Modulation of pathogenic oral biofilms towards health with nisin probiotic

Background

Oral dysbiosis is an imbalance in the oral microbiome and is associated with a variety of oral and systemic diseases, including periodontal disease, caries, and head and neck/oral cancer. Although antibiotics can be used to control this dysbiosis, they can lead to adverse side effects and superinfections. Thus, novel strategies have been proposed to address these shortcomings. One strategy is the use of probiotics as antimicrobial agents, since they are considered safe for humans and the environment. Specifically, the Gram-positive Lactococcus lactis, a species present in the oral and gut microbiota, is able to produce nisin, which has been used worldwide for food preservation.

Objective

The objective of this study was to test whether a nisin probiotic can promote a healthier oral microbiome in pathogen-spiked oral biofilms.

Results

We found that L. lactis can prevent oral biofilm formation and disrupt 24-h and 48-h pre-formed biofilms. Finally, we demonstrate that both treatments, a nisin-producing L. lactis probiotic and nisin can decrease the levels of pathogens in the biofilms and return the diversity levels back to control or ‘healthy’ levels.

Conclusion

A nisin-producing probiotic, can be used to treat ‘disease-altered’ biofilms and promote healthier oral biofilms, which may be useful for improving patient oral health.

Rebuilding the Interproximal Papilla: Description of "Tube" Technique and Two Case Reports

INTRODUCTION

Papilla reconstruction relies on similar principles as those applied to soft tissue grafting for recession defects; however, it is uniquely challenging from a surgical perspective because of the small size and lack of a blood supply. Several techniques have been used to reconstruct lost papilla; however, there are no prescribed techniques for this specific application.

CASE PRESENTATION

This report describes a novel technique, herein called, the "tube technique" for treating interproximal recession and reconstructing the interproximal papilla, and documents two cases using the tube technique. An increase in attachment levels was observed in Case 1 (5 mm) and in Case 2 (4 mm) after using this surgical technique for papilla reconstruction.

CONCLUSION

The tube grafting technique requires technical precision. Although when executed carefully, it results in predictable reconstruction of the interproximal papilla. Use of the tube technique helps mitigate issues associated with inadequate flap thickness, blood supply, and flap retraction.

Host-microbe interactions: Profiles in the transcriptome, the proteome, and the metabolome

Periodontal studies using transcriptomics, proteomics, and metabolomics encompass the collection of mRNA transcripts, proteins, and small-molecule chemicals in the context of periodontal health and disease. The number of studies using these approaches has significantly increased in the last decade and they have provided new insight into the pathogenesis and host-microbe interactions that define periodontal diseases. This review provides an overview of current molecular findings using -omic approaches that underlie periodontal disease, including modulation of the host immune response, tissue homeostasis, and complex metabolic processes of the host and the oral microbiome. Integration of these -omic approaches will broaden our perspective of the molecular mechanisms involved in periodontal disease, advancing and improving the diagnosis and treatment of various stages and forms of periodontal disease.

Polymicrobial periodontal disease triggers a wide radius of effect and unique virome

Periodontal disease is a microbially-mediated inflammatory disease of tooth-supporting tissues that leads to bone and tissue loss around teeth. Although bacterially-mediated mechanisms of alveolar bone destruction have been widely studied, the effects of a polymicrobial infection on the periodontal ligament and microbiome/virome have not been well explored. Therefore, the current investigation introduced a new mouse model of periodontal disease to examine the effects of a polymicrobial infection on periodontal ligament (PDL) properties, changes in bone loss, the host immune response, and the microbiome/virome using shotgun sequencing. Periodontal pathogens, namely Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, and Fusobacterium nucleatum were used as the polymicrobial oral inoculum in BALB/cByJ mice. The polymicrobial infection triggered significant alveolar bone loss, a heightened antibody response, an elevated cytokine immune response, a significant shift in viral diversity and virome composition, and a widening of the PDL space; the latter two findings have not been previously reported in periodontal disease models. Changes in the PDL space were present at sites far away from the site of insult, indicating that the polymicrobial radius of effect extends beyond the bone loss areas and site of initial infection and wider than previously appreciated. Associations were found between bone loss, specific viral and bacterial species, immune genes, and PDL space changes. These findings may have significant implications for the pathogenesis of periodontal disease and biomechanical properties of the periodontium. This new polymicrobial mouse model of periodontal disease in a common mouse strain is useful for evaluating the features of periodontal disease.

