Carcinogenesis of the Oral Cavity: Environmental Causes and Potential Prevention by Black Raspberry

The Effects of Black Raspberry as a Whole Food-Based Approach on Biomarkers of Oxidative Stress in Buccal Cells and Urine of Smokers

Cigarette smoke is a rich source of free radicals that can promote oxidative stress and carcinogenesis, including head and neck squamous cell carcinoma (HNSCC) development; importantly, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-iso-prostaglandin F2α (8-isoprostane) are biomarkers of oxidative stress. Several mechanisms, including the antioxidant properties of black raspberry (BRB), account for their chemopreventive effects. In the present clinical trial, we tested the hypothesis that BRB administration reduces biomarkers levels of oxidative stress in buccal cells and urine of smokers. One week after enrolling 21 smokers, baseline buccal cells and urine samples were collected before the administration of BRB lozenges for 8 weeks (5/day, 1 gm BRB/lozenge). Buccal cells and urine samples were collected at the middle and the end of BRB administration. The last samples were collected after the BRB cessation (washout period). We analyzed levels of 8-oxodG and 8-isoprostane (LC/MS-MS), urinary cotinine (ELISA), and creatinine (spectrophotometry). BRB significantly reduced the levels of 8-oxodG by 17.08% (P = 0.00079) in buccal cells and 12.44% (P = 0.034) in urine at the middle of BRB administration as compared with baseline; the corresponding values at the end of BRB administration were 16.46% (P = 0.026) in buccal cells and 25.72% (P = 0.202) in urine. BRB had no significant effect on the levels of urinary 8-isoprostane. BRB's capacity to inhibit 8-oxodG formation of smokers' buccal cells and urine is clearly evident and the reduction in 8-oxodG suggests that antioxidant abilities are central to BRB's HNSCC chemopreventive properties.

PREVENTION RELEVANCE

Cigarette smoke contains highly active components namely free radicals that can promote oxidative stress and oral cancer. We found that black raspberry (BRB) inhibited the formation of oxidative stress markers in the oral cavity and urine of smokers suggesting the antioxidant abilities of BRB in preventing oral cancer.

The Use of Immune Regulation in Treating Head and Neck Squamous Cell Carcinoma (HNSCC)

Immunotherapy has emerged as a promising new treatment modality for head and neck cancer, offering the potential for targeted and effective cancer management. Squamous cell carcinomas pose significant challenges due to their aggressive nature and limited treatment options. Conventional therapies such as surgery, radiation, and chemotherapy often have limited success rates and can have significant side effects. Immunotherapy harnesses the power of the immune system to recognize and eliminate cancer cells, and thus represents a novel approach with the potential to improve patient outcomes. In the management of head and neck squamous cell carcinoma (HNSCC), important contributions are made by immunotherapies, including adaptive cell therapy (ACT) and immune checkpoint inhibitor therapy. In this review, we are focusing on the latter. Immune checkpoint inhibitors target proteins such as programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) to enhance the immune response against cancer cells. The CTLA-4 inhibitors, such as ipilimumab and tremelimumab, have been approved for early-stage clinical trials and have shown promising outcomes in terms of tumor regression and durable responses in patients with advanced HNSCC. Thus, immune checkpoint inhibitor therapy holds promise in overcoming the limitations of conventional therapies. However, further research is needed to optimize treatment regimens, identify predictive biomarkers, and overcome potential resistance mechanisms. With ongoing advancements in immunotherapy, the future holds great potential for transforming the landscape of oral tumor treatment and providing new hope for patients.

Gender Difference in DNA Damage Induced by the Environmental Carcinogen Dibenzo[def,p]chrysene Individually and in Combination with Mouse Papillomavirus Infection in the Mouse Oral Cavity

Tobacco smoking and human papillomavirus infection are established etiological agents in the development of head and neck squamous cell carcinoma (HNSCC). The incidence and mortality of HNSCC are higher in men than women. To provide biochemical basis for sex differences, we tested the hypothesis that carcinogen treatment using dibenzo[def,p]chrysene, which is an environmental pollutant and tobacco smoke constituent, in the absence or presence of the mouse papillomavirus infection results in significantly higher levels of DNA damage in the oral cavity in male than in female mice. However, the results of the present investigation do not support our hypothesis since we found that females were more susceptible to carcinogen-induced covalent DNA damage than males independent of the viral infection. Since DNA damage represents only a single-step in the carcinogenesis process, additional factors may contribute to sex differences in humans.

Consumption of Berries and Flavonoids in Relation to Mortality in NHANES, 1999-2014

BACKGROUND

Berries are foods that are abundant in nutrients, especially flavonoids, that promote good health; however, the effects of total berries on mortality are not well characterized.

OBJECTIVES

We evaluated whether intakes of total berries and specific berry types including blueberries, strawberries, cranberries, flavonoids, and subclasses of flavonoids (anthocyanidins, flavonols, flavones, flavanones, flavan-3-ols, and isoflavones) in relation to mortality risk in United States adults.

METHODS

A nationally representative sample of the United States adult population was obtained using data from the 1994-2014 NHANES (n = 37,232). Intake of berries was estimated using 24-h food recalls (1999-2014), and flavonoids intake was calculated using the matched USDA's expanded flavonoid database. Mortality outcomes based on 8 y of follow-up were obtained using linked death certificates.

RESULTS

Compared with nonconsumers, the multivariable-adjusted hazard ratio for all-cause mortality was 0.79 [95% confidence intervals (CI): 0.7, 0.89] for any berry consumption, 0.86 (0.75, 0.99) for strawberry consumption 0.79 (0.66, 0.95) for blueberries, and 0.69 (0.51, 0.93) for cranberries. Compared with the lower median of intake, risk of all-cause mortality for greater intake was 0.85 (0.74, 0.97) for total flavonoids, 0.85 (0.76, 0.95) for anthocyanidins, 0.9 (0.82, 0.99) for flavan-3-ols, 0.89 (0.79, 0.9) for flavanols, and 0.89 (0.8, 0.99) for flavones. There was a dose-response relationship between intakes of total flavonoids, anthocyanidins, and flavones and lower all-cause mortality risks (Ptrend < 0.05). Risk for cardiometabolic mortality was 0.75 (0.58, 0.98) for berry consumers and 0.49 (0.25, 0.98) for cranberry consumers. For respiratory disease mortality, risk was 0.41 (0.2, 0.86), compared with blueberry nonconsumers.

