity and salivary glands is defined as the blood-saliva barrier. The functionality of the barrier is regulated by its microenvironment and often altered during diseases. A huge array of cell culture models have been developed to mimic specific parts of the blood-saliva barrier, but no ultimate standard in vitro models have been established. This review provides a comprehensive overview about developed in vitro models of oral mucosal barriers, their applications, various cultivation protocols and corresponding barrier properties.

Glucocorticoids reduce chemotherapeutic effectiveness on OSCC cells via glucose-dependent mechanisms

Synthetic corticosteroids are routinely administered during the treatment of several diseases, including malignancies. However, recent evidence suggests that corticosteroids may have tumor-promoting effects, particularly in epithelial neoplasms. Our aim was to assess the role of the recently characterized cancer-associated glucocorticoid (GC) system in the resistance to chemotherapy of oral malignant keratinocytes. Human malignant oral keratinocyte cell lines H314/H357/H400/BICR16/BICR56 were tested with: two chemotherapeutic agents, doxorubicin (DOXO) and 5-fluorouracil (5-FU), as well as hydrocortisone (HC), adrenocorticotropic hormone (ACTH), 5-pregnen-3-beta-ol-20-one-16-alfa-carbonitrile (PCN), and two glucose uptake inhibitors, Fasentin and WZB. Both DOXO and 5-FU induced apoptosis in a dose-dependent and time-dependent manner. HC administration (100 nM) reduced the effectiveness of both chemotherapeutic agents to a variable extent in all 5 oral squamous cell carcinoma cell lines. ACTH also reduced the effectiveness of DOXO on 2 cell lines tested (H357 and BICR56). The glucose uptake inhibitors Fasentin and WZB were able to partially block the increased resistance to the cytotoxic drugs induced by HC. In summary, we have demonstrated, for the first time, the importance of cortisol on oral cancer cells ability to proliferate and combat the effectiveness of chemotherapeutic agents. This effect appears to be glucose dependent.

Automated noninvasive epithelial cell counting in phase contrast microscopy images with automated parameter selection

Cell counting is commonly used to determine proliferation rates in cell cultures and for adherent cells it is often a ‘destructive’ process requiring disruption of the cell monolayer resulting in the inability to follow cell growth longitudinally. This process is time consuming and utilises significant resource. In this study a relatively inexpensive, rapid and widely applicable phase contrast microscopy‐based technique has been developed that emulates the contrast changes taking place when bright field microscope images of epithelial cell cultures are defocused. Processing of the resulting images produces an image that can be segmented using a global threshold; the number of cells is then deduced from the number of segmented regions and these cell counts can be used to generate growth curves. The parameters of this method were tuned using the discrete mereotopological relations between ground truth and processed images. Cell count accuracy was improved using linear discriminant analysis to identify spurious noise regions for removal.

The proposed cell counting technique was validated by comparing the results with a manual count of cells in images, and subsequently applied to generate growth curves for oral keratinocyte cultures supplemented with a range of concentrations of foetal calf serum. The approach developed has broad applicability and utility for researchers with standard laboratory imaging equipment.

An early report: a modified porphyrin-linked metronidazole targeting intracellular Porphyromonas gingivalis in cultured oral epithelial cells

Porphyromonas gingivalis (P. gingivalis) has a strong association with the pathogenesis of periodontal disease. Recurrence of periodontal disease following therapy is attributed to numerous factors, and of growing interest is the potential problem of intracellular bacteria that are able to persist and multiply within the host cell, thereby facilitating relapse of infection. The effect of antibiotic therapy in controlling P. gingivalis is questionable. Accordingly, while metronidazole is very effective against anaerobic extracellular P. gingivalis by disrupting the DNA of anaerobic microbial cells, this antibiotic does not effectively penetrate into mammalian cells to inhibit intracellular bacteria. Therefore in the present study, a modified porphyrin-linked metronidazole adducts, developed in our laboratory, was used to kill intracellular P. gingivalis. A series of experiments were performed, including cytotoxicity assays and cellular uptake of adducts by flow cytometry coupled with live cell imaging analysis, P. gingivalis invasion and elimination assays, and the analysis of colocalization of P. gingivalis and porphyrin-linked metronidazole by confocal laser scanning microscopy. Findings indicated that P. gingivalis and porphyrin-linked metronidazole were colocalized in the cytoplasm, and this compound was able to kill P. gingivalis intracellular with a sufficient culture time. This is a novel antimicrobial approach in the elimination of P. gingivalis from the oral cavity.

