Acetaldehyde, microbes, and cancer of the digestive tract

De-coding the complex role of microbial metabolites in cancer

The human microbiome, an intricate ecosystem of trillions of microbes residing across various body sites, significantly influences cancer, a leading cause of morbidity and mortality worldwide. Recent studies have illuminated the microbiome's pivotal role in cancer development, either through direct cellular interactions or by secreting bioactive compounds such as metabolites. Microbial metabolites contribute to cancer initiation through mechanisms such as DNA damage, epithelial barrier dysfunction, and chronic inflammation. Furthermore, microbial metabolites exert dual roles on cancer progression and response to therapy by modulating cellular metabolism, gene expression, and signaling pathways. Understanding these complex interactions is vital for devising new therapeutic strategies. This review highlights microbial metabolites as promising targets for cancer prevention and treatment, emphasizing their impact on therapy responses and underscoring the need for further research into their roles in metastasis and therapy resistance.

New Method of Direct Sampling Gas Chromatography-Ion Mobility Spectrometry to Identify the Dynamic Retronasal Volatile Compounds in the Alcoholic Beverage and Their Release Behaviors: A Case Study on Huangjiu

Owing to extremely low concentrations and dynamic changes, it is difficult to detect and trace the retronasal volatile organic compounds (VOCs) generated during the consumption of alcoholic beverages. We developed a direct sampling gas chromatography-ion mobility spectrometry (GC-IMS) method to identify the dynamic VOCs after drinking Huangjiu-a fermented alcoholic beverages. The optimal procedure was obtained: take a sip of 10 mL Huangjiu, holding it in mouth for 10 s and then swallow, and the VOCs in one nasal expiration were collected with gas sampling bag and transferred directly to the injection port of GC-IMS. The repeatability was satisfactory (RSD < 5%). Twenty-two VOCs were detected in Huangjiu, with esters and alcohols being dominant, which were divided into five distinct release behavior groups. Their release was found significantly inhibited by saliva. Overall, this new method offers a technical approach to understanding and assessing the characteristics of retronasal aroma in alcoholic beverages.

Diindoles produced from commensal microbiota metabolites function as endogenous CAR/Nr1i3 ligands

Numerous studies have demonstrated the correlation between human gut bacteria and host physiology, mediated primarily via nuclear receptors (NRs). Despite this body of work, the systematic identification and characterization of microbe-derived ligands that regulate NRs remain a considerable challenge. In this study, we discover a series of diindole molecules produced from commensal bacteria metabolites that act as specific agonists for the orphan constitutive androstane receptor (CAR). Using various biophysical analyses we show that their nanomolar affinities are comparable to those of synthetic CAR agonists, and that they can activate both rodent and human CAR orthologues, which established synthetic agonists cannot. We also find that the diindoles, diindolylmethane (DIM) and diindolylethane (DIE) selectively up-regulate bona fide CAR target genes in primary human hepatocytes and mouse liver without causing significant side effects. These findings provide new insights into the complex interplay between the gut microbiome and host physiology, as well as new tools for disease treatment.

Fungal footprints in oral cancer: unveiling the oral mycobiome

Oral squamous cell carcinoma (OSCC) is the most common type of head and neck cancer, with a high mortality rate. There is growing evidence supporting a link between oral cancer and the microbiome. The microbiome can impact various aspects of cancer, such as pathogenesis, diagnosis, treatment, and prognosis. While there is existing information on bacteria and its connection to oral cancer, the fungi residing in the oral cavity represent a significant component of the microbiome that remains in its early stages of exploration and understanding. Fungi comprise a minuscule part of the human microbiome called the mycobiome. Mycobiome is ubiquitous in the human body but a weakened immune system offers a leeway space for fungi to showcase its virulence. The role of mycobiome as a colonizer, facilitator, or driver of carcinogenesis is still ambiguous. Reactivating the mycobiome that undergoes collateral damage associated with cancer treatment can be watershed event in cancer research. The coordinated, virulent, non-virulent behavior of the fungi once they reach a critical density must be hacked, considering its diagnostic, prognostic and therapeutic implications in cancer. This review highlights the diversity of the mycobiome and its potential role in oral cancer.

Alcohol consumption and oral microbiome composition in a sample of healthy young adults

The oral microbiomes of 24 healthy adults (50% female; mean age = 24.3) were examined using 16 s ribosomal RNA sequencing and compared between light and heavy drinkers. Beta diversity was related at the trend level to drinking group, and light drinkers had significantly higher abundances of key oral taxa such as Lactobacillales. These preliminary results may offer insight into early effects of heavy drinking on the composition of the oral microbiome.

Periodontitis and progression of gastrointestinal cancer: current knowledge and future perspective

Periodontitis is a polymicrobial disorder caused by dysbiosis. Porphyromonas gingivalis (P.gingivalis) and Fusobacterium nucleatum (F.nucleatum) are pathobiont related to periodontitis pathogenesis and were found to be abundant in the intestinal mucosa of inflammatory bowel disease (IBD) and colorectal cancer (CRC) patients. Besides, periodontal infections have been found in a variety of tissues and organs, indicating that periodontitis is not just an inflammation limited to the oral cavity. Considering the possible translocation of pathobiont from the oral cavity to the gastrointestinal (GI) tract, this study aimed to review the published articles in this field to provide a comprehensive view of the existing knowledge about the relationship between periodontitis and GI malignancies by focusing on the oral/gut axis.

Human Gut Microbiota in Heart Failure: Trying to Unmask an Emerging Organ

There is a bidirectional relationship between the heart and the gut. The gut microbiota, the community of gut micro-organisms themselves, is an excellent gut-homeostasis keeper since it controls the growth of potentially harmful bacteria and protects the microbiota environment. There is evidence suggesting that a diet rich in fatty acids can be metabolized and converted by gut microbiota and hepatic enzymes to trimethyl-amine N-oxide (TMAO), a product that is associated with atherogenesis, platelet dysfunction, thrombotic events, coronary artery disease, stroke, heart failure (HF), and, ultimately, death. HF, by inducing gut ischemia, congestion, and, consequently, gut barrier dysfunction, promotes the intestinal leaking of micro-organisms and their products, facilitating their entrance into circulation and thus stimulating a low-grade inflammation associated with an immune response. Drugs used for HF may alter the gut microbiota, and, conversely, gut microbiota may modify the pharmacokinetic properties of the drugs. The modification of lifestyle based mainly on exercise and a Mediterranean diet, along with the use of pre- or probiotics, may be beneficial for the gut microbiota environment. The potential role of gut microbiota in HF development and progression is the subject of this review.

The Influence of the Microbiome on Immunotherapy for Gastroesophageal Cancer

Immunotherapy has shown promise as a treatment option for gastroesophageal cancer, but its effectiveness is limited in many patients due to the immunosuppressive tumor microenvironment (TME) commonly found in gastrointestinal tumors. This paper explores the impact of the microbiome on the TME and immunotherapy outcomes in gastroesophageal cancer. The microbiome, comprising microorganisms within the gastrointestinal tract, as well as within malignant tissue, plays a crucial role in modulating immune responses and tumor development. Dysbiosis and reduced microbial diversity are associated with poor response rates and treatment resistance, while specific microbial profiles correlate with improved outcomes. Understanding the complex interactions between the microbiome, tumor biology, and immunotherapy is crucial for developing targeted interventions. Microbiome-based biomarkers may enable personalized treatment approaches and prediction of patient response. Interventions targeting the microbiome, such as microbiota-based therapeutics and dietary modifications, offer the potential for reshaping the gut microbiota and creating a favorable TME that enhances immunotherapy efficacy. Further research is needed to reveal the underlying mechanisms, and large-scale clinical trials will be required to validate the efficacy of microbiome-targeted interventions.