CONCLUSION

Higher intakes of berries and flavonoids were associated with a lower overall mortality risk in adult Americans. Few adults regularly consume berries, indicating that increased intake of berries and flavonoid-rich foods may be beneficial to health.

The Protective Role of Cranberries and Blueberries in Oral Cancer

BACKGROUND

Oral cancer has a high prevalence worldwide, and this disease is caused by genetic, immunological, and environmental factors. The main risk factors associated with oral cancer are smoking and alcohol.

RESULTS

There are various strategies to reduce risk factors, including prevention programs as well as the consumption of an adequate diet that includes phytochemical compounds derived from cranberries (Vaccinium macrocarpon A.) and blueberries (Vaccinium corymbosum L.); these compounds exhibit antitumor properties.

RESULTS

The main outcome of this review is as follows: the properties of phytochemicals derived from cranberries were evaluated for protection against risk factors associated with oral cancer.

CONCLUSIONS

The secondary metabolites of cranberries promote biological effects that provide protection against smoking and alcoholism. An alternative for the prevention of oral cancer can be the consumption of these cranberries and blueberries.

The Lysyl Oxidase G473A Polymorphism Exacerbates Oral Cancer Development in Humans and Mice

Oral cancer is primarily squamous-cell carcinoma with a 5-year survival rate of approximately 50%. Lysyl oxidase (LOX) participates in collagen and elastin maturation. The propeptide of LOX is released as an 18 kDa protein (LOX-PP) in the extracellular environment by procollagen C-proteinases and has tumor-inhibitory properties. A polymorphism in the propeptide region of LOX (rs1800449, G473A) results in a single amino acid substitution of Gln for Arg. Here we investigated the frequency of rs1800449 in OSCC employing TCGA database resources and determined the kinetics and severity of precancerous oral lesion development in wildtype and corresponding knockin mice after exposure to 4-nitroquinoline oxide (4 NQO) in drinking water. Data show that the OSCC is more common in humans carrying the variant compared to the wildtype. Knockin mice are more susceptible to lesion development. The immunohistochemistry of LOX in mouse tissues and in vitro studies point to a negative feedback pathway of wildtype LOX-PP on LOX expression that is deficient in knockin mice. Data further demonstrate modulations of T cell phenotype in knockin mice toward a more tumor-permissive condition. Data provide initial evidence for rs1800449 as an oral cancer susceptibility biomarker and point to opportunities to better understand the functional mechanism of LOX-PP cancer inhibitory activity.

Expression of Minichromosome Maintenance Protein 2 (MCM2) in Oral Epithelial Dysplasia and Oral Squamous Cell Carcinoma: A Systematic Review

The histopathological investigations of oral lesions are a basic approach for diagnosing ongoing cancer or pre-cancer associated pathological attributes in the dissected biopsy. The early detection and management of potentially malignant disorders of the lip and oral cavity that require intervention may reduce malignant transformations, or in case any malignancy is detected during surveillance, the appropriate treatment may improve survival rates. This would guide the clinicians to decide the appropriate treatment modality or lesion to achieve a more favorable prognosis. MCM2 protein is involved in DNA replication providing additional information about the prognosis of neoplasms. Some authors have pointed out that MCM proteins have been inversely correlated with salivary tumour differentiation and therefore could be an indicator of proliferation potential. Therefore, it is essential to find the expression of the MCM2 gene in oral leukoplakia and oral squamous cell carcinoma. Electronic databases like Ebscohost, Livivo, Google Scholar and PubMed were searched. Based on the inclusion and exclusion criteria, 2 reviewers (MS and SN) independently selected the relevant articles. Any disagreement was discussed until a consensus was reached. We used the QUADAS-2 tool to assess the quality of the included studies over four key domains: patient selection, index test, reference standard and flow and timing of participants through the study. 10 out of 57 titles were found to meet the eligibility criteria. Biopsied tissue with immunohistochemical staining or advanced diagnostic studies were included. A total of 901 samples were included in the study and different groups were normal oral mucosa (NOM), oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC). MCM2 proteins are useful diagnostic markers for distinguishing malignant from benign epithelial dysplasia and for early detection and diagnosis of OSCC as an adjunct to clinicopathological parameters.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-022-03296-7.

Black Raspberry Extract Enhances Glutathione Conjugation of the Fjord-Region Diol Epoxide Derived from the Tobacco Carcinogen Dibenzo[def,p]chrysene in Human Oral Cells

In a series of previous studies we reported that black raspberry (BRB) powder inhibits dibenzo[a,l]pyrene (DBP)-induced DNA damage, mutagenesis, and oral squamous cell carcinoma (OSCC) development in mice. In the present study, using human oral leukoplakia (MSK-Leuk1) and squamous cell carcinoma (SCC1483) cells, we tested the hypothesis that BRB extract (BRBE) will enhance the synthesis of glutathione (GSH) and in turn increase GSH conjugation of the fjord-region DBP diol epoxide (DBPDE) derived from DBP leading to inhibition of DBP-induced DNA damage. The syntheses of DBPDE-GSH conjugate, DBPDE-dA adduct, and the corresponding isotope-labeled internal standards were performed; LC-MS/MS methods were used for their quantification. BRBE significantly (p < 0.05) increased cellular GSH by 31% and 13% at 6 and 24 h, respectively, in OSCC cells; in MSK-LeuK1 cells, the levels of GSH significantly (p < 0.05) increased by 55% and 22%, at 1 and 6 h. Since BRBE significantly enhanced the synthesis of GSH in both cell types, subsequent experiments were performed in MSK-Leuk1 cells. Western blot analysis was performed to determine the types of proteins involved in the synthesis of GSH. BRBE significantly (p < 0.05) increased the protein expression (2.5-fold) of the glutamate-cysteine ligase catalytic subunit (GCLC) but had no effect on the glutamate-cysteine ligase modifier subunit (GCLM) and glutathione synthetase (GSS). LC-MS/MS analysis showed that pretreatment of cells with BRBE followed by DBPDE significantly (p < 0.05) increased the levels of DBPDE-GSH conjugate (2.5-fold) and decreased DNA damage by 74% measured by assessing levels of DBPDE-dA adduct formation. Collectively, the results of this in vitro study clearly support our hypothesis, and the LC-MS/MS methods developed in the present study will be highly useful in testing the same hypothesis initially in our mouse model and ultimately in smokers.