Immune receptors CD40 and CD86 in oral keratinocytes and implications for oral lichen planus

Lichen planus (LP) is a chronic T-cell-mediated mucocutaneous inflammatory disease that targets stratified epithelia, including those lining the oral cavity. The intraoral variant of LP (OLP) is associated with interferon (IFN)-γ production by infiltrating T lymphocytes; however, the role of epithelial cells in the etiopathogenesis OLP is not completely understood. There is however a growing body of evidence regarding the involvement of epithelial-derived cytokines, immune receptors, and costimulatory molecules in the pathobiological processes that promote and sustain OLP. In the present study, we used a reverse transcriptase-polymerase chain reaction assay to assess whether CD40-a receptor found mainly on antigen presenting cells-and the costimulatory molecule CD86 were expressed in oral keratinocytes (three strains of primary normal oral keratinocytes and the H357 cell line) in the presence or absence of IFN-γ. To further characterize the involvement of CD40 in OLP, expression and distribution of receptor and ligand (CD40/CD154) in tissues from OLP were evaluated by immunohistochemistry. The present results are the first to show that both CD40 and CD86 are constitutively expressed at low levels in oral keratinocytes and that their expression was enhanced by IFN-γ stimulation. The intensity of CD40 staining in OLP tissues was strong. Taken together, the results strongly suggest that CD40 and CD86 play a role in the pathophysiology of oral inflammatory diseases such as OLP.

HPV16 increases the number of migratory cancer stem cells and modulates their miRNA expression profile in oropharyngeal cancer

Human papillomavirus type 16 (HPV16) is a major risk for development of oropharyngeal squamous-cell-carcinoma (OPSCC). Although HPV⁺ OPSCC metastasize faster than HPV^- tumors, they have a better prognosis. The molecular and cellular alterations underlying this pathobiology of HPV⁺ OPSCC remain elusive. In this study, we examined whether expression of HPV16-E6E7 targets the number of migratory and stationary cancer stem cells (CSC). Furthermore, we wanted to elucidate if aberrantly expressed miRNAs in migratory CSC may be responsible for progression of OPSCCs and whether they may serve as potential novel biomarkers for increased potential of metastasis. Our studies revealed that HPV16-E6E7 expression leads to an increase in the number of stationary (CD44^high /EpCAM^high ) stem cells in primary keratinocyte cultures. Most importantly, expression of E6E7 in the cell line H357 increased the migratory (CD44^high /EpCAM^low ) CSC pool. This increase in migratory CSCs could also be confirmed in HPV⁺ OPSCC. Differentially expressed miRNAs from HPV16-E6E7 positive CD44^high /EpCAM^low CSCs were validated by RT-qPCR and in situ hybridization on HPV16⁺ OPSCCs. These experiments led to the identification of miR-3194-5p, which is upregulated in primary HPV16⁺ OPSCC and matched metastasis. MiR-1281 was also found to be highly expressed in HPV⁺ and HPV^- metastasis. As inhibition of this miRNA led to a markedly reduction of CD44^high /EpCAM^low cells, it may prove to be a promising drug target. Taken together, our findings highlight the capability of HPV16 to modify the phenotype of infected stem cells and that miR-1281 and miR3194-5p may represent promising targets to block metastatic spread of OPSCC.