Oral microbiota may predict the presence of esophageal squamous cell carcinoma

PURPOSE

Microbial imbalances have been well elucidated in esophageal adenocarcinoma (EAC), but few studies address the oral microbiota in esophageal squamous cell carcinoma (ESCC). In view of the fact, we aimed to explore the associations of oral microbiota with these patients suffering from ESCC.

METHODS

In our study, a total of 109 individuals were enrolled (control = 53, ESCC = 56). We profiled the microbiota in oral swabs from individuals with control (ConT) and ESCC (ESCCT). 16S rRNA gene sequencing was applied to analyze the microbiome. The α and β diversity differences were tested by Tukey Test and Partial Least Squares Discriminant Analysis (PLS-DA) respectively. Linear discriminant analysis effect size (LEfSe) analysis was performed to assess taxonomic differences between the two groups.

RESULTS

Our results showed that the microbial richness and diversity was a slightly higher in ESCCT groups than that in ConT groups. Bacteroidota, Firmicutes, Proteobacteria, Fusobacteria, Actinobacteria and Patescibacteria were the six dominant bacteria of oral flora in the two groups. When compared with control group, increased Fusobacterioa at phylum level, Neisseriaceae at family level and Leptotrichia at genus level were detected. LEfSe analysis indicated a greater abundance of Leptotrichiaceae, Leptotrichia, Fusobacteriales, Fusobacteria and Fusobacteriota in ESCC groups.

CONCLUSION

Our study suggests a potential association between oral microbiome dysbiosis and ESCC and provides insights on a potential screening marker for esophageal cancer.

Alcohol-associated bowel disease: new insights into pathogenesis

Excessive alcohol drinking can cause pathological changes including carcinogenesis in the digestive tract from mouth to large intestine, but the underlying mechanisms are not fully understood. In this review, we discuss the effects of alcohol on small and large intestinal functions, such as leaky gut, dysbiosis and alterations of intestinal epithelium and gut immune dysfunctions, commonly referred to as alcohol-associated bowel disease (ABD). To date, detailed mechanistic insights into ABD are lacking. Accumulating evidence suggests a pathogenic role of ethanol metabolism in dysfunctions of the intestinal tract. Ethanol metabolism generates acetaldehyde and acetate, which could potentially promote functional disruptions of microbial and host components of the intestinal barrier along the gastrointestinal tract. The potential involvement of acetaldehyde and acetate in the pathogenesis of the underlying ABD, including cancer, is discussed. We also highlight some gaps in knowledge existing in the field of ABD. Finally, we discuss future directions in exploring the role of acetaldehyde and acetate generated during chronic alcohol intake in various pathologies affecting different sites of the intestinal tract.

The Influence of the Oral Microbiome on Oral Cancer: A Literature Review and a New Approach

In our recent article (Smędra et al.: Oral form of auto-brewery syndrome. J Forensic Leg Med. 2022; 87: 102333), we showed that alcohol production can occur in the oral cavity (oral auto-brewery syndrome) due to a disruption in the microbiota (dysbiosis). An intermediate step on the path leading to the formation of alcohol is acetaldehyde. Typically, acetic aldehyde is transformed into acetate particles inside the human body via acetaldehyde dehydrogenase. Unfortunately, acetaldehyde dehydrogenase activity is low in the oral cavity, and acetaldehyde remains there for a long time. Since acetaldehyde is a recognised risk factor for squamous cell carcinoma arising from the oral cavity, we decided to analyse the relationship linking the oral microbiome, alcohol, and oral cancer using the narrative review method, based on browsing articles in the PubMed database. In conclusion, enough evidence supports the speculation that oral alcohol metabolism must be assessed as an independent carcinogenic risk. We also hypothesise that dysbiosis and the production of acetaldehyde from non-alcoholic food and drinks should be treated as a new factor for the development of cancer.

Identifying oral microbiome alterations in adult betel quid chewing population of Delhi, India

The study targets to establish a factorial association of oral microbiome alterations (oral dysbiosis) with betel quid chewing habits through a comparison of the oral microbiome of Betel quid chewers and non-chewing individuals. Oral microbiome analysis of 22 adult individuals in the Delhi region of India through the 16S sequencing approach was carried out to observe the differences in taxonomic abundance and diversity. A significant difference in diversity and richness among Betel Quid Chewers (BQC) and Betel Quid Non-Chewers (BQNC) groups was observed. There were significant differences in alpha diversity among the BQC in comparison to BQNC. However, in the age group of 21-30 years old young BQC and BQNC there was no significant difference in alpha diversity. Similar result was obtained while comparing BQC and Smoker-alcoholic BQC. BQ smoker-chewers expressed significant variance in comparison to BQC, based on cluster pattern analysis. The OTU-based Venn Diagram Analysis revealed an altered microbiota, for BQ chewing group with 0-10 years exposure in comparison to those with 10 years and above. The change in the microbial niche in early chewers may be due to abrupt chemical component exposure affecting the oral cavity, and thereafter establishing a unique microenvironment in the long-term BQC. Linear discriminant analysis revealed, 55 significant features among BQC and Alcoholic-Smoker BQC; and 20 significant features among BQC and Smoker BQC respectively. The study shows the abundance of novel bacterial genera in the BQC oral cavity in addition to the commonly found ones. Since the oral microbiome plays a significant role in maintaining local homeostasis, investigating the link between its imbalance in such conditions that are known to have an association with oral diseases including cancers may lead to the identification of specific microbiome-based signatures for its early diagnosis.

Systematic investigation of the clinical significance and prognostic value of the CBXs in esophageal cancer

Esophageal cancer (ESCA), one of the most aggressive malignant tumors, has been announced to be the ninth most common cancer and the sixth leading cause of cancer-related death in the world. Chromobox family members (CBXs) are important epigenetic regulators which are related with the transcription of target genes. The role of CBXs in carcinomas has been reported in many studies. However, the function and prognostic value of different CBXs in ESCA are still largely unknown. In this article, we first performed differential expression analysis through several methods including Oncomine and Gene Expression Profiling Interactive Analysis. The results led us to determine the differential expression of CBXs in pan-cancer, especially ESCA. Then we evaluated the prognostic value of different CBX messenger RNA (mRNA) expression in patients with ESCA through the Kaplan-Meier plotter and the Human Protein Atlas database. In addition, we used cBioPortal to explore all genetic alterations and mutations in the CBXs in ESCA. Simultaneously, the correlation between its expression and the level of immune infiltration of ESCA was visualized by TIMER. Finally, the biological function of CBXs in ESCA is obtained through Biological Enrichment Analysis including gene ontology and Kyoto Encyclopedia of Genes and Genomes. The expression levels of CBX3/4/5 and CBX8 in ESCA tissues increased significantly and the expression level of CBX7 decreased through differential expression analysis. Additionally, CBX1 is significantly related to the clinical cancer stage and disease-free survival of ESCA patients. The high mRNA expression of CBX4 is related to the short overall survival of patients with esophageal squamous cell carcinoma, and the high mRNA expression of CBX3/7/8 is related to the short overall survival of patients with esophageal adenocarcinoma, indicating that CBX1/3/4/7/8 may be a potential prognostic biomarker for the survival of ESCA patients. Besides, the expression of CBXs is significantly related to the infiltration of a variety of immune cells, including six types of CD4-positive T-lymphocytes, macrophages, neutrophils, bursindependentlymphocyte, CD8-positive T-lymphocytes cells and dendritic cells in ESCA. Moreover, we found that CBXs are mainly associated with the inhibition of cell cycle and apoptosis pathway. Further, enrichment analysis indicated that CBXs and correlated genes were enriched in mismatch repair, DNA replication, cancer pathways, and spliceosomes. Our research may provide new insights into the choice of prognosis biomarkers of the CBXs in ESCA.