Bacterial anti-microbial peptides and nano-sized drug delivery systems: The state of the art toward improved bacteriocins

Antimicrobial peptides (AMP) are molecules consisting of 12-100 amino acids synthesized by certain microbes and released extracellularly to inhibit the growth of other microbes. Among the AMP molecules, bacteriocins are produced by both gram-positive and gram-negative bacterial species and are used to kill or inhibit other prokaryotes in the environment. Due to their broad-spectrum antimicrobial activity, some bacteriocins have the potential of becoming the next generation of antibiotics for use in the crisis of multi antibiotic-resistant bacteria. Recently, bacteriocins have even been used to treat cancer. However, bacteriocins present a few drawbacks, such as sensitivity to proteases, immunogenicity issues, and the development of bacteriocin resistance by pathogenic bacteria. In this regard, nanoscale drug delivery systems (Nano-DDS) have led to the expectation that they will eventually improve the treatment of many diseases by addressing these limitations and improving bacteriocin pharmacokinetics and pharmacodynamics. Thus, combining bacteriocins with nano-DDS may be useful in overcoming these drawbacks and thereby reveal the full potential of bacteriocins. In this review article, we highlight the importance of tailoring nano-DDS to address bacteriocin limitations, the successes and failures of this technology thus far, the challenges that this technology still has to overcome before reaching the market, and future perspectives. Therefore, the purpose of this review is to highlight, categorize, compare and contrast the different nano-DDS described in the literature so far, and compare their effectiveness in order to improve the next generation of bacteriocin nano-sized drug delivery systems (Nano-DDS).

Antibiotic prescribing practices in periodontal surgeries with and without bone grafting

BACKGROUND

The prevention of postoperative infection is often the basis for antibiotic prescription; however, the risks of unwarranted antibiotics and lack of guidelines for procedures involving bone grafts creates additional difficulty in decision making for practitioners. This study aims to evaluate practices in antibiotics prescribed for periodontal surgeries with and without bone grafting and acceptability of guidelines.

METHODS

An anonymous survey was distributed to periodontists via the California Society of Periodontists e-mail listserv. The survey questioned prescribing practices for periodontal procedures, prescribing rationale, demographic and dental practice information, and acceptability of guidelines. Results were analyzed using McNemar tests and logistic regression.

RESULTS

Practitioners were significantly less likely to prescribe antibiotics for traditional periodontal surgeries without bone grafting compared with socket preservation, guided tissue regeneration, guided bone regeneration, and sinus augmentation (P < 0.0001). Practitioners were significantly more likely to prescribe antibiotics with more complex bone grafting such as guided bone regeneration and sinus augmentation compared with socket preservation (P < 0.0001). The most common rationale for prescribing antibiotics with bone grafting was to decrease the chances of developing an infection. Seventy-five percent of practitioners reported they would follow guidelines for antibiotic prescription if they were developed by the American Academy of Periodontology.

CONCLUSIONS

Practitioners are more likely to prescribe antibiotics with bone grafting and as complexity of the bone grafting procedure increases. Based on these results, the low incidence of infection in periodontal surgery cited in the literature, and willingness of practitioners to adopt guidelines, the establishment of evidence-based guidelines would be of benefit to the periodontal practicing community.

Treponema denticola increases MMP-2 expression and activation in the periodontium via reversible DNA and histone modifications

Host-derived matrix metalloproteinases (MMPs) and bacterial proteases mediate destruction of extracellular matrices and supporting alveolar bone in periodontitis. The Treponema denticola dentilisin protease induces MMP-2 expression and activation in periodontal ligament (PDL) cells, and dentilisin-mediated activation of pro-MMP-2 is required for cellular fibronectin degradation. Here, we report that T. denticola regulates MMP-2 expression through epigenetic modifications in the periodontium. PDL cells were treated with epigenetic enzyme inhibitors before or after T. denticola challenge. Fibronectin fragmentation, MMP-2 expression, and activation were assessed by immunoblot, zymography, and qRT-PCR, respectively. Chromatin modification enzyme expression in T. denticola-challenged PDL cells and periodontal tissues were evaluated using gene arrays. Several classes of epigenetic enzymes showed significant alterations in transcription in diseased tissue and T. denticola-challenged PDL cells. T. denticola-mediated MMP-2 expression and activation were significantly reduced in PDL cells treated with inhibitors of aurora kinases and histone deacetylases. In contrast, DNA methyltransferase inhibitors had little effect, and inhibitors of histone acetyltransferases, methyltransferases, and demethylases exacerbated T. denticola-mediated MMP-2 expression and activation. Chronic epigenetic changes in periodontal tissues mediated by T. denticola or other oral microbes may contribute to the limited success of conventional treatment of chronic periodontitis and may be amenable to therapeutic reversal.

