Role of bacteria in oral carcinogenesis

Evaluating Alterations of the Oral Microbiome and Its Link to Oral Cancer among Betel Quid Chewers: Prospecting Reversal through Probiotic Intervention

Areca nut and slaked lime, with or without tobacco wrapped in Piper betle leaf, prepared as betel quid, is extensively consumed as a masticatory product in many countries across the world. Betel Quid can promote the malignant transformation of oral lesions as well as trigger benign cellular and molecular changes. In the oral cavity, it causes changes at the compositional level in oral microbiota called dysbiosis. This dysbiosis may play an important role in Oral Cancer in betel quid chewers. The abnormal presence and increase of bacteria Fusobacterium nucleatum, Capnocytophaga gingivalis, Prevotella melaninogenica, Peptostreptococcus sp., Porphyromonas gingivalis, and Streptococcus mitis in saliva and/or other oral sites of the cancer patients has attracted frequent attention for its association with oral cancer development. In the present review, the authors have analysed the literature reports to revisit the oncogenic potential of betel quid and oral microbiome alterations, evaluating the potential of oral microbiota both as a driver and biomarker of oral cancer. The authors have also shared a perspective that the restoration of local microbiota can become a potentially therapeutic or prophylactic strategy for the delay or reversal of lip and oral cavity cancers, especially in high-risk population groups.

Oral Microflora in the Background of Oral Cancer: A Review

Oral cancer exhibits a multifactorial etiology. Microorganisms residing within the oral cavity as normal commensals have long been studied in terms of their role in the process of carcinogenesis. Other factors such as tobacco and alcohol consumption have also been implicated in carcinogenesis as the primary risk factors. Poor oral hygiene, dietary abnormalities, and betel nut chewing can also act as contributory factors in the process of carcinogenesis. Multiple research works have been carried out in the past to shed some light on the role of exogenous bacterial species in the development of cancers. Studies conducted were to assess changes in the oral microflora in patients suffering from oral carcinoma and to evaluate and compare pre-operative and post-operative changes in oral microbiota. For this review, multiple articles were studied and evaluated. Appropriate conclusions were drawn and are presented in the review. A definitive link between cancer and microflora is yet to be established. In the present article, a review of the studies done on the contribution of microbial flora present within the oral cavity and their role in oral cancer is done and its nature and extent are evaluated. A variety of microbiological agents can contribute to the progression of carcinogenesis in the presence of definitive risk factors such as alcoholism and smoking.

Periodontitis and Its Inflammatory Changes Linked to Various Systemic Diseases: A Review of Its Underlying Mechanisms

Periodontitis is a chronic inflammatory disease of the gums. The incidence of periodontitis is increasing all over the world. In patients with periodontitis, there is gradual destruction of the periodontal ligament and the alveolar bone, and later, in advanced stages, there is tooth loss. Different microorganisms, the host’s immune response, and various environmental factors interact in the progression of this chronic inflammatory disease. In the present review, we discuss the epidemiology, clinical features, diagnosis, and complications of periodontitis. We also discuss the association of chronic inflammation found in periodontitis with various other systemic diseases, which include cardiovascular, respiratory, diabetes, Alzheimer’s, cancer, adverse pregnancy, and multiple myeloma, and also highlight microbial carcinogenesis and the microRNAs involved. The latest updates on the molecular mechanism, possible biomarkers, and treatment procedures may be beneficial for diagnostic and therapeutic purposes.

Alterations of the Oral Microbiota Profiles in Chinese Patient With Oral Cancer

Oral cancer is the most common malignant tumor in the oral and maxillofacial region, of which more than 90% is squamous cell carcinoma. The incidence of oral cancer is on the rise worldwide. An imbalance between the microorganism composition and its host may lead to the occurrence of oral malignant tumors. Accumulating evidence suggests that the oral microbiota plays an important role in oral cancer; however, the association between oral microbiota and oral cancer has not yet been comprehensively studied. In this study, metagenomic sequencing was used to compare the microbial composition of three groups of samples from Chinese patients with oral cancer, patients with precancerous lesion, and normal individuals. In terms of microbiota richness, the oral microbiota of patients with precancerous lesions was richer than that of oral cancer patients and healthy controls, whereas in terms of microbiota diversity, there was little difference between the three groups. The three groups of samples exhibited statistically significant differences in microbiota composition and metabolic function at the family, genus, and species levels (P < 0.05). The differentially enriched phylum in oral cancer samples was Bacteroidetes (P < 0.05). At the genus level, the main differentially enriched taxa were Prevotella, Peptostreptococcus, Carnobacterium, and Diastella (P < 0.05). The species level was differentially enriched in Prevotella intermedia and Peptostreptococcus stomatis (p < 0.05). The prediction of microbiota function shows that oral cancer is mainly associated with coenzyme A biosynthesis, phosphopantothenic acid biosynthesis, inosine 5’-phosphate degradation, and riboflavin biosynthesis. Furthermore, the increase in C-reactive protein level in oral cancer patients was found to be closely related to P. intermedia. Overall, oral bacterial profiles showed significant differences between the oral cancer group and normal group. Hence, microbes can be employed as diagnostic markers and treatment targets for oral cancer.