Unlocking the Potential of the Human Microbiome for Identifying Disease Diagnostic Biomarkers

The human microbiome encodes more than three million genes, outnumbering human genes by more than 100 times, while microbial cells in the human microbiota outnumber human cells by 10 times. Thus, the human microbiota and related microbiome constitute a vast source for identifying disease biomarkers and therapeutic drug targets. Herein, we review the evidence backing the exploitation of the human microbiome for identifying diagnostic biomarkers for human disease. We describe the importance of the human microbiome in health and disease and detail the use of the human microbiome and microbiota metabolites as potential diagnostic biomarkers for multiple diseases, including cancer, as well as inflammatory, neurological, and metabolic diseases. Thus, the human microbiota has enormous potential to pave the road for a new era in biomarker research for diagnostic and therapeutic purposes. The scientific community needs to collaborate to overcome current challenges in microbiome research concerning the lack of standardization of research methods and the lack of understanding of causal relationships between microbiota and human disease.

Salivary microbiota may predict the presence of esophageal squamous cell carcinoma

The aim is to explore the predictive value of salivary bacteria for the presence of esophageal squamous cell carcinoma (ESCC). Saliva samples were obtained from 178 patients with ESCC and 101 healthy controls, and allocated to screening and verification cohorts, respectively. In the screening phase, after saliva DNA was extracted, 16S rRNA V4 regions of salivary bacteria were amplified by polymerase chain reaction (PCR) with high-throughput sequencing. Highly expressed target bacteria were screened by Operational Taxonomic Units clustering, species annotation and microbial diversity assessment. In the verification phase, the expression levels of target bacteria identified in the screening phase were verified by absolute quantitative PCR (Q-PCR). Receiver operating characteristic (ROC) curves were plotted to investigate the predictive value of target salivary bacteria. LEfSe analysis revealed higher proportions of Fusobacterium, Streptococcus and Porphyromonas, and Q-PCR assay showed significantly higher numbers of Streptococcus salivarius, Fusobacterium nucleatum and Porphyromonas gingivalis in patients with ESCC, when compared with healthy controls (all P < 0.05). The areas under the ROC curves for Streptococcus salivarius, Fusobacterium nucleatum, Porphyromonas gingivalis and the combination of the three bacteria for predicting patients with ESCC were 69%, 56.5%, 61.8% and 76.4%, respectively. The sensitivities corresponding to cutoff value were 69.3%, 22.7%, 35.2% and 86.4%, respectively, and the matched specificity were 78.4%, 96.1%, 90.2% and 58.8%, respectively. These highly expressed Streptococcus salivarius, Fusobacterium nucleatum and Porphyromonas gingivalis in the saliva, alone or in combination, indicate their predictive value for ESCC.

Acetaldehyde makes a distinct mutation signature in single-stranded DNA

Acetaldehyde (AA), a by-product of ethanol metabolism, is acutely toxic due to its ability to react with various biological molecules including DNA and proteins, which can greatly impede key processes such as replication and transcription and lead to DNA damage. As such AA is classified as a group 1 carcinogen by the International Agency for Research on Cancer (IARC). Previous in vitro studies have shown that AA generates bulky adducts on DNA, with signature guanine-centered (GG→TT) mutations. However, due to its weak mutagenicity, short chemical half-life, and the absence of powerful genetic assays, there is considerable variability in reporting the mutagenic effects of AA in vivo. Here, we used an established yeast genetic reporter system and demonstrate that AA treatment is highly mutagenic to cells and leads to strand-biased mutations on guanines (G→T) at a high frequency on single stranded DNA (ssDNA). We further demonstrate that AA-derived mutations occur through lesion bypass on ssDNA by the translesion polymerase Polζ. Finally, we describe a unique mutation signature for AA, which we then identify in several whole-genome and -exome sequenced cancers, particularly those associated with alcohol consumption. Our study proposes a key mechanism underlying carcinogenesis by acetaldehyde—mutagenesis of single-stranded DNA.

The Mycobiome: Cancer Pathogenesis, Diagnosis, and Therapy

Cancer is among the leading causes of death globally. Despite advances in cancer research, a full understanding of the exact cause has not been established. Recent data have shown that the microbiome has an important relationship with cancer on various levels, including cancer pathogenesis, diagnosis and prognosis, and treatment. Since most studies have focused only on the role of bacteria in this process, in this article we review the role of fungi-another important group of the microbiome, the totality of which is referred to as the "mycobiome"-in the development of cancer and how it can impact responses to anticancer medications. Furthermore, we provide recent evidence that shows how the different microbial communities interact and affect each other at gastrointestinal and non-gastrointestinal sites, including the skin, thereby emphasizing the importance of investigating the microbiome beyond bacteria.

Breath volatile metabolome reveals the impact of dietary fibres on the gut microbiota: Proof of concept in healthy volunteers

Background

Current data suggest that dietary fibre (DF) interaction with the gut microbiota largely contributes to their physiological effects. The bacterial fermentation of DF leads to the production of metabolites, most of them are volatile. This study analyzed the breath volatile metabolites (BVM) profile in healthy individuals (n=15) prior and after a 3-week intervention with chitin-glucan (CG, 4.5 g/day), an insoluble fermentable DF.

Methods

The present exploratory study presents the original data related to the secondary outcomes, notably the analysis of BVM. BVM were analyzed throughout the test days -in fasting state and after standardized meals - using selected ion flow tube mass spectrometry (SIFT-MS). BVM production was correlated to the gut microbiota composition (Illumina sequencing, primary outcome), analyzed before and after the intervention.

Findings

The data reveal that the post-prandial state versus fasting state is a key determinant of BVM fingerprint. Correlation analyses with fecal microbiota spotlighted butyrate-producing bacteria, notably Faecalibacterium, as dominant bacteria involved in butyrate and other BVM expiration. CG intervention promotes interindividual variations of fasting BVM, and decreases or delays the expiration of most exhaled BVM in favor of H₂ expiration, without any consequence on gastrointestinal tolerance.

Interpretation

Assessing BVM is a non-invasive methodology allowing to analyze the influence of DF intervention on the gut microbiota.

Funding

FiberTAG project was initiated from a European Joint Programming Initiative “A Healthy Diet for a Healthy Life” (JPI HDHL) and was supported by the Service Public de Wallonie (SPW-EER, convention 1610365, Belgium).