High-purity Nisin Alone or in Combination with Sodium Hypochlorite Is Effective against Planktonic and Biofilm Populations of Enterococcus faecalis

INTRODUCTION

Nisin, a broad-spectrum bacteriocin, has recently been highlighted for its biomedical applications. To date, no studies have examined the antimicrobial and antibiofilm properties of high-purity (>95%) nisin (nisin ZP) on Enterococcus faecalis and biofilms formed by this species. We hypothesize that nisin can inhibit E. faecalis and reduce biofilm biomass, and combinations of nisin and sodium hypochlorite (NaOCl) will enhance the antibiofilm properties against E. faecalis biofilms.

METHODS

Using broth cultures, disc diffusion assays, and biofilm assays, we examined the effects of nisin on various E. faecalis growth parameters and biofilm properties (biovolume, thickness, and roughness). Confocal microscopy was used in conjunction with Imaris and Comstat2 software (Kongens Lyngby, Copenhagen, Denmark) to measure and analyze the biofilm properties.

RESULTS

Nisin significantly decreased the growth of planktonic E. faecalis dose dependently. The minimum inhibitory concentrations against E. faecalis strains OG-1 and ATCC 29212 were 15 and 50 μg/mL, and the minimum bactericidal concentrations were 150 and 200 μg/mL, respectively. A reduction in biofilm biovolume and thickness was observed for biofilms treated with nisin at ≥10 μg/mL for 10 minutes. In addition, the combination of nisin with low doses of NaOCl enhanced the antibiofilm properties of both antimicrobial agents.

CONCLUSIONS

Nisin alone or in combination with low concentrations of NaOCl reduces the planktonic growth of E. faecalis and disrupts E. faecalis biofilm structure. Our results suggest that nisin has potential as an adjunctive endodontic therapeutic agent and as an alternative to conventional NaOCl irrigation.

Head and Neck Squamous Cell Carcinoma Metabolism Draws on Glutaminolysis, and Stemness Is Specifically Regulated by Glutaminolysis via Aldehyde Dehydrogenase

Cancer cells use alternate energetic pathways; however, cancer stem cell (CSC) metabolic energetic pathways are unknown. The purpose of this study was to define the metabolic characteristics of head and neck cancer at different points of its pathogenesis with a focus on its CSC compartment. UPLC-MS/MS-profiling and GC-MS-validation studies of human head and neck cancer tissue, saliva, and plasma were used in conjunction with in vitro and in vivo models to carry out this investigation. We identified metabolite biomarker panels that distinguish head and neck cancer from healthy controls, and confirmed involvement of glutamate and glutaminolysis. Glutaminase, which catalyzes glutamate formation from glutamine, and aldehyde dehydrogenase (ALDH), a stemness marker, were highly expressed in primary and metastatic head and neck cancer tissues, tumorspheres, and CSC versus controls. Exogenous glutamine induced stemness via glutaminase, whereas inhibiting glutaminase suppressed stemness in vitro and tumorigenesis in vivo. Head and neck CSC (CD44hi/ALDHhi) exhibited higher glutaminase, glutamate, and sphere levels than CD44lo/ALDHlo cells. Glutaminase drove transcriptional and translational ALDH expression, and glutamine directed even CD44lo/ALDHlo cells toward stemness. Glutaminolysis regulates tumorigenesis and CSC metabolism via ALDH. These findings indicate that glutamate is an important marker of cancer metabolism whose regulation via glutaminase works in concert with ALDH to mediate cancer stemness. Future analyses of glutaminolytic-ALDH driven mechanisms underlying tumorigenic transitions may help in the development of targeted therapies for head and neck cancer and its CSC compartment.

