Molecular mechanisms of Barrett's esophagus and adenocarcinoma

The role of smoking and alcohol in mediating the effect of gastroesophageal reflux disease on lung cancer: A Mendelian randomization study

Observational studies have suggested a positive association between gastroesophageal reflux disease and lung cancer, but due to the existence of confounders, it remains undetermined whether gastroesophageal reflux disease (GERD) has a causal association with lung cancer. Therefore, Mendelian randomization (MR) analyses were applied to investigate the relationship between the two conditions. Two-sample Mendelian randomization analysis was utilized with summary genetic data from the European Bioinformatics Institute (602,604 individuals) and International Lung Cancer Consortium, which provides information on lung cancer and its histological subgroups. Furthermore, we used two-step Mendelian randomization and multivariable Mendelian randomization to estimate whether smoking initiation (311,629 cases and 321,173 controls) and alcohol intake frequency (n = 462,346) mediate any effect of gastroesophageal reflux disease on lung cancer risk. The Mendelian randomization analyses indicated that gastroesophageal reflux disease was associated with and significantly increased the risk of lung cancer (OR_IVW = 1.35, 95% CI = 1.18-1.54; p = 1.36 × 10^-5). Smoking initiation and alcohol intake frequency mediated 35% and 3% of the total effect of gastroesophageal reflux disease on lung cancer, respectively. The combined effect of these two factors accounted for 60% of the total effect. In conclusion, gastroesophageal reflux disease is associated with an increased risk of lung cancer, and interventions to reduce smoking and alcohol intake may reduce the incidence of lung cancer.

SPT6 loss permits the transdifferentiation of keratinocytes into an intestinal fate that resembles Barrett's metaplasia

Transient depletion of the transcription elongation factor SPT6 in the keratinocyte has been recently shown to inhibit epidermal differentiation and stratification; instead, they transdifferentiate into a gut-like lineage. We show here that this phenomenon of transdifferentiation recapitulates Barrett's metaplasia, the only human pathophysiologic condition in which a stratified squamous epithelium that is injured due to chronic acid reflux is trans-committed into an intestinal fate. The evidence we present here not only lend support to the notion that the keratinocytes are potentially the cell of origin of Barrett's metaplasia but also provide mechanistic insights linking transient acid exposure, downregulation of SPT6, stalled transcription of the master regulator of epidermal fate TP63, loss of epidermal fate, and metaplastic progression. Because Barrett's metaplasia in the esophagus is a pre-neoplastic condition with no preclinical human models, these findings have a profound impact on the modeling Barrett's metaplasia-in-a-dish.

Oesophageal cancer

Oesophageal cancer is the sixth most common cause of cancer-related death worldwide and is therefore a major global health challenge. The two major subtypes of oesophageal cancer are oesophageal squamous cell carcinoma (OSCC) and oesophageal adenocarcinoma (OAC), which are epidemiologically and biologically distinct. OSCC accounts for 90% of all cases of oesophageal cancer globally and is highly prevalent in the East, East Africa and South America. OAC is more common in developed countries than in developing countries. Preneoplastic lesions are identifiable for both OSCC and OAC; these are frequently amenable to endoscopic ablative therapies. Most patients with oesophageal cancer require extensive treatment, including chemotherapy, chemoradiotherapy and/or surgical resection. Patients with advanced or metastatic oesophageal cancer are treated with palliative chemotherapy; those who are human epidermal growth factor receptor 2 (HER2)-positive may also benefit from trastuzumab treatment. Immuno-oncology therapies have also shown promising early results in OSCC and OAC. In this Primer, we review state-of-the-art knowledge on the biology and treatment of oesophageal cancer, including screening, endoscopic ablative therapies and emerging molecular targets, and we discuss best practices in chemotherapy, chemoradiotherapy, surgery and the maintenance of patient quality of life.

