Deficient aldehyde dehydrogenase 2 is associated with increased risk for esophageal squamous cell carcinoma in the presence of gastric hypochlorhydria

Non-acid reflux and esophageal dysmotility is associated with early esophageal squamous cell carcinoma

BACKGROUND

Studies have demonstrated that non-acid reflux (NAR) is associated with esophageal squamous cell carcinoma (ESCC). Esophageal dysmotility is associated with NAR but few studies have focused on the esophageal motility of ESCC patients. We explored the relationship between ESCC, NAR and esophageal dysmotility with the aid of multichannel intraluminal impedance and pH (MII-pH) and high-resolution manometry (HRM).

METHODS

From Jan 2021 to Oct 2022, 20 patients with superficial ESCC were enrolled as the ESCC group, while 20 age and gender matched individuals without gastroesophageal reflux disease (GERD) symptoms and 20 age and gender matched patients with GERD symptoms were recruited as the control groups. Patients received 24 h MII-pH and HRM procedure before endoscopic submucosal dissection (ESD), and the data were then collected to identify the type of reflux and esophageal dysmotility.

RESULTS

Prevalence of esophageal dysmotility was significantly different among the three groups, 75.0% in the ESCC group, 35.0% in the non-GERD group and 70.0% in the GERD group (P = 0.029). NAR episodes at 15 cm above the lower esophageal sphincter (LES) in the ESCC group were significantly higher than that in the non-GERD group (6.5 (3.5-9.3) vs 1.0 (0.8-4.0), P = 0.001) and were similar with that in the GERD group (6.5 (3.5-9.3) vs 5.5 (3.0-10.5), P > 0.05). NAR episodes at 5 cm above LES was significantly higher in the ESCC group than that in the non-GERD group (38.0 (27.0-60.0) vs 18.0 (11.8-25.8), P = 0.001) and was significantly higher than that in the GERD group (38.0 (27.0-60.0) vs 20.0 (9.8-30.5)), P = 0.010). Prevalence of pathologic non-acid reflux was significantly different among the three groups, 30.0% in the ESCC group, 0.0% in the non-GERD group and 10.0% in the GERD group (P < 0.001).

CONCLUSION

Our study found NAR and esophageal dysfunction frequently occur in ESCC patients. NAR and esophageal dysmotility may be associated with ESCC.

CLINICAL TRIAL REGISTRATION NUMBER

ChiCTR2200061456.

Non-Acid Fluid Exposure and Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) accounts for the large majority of esophageal cancer cases worldwide. In this review, we examine the potential role of non-acidic fluid (NAF) exposure in ESCC carcinogenesis. Esophageal NAF consists of a mixture of salivary, esophageal, gastric, and duodenal fluids, containing inflammatory constituents such as digestive enzymes and bile acids that induce DNA damage, as well as known carcinogens such as acetaldehyde and N-nitrosamines. Exposure to NAF can occur in the setting of increased non-acid reflux, decreased gastric acidity, and decreased esophageal fluid clearance. Non-acid reflux has been associated with ESCC in small observational studies, and in animal models bile reflux can promote the development of ESCC. Associations have been found between increased ESCC risk and atrophic gastritis, a history of partial gastrectomy, and proton pump inhibitor use, all of which raise the pH of refluxate. Additionally, a minimally or non-acidic gastric environment contains an altered microbiome that can increase the production of acetaldehyde and N-nitrosamines. Esophageal motility disorders such as achalasia and opioid-induced esophageal dysfunction result in increased stasis and exposure to these potentially proinflammatory constituents of NAF. NAF may promote the development of ESCC via multiple mechanisms and is an understudied area of research.