Metabolomics of Head and Neck Cancer: A Mini-Review

Metabolomics is used in systems biology to enhance the understanding of complex disease processes, such as cancer. Head and neck cancer (HNC) is an epithelial malignancy that arises in the upper aerodigestive tract and affects more than half a million people worldwide each year. Recently, significant effort has focused on integrating multiple “omics” technologies for oncological research. In particular, research has been focused on identifying tumor-specific metabolite profiles using different sample types (biological fluids, cells and tissues) and a variety of metabolomic platforms and technologies. With our current understanding of molecular abnormalities of HNC, the addition of metabolomic studies will enhance our knowledge of the pathogenesis of this disease and potentially aid in the development of novel strategies to prevent and treat HNC. In this review, we summarize the proposed hypotheses and conclusions from publications that reported findings on the metabolomics of HNC. In addition, we address the potential influence of host-microbe metabolomics in cancer. From a systems biology perspective, the integrative use of genomics, transcriptomics and proteomics will be extremely important for future translational metabolomic-based research discoveries.

Abstract 3294: Treponema denticola, a periodontal pathogen, promotes stemness and migration in oral squamous cell carcinoma

Periodontitis is a chronic infectious disease characterized by inflammation and destruction of periodontal tissues including the periodontal ligament fibers and alveolar bone. Recent epidemiological studies have revealed a significant association between periodontitis and oral cancer. While the precise mechanisms that mediate these associations are not well understood, periodontal pathogens, including Treponema denticola (T. denticola), which are believed to initiate the destructive inflammatory responses and dysbiosis or dysregulation of tissue homeostasis that characterize periodontal disease may contribute to oral cancer. However, knowledge about T. denticola's contribution to oral cancer is limited. Previously, we showed that nisin ZP, a bacteriocin and commonly used food preservative, reduced tumorigenesis in vivo and long term treatment with nisin ZP extended survival. In a separate study, we further showed that nisin ZP exhibits antimicrobial and antibiofilm effects, limiting T. denticola viability. The antimicrobial doses of nisin ZP are two orders of magnitude lower than the antitumor doses. The present study investigated the impact of T. denticola on the stemness, migration, and tumorigenesis of oral squamous cell carcinoma (OSCC), and nisin's potential modulatory effects on these processes. To investigate the role of T. denticola on OSCC tumorigenesis, OSCC cells were treated with T. denticola and with or without nisin ZP then assayed for stemness (orasphere) and migration. Treatment with T. denticola enhanced OSCC orasphere formation and migration without affecting cell viability or inducing apoptosis. Addition of nisin ZP inhibited these T. denticola-mediated processes. These data indicate that the periodontal pathogen T. denticola promotes stemness and migration of OSCC cells, and thereby may contribute to oral cancer tumorigenesis.

Citation Format: Pachiyappan Kamarajan, Islam Ateia, Jae M. Shin, J Christopher Fenno, Yvonne L. Kapila. Treponema denticola, a periodontal pathogen, promotes stemness and migration in oral squamous cell carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3294.

Biomedical applications of nisin

Nisin is a bacteriocin produced by a group of Gram-positive bacteria that belongs to Lactococcus and Streptococcus species. Nisin is classified as a Type A (I) lantibiotic that is synthesized from mRNA and the translated peptide contains several unusual amino acids due to post-translational modifications. Over the past few decades, nisin has been used widely as a food biopreservative. Since then, many natural and genetically modified variants of nisin have been identified and studied for their unique antimicrobial properties. Nisin is FDA approved and generally regarded as a safe peptide with recognized potential for clinical use. Over the past two decades the application of nisin has been extended to biomedical fields. Studies have reported that nisin can prevent the growth of drug-resistant bacterial strains, such as methicillin-resistant Staphylococcus aureus, Streptococcus pneumoniae, Enterococci and Clostridium difficile. Nisin has now been shown to have antimicrobial activity against both Gram-positive and Gram-negative disease-associated pathogens. Nisin has been reported to have anti-biofilm properties and can work synergistically in combination with conventional therapeutic drugs. In addition, like host-defence peptides, nisin may activate the adaptive immune response and have an immunomodulatory role. Increasing evidence indicates that nisin can influence the growth of tumours and exhibit selective cytotoxicity towards cancer cells. Collectively, the application of nisin has advanced beyond its role as a food biopreservative. Thus, this review will describe and compare studies on nisin and provide insight into its future biomedical applications.

