Factors associated with the high prevalence of oesophageal cancer in Western Kenya: a review

Multiple mycotoxin exposure assessment through human biomonitoring in an esophageal cancer case-control study in the Arsi-Bale districts of Oromia region of Ethiopia

BACKGROUND

Esophageal cancer (EC) is a malignancy with a poor prognosis and a five-year survival rate of less than 20%. It is the ninth most frequent cancer globally and the sixth leading cause of cancer-related deaths. The incidence of EC has been found to vary significantly by geography, indicating the importance of environmental and lifestyle factors along with genetic factors in the onset of the disease. In this work, we investigated mycotoxin exposure in a case-control study from the Arsi-Bale districts of Oromia regional state in Ethiopia, where there is a high incidence of EC while alcohol and tobacco use - two established risk factors for EC - are very rare.

METHODS

Internal exposure to 39 mycotoxins and metabolites was assessed by liquid chromatography-tandem mass spectrometry in plasma samples of EC cases (n = 166) and location-matched healthy controls (n = 166) who shared similar dietary sources. Demographic and lifestyle data were collected using structured questionnaires. Principal Component Analysis and machine learning models were used to identify the most relevant demographic, lifestyle, and mycotoxin (co-)exposure variables associated with EC. Multivariate binary logistic regression analysis was used to assess EC risk.

RESULT

Evidence of mycotoxin exposure was observed in all plasma samples, with 10 different mycotoxins being detected in samples from EC cases, while only 6 different mycotoxins were detected in samples from healthy controls. Ochratoxin A was detected in plasma from all cases and controls, while tenuazonic acid was detected in plasma of 145 (87.3%) cases and 71 (42.8%) controls. Using multivariable logistic regression analysis, exposure to tenuazonic acid (AOR = 1.88 [95% CI: 1.68-2.11]) and to multiple mycotoxins (AOR = 2.54 [95% CI: 2.10-3.07]) were positively associated with EC.

CONCLUSION

All cases and controls were exposed to at least one mycotoxin. Cases were exposed to a statistically significantly higher number of mycotoxins than controls. Exposure to tenuazonic acid and to multiple mycotoxins were associated with increased risk of EC in the study population. Although aflatoxin B1-lysine and the ratio of sphinganine to sphingosine (as a biomarker of effect to fumonisin exposure) were not assessed in this study, our result emphasizes the need to characterize the effect of mycotoxin co-exposure as part of the exposome and include it in risk assessment, since the current mycotoxin safety levels do not consider the additive or synergistic effects of mycotoxin co-exposure. Moreover, a prospective study design with regular sampling should be considered in this high incidence area of EC in Ethiopia to obtain conclusive results on the role of mycotoxin exposure in the onset and development of the disease.

Dietary Mycotoxins: An Overview on Toxicokinetics, Toxicodynamics, Toxicity, Epidemiology, Detection, and Their Mitigation with Special Emphasis on Aflatoxicosis in Humans and Animals

Mycotoxins are secondary metabolites of filamentous fungi and ubiquitous dietary contaminants. Aflatoxins, a group of mycotoxins with high prevalence and toxicity, have raised a high level of public health concern, the most prevalent and toxic being aflatoxin B1 (AFB1). Many aspects appertaining to AFB1 poisoning are not well understood. Yet this information is necessary to devise appropriate surveillance and mitigation strategies against human and animal aflatoxicosis. This review provides an in-depth update of work carried out on mycotoxin poisoning, particularly aflatoxicosis in humans and animals, to identify gaps in knowledge. Hypotheses explaining the functional significance of mycotoxins in fungal biology and their dietary epidemiological data are presented and briefly discussed. The toxicology of aflatoxins and the challenges of their mitigation are discussed in depth. It was concluded that the identification of potential mycotoxin-hazard-prone food items and quantification of the associated risk of cancer ailments in humans is a prime priority. There is a dearth of reliable sampling methodologies for estimating AFB1 in animal feed. Data update on AFB1 in animal feed and its implication in animal production, mitigation strategies, and elucidation of risk factors to this hazard is required. To reduce the burden of aflatoxins, surveillance employing predictive technology, and biocontrol strategies seem promising approaches.

Research update on aflatoxins toxicity, metabolism, distribution, and detection: A concise overview

Serious health risks associated with the consumption of food products contaminated with aflatoxins (AFs) are worldwide recognized and depend predominantly on consumed AF concentration by diet. A low concentration of aflatoxins in cereals and related food commodities is unavoidable, especially in subtropic and tropic regions. Accordingly, risk assessment guidelines established by regulatory bodies in different countries help in the prevention of aflatoxin intoxication and the protection of public health. By assessing the maximal levels of aflatoxins in food products which are a potential risk to human health, it's possible to establish appropriate risk management strategies. Regarding, a few factors are crucial for making a rational risk management decision, such as toxicological profile, adequate information concerning the exposure duration, availability of routine and some novel analytical techniques, socioeconomic factors, food intake patterns, and maximal allowed levels of each aflatoxin in different food products which may be varied between countries.