Risk Factors of Esophageal Squamous Cell Carcinoma beyond Alcohol and Smoking

Esophageal squamous cell carcinoma (ESCC) is the sixth most common cause of death worldwide. Incidence rates vary internationally, with the highest rates found in Southern and Eastern Africa, and central Asia. Initial observational studies identified multiple factors associated with an increased risk of ESCC, with subsequent work then focused on developing plausible biological mechanistic associations. The aim of this review is to summarize the role of risk factors in the development of ESCC and propose future directions for further research. A systematic search of the literature was conducted by screening EMBASE, MEDLINE/PubMed, and CENTRAL for relevant publications. In total, 73 studies were included that sought to identify risk factors associated with the development of esophageal squamous cell carcinoma. Risk factors were divided into seven subcategories: genetic, dietary and nutrition, gastric atrophy, infection and microbiome, metabolic, epidemiological and environmental and other risk factors. Risk factors from each subcategory were summarized and explored with mechanistic explanations for these associations. This review highlights several current risk factors of ESCC. These risk factors were explored, and explanations dissected. Most studies focused on investigating genetic and dietary and nutritional factors, whereas this review identified other potential risk factors that have yet to be fully explored. Furthermore, there is a lack of literature on the association of these risk factors with tumor factors and disease prognosis. Further research to validate these results and their effects on tumor biology is absolutely necessary.

Slow-release L-cysteine capsule prevents gastric mucosa exposure to carcinogenic acetaldehyde: results of a randomised single-blinded, cross-over study of Helicobacter-associated atrophic gastritis

INTRODUCTION

Helicobacter-induced atrophic gastritis with a hypochlorhydric milieu is a risk factor for gastric cancer. Microbes colonising acid-free stomach oxidise ethanol to acetaldehyde, a recognised group 1 carcinogen.

OBJECTIVE

To assess gastric production of acetaldehyde and its inert condensation product, non-toxic 2-methyl-1,3-thiazolidine-4-carboxylic acid (MTCA), after alcohol intake under treatment with slow-release L-cysteine or placebo.

METHODS

Seven patients with biopsy-confirmed atrophic gastritis, low serum pepsinogen and high gastrin-17 were studied in a cross-over single-blinded design. On separate days, patients randomly received 200 mg slow-release L-cysteine or placebo with intragastric instillation of 15% (0.3 g/kg) ethanol. After intake, gastric concentrations of ethanol, acetaldehyde, L-cysteine and MTCA were analysed.

RESULTS

Administration of L-cysteine increased MTCA (p < .0004) and decreased gastric acetaldehyde concentrations by 68% (p < .0001). The peak L-cysteine level was 7552 ± 2687 μmol/L at 40 min and peak MTCA level 196 ± 98 μmol/L at 80 min after intake. Gastric L-cysteine and MTCA concentrations were maintained for 3 h. The AUC for MTCA was 11-fold higher than acetaldehyde, indicating gastric first-pass metabolism of ethanol. With placebo, acetaldehyde remained elevated also at low ethanol concentrations representing 'non-alcoholic' beverages and food items.

CONCLUSIONS

After gastric ethanol instillation, slow-release L-cysteine eliminates acetaldehyde to form inactive MTCA, which remains in gastric juice for up to 3 h. High acetaldehyde levels indicate a marked gastric first-pass metabolism of ethanol resulting in gastric accumulation of carcinogenic acetaldehyde. Local exposure of the gastric mucosa to acetaldehyde can be mitigated by slow-release L-cysteine capsules.

Effects of ALDH2 genotype, PPI treatment and L-cysteine on carcinogenic acetaldehyde in gastric juice and saliva after intragastric alcohol administration