A Novel Sirtuin-3 Inhibitor, LC-0296, Inhibits Cell Survival and Proliferation, and Promotes Apoptosis of Head and Neck Cancer Cells

BACKGROUND

The survival rate of patients with head and neck squamous cell carcinoma (HNSCC) stands at approximately 50% and this has not improved in decades. This study developed a novel sirtuin-3 (SIRT3) inhibitor (LC-0296) and examined its role in altering HNSCC tumorigenesis.

MATERIALS AND METHODS

The effect of the SIRT3 inhibitor, LC-0296, on cell survival, proliferation, and apoptosis, and reactive oxygen species levels in HNSCC cells were studied.

RESULTS

LC-0296 reduces cell proliferation and promotes apoptosis of HNSCC cells but not of normal human oral keratinocytes. This inhibitory effect is mediated, in part, via modulation of reactive oxygen species levels. Additionally, LC-0296 works synergistically to increase the sensitivity of HNSCC cells to radiation and cisplatin treatment.

CONCLUSION

Development of novel SIRT3 inhibitors, such as LC-0296, might enable the development of new targeted therapies to treat and improve the survival rate of patients with head and neck cancer.

Abstract 1192: Glutamic acid and glutaminolysis mark aggressive tumorigenesis in head and neck squamous cell carcinoma

The purpose of this study was to identify markers of aggressive tumor behavior to inform processes underlying tumor aggressivity in head and neck squamous cell carcinoma (HNSCC). To this end, metabolomic profiling and validation of biomarkers of aggressive HNSCC tumorigenesis were assessed in HNSCC human specimens and cell lines. Using LG/GC-MS, we found that glutamic acid is one of the most highly differentially elevated metabolites in HNSCC specimens. In subsequent validation studies, where we incorporated metastatic tissues, glutamic acid was further verified as differentially elevated in metastatic tissues compared to primary HNSCC and normal adjacent tissues. In addition, significantly elevated expression levels of c-Myc and glutaminase, the enzyme that regulates glutamic acid levels, were highest in metastatic tissues compared to primary HNSCC and normal tissues. Parallel changes in c-Myc and glutaminase expression in HNSCC tissues suggest a link between c-Myc regulation and glutamine metabolism. Furthermore, Western Blot analyses show similar expression patterns for c-Myc and glutaminase in oral cancer cell lines. Inhibiting glutamic acid levels by stably suppressing glutaminase expression in HNSCC cells, led to suppression of aggressive tumorigenesis in vitro, whereas enrichment with external glutamine or glutamic acid further enhanced tumorigenesis. Together, this data suggest that oncogenic levels of c-Myc may induce a transcriptional program that promotes elevated levels of glutamic acid and glutaminolysis via glutaminase to promote tumor aggressivity in head and neck cancer.

Citation Format: Adam D. Banda, Mercedes Bermudez Cortes, Pachiyappan Kamarajan, Thekkenlnaycke Rajendiran, Arul M. Chinnaiyan, Yvonne L. Kapila. Glutamic acid and glutaminolysis mark aggressive tumorigenesis in head and neck squamous cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1192. doi:10.1158/1538-7445.AM2015-1192

Antimicrobial nisin acts against saliva derived multi-species biofilms without cytotoxicity to human oral cells

Objectives: Nisin is a lantibiotic widely used for the preservation of food and beverages. Recently, investigators have reported that nisin may have clinical applications for treating bacterial infections. The aim of this study was to investigate the effects of ultra pure food grade Nisin ZP (>95% purity) on taxonomically diverse bacteria common to the human oral cavity and saliva derived multi-species oral biofilms, and to discern the toxicity of nisin against human cells relevant to the oral cavity.

Methods: The minimum inhibitory concentrations and minimum bactericidal concentrations of taxonomically distinct oral bacteria were determined using agar and broth dilution methods. To assess the effects of nisin on biofilms, two model systems were utilized: a static and a controlled flow microfluidic system. Biofilms were inoculated with pooled human saliva and fed filter-sterilized saliva for 20–22 h at 37°C. Nisin effects on cellular apoptosis and proliferation were evaluated using acridine orange/ethidium bromide fluorescent nuclear staining and lactate dehydrogenase activity assays.