Epigenetic Regulations of Perineural Invasion in Head and Neck Squamous Cell Carcinoma

Carcinomas of the oral cavity and oropharynx belong among the ten most common malignancies in the human population. The prognosis of head and neck squamous cell carcinoma (HNSCC) is determined by the degree of invasiveness of the primary tumor and by the extent of metastatic spread into regional and distant lymph nodes. Moreover, the level of the perineural invasion itself associates with tumor localization, invasion's extent, and the presence of nodal metastases. Here, we summarize the current knowledge about different aspects of epigenetic changes, which can be associated with HNSCC while focusing on perineural invasion (PNI). We review epigenetic modifications of the genes involved in the PNI process in HNSCC from the omics perspective and specific epigenetic modifications in OSCC or other neurotropic cancers associated with perineural invasion. Moreover, we summarize DNA methylation status of tumor-suppressor genes, methylation and demethylation enzymes and histone post-translational modifications associated with PNI. The influence of other epigenetic factors on the HNSCC incidence and perineural invasion such as tobacco, alcohol and oral microbiome is overviewed and HPV infection is discussed as an epigenetic factor associated with OSCC and related perineural invasion. Understanding epigenetic regulations of axon growth that lead to tumorous spread or uncovering the molecular control of axon interaction with cancer tissue can help to discover new therapeutic targets for these tumors.

Molecular Biologic and Epidemiologic Insights for Preventability of Colorectal Cancer

The etiology of colorectal cancer (CRC) has been informed from both a molecular biology perspective, which concerns the study of the nature, timing, and consequences of mutations in driver genes, and epidemiology, which focuses on identifying risk factors for cancer. For the most part, these fields have developed independently, and it is thus important to consider them in a more integrated manner. The molecular mutational perspective has stressed the importance of mutations due to replication of adult stem cells, and the molecular fingerprint of most CRCs does not suggest the importance of direct carcinogens. Epidemiology has identified numerous modifiable risk factors that account for most CRCs, most of which are not direct mutagens. The distribution of CRCs across the large bowel is not uniform, which is possibly caused by regional differences in the microbiota. Some risk factors are likely to act through or interact with the microbiota. The mutational perspective informs when risk factors may begin to operate in life and when they may cease to operate. Evidence from the mutational model and epidemiology supports that CRC risk factors begin early in life and may contribute to the risk of early-onset CRC. Later in carcinogenesis, there may be a "point of no return" when sufficient mutations have accumulated, and some risk factors do not affect cancer risk. This period may be at least 5-15 years for some risk factors. A more precise knowledge of timing of risk factor to cancer is required to inform preventive efforts.

Cigarette Smoking and Human Gut Microbiota in Healthy Adults: A Systematic Review

The intestinal microbiota is a crucial regulator of human health and disease because of its interactions with the immune system. Tobacco smoke also influences the human ecosystem with implications for disease development. This systematic review aims to analyze the available evidence, until June 2021, on the relationship between traditional and/or electronic cigarette smoking and intestinal microbiota in healthy human adults. Of the 2645 articles published in PubMed, Scopus, and Web of Science, 13 were included in the review. Despite differences in design, quality, and participants’ characteristics, most of the studies reported a reduction in bacterial species diversity, and decreased variability indices in smokers’ fecal samples. At the phylum or genus level, the results are very mixed on bacterial abundance both in smokers and non-smokers with two exceptions. Prevotella spp. appears significantly increased in smokers and former smokers but not in electronic cigarette users, while Proteobacteria showed a progressive increase in Desulfovibrio with the number of pack-years of cigarette (p = 0.001) and an increase in Alphaproteobacteria (p = 0.04) in current versus never smokers. This attempt to systematically characterize the effects of tobacco smoking on the composition of gut microbiota gives new perspectives on future research in smoking cessation and on a new possible use of probiotics to contrast smoke-related dysbiosis.

The Role of Gut Microbiota in Gastrointestinal Tract Cancers

Disturbances in gastrointestinal (GI) microbiota could play a significant role in the development of GI cancers, but the underlying mechanisms remain largely unclear. While some bacteria seem to facilitate carcinogenesis, others appear to be protective. So far only one bacterium (Helicobacter pylori) has been classified by the International Agency for Cancer Research as carcinogenic in humans but many other are the subject of intense research. Most studies on the role of microbiota in GI tract oncogenesis focus on pancreatic and colorectal cancers with the following three species: Helicobacter pylori, Escherichia coli, and Porphyromonas gingivalis as likely causative factors. This review summarizes the role of bacteria in GI tract oncogenesis.

Ethanol- and Cigarette Smoke-Related Alternations in Oral Redox Homeostasis

Alcohol abuse as well as smoking cigarettes has been proven to negatively affect the oral environment. The aim of this work was to provide a systematic review of the literature on the influence of ethanol and cigarette smoking on oral redox homeostasis. A search was performed for scientific articles indexed in the PubMed, Medline and Web of Science databases. We identified 32,300 articles, of which 54 were used for the final review, including the results from 2000 to 2021. Among the publications used to write this article, n = 14 were related to the influence of alcohol consumption (clinical studies n = 6, experimental studies n = 8) and n = 40 were related to the influence of smoking (clinical studies n = 33, experimental studies n = 7) on oral redox homeostasis. The reviewed literature indicates that alcohol abusers and smokers are more likely to suffer from salivary gland dysfunction, as well as develop precancerous lesions due to DNA damage. Compared to alcohol abstainers and non-smokers, alcohol drinkers and smokers are also characterized by a deterioration in periodontal health measured by various indicators of periodontal status. In summary, alcohol abuse and smoking are associated with disrupted oral redox homeostasis, which may lead not only to tooth loss, but also contribute to various adverse effects related to mental health, digestive processes and chronic inflammation throughout the human body.

Is There an Interplay between Oral Microbiome, Head and Neck Carcinoma and Radiation-Induced Oral Mucositis?

Head and neck carcinoma is one of the most common human malignancy types and it ranks as the sixth most common cancer worldwide. Nowadays, a great potential of microbiome research is observed in oncology-investigating the effect of oral microbiome in oncogenesis, occurrence of treatment side effects and response to anticancer therapies. The microbiome is a unique collection of microorganisms and their genetic material, interactions and products residing within the mucous membranes. The aim of this paper is to summarize current research on the oral microbiome and its impact on the development of head and neck cancer and radiation-induced oral mucositis. Human microbiome might determine an oncogenic effect by, among other things, inducing chronic inflammatory response, instigating cellular antiapoptotic signals, modulation of anticancer immunity or influencing xenobiotic metabolism. Influence of oral microbiome on radiation-induced oral mucositis is expressed by the production of additional inflammatory cytokines and facilitates progression and aggravation of mucositis. Exacerbated acute radiation reaction and bacterial superinfections lead to the deterioration of the patient's condition and worsening of the quality of life. Simultaneously, positive effects of probiotics on the course of radiation-induced oral mucositis have been observed. Understanding the impact on the emerging acute radiation reaction on the composition of the microflora can be helpful in developing a multifactorial model to forecast the course of radiation-induced oral mucositis. Investigating these processes will allow us to create optimized and personalized preventive measures and treatment aimed at their formation mechanism. Further studies are needed to better establish the structure of the oral microbiome as well as the dynamics of its changes before and after therapy. It will help to expand the understanding of the biological function of commensal and pathogenic oral microbiota in HNC carcinogenesis and the development of radiation-induced oral mucositis.

Effect of Cigarette Smoke on Gut Microbiota: State of Knowledge

Cigarette smoke is a representative source of toxic chemical exposures to humans, and the adverse consequences of cigarette smoking are mediated by its effect on both neuronal and immune-inflammatory systems. Cigarette smoking also is a major risk factor for intestinal disorders, such as Crohn's disease and peptic ulcer. On the other hand, cigarette smoking is protective against developing ulcerative colitis. The effects of cigarette smoking on intestinal disorders include changes in intestinal irrigation and microbiome, increases in permeability of the mucosa, and impaired mucosal immune responses. However, the underlying mechanism linking cigarette smoking with intestinal microbiota dysbiosis is largely unknown. In this communication, we first review the current knowledge about the mechanistic interaction between cigarette smoke and intestinal microbiota dysbiosis, which include the likely actions of nicotine, aldehydes, polycyclic aromatic hydrocarbons, heavy metals, volatile organic compounds and toxic gases, and then reveal the potential mechanisms of the lung-gut cross talk and skin-gut cross talk in regulating the balance of intestinal microbiota and the interrelation of intestinal microbiota dysbiosis and systemic disorders.