GENIPAC: A Genomic Information Portal for Head and Neck Cancer Cell Systems

Head and neck cancer (HNC)–derived cell lines represent fundamental models for studying the biological mechanisms underlying cancer development and precision therapies. However, mining the genomic information of HNC cells from available databases requires knowledge on bioinformatics and computational skill sets. Here, we developed a user-friendly web resource for exploring, visualizing, and analyzing genomics information of commonly used HNC cell lines. We populated the current version of GENIPAC with 44 HNC cell lines from 3 studies: ORL Series, OPC-22, and H Series. Specifically, the mRNA expressions for all the 3 studies were derived with RNA-seq. The copy number alterations analysis of ORL Series was performed on the Genome Wide Human Cytoscan HD array, while copy number alterations for OPC-22 were derived from whole exome sequencing. Mutations from ORL Series and H Series were derived from RNA-seq information, while OPC-22 was based on whole exome sequencing. All genomic information was preprocessed with customized scripts and underwent data validation and correction through data set validator tools provided by cBioPortal. The clinical and genomic information of 44 HNC cell lines are easily assessable in GENIPAC. The functional utility of GENIPAC was demonstrated with some of the genomic alterations that are commonly reported in HNC, such as TP53, EGFR, CCND1, and PIK3CA. We showed that these genomic alterations as reported in The Cancer Genome Atlas database were recapitulated in the HNC cell lines in GENIPAC. Importantly, genomic alterations within pathways could be simultaneously visualized. We developed GENIPAC to create access to genomic information on HNC cell lines. This cancer omics initiative will help the research community to accelerate better understanding of HNC and the development of new precision therapeutic options for HNC treatment. GENIPAC is freely available at http://genipac.cancerresearch.my/ .

Analysis of differential expression of tight junction proteins in cultured oral epithelial cells altered by Porphyromonas gingivalis, Porphyromonas gingivalis lipopolysaccharide, and extracellular adenosine triphosphate

Tight junctions (TJs) are the most apical intercellular junctions of epithelial cells formed by occludin, claudins, junctional adhesion molecules (JAMs), and zonula occludens (ZO). Tight junction proteins can sense the presence of bacteria and regulate the transcription of target genes that encode effectors and regulators of the immune response. The aim of this study was to determine the impact of TJ proteins in response to Porphyromonas gingivalis (P. gingivalis), P. gingivalis lipopolysaccharide (P. gingivalis LPS), and extracellular adenosine triphosphate (ATP) in the oral epithelial cell culture model. Quantified real time-polymerase chain reaction (RT-PCR), immunoblots, and immunostaining were performed to assess the gene and protein expression in TJs. It was found that P. gingivalis infection led to transient upregulation of the genes encoding occludin, claudin-1, and claudin-4 but not JAM-A, claudin-15, or ZO-1, while P. gingivalis LPS increased claudin-1, claudin-15, and ZO-1 and decreased occludin, JAM-A, and claudin-4. Tight junction proteins showed significant upregulation in the above two groups when cells were pretreated with ATP for 3 h. The findings indicated that P. gingivalis induced the host defence responses at an early stage. P. gingivalis LPS exerted a more powerful stimulatory effect on the disruption of the epithelial barrier than P. gingivalis. ATP stimulation enhanced the reaction of TJ proteins to P. gingivalis invasion and LPS destruction of the epithelium.

Oral keratinocytes synthesize CTACK: A new insight into the pathophysiology of the oral mucosa

The skin-associated chemokine CTACK plays a key role in many inflammatory conditions and could be instrumental in the pathophysiology of tissue-specific immunological diseases such as oral lichen planus (OLP). In this study, we investigated, by RT-PCR, ELISA, chemotaxis assays, and fluorescence-activated cell sorting (FACS), the production of CTACK in oral keratinocytes, its expression in tissues from normal and OLP patients, and its role in T-cell recruitment.CTACK was produced by the oral epithelium, and it affects chemotaxis of memory CLA+ cells to the oral epithelium. CTACK mRNA was expressed constitutively in primary oral epithelium and was increased during pro-inflammatory IFN-γ treatment. We found a constitutive production of CTACK at a protein level in oral primary cells that increased after IFN-γ treatment. Moreover, we confirmed that CTACK attracts memory T cells and those T cells that express CLA above the level of basal migration.