Mycotoxin Regulatory Status in Africa: A Decade of Weak Institutional Efforts

Food safety problems are a major hindrance to achieving food security, trade, and healthy living in Africa. Fungi and their secondary metabolites, known as mycotoxins, represent an important concern in this regard. Attempts such as agricultural, storage, and processing practices, and creation of awareness to tackle the menace of fungi and mycotoxins have yielded measurable outcomes especially in developed countries, where there are comprehensive mycotoxin legislations and enforcement schemes. Conversely, most African countries do not have mycotoxin regulatory limits and even when available, are only applied for international trade. Factors such as food insecurity, public ignorance, climate change, poor infrastructure, poor research funding, incorrect prioritization of resources, and nonchalant attitudes that exist among governmental organisations and other stakeholders further complicate the situation. In the present review, we discuss the status of mycotoxin regulation in Africa, with emphasis on the impact of weak mycotoxin legislations and enforcement on African trade, agriculture, and health. Furthermore, we discuss the factors limiting the establishment and control of mycotoxins in the region.

Research Progress on Fumonisin B1 Contamination and Toxicity: A Review

Fumonisin B1 (FB1), belonging to the member of fumonisins, is one of the most toxic mycotoxins produced mainly by Fusarium proliferatum and Fusarium verticillioide. FB1 has caused extensive contamination worldwide, mainly in corn, rice, wheat, and their products, while it also poses a health risk and is toxic to animals and human. It has been shown to cause oxidative stress, endoplasmic reticulum stress, cellular autophagy, and apoptosis. This review focuses on the current stage of FB1 contamination, its toxic effects of acute toxicity, immunotoxicity, organ toxicity, and reproductive toxicity on animals and humans. The potential toxic mechanisms of FB1 are discussed. One of the main aims of the work is to provide a reliable reference strategy for understanding the occurrence and toxicity of FB1.

Biomonitoring of Multiple Mycotoxins in Urine by GC-MS/MS: A Pilot Study on Patients with Esophageal Cancer in Golestan Province, Northeastern Iran

A pilot study to investigate the occurrence of 10 mycotoxins (deoxynivalenol, DON; 3-acetyldeoxynivalenol, 3-ADON; 15-acetyldeoxynivalenol, 15-ADON; fusarenon-X, FUS-X; diacetoxyscirpenol, DAS; nivalenol, NIV; neosolaniol, NEO; zearalenone, ZON; zearalanone, ZAN; T-2 toxin, T-2; and HT-2 toxin, HT-2) in esophageal cancer patients was performed with the urinary biomarkers approach in Golestan, Iran. Urine multimycotoxin analysis was performed by dispersive liquid–liquid microextraction and gas chromatography–tandem mass spectrometry (GC–MS/MS) analysis, and values were normalized with urinary creatinine (μg/g). Four mycotoxins, namely NEO (40%), HT-2 (17.6%), DON (10%), and HT-2 (5.8%), were detected in the analyzed urine samples. DON was only detected in the control group (5.09 μg/g creatinine), while T-2 (44.70 μg/g creatinine) was only present in the esophageal cancer group. NEO and HT-2 were quantified in both control and case groups, showing average of positive samples of 9.09 and 10.45 μg/g creatinine for NEO and 16.81 and 29.09 μg/g creatinine for HT-2, respectively. Mycotoxin co-occurrence was observed in three samples as binary (NEO/HT-2 and T-2/HT-2) and ternary (DON/NEO/HT-2) combinations, reaching total concentrations of 44.58, 79.13, and 30.04 µg/g creatinine, respectively. Further investigations are needed to explore a causal association between mycotoxin contamination and esophageal cancer. For this pilot study in Golestan, the low sample size was a very limiting factor.

The Upper Digestive Tract Microbiome and Oesophageal Squamous Cell Carcinoma: Epidemiology, Pathogenesis, and Clinical Implications in Africa

The study of the microbiome has significantly contributed to our understanding of complex diseases including cancer, with a profound influence of the microbiota on clinical prognosis and the efficacy of cancer treatments. Oesophageal cancer is positioned amongst the most aggressive malignant diseases, resulting from a complex interaction between anthropometric, genetic, immune response, and environmental factors. Oesophageal squamous cell carcinoma (OSCC) is the most common type of oesophageal cancer and is a serious burden in Eastern Africa, in the area known as the African oesophageal cancer corridor (AOCC). OSCC is often diagnosed at a late stage, with patients already suffering from severe malnutrition and dehydration due to swallowing difficulties, leading to high mortality rates. So far, aetiological factors have been individually analysed with an inappropriate contextualisation. The upper digestive tract microbiome has been proposed to contribute to the onset and progression of OSCC but with limited understanding of the mechanisms behind this interaction. Data on African populations are limited, and the aetiology of AOCC is still poorly understood. This review discusses the current knowledge of the aetiology of OSCC in Africa, with special focus on the probable influence of the upper digestive tract microbiota.