Treatment of Human HeLa Cells with Black Raspberry Extracts Enhances the Removal of DNA Lesions by the Nucleotide Excision Repair Mechanism

As demonstrated by us earlier and by other researchers, a diet containing freeze-dried black raspberries (BRB) inhibits DNA damage and carcinogenesis in animal models. We tested the hypothesis that the inhibition of DNA damage by BRB is due, in part, to the enhancement of DNA repair capacity evaluated in the human HeLa cell extract system, an established in vitro system for the assessment of cellular DNA repair activity. The pre-treatment of intact HeLa cells with BRB extracts (BRBE) enhances the nucleotide excision repair (NER) of a bulky deoxyguanosine adduct derived from the polycyclic aromatic carcinogen benzo[a]pyrene (BP-dG) by ~24%. The NER activity of an oxidatively-derived non-bulky DNA lesion, guanidinohydantoin (Gh), is also enhanced by ~24%, while its base excision repair activity is enhanced by only ~6%. Western Blot experiments indicate that the expression of selected, NER factors is also increased by BRBE treatment by ~73% (XPA), ~55% (XPB), while its effects on XPD was modest (<14%). These results demonstrate that BRBE significantly enhances the NER yields of a bulky and a non-bulky DNA lesion, and that this effect is correlated with an enhancement of expression of the critically important NER factor XPA and the helicase XPB, but not the helicase XPD.

Detection of DNA adducts derived from the tobacco carcinogens, benzo[a]pyrene and dibenzo[def,p]chrysene in human oral buccal cells

Polycyclic aromatic hydrocarbons (PAHs) are recognized as potential etiological agents in the development of oral cancer in smokers. In particular, benzo[a]pyrene (B[a]P) and dibenzo[def,p]chrysene (DB[a,l]P) are detected in cigarette smoke and the environment and can induce DNA damage, mutagenesis and carcinogenesis in the oral cavity of rodents. Consequently, DNA adducts are regarded as the most direct markers of genotoxicity and can be used as biomarkers of cancer risk. Thus, this study used LC-MS/MS analysis with isotope labeled internal standard to detect and quantify DNA adducts derived from B[a]P and DB[a,l]P in buccal cells of cigarette smokers and non-smokers. Participants in this study include 21 smokers and 16 non-smokers. Our data are the first to report that levels (mean ± SD) of BPDE-N2-dG were significantly (P < 0.001) higher in smokers (20.18 ± 8.40 adducts/108 dG) than in non-smokers (0.84 ± 1.02 adducts/108 dG). Likewise, levels of DBPDE-N6-dA in smokers (5.49 ± 3.41 adducts/108 dA) were significantly higher (P = 0.019) than non-smokers (2.76 ± 2.29 adducts/108 dA). Collectively, the results of this clinical study support that PAHs in tobacco smoke can contribute to the development of oral cancer in humans.

4-nitroquinoline-1-oxide (4NQO) induced oral carcinogenesis: A systematic literature review

OBJECTIVE

Based on a critical review of published studies, we aimed to develop a good practice guide for using 4-nitroquinoline-1-oxide (4NQO) as an inducer of oral carcinogenesis in Wistar rats.

DESIGN

A systematic search was performed on Medline Ovid, PubMed, Embase, Web of Science, and Scopus databases. The SYRCLE's risk of bias tool was used to assess the quality of the studies.

RESULTS

Thirty-five articles met the selection criteria; 22 (62.9%) of them administered 4NQO systemically in drinking water, with a mean concentration of 30.2 ppm (SD±15.9) and during a mean period of 20.8 (SD±7.8) weeks. The other 13 (37.1%) studies performed topical applications of 4NQO painting the oral mucosa of the animals three times a week (100%) with a mean period of administration of 16.8 (SD±7.0) weeks. Different 4NQO concentrations used for other periods achieved significant tumor development. Most studies didn't perform quantitative clinical analysis, and the histopathological diagnosis/grading criteria varied considerably.

CONCLUSIONS

A poor description of solution care, adverse effects, and the number of losses were observed, and the reporting of these features needs to be improved. Suggestions to guide the development of future research are provided.

Immunomodulatory effects and associated mechanisms of Momordica charantia and its phytochemicals

Momordica charantia L. (M. charantia), which is a member of the Cucurbitaceae family and widely distributed in tropical and subtropical regions, has been consumed as a vegetable and also used as herbal medicine for thousands of years worldwide.

Black raspberry restores the expression of the tumor suppressor p120ctn in the oral cavity of mice treated with the carcinogen dibenzo[a,l]pyrene diol epoxide

One of the major risk factors for head and neck squamous cell carcinoma (HNSCC) is tobacco smoke exposure, but the mechanisms that can account for disease development remain to be fully defined. Utilizing our HNSCC mouse model, we analyzed oral squamous cell carcinomas (OSCC) induced by the active metabolite of a common smoke constituent, dibenzo[a,l]pyrene diol-epoxide (DBPDE). Analyzing protein expression by either immunofluorescence or immunohistochemistry, we identified biologic processes that are dysregulated in premalignant and invasive cancer lesions induced by DBPDE. Interestingly, p120ctn expression is downregulated in both stages of the disease. In addition to decreased p120ctn expression, there was also increased proliferation (as measured by Ki67), inflammation (as measured by NFkB (p65) expression), neovascularization (as measured by CD31) and recruitment of Ly6G-positive immune cells as well as strong EGFR expression. We also examined the effect of the chemopreventive agent black raspberry (BRB) on p120ctn and EGFR protein expression in DBPDE treated mice. p120ctn, but not EGFR, protein expression increased in mice treated with BRB. Our results suggest that modulation of p120ctn may, in part, account for the mechanism by which BRB inhibits DBPDE induced OSCC in mice.