MiR-21 in the Cancers of the Digestive System and Its Potential Role as a Diagnostic, Predictive, and Therapeutic Biomarker

MicroRNAs (miRNAs) are small non-coding RNAs. They can regulate the expression of their target genes, and thus, their dysregulation significantly contributes to the development of cancer. Growing evidence suggests that miRNAs could be used as cancer biomarkers. As an oncogenic miRNA, the roles of miR-21 as a diagnostic and prognostic biomarker, and its therapeutic applications have been extensively studied. In this review, the roles of miR-21 are first demonstrated via its different molecular networks. Then, a comprehensive review on the potential targets and the current applications as a diagnostic and prognostic cancer biomarker and the therapeutic roles of miR-21 in six different cancers in the digestive system is provided. Lastly, a brief discussion on the challenges for the use of miR-21 as a therapeutic tool for these cancers is added.

Kinetic modeling of malondialdehyde reactivity in oil to simulate actual malondialdehyde formation upon lipid oxidation

The reactivity of malondialdehyde in saturated glycerol triheptanoate oil was studied over a wide temperature range (298.15-453.15 K). With respect to the non-ideal character of a lipid medium, a kinetic model was proposed that described the experimental malondialdehyde data by a reversible hydrolytic cleavage and an irreversible aldol self-condensation reaction. Significant parameter estimates were obtained by using a global one-step non-linear regression procedure. The aldol self-condensation of malondialdehyde showed to be the main degradation route of malondialdehyde in oils. Simulation of the malondialdehyde formation during lipid oxidation of sunflower oil demonstrated that, depending on the heating time, the experimentally obtained malondialdehyde concentrations can substantially underestimate the ongoing lipid oxidation.

The History of Alcoholic Liver Disease: From an Unrecognized Disease to One of the Most Frequent Diseases in Hepatology

This review describes the history of alcoholic liver disease from the beginning of the 1950s until now. It details how the hepatotoxicity of alcohol was discovered by epidemiology and basic research primarily by using new feeding techniques in rodents and primates. The article also recognizes the pioneering work of scientists who contributed to the understanding of the pathophysiology of alcoholic liver disease. In addition, clinical aspects, such as the development of diagnostics and treatment options for alcoholic liver disease, are discussed. Up-to-date knowledge of the mechanism of the disease in 2020 is presented.

Differences in the bacteriome of swab, saliva, and tissue biopsies in oral cancer

Microbial dysbiosis has been implicated in the pathogenesis of oral cancer. We analyzed the compositional and metabolic profile of the bacteriome in three specific niches in oral cancer patients along with controls using 16SrRNA sequencing (Illumina Miseq) and DADA2 software. We found major differences between patients and control subjects. Bacterial communities associated with the tumor surface and deep paired tumor tissue differed significantly. Tumor surfaces carried elevated abundances of taxa belonging to genera Porphyromonas, Enterobacteriae, Neisseria, Streptococcus and Fusobacteria, whereas Prevotella, Treponema, Sphingomonas, Meiothermus and Mycoplasma genera were significantly more abundant in deep tissue. The most abundant microbial metabolic pathways were those related to fatty-acid biosynthesis, carbon metabolism and amino-acid metabolism on the tumor surface: carbohydrate metabolism and organic polymer degradation were elevated in tumor tissues. The bacteriome of saliva from patients with oral cancer differed significantly from paired tumor tissue in terms of community structure, however remained similar at taxonomic and metabolic levels except for elevated abundances of Streptococcus, Lactobacillus and Bacteroides, and acetoin-biosynthesis, respectively. These shifts to a pro-inflammatory profile are consistent with other studies suggesting oncogenic properties. Importantly, selection of the principal source of microbial DNA is key to ensure reliable, reproducible and comparable results in microbiome studies.

Potential Patient-Reported Toxicities With Disulfiram Treatment in Late Disseminated Lyme Disease

Recently, disulfiram has been proposed as a promising treatment for people suffering from persistent symptoms of Lyme Disease. Disulfiram has several distinct molecular targets. The most well-known is alcohol dehydrogenase, a key enzyme for detoxifying the organism after alcohol ingestion. Other targets and modes of action of disulfiram, that may present problematic side effects, are less commonly mentioned. The French Federation against Tick Borne Diseases (French acronym, FFMVT), which associates three main Lyme patient organizations, MDs and PhDs, has recently been alerted to severe and persistent toxic events in a patient suffering from a late disseminated form of Lyme Disease following disulfiram intake. FFMVT reacted by launching a national call to examine whether other patients in France following a similar treatment could be identified, and what benefits, or side effects could be reported. The statements of 16 patients taking disulfiram have been collected and are presented here. Thirteen out of 16 patients reported toxic events, and seven out of 16 reported benefits for at least part of their symptoms. Based on the collected observations, it seems too early to promote disulfiram as a promising new treatment until the reasons underlying the reported toxicities have been explored, and the results of a well-conducted double blind clinical trial published. The importance of taking into account patient-reported outcomes in Lyme Disease is underlined by the present study.

Molecular docking explores heightened immunogenicity and structural dynamics of acetaldehyde human immunoglobulin G adduct

Acetaldehyde is a metabolite of ethanol, an important constituent of tobacco pyrolysis and the aldehydic product of lipid peroxidation. Acetaldehyde induced toxicity is mainly due to its binding to cellular macromolecules resulting in the formation of stable adducts accompanied by oxidative stress. The aim of this study was to characterize structural and immunological alterations in human immunoglobulin G (IgG) modified with acetaldehyde in the presence of sodium borohydride, a reducing agent. The IgG modifications were studied by various physicochemical techniques such as fluorescence and CD spectroscopy, free amino group estimation, 2,2-azobis 2-amidinopropane (AAPH) induced red blood cell hemolysis as well as transmission electron microscopy. Molecular docking was also employed to predict the preferential binding of acetaldehyde to IgG. The immunogenicity of native and acetaldehyde-modified IgG was investigated by immunizing female New Zealand white rabbits using native and modified IgG as antigens. Binding specificity and cross reactivity of rabbit antibodies was screened by competitive inhibition ELISA and band shift assays. The modification of human IgG with acetaldehyde results in quenching of the fluorescence of tyrosine residues, decrease in free amino group content, a change in the antioxidant property as well as formation of cross-linked structures in human IgG. Molecular docking reveals strong binding of IgG to acetaldehyde. Moreover, acetaldehyde modified IgG induced high titer antibodies (>1:12800) in the experimental animals. The antibodies exhibited high specificity in competitive binding assay toward acetaldehyde modified human IgG. The results indicate that acetaldehyde induces alterations in secondary and tertiary structure of IgG molecule that leads to formation of neo-epitopes on IgG that enhances its immunogenicity.