Oral microbiome and oral cancer - The probable nexus

Oral squamous cell carcinoma is one of the most common malignancies and is the leading cause of morbidity and mortality. The known risk factors for oral cancer are tobacco, alcohol consumption and betel quid chewing. Nutritional deficiencies and certain microorganisms are also associated with oral cancer. Oral cavity is a host to numerous microorganisms, majority of which are bacterial communities along with fungi and viruses. A possibility of the dysregulation of the oral microbiome cannot be ignored. Oral microbiome is defined as the collective genome of microorganisms that reside in the oral cavity. With the development of culture-independent techniques, the detection and identification of the bacteria which cannot be cultured has become possible. Revolution in technology has led to increased research in this area in an attempt to find the role of microbiome in health and disease. Before identifying the exact role the microbiome plays in the development of oral cancer, it is essential to profile the microbiome in healthy individuals and patients with oral cancer. It is essential to note that oral cancer may sometimes occur without any habit too!! This article is an attempt to review the role of oral microbiome in oral cancer with a focus on the bacteriome, its related studies and in brief about the omics technologies in understanding the microbiome.

Dual Role of Bacteria in Carcinoma: Stimulation and Inhibition

Although what unifies the carcinogenic microorganisms has not been determined by multiple studies, the role of bacteria in the development of neoplasms has not been properly elucidated. In this review, we discuss links between the bacterial species and cancer, with focus on immune responses for the stimulation of tumor cells such as induction of inflammation. Finally, we will describe the potential therapeutic strategies of bacteria on target tumors to improve treatment while mitigating adverse reactions. Cancer is a series of genetic changes that transform normal cells into tumor cells. These changes come from several reasons, including smoking, drinking alcohol, sunlight, exposure to chemical or physical factors, and finally chronic infection with microorganisms, including bacteria. In fact, bacterial infections are not carcinogenic, but recently it was discovered that the association between bacteria and cancer is through two mechanisms, the first stimulating chronic inflammation and the second producing carcinogenic metabolites. While bacteria are carcinogenic agents also, they have a dual role eliminating and removing tumor cells. However, the traditional cancer treatments that include chemotherapy, radiotherapy, surgery, and immunotherapy increase the chances of survival, and there are many side effects of these therapies, including the high toxicity of tissues and normal cells, could not penetrate the tumor cells, and resistance of these therapies by tumor cells. Therefore, the world has turned to an alternative solution, which is the use of genetically engineered microorganisms; thus, the use of living bacteria targeting cancerous cells is the unique option to overcome these challenges. Bacterial therapies, whether used alone or combination with chemotherapy, give a positive effect to treat multiple conditions of cancer. Also, bacteria can be used as vectors for drug, gene, or therapy, and this is a great step to treat cancer. Thus, we review the mechanisms underlying the interaction of the microbiota residents with cancer. Cancer-associated bacteria differ from those in healthy human and are linked with gene-expression profile. We also discuss how live bacteria interact with tumor microenvironments to induce tumor regression through colonization and spread. Finally, we provide past and ongoing clinical trials that include bacteria targeting tumors.

Periodontitis and oral cancer - current concepts of the etiopathogenesis

Gingival tissues are attacked by oral pathogens which can induce inflammatory reactions. The immune-inflammatory responses play essential roles in the patient susceptibility to periodontal diseases. There is a wealth of evidence indicating a link between chronic inflammation and risk of malignant transformation of the affected oral epithelium. Periodontitis is associated with an increased risk of developing chronic systemic conditions including autoimmune diseases and different types of cancers. Besides, some risk factors such as smoking, alcohol consumption and human papilloma virus have been found to be associated with both periodontitis and oral cancer. This review article aimed to study the current concepts in pathogenesis of chronic periodontitis and oral cancer by reviewing the related articles.