Acetaldehyde (ACH) associated with alcoholic beverages is Group 1 carcinogen to humans (IARC/WHO). Aldehyde dehydrogenase (ALDH2), a major ACH eliminating enzyme, is genetically deficient in 30-50% of Eastern Asians. In alcohol drinkers, ALDH2-deficiency is a well-known risk factor for upper aerodigestive tract cancers, i.e., head and neck cancer and esophageal cancer. However, there is only a limited evidence for stomach cancer. In this study we demonstrated for the first time that ALDH2 deficiency results in markedly increased exposure of the gastric mucosa to acetaldehyde after intragastric administration of alcohol. Our finding provides concrete evidence for a causal relationship between acetaldehyde and gastric carcinogenesis. A plausible explanation is the gastric first pass metabolism of ethanol. The gastric mucosa expresses alcohol dehydrogenase (ADH) enzymes catalyzing the oxidation of ethanol to acetaldehyde, especially at the high ethanol concentrations prevailing in the stomach after the consumption of alcoholic beverages. The gastric mucosa also possesses the acetaldehyde-eliminating ALDH2 enzyme. Due to decreased mucosal ALDH2 activity, the elimination of ethanol-derived acetaldehyde is decreased, which results in its accumulation in the gastric juice. We also demonstrate that ALDH2 deficiency, proton pump inhibitor (PPI) treatment, and L-cysteine cause independent changes in gastric juice and salivary acetaldehyde levels, indicating that intragastric acetaldehyde is locally regulated by gastric mucosal ADH and ALDH2 enzymes, and by oral microbes colonizing an achlorhydric stomach. Markedly elevated acetaldehyde levels were also found at low intragastric ethanol concentrations corresponding to the ethanol levels of many foodstuffs, beverages, and dairy products produced by fermentation. A capsule that slowly releases L-cysteine effectively eliminated acetaldehyde from the gastric juice of PPI-treated ALDH2-active and ALDH2-deficient subjects. These results provide entirely novel perspectives for the prevention of gastric cancer, especially in established risk groups.

Association between Glu504Lys polymorphism of ALDH2 gene and cancer risk: a meta-analysis

Background

The association of the aldehyde dehydrogenases-2 (ALDH2) Glu504Lys polymorphism (also named Glu487Lys, or rs671) and cancers has been investigated. This meta-analysis aims to comprehensively assess the influence of this polymorphism on the overall cancer risk.

Methods

Eligible publications were retrieved according to inclusion/exclusion criteria and the data were analyzed using the Review Manager software (V5.2).

Results

A meta-analysis based on 51 case-control studies consisting of 16774 cases and 32060 controls was performed to evaluate the association between the ALDH2 Glu504Lys polymorphism and cancer risk. The comparison of genotypes Lys+ (Lys/Lys and Lys/Glu) with Glu/Glu yielded a significant 20% increased cancer risk (OR = 1.20, 95%CI: 1.03–1.39, P = 0.02, I² = 92%). Subgroup analysis by cancer type indicated a significantly increased UADT cancer risk (OR = 1.39, 95%CI: 1.11–1.73, P = 0.004, I² = 94%) in individuals with the Lys+ genotypes. Subgroup analysis by country indicated that individuals from Japan with the Lys+ genotypes had a significant 38% increased cancer risk (OR = 1.38, 95%CI: 1.12–1.71, P = 0.003, I² = 93%).

Conclusions

Our results indicated that the ALDH2 Glu504Lys polymorphism is a susceptible loci associated with overall cancers, especially esophageal cancer and among Japanese population.

Selected ion flow tube-MS analysis of headspace vapor from gastric content for the diagnosis of gastro-esophageal cancer

Gastric content is a complex biofluid within the human stomach which has an important role in digestive processes. It is believed that gastric content may be a contributory factor in the development of upper gastro-intestinal diseases. In this work, selected ion flow tube mass spectrometry (SIFT-MS) has been applied to the quantification of volatile organic compounds (VOCs) in the headspace vapor of gastric content samples, which were retrieved from three groups of patients, including those with gastro-esophageal cancer, noncancer diseases of the upper gastro-intestinal tract, and a healthy cohort. Twelve VOCs have been investigated in this study; the following 7 VOCs, acetone, formaldehyde, acetaldehyde, hexanoic acid, hydrogen sulphide, hydrogen cyanide, and methyl phenol, were found to be significantly different between cancer and healthy groups by the Mann-Whitney U test. Receiver operating characteristics (ROC) analysis was applied for the combined VOCs of acetaldehyde, formaldehyde, hydrogen sulphide, and methyl phenol to discriminate cancer patients from healthy controls. The area under the curve (AUC) was 0.9. This result raises the prospect that a VOC profile rather than a single biomarker may be preferable in the molecular-orientated diagnosis of gastro-oseophageal cancer, and this warrants further investigation to assess its potential application as a new diagnostic test.