Inhibition of Notch signaling pathway using γ-secretase inhibitor delivered by a low dose of Triton-X100 in cultured oral cancer cells

How to effectively delivering therapeutic agents, including γ-secretase inhibitors (GSIs), into live cells, remains a significant challenge. This study assessed the effect of Notch signaling inhibition by examining levels of the Notch1 intracellular domain (N1ICD) in cultured oral cancer cells analyzed with random stitched images (2D) and 3D visualizations using confocal microscopy and quantitative gene analysis. Substantially, we have developed a novel method to assist the delivery of γ-secretase inhibitor, DAPT, into live cells in the presence of an effective minimum concentration of Triton-X100 (0.001%) without damaging cell activity and membrane integrity assessed with cell proliferation assays. The images obtained in this study showed that DAPT alone could not block the γ-secretase inhibitor despite inhibiting cell growth. Further analysis of quantitative gene expressions of Notch signaling canonical pathway to verify the effectiveness of the novel method for delivering inhibitor into live cells, displayed deregulation of Notch1, Delta-like ligand 1 (DLL1) and hairy and enhancer of split 1 (Hes1). Our data suggest that Notch1/Hes1 signaling pathway is deactivated using DAPT with a low dose of Triton-X100 in this cancer cells. And the finding also suggests that Notch1 could be engaged by DLL1 to promote differentiation in oral cancer cells. Using this approach, we demonstrate that Triton-X100 is a promising and effective permeabilization agent to deliver γ-secretase inhibitor DAPT into live oral epithelial cells. This strategy has the potential to implicate in the treatment of cancer diseases.

Genetically-defined novel oral squamous cell carcinoma cell lines for the development of molecular therapies

Emerging biological and translational insights from large sequencing efforts underscore the need for genetically-relevant cell lines to study the relationships between genomic alterations of tumors, and therapeutic dependencies. Here, we report a detailed characterization of a novel panel of clinically annotated oral squamous cell carcinoma (OSCC) cell lines, derived from patients with diverse ethnicity and risk habits. Molecular analysis by RNAseq and copy number alterations (CNA) identified that the cell lines harbour CNA that have been previously reported in OSCC, for example focal amplications in 3q, 7p, 8q, 11q, 20q and deletions in 3p, 5q, 8p, 18q. Similarly, our analysis identified the same cohort of frequently mutated genes previously reported in OSCC including TP53, CDKN2A, EPHA2, FAT1, NOTCH1, CASP8 and PIK3CA. Notably, we identified mutations (MLL4, USP9X, ARID2) in cell lines derived from betel quid users that may be associated with this specific risk factor. Gene expression profiles of the ORL lines also aligned with those reported for OSCC. By focusing on those gene expression signatures that are predictive of chemotherapeutic response, we observed that the ORL lines broadly clustered into three groups (cell cycle, xenobiotic metabolism, others). The ORL lines noted to be enriched in cell cycle genes responded preferentially to the CDK1 inhibitor RO3306, by MTT cell viability assay. Overall, our in-depth characterization of clinically annotated ORL lines provides new insight into the molecular alterations synonymous with OSCC, which can facilitate in the identification of biomarkers that can be used to guide diagnosis, prognosis, and treatment of OSCC.