A review on network pharmacology based phytotherapy in treating diabetes- An environmental perspective

Diabetes has become common lifestyle disorder associated with obesity and cardiovascular diseases. Environmental factors like physical inactivity, polluted surroundings and unhealthy dieting also plays a vital role in diabetes pathogenesis. As the current anti-diabetic drugs possess unprecedented side effects, traditional herbal medicine can be used an alternative therapy. The paramount challenge with the herbal formulation usage is the lack of standardized procedure, entangled with little knowledge on drug safety and mechanism of drug action. Heavy metal contamination is a major environmental hazard where plants tend to accumulate toxic metals like nickel, chromium and lead through industrial and agricultural activities. It becomes inappropriate to use these plants for phytotherapy as it may affect the human health on long term consumption. This review discuss about the environmental risk factors related to diabetes and better implication of medicinal plants in anti-diabetic therapy using network pharmacology. It is an in silico analytical tool that helps to unravel the multi-targeted action of herbal formulations rich in secondary metabolites. Also, a special focus is attempted to pool the databases regarding the medicinal plants for diabetes and associated diseases, their bioactive compounds, possible diabetic targets, drug-target interaction and toxicology reports that may open an aisle in safer, effective and toxicity-free drug discovery.

Bilberry (Vaccinium myrtillus L.) Powder Has Anticarcinogenic Effects on Oral Carcinoma In Vitro and In Vivo

Previous studies indicate that bilberry with high amounts of phenolic compounds can inhibit carcinogenic processes of colorectal cancer in vitro and in vivo. However, no studies have focused on the effects of bilberry on oral cancer. In this study, we aimed to examine the effects of bilberry powder on oral squamous cell carcinoma (OSCC) cells using both in vitro and in vivo assays. The effects of 0, 1, 10, and 25 mg/mL of whole bilberry powder on the viability, proliferation, migration, and invasion of OSCC (HSC-3) cells were examined and compared with 0.01 mg/mL of cetuximab. Two oral keratinocyte cell lines served as controls. Tumor area was analyzed in zebrafish microinjected with HSC-3 cells and treated with 2.5, 10, or 25 µg/mL of bilberry powder. Metastases in the head or tail areas were counted. Bilberry powder inhibited the viability, proliferation, migration, and invasion of HSC-3 cells (p < 0.05), which was more pronounced with higher concentrations. Cetuximab had no effect on HSC-3 cell migration or invasion. Compared to controls, the tumor area in zebrafish treated with bilberry powder (10 and 25 µg/mL) was reduced significantly (p = 0.038 and p = 0.021, respectively), but the number of fish with metastases did not differ between groups. Based on our in vitro and in vivo experiments, we conclude that whole bilberry powder has anti-tumor effects on OSCC cells.

EGCG inhibits growth of tumoral lesions on lip and tongue of K-Ras transgenic mice through the Notch pathway

Epigallocatechin-3-gallate (EGCG), the main active ingredient of green tea, exhibits low toxic side effect and versatile bioactivities, and its anti-cancer effect has been extensively studied. Most of the studies used cancer cell lines and xenograft models. However, whether EGCG can prevent tumor onset after cancer-associated mutations occur is still controversial. In the present study, Krt14-cre/ERT-Kras transgenic mice were developed and the expression of K-RasG12D was induced by tamoxifen. Two weeks after induction, the K-Ras mutant mice developed exophytic tumoral lesions on the lips and tongues, with significant activation of Notch signaling pathway. Administration of EGCG effectively delayed the time of appearance, decreased the size and weight of tumoral lesions, relieved heterotypic hyperplasia of tumoral lesions, and prolonged the life of the mice. The Notch signaling pathway was significantly inhibited by EGCG in the tumoral lesions. Furthermore, EGCG significantly induced cell apoptosis and inhibited the proliferation of tongue cancer cells by blocking the activation of Notch signaling pathway. Taken together, these results indicate EGCG as an effective chemotherapeutic agent for tongue cancer by targeting Notch pathway.

The environmental pollutant and tobacco smoke constituent dibenzo[def,p]chrysene is a co-factor for malignant progression of mouse oral papillomavirus infections

HPV infections in the oral cavity that progress to cancer are on the increase in the USA. Model systems to study co-factors for progression of these infections are lacking as HPVs are species-restricted and cannot grow in preclinical animal models. We have recently developed a mouse papillomavirus (MmuPV1) oral mucosal infection model that provides opportunities to test, for the first time, the hypothesis that tobacco carcinogens are co-factors that can impact the progression of oral papillomas to squamous cell carcinoma (SCC). Four cohorts of mice per sex were included: (1) infected with MmuPV1 and treated orally with DMSO-saline; (2) infected with MmuPV1 and treated orally with the tobacco carcinogen, dibenzo[def,p]chrysene (DBP); (3) uninfected and treated orally with DMSO-saline, and (4) uninfected and treated orally with DBP. Oral swabs were collected monthly for subsequent assessment of viral load. Oral tissues were collected for in situ viral DNA/RNA detection, viral protein staining, and pathological assessment for hyperplasia, papillomas and SCC at study termination. We observed increased rates of SCC in oral tissue infected with MmuPV1 and treated with DBP when compared to mice treated with DBP or virus individually, each of which showed minimal disease. Virally-infected epithelium showed strong levels of viral DNA/RNA and viral protein E4/L1 staining. In contrast, areas of SCC showed reduced viral DNA staining indicative of lower viral copy per nucleus but strong RNA signals. Several host markers (p120 ctn, p53, S100A9) were also examined in the mouse oral tissues; of particular significance, p120 ctn discriminated normal un-infected epithelium from SCC or papilloma epithelium. In summary, we have confirmed that our infection model is an excellent platform to assess the impact of co-factors including tobacco carcinogens for oral PV cancerous progression. Our findings can assist in the design of novel prevention/treatment strategies for HPV positive vs. HPV negative disease.