Oropharyngeal Squamous Cell Carcinoma: Human Papilloma Virus Coinfection with Streptococcus anginosus

Abstract Introduction: Human papilloma virus (HPV) and oral bacteria capable of acetaldehyde production from ethanol, such as Streptococcus anginosus, Prevotella melaninogenica, and Fusobacterium naviforme are among oropharyngeal squamous cell carcinoma (OSCC) infectious risk factors. Objective: Determine associations with HPV and S. anginosus, P. melaninogenica, and F. naviforme in patients with and without OSCC. Methods: Presence of HPV and HPV-16 was determined in 26 patients with OSCC and 26 without OSCC by conventional PCR and simultaneous presence of S. anginosus, P. melaninogenica, and F. naviforme quantification through q-PCR. Statistical analysis was carried out using Pearson’s X² and Student’s-t test. Results: Patients with OSCC had HPV and HPV-16 frequencies of 84% and 61.5%, respectively, in contrast for patients without OSCC frequencies were 34.6 and 30.7%. P. melaninogenica, and F. naviforme microorganisms were not present in any participant in this study. S. anginosus frequency in patients with OSC was 38.4% and in patients without OSCC was 30.7%. Patients with OSCC had S. anginosus + HPV co-infection at a 38.4% frequency and S. anginosus + HPV-16 at a 23.1% frequency. For individuals without OSCC S. anginosus + HPV co-infection was 3.8% and S. anginosus + HPV-16 3.8%. A greater frequency of S. anginosus + HPV co-infection and S. anginosus + HPV-16 was observed in patients with OSCC in comparison with individuals without OSCC, suggesting the importance of detecting HPV/HPV-16 and S. anginosus simultaneously in individuals at risk of developing OSCC

Clinical update on head and neck cancer: molecular biology and ongoing challenges

Head and neck squamous cell carcinomas (HNSCCs) are an aggressive, genetically complex and difficult to treat group of cancers. In lieu of truly effective targeted therapies, surgery and radiotherapy represent the primary treatment options for most patients. But these treatments are associated with significant morbidity and a reduction in quality of life. Resistance to both radiotherapy and the only available targeted therapy, and subsequent relapse are common. Research has therefore focussed on identifying biomarkers to stratify patients into clinically meaningful groups and to develop more effective targeted therapies. However, as we are now discovering, the poor response to therapy and aggressive nature of HNSCCs is not only affected by the complex alterations in intracellular signalling pathways but is also heavily influenced by the behaviour of the extracellular microenvironment. The HNSCC tumour landscape is an environment permissive of these tumours' aggressive nature, fostered by the actions of the immune system, the response to tumour hypoxia and the influence of the microbiome. Solving these challenges now rests on expanding our knowledge of these areas, in parallel with a greater understanding of the molecular biology of HNSCC subtypes. This update aims to build on our earlier 2014 review by bringing up to date our understanding of the molecular biology of HNSCCs and provide insights into areas of ongoing research and perspectives for the future.

Pre- and post-operative antibiotics in conjunction with cytoreductive surgery and heated intraperitoneal chemotherapy (HIPEC) should be considered for pseudomyxoma peritonei (PMP) treatment

Pseudomyxoma peritonei (PMP) is a subtype of peritoneal carcinomatosis that is traditionally treated by cytoreductive surgery (CRS) followed by hyperthermic intraperitoneal chemotherapy (HIPEC). A growing body of evidence suggests that microbes are associated with various tumor types and have been found in organs and cavities that were once considered sterile. Prior and ongoing research from our consortium of PMP researchers strongly suggests that bacteria are associated with PMP tumors. While the significance of this association is unclear, in our opinion, further research is warranted to understand whether these bacteria contribute to the development, maintenance and/or progression of PMP. Elucidation of a possible causal role for bacteria in PMP could suggest a benefit for supplementation of antibiotics to current treatment protocols.

Oral bacterial flora and oral cancer: The possible link?

Oral cancer exhibits multifactorial etiology with tobacco and alcohol long been implicated as the primary risk factors. In addition, betel nut, dietary factors and poor oral hygiene have also been found to have a role in the etiology of oral cancer. Past research has uncovered a great deal of information regarding the association of exogenous bacteria with cancer. However, our definitive knowledge of the oral commensal bacteria and oral cancer link remains inadequate. In the present article, we hypothesize a causal role for oral bacterial flora in oral cancer although an indirect one. We propose that the normal bacterial flora in conjunction with the already established risk factors such as alcohol consumption may play a role in cancer development. The continued exploration of this topic may aid in better understanding of the pathogenesis of oral cancer thereby helping in appropriate treatment and better prognosis.