Characteristics of the Salivary Microbiota in Patients With Various Digestive Tract Cancers

The salivary microbiota is constantly swallowed and delivered to the digestive tract. These bacteria may be associated with gastrointestinal diseases. This case-control study examined the salivary microbiota in patients with digestive tract cancer (DTC) and evaluated their differential distribution based on the cancer sites. We collected saliva samples from 59 patients with cancer in any part of the digestive tract (tongue/pharynx, esophagus, stomach, and large intestine) and from 118 age- and sex-matched control subjects. There was no significant difference in periodontal status between DTC patients and control subjects (P = 0.72). We examined the bacterial diversity and composition in saliva by 16S ribosomal RNA gene sequencing. Salivary bacterial diversity in DTC patients was significantly higher than that in control subjects [number of operational taxonomic units (OTUs), P = 0.02; Shannon index, P < 0.01; Chao1, P = 0.04]. Eleven differentially abundant OTUs in DTC patients were identified using the linear discriminant analysis effect size (LEfSe) method. Based on the cancer sites, the diversity of salivary bacteria was especially higher in tongue/pharyngeal or esophageal cancer patients than in control subjects. Among the 11 differentially abundant OTUs in DTC patients, an OTU corresponding to Porphyromonas gingivalis was more abundant in the saliva of all groups of DTC patients compared to that in control subjects, and an OTU corresponding to Corynebacterium species was more abundant in all groups other than gastric cancer patients (P < 0.01). In addition, the relative abundances of OTUs corresponding to Fusobacterium nucleatum, Streptococcus parasanguinis II, and Neisseria species were significantly higher in tongue/pharyngeal cancer patients compared to their abundances in control subjects (P < 0.01). The relative abundance of an OTU corresponding to the Neisseria species was also significantly higher in gastric cancer patients and that of an OTU corresponding to Actinomyces odontolyticus was significantly higher in colorectal cancer patients (P < 0.01). These results suggest that the salivary microbiota might be associated with various digestive tract cancers.

Evaluation of Herbal Mouthwashes Containing Zataria Multiflora Boiss, Frankincense and Combination Therapy on Patients with Gingivitis: A Double-Blind, Randomized, Controlled, Clinical Trial

Background

Dental plaques as adhesive microbial aggregates on tooth surfaces are considered the first stage of tooth decay as well as gingivitis. Accordingly, the effect of different antimicrobial mouthwashes on removing dental plaques and preventing their formation has been evaluated in various studies. This study aimed to evaluate the efficacy of herbal mouthwashes containing hydro-alcoholic extract of Zataria multiflora (ZM), Frankincense (FR), and a combination of both (ZM+FR) and compare it with chlorhexidine (CHX) mouthwash in subjects with gingivitis.

Materials and Methods

In this randomized, controlled, clinical trial a total of 140 patients with gingivitis were divided into four groups including CHX (control group), ZM, FR, and ZM+FR groups. Plaque index (PI), gingival index (GI), and gingival bleeding index (GBI) were measured in days 1, 14, and 21.

Results

All three herbal types of mouthwash significantly improved plaque, gingivitis, and gingival bleeding throughout days 14 to 21 (P<0.001). There was no difference between herbal mouthwash with CHX groups. CHX mouthwash showed the most side effects (54.3%), while ZM mouthwash showed the least side effects and the highest consumer satisfaction (5.7% and 94%, respectively).

Conclusion

All of the herbal mouthwashes can be good candidates for controlling gingivitis. Comparing with CHX mouthwash, herbal mouthwashes have lower side effects and negligible alcohol content. Among the herbal mouthwashes, ZM outperforms FR and FR+ZM due to its lower side effects and higher levels of patients' satisfaction.

Porphyromonas gingivalis and digestive system cancers

Porphyromonas gingivalis (P. gingivalis) is an anaerobic gram-negative bacterium that colonizes in the epithelium and has been strongly associated with periodontal disease. Recently, various degrees of associations between P. gingivalis and digestive system cancers, including oral squamous cell carcinoma in the oral cavity, oesophageal squamous carcinoma in the digestive tract, and pancreatic cancer in pancreatic tissues, have been displayed in multiple clinical and experimental studies. Since P. gingivalis has a strong association with periodontal diseases, not only the relationships between P. gingivalis and digestive system tumours but also the effects induced by periodontal diseases on cancers are well-illustrated in this review. In addition, the prevention and possible treatments for these digestive system tumours induced by P. gingivalis infection are also included in this review. At the end, we also highlighted the possible mechanisms of cancers caused by P. gingivalis. One important carcinogenic effect of P. gingivalis is inhibiting the apoptosis of epithelial cells, which also plays an intrinsic role in protecting cancerous cells. Some signalling pathways activated by P. gingivalis are involved in cell apoptosis, tumourigenesis, immune evasion and cell invasion of tumour cells. In addition, metabolism of potentially carcinogenic substances caused by P. gingivalis is also one of the connections between this bacterium and cancers.

Systematic review: the etiology of esophageal squamous cell carcinoma in low-income settings

Esophageal carcinoma causes over 380 000 deaths per year, ranking sixth worldwide in mortality amongst all malignancies. Globally, the squamous cell subtype is most common and accounts for 80% of esophageal cancers. Nonetheless, esophageal squamous cell carcinoma is much more poorly understood than esophageal adenocarcinoma, including what is driving such high prevalences, why it often presents in young patients, and shows such marked geographical delineations Areas covered: The current literature was searched for articles focusing on aetiopathogenesis of squamous cell esophageal carcinoma via a systematic review, particularly in low-resource settings. This was supplemented by papers of interest known to the authors. Expert commentary: Current putative mechanisms include polycyclic aromatic hydrocarbons, nitrosamines, acetaldehyde, cyclo-oxygenase-2 pathways, androgen and their receptor levels, as well as smoking & alcohol, micronutrient deficiencies and diet, mycotoxins, thermal damage, oral hygiene and microbiotal factors, inhaled smoke, viral infections such as HPV, and chronic irritative states. Etiology is likely multifactorial and varies geographically. Though smoking and alcohol play a predominant role in high-income settings, there is strong evidence that mycotoxins, diet and temperature effects may play an under-recognized role in low and middle-income settings.

Non-invasive method for the assessment of gastric acid secretion

Methods for the measure of gastric acid secretion include invasive and non-invasive tests. The gold-standard to measure the acid output is the collection of gastric after in basal condition (Basal Acid Output, B.A.O.) and after an i.m. injection of pentagastrin (Maximal Acid Output, M.A.O.). However, direct measurement of gastric acid production is out of order in clinical practice, but many GI symptoms are claimed to be related with acid disorders and empirically cured. Hypochlorhydria is associated with precancerous conditions such as chronic atrophic gastritis (CAG). Acid measurement with non-invasive methods (pepsinogens) is supported by international guidelines.

Characterization of oral microbiota and acetaldehyde production

Background: Neisseria has been reported to be a high producer of acetaldehyde (ACH), a carcinogen, from ethanol in vitro, but no information exists regarding whether the ACH production depends on oral microbiota profiles. Objective and Design: To explore the salivary microbiota profiles with respect to ACH production ability in the oral cavity using a cross-sectional design. Results: Using 16S rRNA gene amplicon sequencing, we classified 100 saliva samples into two types of communities (I and II). Salivary ACH production ability from ethanol was measured using gas chromatography and was found to vary over a 30-fold range. ACH production ability was significantly higher in the type I community, wherein the relative abundance of Neisseria species was significantly lower. Multivariate logistic regression analysis showed that the subjects with the type I community exhibited significantly higher probability of high ACH production ability than those with the type II community (P = 0.014). Moreover, the relative abundance of Neisseria species was inversely correlated with the ACH production ability (P = 0.002). Conclusion: The salivary microbiota profile with a lower relative abundance of Neisseria species was independently associated with high ACH production ability, despite Neisseria species are dominant producers of ACH in vitro.