Mutations in long-lived epithelial stem cells and their clonal progeny in pre-malignant lesions and in oral squamous cell carcinoma

Oral squamous cell carcinomas (OSCCs) are the most common cancers of the oral cavity, but the molecular mechanisms driving OSCC carcinogenesis remain unclear. Our group previously established a murine OSCC model based on a 10-week carcinogen [4-nitroquinoline 1-oxide (4-NQO)] treatment. Here we used K14CreERTAM;Rosa26LacZ mice to perform lineage tracing to delineate the mutational profiles in clonal cell populations resulting from single, long-lived epithelial stem cells, here called LacZ+ stem cell clones (LSCCs). Using laser-capture microdissection, we examined mutational changes in LSCCs immediately after the 10-week 4-NQO treatment and >17 weeks after 4-NQO treatment. We found a 1.8-fold ±0.4 (P = 0.009) increase in single-nucleotide variants and insertions/deletions (indels) in tumor compared with pre-neoplastic LSCCs. The percentages of indels and of loss of heterozygosity events were 1.3-fold±0.3 (P = 0.02) and 2.2-fold±0.7 (P = 0.08) higher in pre-neoplastic compared with tumor LSCCs. Mutations in cell adhesion- and development-associated genes occurred in 83% of the tumor LSCCs. Frequently mutated genes in tumor LSCCs were involved in planar cell polarity (Celsr1, Fat4) or development (Notch1). Chromosomal amplifications in 50% of the tumor LSCCs occurred in epidermal growth factor receptor, phosphoinositide 3-kinase and cell adhesion pathways. All pre-neoplastic and tumor LSCCs were characterized by key smoking-associated changes also observed in human OSCC, C>A and G>T. DeconstructSigs analysis identified smoking and head and neck cancer as the most frequent mutational signatures in pre-neoplastic and tumor LSCCs. Thus, this model recapitulates a smoking-associated mutational profile also observed in humans and illustrates the role of LSCCs in early carcinogenesis and OSCCs.

Optimization of the classical oral cancerization protocol in hamster to study oral cancer therapy

OBJECTIVE(S)

The hamster carcinogenesis model recapitulates oral oncogenesis. Dimethylbenz[a]anthracene (DMBA) cancerization induces early severe mucositis, affecting animal's welfare and causing tissue loss and pouch shortening. "Short" pouches cannot be everted for local irradiation for boron neutron capture therapy (BNCT). Our aim was to optimize the DMBA classical cancerization protocol to avoid severe mucositis, without affecting tumor development. We evaluated BNCT in animals cancerized with this novel protocol.

MATERIALS AND METHODS

We studied: Classical cancerization protocol (24 applications) and Classical with two interruptions (completed at the end of the cancerization protocol). BNCT mediated by boronophenylalanine (BPA) was performed in both groups.

RESULTS

The twice-interrupted group exhibited a significantly lower percentage of animals with severe mucositis versus the non-interrupted group (17% versus 71%) and a significantly higher incidence of long pouches (100% versus 53%). Tumor development and the histologic characteristics of tumor and precancerous tissue were not affected by the interruptions. For both groups, overall tumor response was more than 80%, with a similar incidence of BNCT-induced severe mucositis.

CONCLUSION(S)

The twice-interrupted protocol reduced severe mucositis during cancerization without affecting tumor development. This favored the animal's welfare and reduced the number of animals to be cancerized for our studies, without affecting BNCT response.

Quantitative Liquid Chromatography-Nanoelectrospray Ionization-High-Resolution Tandem Mass Spectrometry Analysis of Acrolein-DNA Adducts and Etheno-DNA Adducts in Oral Cells from Cigarette Smokers and Nonsmokers

Cigarette smoking is an important source of human exposure to toxicants and carcinogens and contributes significantly to cancer morbidity and mortality worldwide. Acrolein, a widespread environmental pollutant, is present in relatively high amounts in cigarette smoke and can react directly with DNA to form DNA adducts, which serve as important biomarkers for the assessment of exposure to acrolein and its potential role in smoking related cancer. Etheno-DNA adducts are promutagenic DNA lesions that can derive from exogenous chemicals as well as endogenous sources, including lipid peroxidation. In this study, we developed a combined method for the quantitation of (6R/S)-3-(2'-deoxyribos-1'-yl)-5,6,7,8,-tetrahydro-6-hydroxypyrimido[1,2-a]purine-10(3H)-one (α-OH-Acr-dGuo), (8R/S)-3-(2'-deoxyribos-1'-yl)-5,6,7,8,-tetrahydro-8-hydroxypyrimido[1,2-a]purine-10(3H)-one (γ-OH-Acr-dGuo), 1,N6-etheno-dAdo (εdAdo), and 3,N4-etheno-dCyd (εdCyd) adducts in oral rinse and cytobrush DNA from smokers and nonsmokers by liquid chromatography-nanoelelctrospray ionization-high-resolution tandem mass spectrometry (LC-NSI-HRMS/MS). For oral rinse samples, there was a statistically significant difference between the levels of α-OH-Acr-dGuo, γ-OH-Acr-dGuo, εdAdo, and εdCyd in smokers (12.1 ± 17.9, 163 ± 227, 182 ± 568, and 194 ± 400 adducts/109 nucleotides, respectively) and nonsmokers (1.85 ± 2.08, 5.95 ± 4.23, 7.69 ± 11.7, and 6.07 ± 10.9 adducts/109 nucleotides, respectively). For cytobrush samples, there was a statistically significant difference between the levels of γ-OH-Acr-dGuo and εdAdo in smokers (259 ± 540 and 82.9 ± 271 adducts/109 nucleotides, respectively) and nonsmokers (7.37 ± 5.09 and 16.2 ± 30.2 adducts/109 nucleotides, respectively) but not for α-OH-Acr-dGuo and εdCyd. Our results demonstrate that oral mucosa cells are an excellent source of material for evaluating DNA adducts to be used as biomarkers of tobacco smoke exposure and molecular changes potentially related to cancer.