Eradication of gastric Helicobacter pylori ameliorates halitosis and tongue coating

BACKGROUND

The influence of gastric Helicobacter pylori infection on the development of oral pathoses remains unclear. The aim of this study is to examine the influence of gastric H. pylori infection on occurrence of halitosis and coated tongue.

MATERIALS AND METHODS

Ninety-eight patients with dyspepsia were included in the study and their salivary samples and gastric biopsies were analyzed for the presence of H. pylori by Nested-PCR. Halitosis and coated tongue were assessed at the initial examination and 3 months after systemic eradication therapy against H. pylori.

RESULTS

Gastric biopsies of 66 patients were positive for H. pylori. Only one saliva sample was H. pylori positive. At initial examination, halitosis was observed in 20 patients (30.3%) out of 66 who had gastric H. pylori infection and in only 3 patients (9.4%) out of 32 without H. pylori infection (p = 0.0236). Coated tongue was diagnosed in 18 (27.2%) patients with the infection compared to only 2 (6.25%) patients negative for gastric H. pylori (p = 0.0164). Patients with gastric infection were treated with the triple eradication therapy (Amoxicillin, Clarythromycin, Pantoprazol) and their gastric biopsies and oral status were examined 3 months later. Halitosis was significantly more prevalent in the group of patients with persistent H. pylori infection (42.1%) compared to only 6.4% of patients in the group where infection was successfully eradicated (p = 0.0012). Coated tongue was diagnosed in 47.4% of patients where H. pylori was still present after eradication therapy and in only 6.4% where eradication succeeded (p = 0.0003).

CONCLUSION

Our findings suggest that eradication of gastric H. pylori significantly alleviates halitosis and coated tongue, the two oral conditions that may be considered as extragastric manifestations of this common chronic bacterial infection.

Role of bacteria in oral carcinogenesis

Oral cancer appears to be increasing in incidence, and mortality has hardly improved over the past 25 years. Better understanding of the etiopathogenesis should lead to more accurate and earlier diagnosis and more effective treatments with fewer adverse effects. Despite increasing interest in the possible relationships between bacteria and the different stages of cancer development, the association of bacteria with cancer of the oral cavity has yet to be adequately examined. Different bacteria have been proposed to induce carcinogenesis, either through induction of chronic inflammation or by interference, either directly or indirectly, with eukaryotic cell cycle and signaling pathways or by metabolism of potentially carcinogenic substances like acetaldehyde, causing mutagenesis. This review presents the possible carcinogenesis pathway involved in bacterial carcinogenesis, commonly implicated bacteria in oral carcinogenesis and their role in cancer therapeutics as well.

Bactericidal application and cytotoxic activity of biosynthesized silver nanoparticles with an extract of the red seaweed Pterocladiella capillacea on the HepG2 cell line

BACKGROUND

Nano-biotechnology is recognized as offering revolutionary changes in various fields of medicine. Biologically synthesized silver nanoparticles have a wide range of applications.

MATERIALS AND METHODS

Silver nanoparticles (AgNPs) were biosynthesized with an aqueous extract of Pterocladiella (Pterocladia) capillacea, used as a reducing and stabilizing agent, and characterized using UV-VIS spectroscopy, Fourier Transform Infra red (FT-IR) spectroscopy, transmission electron microscopy (TEM) and energy dispersive analysis (EDX). The biosynthesized AgNPs were tested for cytotoxic activity in a human hepatocellular carcinoma (HepG2) cell line cultured in Dulbecco's modified Eagle medium supplemented with 10% fetal bovine serum, 1% antibiotic and antimycotic solution and 2 mM glutamine. Bacterial susceptibility to AgNPs was assessed with Staphylococcus aureus, Bacillus subtilis [Gram+ve] and Pseudomonas aeruginosa and Escherichia coli [Gram-ve]. The agar well diffusion technique was adopted to evaluate the bactericidal activity of the biosynthesized AgNPs using Ampicillin and Gentamicin as gram+ve and gram-ve antibacterial standard drugs, respectively.

RESULTS

The biosynthesized AgNPs were 11.4±3.52 nm in diameter. FT-IR analysis showed that carbonyl groups from the amino acid residues and proteins could assist in formation and stabilization of AgNPs. The AgNPs showed potent cytotoxic activity against the human hepatocellular carcinoma (HepG2) cell line at higher concentrations. The results also showed that the biosynthesized AgNPs inhibited the entire panel of tested bacteria with a marked specificity towards Bacillus subtillus.

CONCLUSIONS

Cytotoxic activity of the biosynthesized AgNPs may be due to the presence of alkaloids present in the algal extract. Our AgNPs appear more bactericidal against gram-positive bacteria (B. subtillus).