A miR-335/COX-2/PTEN axis regulates the secretory phenotype of senescent cancer-associated fibroblasts

Senescent cancer-associated fibroblasts (CAF) develop a senescence-associated secretory phenotype (SASP) that is believed to contribute to cancer progression. The mechanisms underlying SASP development are, however, poorly understood. Here we examined the functional role of microRNA in the development of the SASP in normal fibroblasts and CAF. We identified a microRNA, miR-335, up-regulated in the senescent normal fibroblasts and CAF and able to modulate the secretion of SASP factors and induce cancer cell motility in co-cultures, at least in part by suppressing the expression of phosphatase and tensin homologue (PTEN). Additionally, elevated levels of cyclo-oxygenase 2 (PTGS2; COX-2) and prostaglandin E2 (PGE2) secretion were observed in senescent fibroblasts, and inhibition of COX-2 by celecoxib reduced the expression of miR-335, restored PTEN expression and decreased the pro-tumourigenic effects of the SASP. Collectively these data demonstrate the existence of a novel miRNA/PTEN-regulated pathway modulating the inflammasome in senescent fibroblasts.

Periodontal pathogens promote epithelial-mesenchymal transition in oral squamous carcinoma cells in vitro

Epithelial-mesenchymal transition (EMT) is potentially involved in increasing metastasis of oral squamous cell carcinoma (OSCC). Periodontal pathogens are well-known for their ability to induce intense immune responses and here we investigated whether they are involved in inducing EMT. Cultures of OSCC cell line (H400) were treated separately with heat-killed periodontal pathogens F. nucleatum, or P. gingivalis or E. coli LPS for 8 d. EMT-associated features were assayed using sq-PCR and PCR-arrays, for EMT-related markers, and ELISAs for TGF-β1, TNF-α, and EGF. The migratory ability of cells was investigated using scratch and transwell migration assays. E-cadherin and vimentin expression was assessed using immunofluorescence while Snail activation was detected with immunocytochemistry. In addition, the integrity of the cultured epithelial layer was investigated using transepithelial electrical resistance (TEER). PCR data showed significant upregulation after 1, 5, and 8 d in transcription of mesenchymal markers and downregulation of epithelial ones compared with unstimulated controls, which were confirmed by immunofluorescence. Periodontal pathogens also caused a significant increase in level of all cytokines investigated which could be involved in EMT-induction and Snail activation. Exposure of cells to the bacteria increased migration and the rate of wound closure. Downregulation of epithelial markers also resulted in a significant decrease in impedance resistance of cell monolayers to passage of electrical current. These results suggested that EMT was likely induced in OSCC cells in response to stimulation by periodontal pathogens.

Comprehensive microRNA-sequencing of exosomes derived from head and neck carcinoma cells in vitro reveals common secretion profiles and potential utility as salivary biomarkers

Exosomes are nano-scale, membrane encapsulated vesicles that are released by cells into the extracellular space and function as intercellular signaling vectors through horizontal transfer of biologic molecules, including microRNA (miRNA). There is evidence that cancer-derived exosomes enable the tumor to manipulate its microenvironment, thus contributing to the capacity of the tumor for immune evasion, growth, invasion, and metastatic spread. The objective of this study was to characterize differential secretion of exosomal miRNA by head and neck squamous cell carcinoma (HNSCC) and identify a set of candidate biomarkers that could be detected in non-invasive saliva samples. We isolated exosomes from conditioned media from 4 HNSCC cell lines and oral epithelial control cells and applied miRNA-sequencing to comprehensively characterize their miRNA cargo and compare transcript levels of each HNSCC cell line to that of oral epithelial control cells. A candidate set of miRNA differentially secreted by all 4 HNSCC cell lines was further evaluated in saliva collected from HNSCC patients and healthy controls. We observed extensive differences in exosomal miRNA content between HNSCC cells when compared to normal oral epithelial control cells, with a high degree of overlap in exosomal miRNA profiles between the 4 distinct HNSCC cell lines. Importantly, several of the exosomal miRNA secreted solely by cancer cells in culture were detected at substantially elevated levels in saliva from HNSCC patients relative to saliva from healthy controls. These findings provide important insight into tumor biology and yields a promising set of candidate HNSCC biomarkers for use with non-invasive saliva samples.