The Potential of Phytochemicals in Oral Cancer Prevention and Therapy: A Review of the Evidence

The etiological factors of oral cancer are complex including drinking alcohol, smoking tobacco, betel quid chewing, human papillomavirus infection, and nutritional deficiencies. Understanding the molecular mechanism of oral cancer is vital. The traditional treatment for patients with oral squamous cell carcinoma (e.g., surgery, radiotherapy, and chemotherapy) and targeted molecular therapy still have numerous shortcomings. In recent years, the use of phytochemical factors to prevent or treat cancer has received increasing attention. These phytochemicals have little or no toxicity against healthy tissues and are thus ideal chemopreventive agents. However, phytochemicals usually have low water solubility, low bioavailability, and insufficient targeting which limit therapeutic use. Numerous studies have investigated the development of phytochemical delivery systems to address these problems. The present article provides an overview of oral cancer including the etiological factors, diagnosis, and traditional therapy. Furthermore, the classification, dietary sources, anticancer bioactivity, delivery system improvements, and molecular mechanisms against oral cancer of phytochemicals are also discussed in this review.

An Integrated Approach for Preventing Oral Cavity and Oropharyngeal Cancers: Two Etiologies with Distinct and Shared Mechanisms of Carcinogenesis

Head and neck squamous cell carcinoma (HNSCC) was the 7th most common malignancy worldwide in 2018 and despite therapeutic advances, the overall survival rate for oral squamous cell carcinoma (OSCC; ∼50%) has remained unchanged for decades. The most common types are OSCC and oropharyngeal squamous cell carcinoma (OPSCC, survival rate ∼85%). Tobacco smoking is a major risk factor of HNSCC. In the developed world, the incidence of OSCC is declining as a result of tobacco cessation programs. However, OPSCC, which is also linked to human papillomavirus (HPV) infection, is on the rise and now ranks as the most common HPV-related cancer. The current state of knowledge indicates that HPV-associated disease differs substantially from other types of HNSCC and distinct biological differences between HPV-positive and HPV-negative HNSCC have been identified. Although risk factors have been extensively discussed in the literature, there are multiple clinically relevant questions that remain unanswered and even unexplored. Moreover, existing approaches (e.g., tobacco cessation, vaccination, and chemoprevention) to manage and control this disease remain a challenge. Thus, in this review, we discuss potential future basic research that can assist in a better understanding of disease pathogenesis which may lead to novel and more effective preventive strategies for OSCC and OPSCC.

Black Raspberry Inhibits Oral Tumors in Mice Treated with the Tobacco Smoke Constituent Dibenzo(def,p)chrysene Via Genetic and Epigenetic Alterations

We previously reported that the environmental pollutant and tobacco smoke constituent dibenzo[def,p]chrysene (DBP) induced DNA damage, altered DNA methylation and induced oral squamous cell carcinoma (OSCC) in mice. In the present study, we showed that 5% dietary black raspberry (BRB) significantly reduced (P < 0.05) the levels of DBP-DNA adducts in the mouse oral cavity with comparable effect to those of its constitutes. Thus, only BRB was selected to examine if aberrant DNA methylation induced by DBP can be altered by BRB. Using comparative genome-wide DNA methylation analysis, we identified 479 hypermethylated and 481 hypomethylated sites (q < 0.01, methylation difference >25%) between the oral tissues of mice treated with DBP and fed control diet or diet containing BRB. Among the 30 differential methylated sites (DMS) induced by DBP, we found DMS mapped to Fgf3, Qrich2, Rmdn2, and Cbarp were hypermethylated by BRB whereas hypomethylated by DBP at either the exact position or proximal sites; DMS mapped to Vamp3, Ppp1rB1, Pkm, and Zfp316 were hypomethylated by BRB but hypermethylated by DBP at proximal sites. In addition to Fgf3, 2 DMS mapped to Fgf4 and Fgf13 were hypermethylated by BRB; these fibroblast growth factors are involved in regulation of the epithelial-mesenchymal transition (EMT) pathway as identified by IPA. Moreover, BRB significantly reduced (P < 0.05) the tumor incidence from 70% to 46.7%. Taken together, the inhibitory effects of BRB on DNA damage combined with its effects on epigenetic alterations may account for BRB inhibition of oral tumorigenesis induced by DBP. SIGNIFICANCE: We provided mechanistic insights that can account for the inhibition of oral tumors by BRB, which could serve as the framework for future chemopreventive trials for addicted smokers as well as non- or former smokers who are exposed to environmental carcinogens.

Mouse Tumor-Bearing Models as Preclinical Study Platforms for Oral Squamous Cell Carcinoma

Preclinical animal models of oral squamous cell carcinoma (OSCC) have been extensively studied in recent years. Investigating the pathogenesis and potential therapeutic strategies of OSCC is required to further progress in this field, and a suitable research animal model that reflects the intricacies of cancer biology is crucial. Of the animal models established for the study of cancers, mouse tumor-bearing models are among the most popular and widely deployed for their high fertility, low cost, and molecular and physiological similarity to humans, as well as the ease of rearing experimental mice. Currently, the different methods of establishing OSCC mouse models can be divided into three categories: chemical carcinogen-induced, transplanted and genetically engineered mouse models. Each of these methods has unique advantages and limitations, and the appropriate application of these techniques in OSCC research deserves our attention. Therefore, this review comprehensively investigates and summarizes the tumorigenesis mechanisms, characteristics, establishment methods, and current applications of OSCC mouse models in published papers. The objective of this review is to provide foundations and considerations for choosing suitable model establishment methods to study the relevant pathogenesis, early diagnosis, and clinical treatment of OSCC.

Oral Health Effects of Combusted and Smokeless Tobacco Products

The oral cavity is usually the first part of a consumer's body exposed to the constituents of tobacco products or their emissions. Consequently, the oral cavity is a frequent site for carcinogenic, microbial, immunologic, and clinical effects of tobacco use. This article summarizes 5 presentations on various aspects of oral health affected by combusted or noncombusted tobacco products from a recent conference, "Oral Health Effects of Tobacco Products: Science and Regulatory Policy," sponsored by the American Association for Dental Research and the Food and Drug Administration.