Genetic variants of ALDH2-rs671 and CYP2E1-rs2031920 contributed to risk of hepatocellular carcinoma susceptibility in a Chinese population

Objective

Acetaldehyde dehydrogenase 2 (ALDH2) and cytochrome P450 2E1 (CYP2E1) have been associated with hepatocellular carcinoma (HCC) susceptibility and prognosis. The polymorphisms ALDH2 rs671 and CYP2E1 rs2031920 are reportedly correlated with the prevalence of HCC in other countries. The aim of this study was to investigate associations between ALDH2 and CYP2E1, and HCC susceptibility in a population of Guangxi, southern China, an area with a high incidence of HCC.

Patients and methods

The study cohort included 300 HCC cases, 292 healthy controls for HCC susceptibility analysis, and another 20 HCC cases and 10 healthy controls for ascertainment. Genotyping was performed using the polymerase chain reaction-restriction fragment length polymorphism method.

Results

The study results demonstrated that mutant genotypes of ALDH2 (G/A and A/A) led to significant differences in HCC susceptibility, as compared with the wild genotype (G/G) with the same C1/C1 genotype in non-drinking individuals (adjusted P=0.010, OR=0.20, 95% CI=0.06–0.68). The mutant genotypes of CYP2E1 (C1/C2 and C2/C2) brought about significant differences in HCC susceptibility, as compared with the wild genotype (C1/C1) and the same G/G genotype (adjusted P=0.025, OR=0.42, 95% CI=0.20–0.90). Drinking plays a role in HCC susceptibility in the same G/G genotype individuals (adjusted P=0.004, OR=0.32, 95% CI=0.15–0.69), but had no impact when combined with CYP2E1 for analysis (all P>0.05).

Conclusion

These results suggest that the mutant genotypes of ALDH2 and CYP2E1 may be protective factors for HCC susceptibility in Guangxi province, China.

Alcohol-Derived Acetaldehyde Exposure in the Oral Cavity

Alcohol is classified by the International Agency for Research on Cancer (IARC) as a human carcinogen and its consumption has been associated to an increased risk of liver, breast, colorectum, and upper aerodigestive tract (UADT) cancers. Its mechanisms of carcinogenicity remain unclear and various hypotheses have been formulated depending on the target organ considered. In the case of UADT cancers, alcohol's major metabolite acetaldehyde seems to play a crucial role. Acetaldehyde reacts with DNA inducing modifications, which, if not repaired, can result in mutations and lead to cancer development. Despite alcohol being mainly metabolized in the liver, several studies performed in humans found higher levels of acetaldehyde in saliva compared to those found in blood immediately after alcohol consumption. These results suggest that alcohol-derived acetaldehyde exposure may occur in the oral cavity independently from liver metabolism. This hypothesis is supported by our recent results showing the presence of acetaldehyde-related DNA modifications in oral cells of monkeys and humans exposed to alcohol, overall suggesting that the alcohol metabolism in the oral cavity is an independent cancer risk factor. This review article will focus on illustrating the factors modulating alcohol-derived acetaldehyde exposure and effects in the oral cavity.

Epidemiology of Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) accounts for about 90% of the 456,000 incident esophageal cancers each year. Regions of high incidence include Eastern to Central Asia, along the Rift Valley in East Africa, and into South Africa. There are many causes of ESCC, which vary among regions. Early studies in France associated smoking cigarettes and heavy alcohol consumption with high rates of ESCC, but these factors cannot explain the high incidence in other regions. We discuss other risk factors for ESCC, including polycyclic aromatic hydrocarbons from a variety of sources, high-temperature foods, diet, and oral health and the microbiome-all require further research. A growing list of defined genomic regions affects susceptibility, but large genome-wide association studies have been conducted with ethnic Chinese subjects only; more studies are called for in the rest of Asia and Africa. ESCC has been understudied, but growing infrastructure in more high-incidence countries will allow rapid progress in our understanding.

Alcohol metabolism and oesophageal cancer: a systematic review of the evidence

Alcohol is a major risk factor for oesophageal squamous cell carcinoma (OSCC), the most prevalent histological subtype of oesophageal cancer (OC) worldwide. The metabolism of alcohol is regulated by specific enzymes whose activity and expression is influenced by genetic polymorphisms. We conducted a systematic review of current epidemiological evidence of the relationship between alcohol intake and OC risk, including the role of tobacco smoking and functional polymorphisms of alcohol dehydrogenases (ADHs) and aldehyde dehydrogenases (ALDHs). Potential biological mechanisms underlying oesophageal carcinogenesis are also discussed. Frequency and intensity of alcohol intake have been consistently associated with an increased risk of OSCC in regions with low and high incidence of the disease. The highest risk was reported among tobacco smokers, whereas the association between alcohol and OSCC risk was weak in the absence of tobacco use. The ADH1B, ADH1C and ALDH2 gene polymorphisms influence the risk of OSCC through modulation of acetaldehyde metabolism and propensity to alcohol intake. These functional variants may be suitable proxies of alcohol exposure for use in Mendelian randomization studies if complemented by reported alcohol intake data. Recent epidemiological and experimental studies investigating the role of alcohol consumption in OC development have implicated the microbiome as a new promising avenue for research, which entail novel potential mechanisms of alcohol-related oesophageal carcinogenesis. Microbial communities associated with alcohol consumption might be used as biomarkers to raise the potential of intervening among susceptible individuals.

Molecular Mechanisms of Acetaldehyde-Mediated Carcinogenesis in Squamous Epithelium

Acetaldehyde is a highly reactive compound that causes various forms of damage to DNA, including DNA adducts, single- and/or double-strand breaks (DSBs), point mutations, sister chromatid exchanges (SCEs), and DNA-DNA cross-links. Among these, DNA adducts such as N²-ethylidene-2'-deoxyguanosine, N²-ethyl-2'-deoxyguanosine, N²-propano-2'-deoxyguanosine, and N²-etheno-2'-deoxyguanosine are central to acetaldehyde-mediated DNA damage because they are associated with the induction of DNA mutations, DNA-DNA cross-links, DSBs, and SCEs. Acetaldehyde is produced endogenously by alcohol metabolism and is catalyzed by aldehyde dehydrogenase 2 (ALDH2). Alcohol consumption increases blood and salivary acetaldehyde levels, especially in individuals with ALDH2 polymorphisms, which are highly associated with the risk of squamous cell carcinomas in the upper aerodigestive tract. Based on extensive epidemiological evidence, the International Agency for Research on Cancer defined acetaldehyde associated with the consumption of alcoholic beverages as a "group 1 carcinogen" (definite carcinogen) for the esophagus and/or head and neck. In this article, we review recent advances from studies of acetaldehyde-mediated carcinogenesis in the squamous epithelium, focusing especially on acetaldehyde-mediated DNA adducts. We also give attention to research on acetaldehyde-mediated DNA repair pathways such as the Fanconi anemia pathway and refer to our studies on the prevention of acetaldehyde-mediated DNA damage.