Hepatic gene therapy rescues high-fat diet responses in circadian Clock mutant mice

OBJECTIVE

Circadian Clock gene mutant mice show dampened 24-h feeding rhythms and an increased sensitivity to high-fat diet (HFD) feeding. Restricting HFD access to the dark phase counteracts its obesogenic effect in wild-type mice. The extent to which altered feeding rhythms are causative for the obesogenic phenotype of Clock mutant mice, however, remains unknown.

METHODS

Metabolic parameters of wild-type (WT) and ClockΔ19 mutant mice (MT) were investigated under ad libitum and nighttime restricted HFD feeding. Liver circadian clock function was partially rescued by hydrodynamic tail vein delivery of WT-Clock DNA vectors in mutant mice and transcriptional, metabolic, endocrine and behavioral rhythms studied.

RESULTS

Nighttime-restricted feeding restored food intake, but not body weight regulation in MT mice under HFD, suggesting Clock-dependent metabolic dysregulation downstream of circadian appetite control. Liver-directed Clock gene therapy partially restored liver circadian oscillator function and transcriptome regulation without affecting centrally controlled circadian behaviors. Under HFD, MT mice with partially restored liver clock function (MT-LR) showed normalized body weight gain, rescued 24-h food intake rhythms, and WT-like energy expenditure. This was associated with decreased nighttime leptin and daytime ghrelin levels, reduced hepatic lipid accumulation, and improved glucose tolerance. Transcriptome analysis revealed that hepatic Clock rescue in MT mice affected a range of metabolic pathways.

CONCLUSION

Liver Clock gene therapy improves resistance against HFD-induced metabolic impairments in mice with circadian clock disruption. Restoring or stabilizing liver clock function might be a promising target for therapeutic interventions in obesity and metabolic disorders.

Tissue-specific regulation of CXCL9/10/11 chemokines in keratinocytes: Implications for oral inflammatory disease

The IFN-γ-inducible chemokines CXCL9, CXCL10, and CXCL11 play a key role in many inflammatory conditions, particularly those mediated by T cells. Therefore, the production of these chemokines in peripheral tissues could be instrumental in the pathophysiology of tissue-specific immunological diseases such as oral lichen planus (OLP). In the present study, we assessed the production of keratinocyte-derived CXCL9/10/11 under basal and inflammatory conditions and investigated whether these chemokines were involved in the pathogenesis of OLP. We used semi-quantitative PCR, ELISA, chemotaxis assays, and fluorescence-activated cell sorting (FACS) to assess the expression and functional role of CXCL9/10/11 in oral keratinocytes (three strains of normal human oral keratinocytes (NHOK), and the H357 oral cancer cell line) in the presence or absence of IFN-γ. CXCL9/10/11 were also assessed in tissues from normal patients and those with oral lichen planus (OLP). The time course study in oral keratinocytes treated with IFN-γ showed that expression of CXCL9/10/11 chemokines was significantly enhanced by IFN-γ in a time-dependent manner. In particular, CXCL10, a prominent chemokine that was overexpressed by IFN-γ-stimulated NHOK, was able to effectively recruit CD4 lymphocytes, mainly CD4+CD45RA- cells. Significantly higher levels of CXCL9/10/11 were found in tissues from patients with OLP compared to normal oral mucosa. Taken together, the results demonstrate that normal oral keratinocytes produce chemotactic molecules that mediate T cell recruitment. This study furthers understanding of chemokine production in oral keratinocytes and their role in the pathophysiology of oral mucosa, with particular relevance to OLP.

Oral Epithelial Cell Culture Model for Studying the Pathogenesis of Chronic Inflammatory Disease

The interactions between bacteria, epithelium, and neutrophilic polymorphonuclear leukocytes (neutrophils) are the key to the initiation and progression of many chronic inflammatory-immune diseases. In addition, all can be influenced by external factors, such as micronutrients, thereby providing potentially novel approaches to therapy. This chapter will therefore provide detailed methods for core techniques involved in studying cellular and molecular epithelial responses to a bacterial challenge in relation to chronic inflammatory disease pathogenesis and therapy.