Results: Nisin inhibited planktonic growth of oral bacteria at low concentrations (2.5–50 μg/ml). Nisin also retarded development of multi-species biofilms at concentrations ≥1 μg/ml. Specifically, under biofilm model conditions, nisin interfered with biofilm development and reduced biofilm biomass and thickness in a dose-dependent manner. The treatment of pre-formed biofilms with nisin resulted in dose- and time-dependent disruption of the biofilm architecture along with decreased bacterial viability. Human cells relevant to the oral cavity were unaffected by the treatment of nisin at anti-biofilm concentrations and showed no signs of apoptotic changes unless treated with much higher concentrations (>200 μg/ml).

Conclusion: This work highlights the potential therapeutic value of high purity food grade nisin to inhibit the growth of oral bacteria and the development of biofilms relevant to oral diseases.

Shedding of NG2 by MMP-13 attenuates anoikis

Disruption of cell-matrix interactions can lead to anoikis-apoptosis due to loss of matrix contacts. We previously showed that Nerve/glial antigen 2 (NG2) is a novel anoikis receptor. Specifically, overexpression of NG2 leads to anoikis propagation, whereas its suppression leads to anoikis attenuation. Interestingly, NG2 expression decreases in late anoikis, suggesting that NG2 reduction is also critical to this process. Thus, we hypothesized that NG2 undergoes cleavage to curtail anoikis propagation. Further, since matrix metalloproteinases (MMPs) cleave cell surface receptors, play a major role in modulating apoptosis, and are associated with death receptor cleavage during apoptosis, we further hypothesized that cleavage of NG2 could be mediated by MMPs to regulate anoikis. Indeed, anoikis conditions triggered release of the NG2 extracellular domain into condition media during late apoptosis, and this coincided with increased MMP-13 expression. Treatment with an MMP-13 inhibitor and MMP-13 siRNA increased anoikis, since these treatments blocked NG2 release. Further, NG2-positive cells exhibited increased anoikis upon MMP-13 inhibition, whereas MMP-13 inhibition did not increase anoikis in NG2-null cells, corroborating that retention of NG2 on the cell membrane is critical for sustaining anoikis, and its cleavage for mediating anoikis attenuation. Similarly, NG2 suppression with siRNA inhibited NG2 release and anoikis. In contrast, MMP-13 overexpression or exogenous MMP-13 reduced anoikis by more effectively shedding NG2. In conclusion, maintenance of NG2 on the cell surface promotes anoikis propagation, whereas its shedding by MMP-13 actions attenuates anoikis. Given that these findings are derived in the context of periodontal ligament fibroblasts, these data have implications for periodontal inflammation and periodontal disease pathogenesis.

Treponema denticola upregulates MMP-2 activation in periodontal ligament cells: interplay between epigenetics and periodontal infection

OBJECTIVE

Periodontal pathogens initiate chronic dysregulation of inflammation and tissue homeostasis that characterize periodontal disease. To better understand oral microbe-host tissue interactions, we investigated expression and activation of MMP-2 in periodontal ligament cells following Treponema denticola challenge.

DESIGN

Cultured PDL cells were challenged with T. denticola, and bacterial adherence, internalization and survival were assayed by immunofluorescence microscopy and antibiotic protection assays, respectively. MMP-2 activation was detected by zymography. MMP-2, MT1/MMP and TIMP-2 expression following T. denticola challenge was determined by qRT-PCR. Promoter methylation of MMP-2 and MT1/MMP was screened by methylation-sensitive restriction analysis and by bisulfite DNA sequencing.

RESULTS

T. denticola adhered to and was internalized by PDL cells but did not survive intracellularly beyond 24h. Importantly, while dentilisin activity in PDL culture supernatants gradually decreased following T. denticola challenge, MMP-2 activation persisted for up to 5 days, suggesting involvement of other regulatory mechanisms. Transcription and expression of MT1/MMP and TIMP-2 increased in response to T. denticola challenge. However, consistent with previously reported constitutive pro-MMP-2 expression in PDL cells, the MMP-2 promoter was hypomethylated, independent of T. denticola challenge.

CONCLUSIONS

MMP-2 promoter hypomethylation is consistent with constitutive pro-MMP-2 expression in PDL cells. This, coupled with T. denticola-mediated upregulation of MMP-2-related genes and chronic activation of pro-MMP-2, mimics key in vivo mechanisms of periodontal disease chronicity, in particular MMP-2-dependent matrix degradation and bone resorption. Adherence and/or internalization of T. denticola may contribute to these processes by one or more regulatory mechanisms, including contact-dependent signal transduction or other epigenetic mechanisms.