Effects of the Tobacco Carcinogens N'-Nitrosonornicotine and Dibenzo[a,l]pyrene Individually and in Combination on DNA Damage in Human Oral Leukoplakia and on Mutagenicity and Mutation Profiles in lacI Mouse Tongue

In previous studies, we showed that the topical application of dibenzo[a,l]pyrene (DB[a,l]P), also known as dibenzo[def,p]chrysene, to the oral cavity of mice induced oral squamous cell carcinoma. We also showed that dA and dG adducts likely account for most of the mutagenic activity of DB[a,l]P in the oral tissues in vivo. Here we report for the first time that the oral treatment of lacI mice with a combination of tobacco smoke carcinogens, DB[a,l]P and N'-nitrosonornicotine (NNN), induces a higher fraction of mutations than expected from a simple sum of their induced individual mutation fractions, and a change in the mutational profile compared with that expected from the sum of the individual agents. The mutational profile of the combination of agents resembled that of the P53 gene in human head and neck cancers more than that of either of the individual agents, in that the percentage of the major class of mutations (GC > AT transitions) is similar to that seen in the P53 gene. A preliminary study was performed to understand the origin of the unexpected mutagenesis observations by measuring specific DNA adducts produced by both NNN and DB[a,l]P in human oral leukoplakia cells. No significant differences in the expected and observed major adduct levels from either agent were observed between individual or combined treatments, suggesting that additional adducts are important in mutagenesis induced by the mixture. Taken together, the above observations support the use of this animal model not only to investigate tobacco smoke-induced oral cancer but also to study chemoprevention.

Different oral cancer scenarios to personalize targeted therapy: Boron Neutron Capture Therapy translational studies

Boron neutron capture therapy (BNCT) is a targeted therapy, which consists of preferential accumulation of boron carriers in tumor followed by neutron irradiation. Each oral cancer patient has different risks of developing one or more carcinomas and/or oral mucositis induced after treatment. Our group proposed the hamster oral cancer model to study the efficacy of BNCT and associated mucositis. Translational studies are essential to the advancement of novel boron delivery agents and targeted strategies. Herein, we review our work in the hamster model in which we studied BNCT induced mucositis using three different cancerization protocols, mimicking three different clinical scenarios. The BNCT-induced mucositis increases with the aggressiveness of the carcinogenesis protocol employed, suggesting that the study of different oral cancer patient scenarios would help to develop personalized therapies.

Tobacco and alcohol-induced epigenetic changes in oral carcinoma

PURPOSE OF REVIEW

The present review aims to describe the epigenetic alterations observed in oral cancer linked to the exposure to alcohol and/or tobacco.

RECENT FINDINGS

Recent findings emphasize the importance of epigenetics in oral cancer progression and in how risk factors (as tobacco and alcohol) affect the basal epigenetic profiles. Deeper techniques and detailed approaches allowed the perception that individual CG changes and even subtle changes may represent important epigenetic alterations resulting in expression changes and other carcinogenic consequences. New classes of epigenetic alterations including noncoding RNAs have been gaining attention.

SUMMARY

Many epigenetic alterations have been described in oral carcinoma progression induced by tobacco and/or alcohol, including: promoter hypermethylation in genes with tumor suppressive activity, global (genome-wide) hypomethylation, change in methylation patterns throughout the genes, alteration in noncoding RNAs, and histones modifications. These changes represent progress in the knowledge of how these risk factors act in a molecular level. There is an urgent need for large independent studies to move these potential makers further and validate them to identify risk assessment, early diagnostic markers, and therapeutic targets, as well as to be the base for prevention and intervention strategies.

Comparative Tumorigenicity and DNA Damage Induced by Dibenzo[ def,p]chrysene and Its Metabolites in the Mouse Ovary

Ovarian cancer ranked second in incidence among gynecologic cancers, but it causes more deaths than any other gynecologic cancer; at present there is no curative treatment beyond surgery. Animal models that employ carcinogens found in the human environment can provide a realistic platform to understand the mechanistic basis for disease development and to design rational chemopreventive/therapeutic strategies. We and others have shown that the administration of the environmental pollutant and tobacco smoke constituent dibenzo[ def,p]chrysene (DBP) to mice by several routes of exposure can induce tumors in multiple sites including the ovary. In the present study we compared, for the first time, the tumorigenicity and DNA damage induced by DBP and its metabolites DBP-dihydrodiol (DBPDHD) and DBP-dihydrodiol epoxide (DBPDE) in the mouse ovary. Compounds were dissolved in dimethyl sulfoxide (DMSO) as the vehicle and administered by topical application into the mouse oral cavity three times per week for 38 weeks. No tumors were observed in mice treated with DMSO. At equal dose (24 nmol/30 μL DMSO), the incidence of ovarian tumors induced by DBPDHD was higher (60.7%), although not significantly, than that induced by DBP (44.8%). Similarly the levels of DNA damage induced by DBPDHD in the ovary were higher than those observed with DBP. We did not observe any histological abnormality in the ovary of mice treated with DBPDE, which is consistent with lack of DNA damage. Our results suggested that both DBP and DBPDHD can be metabolized in the mouse ovary leading to the formation of DBPDE that can damage DNA, which is a prerequisite step in the initiation stage of carcinogenesis.

Storage conditions modulate the metabolomic profile of a black raspberry nectar with minimal impact on bioactivity

Pre-clinical and clinical studies suggest black raspberries (BRBs) may inhibit the development of oral cancer. Lyophilized BRB powder is commonly used in these studies, but processed BRB products are more often consumed. The objective of this work was to understand how storage conditions influence the phytochemical profile and anti-proliferative activity of a BRB nectar beverage. Untargeted UHPLC-Q-TOF-MS based metabolomics analyses demonstrated that large chemical variation was introduced by storage above -20 °C over 60 days. However, minimal change in anti-proliferative activity was observed when stored nectar extracts were applied to SCC-83-01-82 premalignant oral epithelial cells. As proof of concept, cyanidin-3-O-rutinoside and its degradation product, protocatechuic acid, were administered in different ratios maintaining an equimolar dose, and anti-proliferative activity was maintained. This study shows the utility of metabolomics to profile global chemical changes in foods, while demonstrating that isolated phytochemicals do not explain the complete bioactivity of a complex food product.