HOPX functions as a tumour suppressor in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is generalized term that encompasses a diverse group of cancers that includes tumours of the oral cavity (OSCC), oropharynx (OPSCC) and nasopharynx (NPC). Genetic alterations that are common to all HNSCC types are likely to be important for squamous carcinogenesis. In this study, we have investigated the role of the homeodomain-only homeobox gene, HOPX, in the pathogenesis of HNSCC. We show that HOPX mRNA levels are reduced in OSCC and NPC cell lines and tissues and there is a general reduction of HOPX protein expression in these tumours and OPSCCs. HOPX promoter methylation was observed in a subset of HNSCCs and was associated with a worse overall survival in HPV negative tumours. RNAseq analysis of OSCC cells transfected with HOPX revealed a widespread deregulation of the transcription of genes related to epithelial homeostasis and ectopic over-expression of HOPX in OSCC and NPC cells inhibited cell proliferation, plating efficiency and migration, and enhanced sensitivity to UVA-induced apoptosis. Our results demonstrate that HOPX functions as a tumour suppressor in HNSCC and suggest a central role for HOPX in suppressing epithelial carcinogenesis.

Copper supplementation amplifies the anti-tumor effect of curcumin in oral cancer cells

BACKGROUND

Oral cancer is the sixth most common cancer worldwide and 90% of oral malignancies are caused by oral squamous cell carcinoma (OSCC). Curcumin, a phytocompound derived from turmeric (Curcuma longa) was observed to have anti-cancer activity which can be developed as an alternative treatment option for OSCC. However, OSCC cells with various clinical-pathological features respond differentially to curcumin treatment.

HYPOTHESIS

Intracellular copper levels have been reported to correlate with tumor pathogenesis and affect the sensitivity of cancer cells to cytotoxic chemotherapy. We hypothesized that intracellular copper levels may affect the sensitivity of oral cancer cells to curcumin.

METHODS

We analysed the correlation between intracellular copper levels and response to curcumin treatment in a panel of OSCC cell lines derived from oral cancer patients. Exogenous copper was supplemented in curcumin insensitive cell lines to observe the effect of copper on curcumin-mediated inhibition of cell viability and migration, as well as induction of oxidative stress and apoptosis. Protein markers of cell migration and oxidative stress were also analysed using Western blotting.

RESULTS

Concentrations of curcumin which inhibited 50% OSCC cell viability (IC₅₀) was reduced up to 5 times in the presence of 250 µM copper. Increased copper level in curcumin-treated OSCC cells was accompanied by the induction of intracellular ROS and increased level of Nrf2 which regulates oxidative stress responses in cells. Supplemental copper also inhibited migration of curcumin-treated cells with enhanced level of E-cadherin and decreased vimentin, indications of suppressed epithelial-mesenchymal transition. Early apoptosis was observed in combined treatment but not in treatment with curcumin or copper alone.

CONCLUSION

Supplement of copper significantly enhanced the inhibitory effect of curcumin treatment on migration and viability of oral cancer cells. Together, these findings provide molecular insight into the role of copper in overcoming insensitivity of oral cancer cells to curcumin treatment, suggesting a new strategy for cancer therapy.