ADAM17-mediated CD44 cleavage promotes orasphere formation or stemness and tumorigenesis in HNSCC

CD44, an extracellular matrix (ECM) receptor, has been described as a cancer stem cell marker in multiple cancers, including head and neck squamous cell carcinoma (HNSCC). HNSCC orasphere formation or stemness was characterized by cleavage of CD44, and thus we hypothesized that this proteolytic processing may be critical to stemness and tumorigenesis. We tested this hypothesis by examining the mechanisms that regulate this process in vitro and in vivo, and by exploring its clinical relevance in human specimens. Sphere assays have been used to evaluate stemness in vitro. Spheres comprised of HNSCC cells or oraspheres and an oral cancer mouse model were used to examine the significance of CD44 cleavage using stable suppression and inhibition approaches. These mechanisms were also examined in HNSCC specimens. Oraspheres exhibited increased levels of CD44 cleavage compared to their adherent counterparts. Given that disintegrin and metalloproteinase domain-containing protein 17 (ADAM17) is a major matrix metalloproteinase known to cleave CD44, we chemically inhibited and stably suppressed ADAM17 expression in HNSCC cells and found that these treatments blocked CD44 cleavage and abrogated orasphere formation. Furthermore, stable suppression of ADAM17 in HNSCC cells also diminished tumorigenesis in an oral cancer mouse model. Consistently, stable suppression of CD44 in HNSCC cells abrogated orasphere formation and inhibited tumorigenesis in vivo. The clinical relevance of these findings was confirmed in matched primary and metastatic human HNSCC specimens, which exhibited increased levels of ADAM17 expression and concomitant CD44 cleavage compared to controls. CD44 cleavage by ADAM17 is critical to orasphere formation or stemness and HNSCC tumorigenesis.

Sirtuin-3 (SIRT3) and the Hallmarks of Cancer

Sirtuins (SIRT1-SIRT7), the mammalian homologs of the silent information regulator 2 (Sir2) in Saccharomyces cerevisiae, have been a major focus of study in the scientific community this past decade because of their emerging role in cancer biology and other age-related diseases. Emerging functions for this unique family of enzymes include roles in genomic stability, angiogenesis, metabolism, and anoikis. Here, we review recent developments on the role of sirtuins in cancer with a particular focus on SIRT3 and its role in the hallmarks of cancer and as a potential drug target for cancer treatment.

Apoptotic activity of gingival crevicular fluid from localized aggressive periodontitis

INTRODUCTION

The aim of this study was to examine a potential link between apoptotic biomarkers in gingival crevicular fluid (GCF) and periodontal destruction in four cases of localized aggressive periodontitis (LAP), diagnostically enhanced by cone beam computed tomography.

CASE SERIES

This study examined the GCF in four patients diagnosed with LAP (formerly localized juvenile periodontitis) at a routine periodontal examination. The LAP diseased sites had attachment loss ranging from 5-12 mm. Atotal of 62 samples of GCF were collected from diseased sites and from contralateral, matched healthy sites with minimal or no attachment loss. All samples were assayed for apoptotic markers, including Fas/FasL, DNAfragmentation, and nitric oxide. The GCF samples were analyzed utilizing enzyme-linked immunosorbent assays for DNA fragments and nitric oxide levels, whereas Western blotting was used for Fas/FasL analyses. Our results showed a significant increase in the apoptotic markers Fas/FasL and DNA fragmentation when comparing GCF from diseased versus non-diseased sites in patients with LAP.

CONCLUSION

To our knowledge, this is the first report of apoptotic biomarkers associated with patients diagnosed with LAP. Finding significantly increased levels of these markers in localized areas may help us understand the pathophysiology associated with this specific form of periodontitis, and, furthermore, may provide a basis for a quantifiably prognostic test when attempting to treat this disease.