FvatfA regulates growth, stress tolerance as well as mycotoxin and pigment productions in Fusarium verticillioides

FvatfA from the maize pathogen Fusarium verticillioides putatively encodes the Aspergillus nidulans AtfA and Schizasaccharomyces pombe Atf1 orthologous bZIP-type transcription factor, FvAtfA. In this study, a ΔFvatfA deletion mutant was constructed and then genetically complemented with the fully functional FvatfA gene. Comparing phenotypic features of the wild-type parental, the deletion mutant and the restored strains shed light on the versatile regulatory functions played by FvAtfA in (i) the maintenance of vegetative growth on Czapek-Dox and Potato Dextrose agars and invasive growth on unwounded tomato fruits, (ii) the preservation of conidiospore yield and size, (iii) the orchestration of oxidative (H₂O₂, menadione sodium bisulphite) and cell wall integrity (Congo Red) stress defences and (iv) the regulation of mycotoxin (fumonisins) and pigment (bikaverin, carotenoid) productions. Expression of selected biosynthetic genes both in the fumonisin (fum1, fum8) and the carotenoid (carRA, carB) pathways were down-regulated in the ΔFvatfA strain resulting in defected fumonisin production and considerably decreased carotenoid yields. The expression of bik1, encoding the polyketide synthase needed in bikaverin biosynthesis, was not up-regulated by the deletion of FvatfA meanwhile the ΔFvatfA strain produced approximately ten times more bikaverin than the wild-type or the genetically complemented strains. The abolishment of fumonisin production of the ΔFvatfA strain may lead to the development of new-type, biology-based mycotoxin control strategies. The novel information gained on the regulation of pigment production by this fungus can be interesting for experts working on new, Fusarium-based biomass and pigment production technologies.

Key points • FvatfA regulates vegetative and invasive growths of F. verticillioides. • FvatfA also orchestrates oxidative and cell wall integrity stress defenses. • The ΔFvatfA mutant was deficient in fumonisin production. • FvatfA deletion resulted in decreased carotenoid and increased bikaverin yields.

Esophageal cancer in Mozambique: should mycotoxins be a concern?

Fumonisin B1 (FB1) is a mycotoxin frequently found in agricultural commodities. The toxin poses a considerable risk for human and animal health. FB1 is among several mycotoxins produced by Fusarium spp. contaminating virtually any cereal and other Poaceae. Their intracellular action includes the promotion of oxidative stress through the generation of reactive oxygen species (ROS) that damage biomolecules such as DNA. These toxic effects were observed in vivo and in vitro. However, the association between esophageal lesions and oxidative stress induced by FB1. Studies in China, Iran and South Africa showed higher exposure to fumonisins in areas with higher risk of esophageal cancer (EC). Exposure to mycotoxins may be inevitable in Mozambique. How mycotoxins, particularly fumonisins from the contaminated food, can be associated with the emergence of EC in Mozambique? Herein, we revise the literature and present some pieces of evidence in order to highlight the burden of mycotoxins and to provide evidence-based considerations for the stakeholders involved in the management of the EC agenda in Mozambique. The information presented herein supports the need to implement novel and/or to revisit the existent detoxification methods to reduce the global burden of mycotoxins and its outcomes in health management.

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.

Clinical and Pathologic Profiles of Esophageal Cancer in Mozambique: A Study of Consecutive Patients Admitted to Maputo Central Hospital

PURPOSE

Eastern Africa was recently described as a high-incidence geographic area for esophageal cancer. Mozambique is included in this region. This study aimed to characterize this malignant disease at Maputo Central Hospital (MCH) to develop a global program for esophageal cancer management in Mozambique.

METHODS

MCH records from between 2012 and 2016 were used to assess the clinical, pathologic, and outcome profiles of esophageal tumors. A descriptive analysis of data collected was performed. Overall survival was evaluated using Kaplan-Meier curves.

RESULTS

In the study, 522 consecutive patient cases of esophageal cancer were recorded. The median patient age was 56.1 years (range, 27 to 97 years); 291 (55.7%) patients were women, and 230 (44.1%) were men. Regarding tumor site, 113 patients (21.6%) had a tumor in the lower third, 154 (29.5%) in the middle, and 50 (9.6%) in the upper third of the esophagus; in the remaining 196 (37.5%), tumor site was unknown. Squamous cell carcinoma comprised 94.4% of cases with documented histopathology (74.9% of the sample). Surgical treatment was possible in 32 patients (6.1%). Disease stage was documented only in these 32 surgical patients; 28.1%, 53.1%, and 18.8% had stage I, II, and III disease, respectively. The remaining patient cases seemed to involve clinically advanced tumors. The median follow-up time was of 1.6 months. The median survival time was of 3.5 months for all patients; for patients treated with curative intent, it was of 8.7 months.

CONCLUSION

Esophageal carcinoma is a common malignant tumor at MCH and is diagnosed in the advanced stages resulting in poor prognosis. Therefore, implementation of an Esophageal Cancer Program in Mozambique is essential.