Antimicrobial activity and regulation of CXCL9 and CXCL10 in oral keratinocytes

Chemokine (C-X-C motif) ligand (CXCL)9 and CXCL10 are dysregulated in oral inflammatory conditions, and it is not known if these chemokines target microorganisms that form oral biofilm. The aim of this study was to investigate the antimicrobial activity of CXCL9 and CXCL10 on oral microflora and their expression profiles in oral keratinocytes following exposure to inflammatory and infectious stimuli. Streptococcus sanguinis was used as a model and Escherichia coli as a positive control. The antimicrobial effect of CXCL9/CXCL10 was tested using a radial diffusion assay. mRNA transcripts were isolated from lipopolysaccharide (LPS)-treated and untreated (control) oral keratinocyte cell lines at 2-, 4-, 6-, and 8-h time-points of culture. The CXCL9/10 expression profile in the presence or absence of interferon-γ (IFN-γ) was assessed using semiquantitative PCR. Although both chemokines demonstrated antimicrobial activity, CXCL9 was the most effective chemokine against both S. sanguinis and E coli. mRNA for CXCL10 was expressed in control cells and its production was enhanced at all time-points following stimulation with LPS. Conversely, CXCL9 mRNA was not expressed in control or LPS-stimulated cells. Finally, stimulation with IFN-γ enhanced basal expression of both CXCL9 and CXCL10 in oral keratinocytes. Chemokines derived from oral epithelium, particularly CXCL9, demonstrate antimicrobial properties. Bacterial and inflammatory-stimulated up-regulation of CXCL9/10 could represent a key element in oral bacterial colonization homeostasis and host-defense mechanisms.

Three/four-dimensional (3D/4D) microscopic imaging and processing in clinical dental research

BACKGROUND

Confocal laser scanning microscope (CLSM) has been widely employed in our laboratory for structural and functional analysis of clinical dental specimens and live cell imaging of cultured oral epithelial cells.

METHODS

In this vitro study, a Fluoview 1000 (Olympus) confocal system was utilised to study thick sections of carious lesions (40-100 μm) and periodontal disease tissue samples (20-40 μm) by 2D Z stacking imaging and 3-dimentional (3D) reconstruction. Four-dimensional (4D) imaging when including time or position points was used for live cells to assess penetration/localisation/co-localization of oral pathogen proteins and therapeutic drugs.

RESULTS

Three-dimensional (3D) reconstruction revealed latent features of carious hard tissues (strongly expressed amelogenin proteins in dentin tubules), and soft tissues (increased glial markers GFAP and S100B in pulp components). We also found the oral microbial specific pathogens, Porphyromonas gingivalis to be widely localised inside the periodontal pocket epithelial tissues as detected by 3D reconstruction from a series of 2D sections from periodontal disease tissue samples. 4D live cell imaging showed the diffusion patterns of fluorescent molecules in response to a bacterial virulence factor, the pathogen (gingipain haemagglutinin) domain that attacked epithelial integrity. This technology also showed uptake of a novel porphyrin-linked metronidazole antibiotic into epithelial cells to kill intracellular oral pathogen, P. gingivalis.

CONCLUSIONS

Three/four-dimensional (3D/4D) imaging and processing in confocal microscopy is of great interest and benefit to clinical dental researchers.

Aberrant expression of the S1P regulating enzymes, SPHK1 and SGPL1, contributes to a migratory phenotype in OSCC mediated through S1PR2

Oral squamous cell carcinoma (OSCC) is a lethal disease with a 5-year mortality rate of around 50%. Molecular targeted therapies are not in routine use and novel therapeutic targets are required. Our previous microarray data indicated sphingosine 1-phosphate (S1P) metabolism and signalling was deregulated in OSCC. In this study, we have investigated the contribution of S1P signalling to the pathogenesis of OSCC. We show that the expression of the two major enzymes that regulate S1P levels were altered in OSCC: SPHK1 was significantly upregulated in OSCC tissues compared to normal oral mucosa and low levels of SGPL1 mRNA correlated with a worse overall survival. In in vitro studies, S1P enhanced the migration/invasion of OSCC cells and attenuated cisplatin-induced death. We also demonstrate that S1P receptor expression is deregulated in primary OSCCs and that S1PR2 is over-expressed in a subset of tumours, which in part mediates S1P-induced migration of OSCC cells. Lastly, we demonstrate that FTY720 induced significantly more apoptosis in OSCC cells compared to non-malignant cells and that FTY720 acted synergistically with cisplatin to induce cell death. Taken together, our data show that S1P signalling promotes tumour aggressiveness in OSCC and identify S1P signalling as a potential therapeutic target.