Nisin, an apoptogenic bacteriocin and food preservative, attenuates HNSCC tumorigenesis via CHAC1

Nisin, a bacteriocin and commonly used food preservative, may serve as a novel potential therapeutic for treating head and neck squamous cell carcinoma (HNSCC), as it induces preferential apoptosis, cell cycle arrest, and reduces cell proliferation in HNSCC cells, compared with primary keratinocytes. Nisin also reduces HNSCC tumorigenesis in vivo. Mechanistically, nisin exerts these effects on HNSCC, in part, through CHAC1, a proapoptotic cation transport regulator, and through a concomitant CHAC1-independent influx of extracellular calcium. In addition, although CHAC1 is known as an apoptotic mediator, its effects on cancer cell apoptosis have not been examined. Our studies are the first to report CHAC1's new role in promoting cancer cell apoptosis under nisin treatment. These data support the concept that nisin decreases HNSCC tumorigenesis in vitro and in vivo by inducing increased cell apoptosis and decreased cell proliferation; effects that are mediated by activation of CHAC1, increased calcium influxes, and induction of cell cycle arrest. These findings support the use of nisin as a potentially novel therapeutic for HNSCC, and as nisin is safe for human consumption and currently used in food preservation, its translation into a clinical setting may be facilitated.

Receptor-interacting protein (RIP) and Sirtuin-3 (SIRT3) are on opposite sides of anoikis and tumorigenesis

BACKGROUND

Regulating cross-talk between anoikis and survival signaling pathways is crucial to regulating tissue processes and mitigating diseases like cancer. Previously, the authors demonstrated that anoikis activates a signaling pathway involving the CD95/Fas-mediated signaling pathway that is regulated by receptor-interacting protein (RIP), a kinase that shuttles between Fas-mediated cell death and integrin/focal adhesion kinase (FAK)-mediated survival pathways. Because it is known that sirtuin-3 (SIRT3), a nicotinamide adenine dinucleotide-dependent deacetylase, regulates cell survival, metabolism, and tumorigenesis, the authors hypothesized that SIRT3 may engage in cross-talk with Fas/RIP/integrin/FAK survival-death pathways in cancer cell systems.

METHODS

Using immunohistochemical staining, immunoblotting, human tissue microarrays, and overexpression and suppression approaches in vitro and in vivo, the roles of RIP and SIRT3 were examined in oral squamous cell carcinoma (OSCC) anoikis resistance and tumorigenesis.

RESULTS

RIP and SIRT3 had opposite expression profiles in OSCC cells and tissues. Stable suppression of RIP enhanced SIRT3 levels, whereas stable suppression of SIRT3 did not impact RIP levels in OSCC cells. The authors observed that, as OSCC cells became anoikis-resistant, they formed multicellular aggregates or oraspheres in suspension conditions, and their expression of SIRT3 increased as their RIP expression decreased. Also, anoikis-resistant OSCC cells with higher SIRT3 and low RIP expression induced an increased tumor burden and incidence in mice, unlike their adherent OSCC cell counterparts. Furthermore, stable suppression of SIRT3 inhibited anoikis resistance and reduced tumor incidence.

CONCLUSIONS

The current results indicted that RIP is a likely upstream, negative regulator of SIRT3 in anoikis resistance, and an anoikis-resistant orasphere phenotype defined by higher SIRT3 and low RIP expression contributes to a more aggressive phenotype in OSCC development.

Magic angle spinning NMR-based metabolic profiling of head and neck squamous cell carcinoma tissues

High-resolution magic-angle spinning (HR-MAS) proton NMR spectroscopy is used to explore the metabolic signatures of head and neck squamous cell carcinoma (HNSCC) which included matched normal adjacent tissue (NAT) and tumor originating from tongue, lip, larynx and oral cavity, and associated lymph-node metastatic (LN-Met) tissues. A total of 43 tissues (18 NAT, 18 Tumor and 7 LN-Met) from 22 HNSCC patients were analyzed. Principal Component Analysis of NMR data showed a clear classification between NAT and tumor tissues, however, LN-Met tissues were classified among tumor. A partial least-squares discriminant analysis model generated from NMR metabolic profiles was used to differentiate normal from tumor samples (Q(2) > 0.80, Receiver Operator Characteristic area under the curve >0.86, using 7-fold cross validation). HNSCC and LN-Met tissues showed elevated levels of lactate, amino acids including leucine, isoleucine, valine, alanine, glutamine, glutamate, aspartate, glycine, phenylalanine and tyrosine, choline containing compounds, creatine, taurine, glutathione, and decreased levels of triglycerides. These elevated metabolites were associated with highly active glycolysis, increased amino acids influx (anaplerosis) into the TCA cycle, altered energy metabolism, membrane choline phospholipid metabolism, and oxidative and osmotic defense mechanisms. Moreover, decreased levels of triglycerides may indicate lipolysis followed by β-oxidation of fatty acids that may exist to deliver bioenergy for rapid tumor cell proliferation and growth.