Mouse Models for Studying Oral Cancer: Impact in the Era of Cancer Immunotherapy

Model systems for oral cancer research have progressed from tumor epithelial cell cultures to in vivo systems that mimic oral cancer genetics, pathological characteristics, and tumor-stroma interactions of oral cancer patients. In the era of cancer immunotherapy, it is imperative to use model systems to test oral cancer prevention and therapeutic interventions in the presence of an immune system and to discover mechanisms of stromal contributions to oral cancer carcinogenesis. Here, we review in vivo mouse model systems commonly used for studying oral cancer and discuss the impact these models are having in advancing basic mechanisms, chemoprevention, and therapeutic intervention of oral cancer while highlighting recent discoveries concerning the role of immune cells in oral cancer. Improvements to in vivo model systems that highly recapitulate human oral cancer hold the key to identifying features of oral cancer initiation, progression, and invasion as well as molecular and cellular targets for prevention, therapeutic response, and immunotherapy development.

Immunomodulatory Effects of Momordica charantia Extract in the Prevention of Oral Cancer

In recent times, bitter melon extract (BME) has gained significant attention for its anticancer efficacy against various malignancies. In this issue, Sur and colleagues show that BME prevents the development of 4-nitronitroquinoline 1-oxide-induced oral dysplasia and squamous cell carcinoma (SCC) in an immunocompetent mouse model. Importantly, gene ontology and pathway analyses revealed an elevated expression of s100a9, IL23a, IL1β, and PDCD1/PD1 of immune system during oral cancer development, which was significantly suppressed by BME. Overall, this study demonstrates the potential clinical benefits of BME in preventing and delaying the progression of oral dysplasia to SCC. Cancer Prev Res; 11(4); 185-6. ©2018 AACRSee related article by Sur et al., p. 191.

Effects of Black Raspberry on Dibenzo[a,l]Pyrene Diol Epoxide Induced DNA Adducts, Mutagenesis, and Tumorigenesis in the Mouse Oral Cavity

We previously showed that metabolic activation of the environmental and tobacco smoke constituent dibenzo[a,l]pyrene (DB[a,l]P) to its active fjord region diol epoxide (DB[a,l]PDE) is required to induce DNA damage, mutagenesis, and squamous cell carcinoma (SCC) in the mouse oral cavity. In contrast to procarcinogens, which were employed previously to induce SCC, DB[a,l]PDE does not require metabolic activation to exert its biological effects, and thus, this study was initiated to examine, for the first time, whether black raspberry powder (BRB) inhibits postmetabolic processes, such as DNA damage, mutagenesis, and tumorigenesis. Prior to long-term chemoprevention studies, we initially examined the effect of BRB (5% added to AIN-93M diet) on DNA damage in B6C3F1 mice using LC/MS-MS and on mutagenesis in the lacI gene in the mouse oral cavity. We showed that BRB inhibited DB[a,l]PDE-induced DNA damage (P < 0.05) and mutagenesis (P = 0.053) in the oral cavity. Tumor incidence in the oral cavity (oral mucosa and tongue) of mice fed diet containing 5% BRB was significantly (P < 0.05) reduced from 93% to 66%. Specifically, the incidence of benign tumor was significantly (P < 0.001) reduced from 90% to 31% (62% to 28% in the oral cavity and 28% to 2% in the tongue), a nonsignificant reduction of malignant tumors from 52% to 45%. Our preclinical findings demonstrate for the first time that the chemopreventive efficacy of BRB can be extended to direct-acting carcinogens that do not require phase I enzymes and is not just limited to procarcinogens. Cancer Prev Res; 11(3); 157-64. ©2017 AACR.

Hypomethylated Fgf3 is a potential biomarker for early detection of oral cancer in mice treated with the tobacco carcinogen dibenzo[def,p]chrysene

Genetic and epigenetic alterations observed at end stage OSCC formation could be considered as a consequence of cancer development and thus changes in normal or premalignant tissues which had been exposed to oral carcinogens such as Dibenzo[def,p]chrysene (DBP) may better serve as predictive biomarkers of disease development. Many types of DNA damage can induce epigenetic changes which can occur early and in the absence of evident morphological abnormalities. Therefore we used ERRBS to generate genome-scale, single-base resolution DNA methylomes from histologically normal oral tissues of mice treated with DBP under experimental conditions known to induce maximum DNA damage which is essential for the development of OSCC induced by DBP in mice. After genome-wide correction, 30 and 48 differentially methylated sites (DMS) were identified between vehicle control and DBP treated mice using 25% and 10% differences in methylation, respectively. RT-PCR was further performed to examine the expressions of nine selected genes. Among them, Fgf3, a gene frequently amplified in head and neck cancer, showed most prominent and significant gene expression change (2.4× increases), despite the hypomethylation of Fgf3 was identified at >10kb upstream of transcription start site. No difference was observed in protein expression between normal oral tissues treated with DBP or vehicle as examined by immunohistochemistry. Collectively, our results indicate that Fgf3 hypomethylation and gene overexpression, but not protein expression, occurred in the early stage of oral carcinogenesis induced by DBP. Thus, Fgf3 hypomethylation may serve as a potential biomarker for early detection of OSCC.

Effects of chronic alcohol consumption on DNA damage and immune regulation induced by the environmental pollutant dibenzo[a,l]pyrene in oral tissues of mice

Previously, we showed that oral application of the environmental pollutant dibenzo[a,l]pyrene (DB[a,l]P) induces oral tumors in mice. Thus, in the present investigation we examined the effect of alcohol on DB[a,l]P-induced DNA damage and immune regulation; we showed that alcohol (6.4% v/v in the diet, 35% of Calories) significantly enhanced the levels of (-)-anti-trans-DB[a,l]P-dA while decreased the levels of GSH in the mouse oral tissues. Analysis of RNA expression revealed that DB[a,l]P alone upregulates inflammatory genes while alcohol suppresses several markers of immune surveillance. Collectively, these results suggest that alcohol may enhance oral carcinogenesis induced by DB[a,l]P.