The potential role of microbes in oncogenesis with particular emphasis on oral cancer

For over a century, non-virus microorganisms, notably bacteria have been implicated as causal agents of cancers, a relatively small number of researchers have provided evidence to support the so-called “cancer germ” hypothesis. With the exception of the link between Helicobacter pylori and stomach cancer, other supposed links have been ignored. A wide range of bacteria and other non-virus microbes, including fungi, have been implicated over the years in oncogenesis, as well as the ability to induce inflammation, which may cause cancer. It seems that there is no single “cancer germ,” as most bacteria can apparently induce cancer. Here, the role of bacteria and other non-virus microorganisms and oral cancers will be discussed. By ignoring bacteria as a causal agent of cancer, we set back our understanding of this crucially important disease and, as a result, have hindered the development of potential cures.

Reactivity of Free Malondialdehyde during In Vitro Simulated Gastrointestinal Digestion

An aqueous buffer, a saturated glycerol triheptanoate oil, and a Tween 20 stabilized fully hydrogenated coconut oil-in-water emulsion, all spiked with malondialdehyde, were subjected to in vitro digestion. A dynamic equilibrium between malondialdehyde, its aldol self-condensation products, and its hydrolytic cleavage products was observed. This equilibrium depended upon the kind of sample and the temperature at which these samples were preincubated during 24 h. The presence of oil during gastric digestion protected the aldol self-condensation and cleavage products from conversion to malondialdehyde, which occurred in the aqueous acidic gastric chyme. In parallel, the presence of oil enhanced the reactivity of malondialdehyde throughout the gastrointestinal digestion process. Malondialdehyde recoveries after digestion varied between 42 and 90%, depending upon the model system studied, with the aldol self-condensation as the main reaction pathway. In conclusion, this study revealed that malondialdehyde is a very reactive molecule whose reactivity does not stop at the point of ingestion.

ALDH2-deficiency as genetic epidemiologic and biochemical model for the carcinogenicity of acetaldehyde

Humans are cumulatively exposed to acetaldehyde from various sources including alcoholic beverages, tobacco smoke, foods and beverages. The genetic-epidemiologic and biochemical evidence in ALDH2-deficient humans provides strong evidence for the causal relationship between acetaldehyde-exposure due to alcohol consumption and cancer of the upper digestive tract. The risk assessment has so far relied on thresholds based on animal toxicology with lower one-sided confidence limit of the benchmark dose values (BMDL) typically ranging between 11 and 63 mg/kg bodyweight (bw)/day dependent on species and endpoint. The animal data is problematic for regulatory toxicology for various reasons (lack in study quality, problems in animal models and appropriateness of endpoints - especially cancer - for transfer to humans). In this study, data from genetic epidemiologic and biochemical studies are reviewed. The increase in the daily exposure dose to acetaldehyde in alcohol-consuming ALDH2-deficients vs. ALDH2-actives was about twofold. The acetaldehyde increase due to ALDH2 inactivity was calculated to be 6.7 μg/kg bw/day for heavy drinkers, which is associated with odds ratios of up to 7 for head and neck as well as oesophageal cancer. Previous animal toxicology based risk assessments may have underestimated the risk of acetaldehyde. Risk assessments of acetaldehyde need to be revised using this updated evidence.

Alcohol, microbiome, life style influence alcohol and non-alcoholic organ damage

This paper is based upon the "8th Charles Lieber's Satellite Symposium" organized by Manuela G. Neuman at the Research Society on Alcoholism Annual Meeting, on June 25, 2016 at New Orleans, Louisiana, USA. The integrative symposium investigated different aspects of alcohol-induced liver disease (ALD) as well as non-alcohol-induced liver disease (NAFLD) and possible repair. We revealed the basic aspects of alcohol metabolism that may be responsible for the development of liver disease as well as the factors that determine the amount, frequency and which type of alcohol misuse leads to liver and gastrointestinal diseases. We aimed to (1) describe the immuno-pathology of ALD, (2) examine the role of genetics in the development of alcoholic hepatitis (ASH) and NAFLD, (3) propose diagnostic markers of ASH and non-alcoholic steatohepatitis (NASH), (4) examine age and ethnic differences as well as analyze the validity of some models, (5) develop common research tools and biomarkers to study alcohol-induced effects, 6) examine the role of alcohol in oral health and colon and gastrointestinal cancer and (7) focus on factors that aggravate the severity of organ-damage. The present review includes pre-clinical, translational and clinical research that characterizes ALD and NAFLD. Strong clinical and experimental evidence lead to recognition of the key toxic role of alcohol in the pathogenesis of ALD with simple fatty infiltrations and chronic alcoholic hepatitis with hepatic fibrosis or cirrhosis. These latter stages may also be associated with a number of cellular and histological changes, including the presence of Mallory's hyaline, megamitochondria, or perivenular and perisinusoidal fibrosis. Genetic polymorphisms of ethanol metabolizing enzymes and cytochrome p450 (CYP) 2E1 activation may change the severity of ASH and NASH. Other risk factors such as its co-morbidities with chronic viral hepatitis in the presence or absence of human deficiency virus were discussed. Dysregulation of metabolism, as a result of ethanol exposure, in the intestine leads to colon carcinogenesis. The hepatotoxic effects of ethanol undermine the contribution of malnutrition to the liver injury. Dietary interventions such as micro and macronutrients, as well as changes to the microbiota have been suggested. The clinical aspects of NASH, as part of the metabolic syndrome in the aging population, have been presented. The symposium addressed mechanisms and biomarkers of alcohol induced damage to different organs, as well as the role of the microbiome in this dialog. The microbiota regulates and acts as a key element in harmonizing immune responses at intestinal mucosal surfaces. It is known that microbiota is an inducer of proinflammatory T helper 17 cells and regulatory T cells in the intestine. The signals at the sites of inflammation mediate recruitment and differentiation in order to remove inflammatory inducers and promote tissue homeostasis restoration. The change in the intestinal microbiota also influences the change in obesity and regresses the liver steatosis. Evidence on the positive role of moderate alcohol consumption on heart and metabolic diseases as well on reducing steatosis have been looked up. Moreover nutrition as a therapeutic intervention in alcoholic liver disease has been discussed. In addition to the original data, we searched the literature (2008-2016) for the latest publication on the described subjects. In order to obtain the updated data we used the usual engines (Pub Med and Google Scholar). The intention of the eighth symposia was to advance the international profile of the biological research on alcoholism. We also wish to further our mission of leading the forum to progress the science and practice of translational research in alcoholism.

Emerging role of bacteria in oral carcinogenesis: a review with special reference to perio-pathogenic bacteria

Oral cancer, primarily oral squamous cell carcinoma (OSCC), continues to be a major global health problem with high incidence and low survival rates. While the major risk factors for this malignancy, mostly lifestyle related, have been identified, around 15% of oral cancer cases remain unexplained. In light of evidence implicating bacteria in the aetiology of some cancer types, several epidemiological studies have been conducted in the last decade, employing methodologies ranging from traditional culture techniques to 16S rRNA metagenomics, to assess the possible role of bacteria in OSCC. While these studies have demonstrated differences in microbial composition between cancerous and healthy tissues, they have failed to agree on specific bacteria or patterns of oral microbial dysbiosis to implicate in OSCC. On the contrary, some oral taxa, particularly Porphyromonas gingivalis and Fusobacterium nucleatum, show strong oral carcinogenic potential in vitro and in animal studies. Bacteria are thought to contribute to oral carcinogenesis via inhibition of apoptosis, activation of cell proliferation, promotion of cellular invasion, induction of chronic inflammation, and production of carcinogens. This narrative review provides a critical analysis of and an update on the association between bacteria and oral carcinogenesis and the possible mechanisms underlying it.