Esophageal sensitivity to acid in patients with Barrett's esophagus is not related to preserved esophageal mucosal integrity

BACKGROUND

Patients with Barrett's esophagus (BE) usually have severe gastroesophageal reflux. However, they often have surprisingly few reflux symptoms. We hypothesized that BE patients are less sensitive to acid than gastroesophageal reflux disease (GERD) patients without Barrett and that this is due to an unusual preservation of mucosal integrity of the squamous epithelium prohibiting transepithelial acid diffusion.

METHODS

We prospectively analyzed esophageal sensitivity and esophageal mucosal integrity in GERD patients with and without BE and healthy subjects. An acid perfusion test was performed and mucosal integrity was assessed in vivo by electrical tissue impedance spectroscopy and ex vivo by Ussing chamber experiments with biopsy specimens.

KEY RESULTS

Gastroesophageal reflux disease patients with BE were less sensitive to acid than GERD patients without BE, but more sensitive to acid than healthy controls (time to perception Barrett's 14.0 minutes, GERD 4.6 minutes, controls 17.5 minutes). However, extracellular impedance (6.2 and 5.7 vs 8.4×10³  Ω/m) and transepithelial resistance (94.0 and 89 vs 118 Ω/cm² ) was similar in BE and GERD patients and significantly lower than in healthy subjects. Transepithelial fluorescein flux was equally increased in GERD patients with and without BE (1.6 and 1.7×10³ vs 0.6×10³  nmol/cm² /h).

CONCLUSIONS & INFERENCES

Esophageal hypersensitivity to acid is less pronounced in BE patients than in GERD patients without Barrett. However, mucosal integrity of the squamous epithelium is equally impaired in GERD patients with and without Barrett, indicating that factors other than esophageal mucosal barrier integrity explain the difference in acid sensitivity between those with BE and those without.

Risk of lung cancer in patients with gastro-esophageal reflux disease: a population-based cohort study

This large-scale, controlled cohort study estimated the risks of lung cancer in patients with gastro-esophageal reflux disease (GERD) in Taiwan. We conducted this population-based study using data from the National Health Insurance Research Database of Taiwan during the period from 1997 to 2010. Patients with GERD were diagnosed using endoscopy, and controls were matched to patients with GERD at a ratio of 1:4. We identified 15,412 patients with GERD and 60,957 controls. Compared with the controls, the patients with GERD had higher rates of osteoporosis, diabetes mellitus, asthma, chronic obstructive pulmonary disease, pneumonia, bronchiectasis, depression, anxiety, hypertension, dyslipidemia, chronic liver disease, congestive heart failure, atrial fibrillation, stroke, chronic kidney disease, and coronary artery disease (all P < .05). A total of 85 patients had lung cancer among patients with GERD during the follow-up of 42,555 person-years, and the rate of lung cancer was 0.0020 per person-year. By contrast, 232 patients had lung cancer among patients without GERD during the follow-up of 175,319 person-years, and the rate of lung cancer was 0.0013 per person-year. By using stepwise Cox regression model, the overall incidence of lung cancer remained significantly higher in the patients with GERD than in the controls (hazard ratio, 1.53; 95% CI [1.19–1.98]). The cumulative incidence of lung cancer was higher in the patients with GERD than in the controls (P = .0012). In conclusion, our large population-based cohort study provides evidence that GERD may increase the risk of lung cancer in Asians.

Preventing Age-Related Decline of Gut Compartmentalization Limits Microbiota Dysbiosis and Extends Lifespan

Compartmentalization of the gastrointestinal (GI) tract of metazoans is critical for health. GI compartments contain specific microbiota, and microbiota dysbiosis is associated with intestinal dysfunction. Dysbiosis develops in aging intestines, yet how this relates to changes in GI compartmentalization remains unclear. The Drosophila GI tract is an accessible model to address this question. Here we show that the stomach-like copper cell region (CCR) in the middle midgut controls distribution and composition of the microbiota. We find that chronic activation of JAK/Stat signaling in the aging gut induces a metaplasia of the gastric epithelium, CCR decline, and subsequent commensal dysbiosis and epithelial dysplasia along the GI tract. Accordingly, inhibition of JAK/Stat signaling in the CCR specifically prevents age-related metaplasia, commensal dysbiosis and functional decline in old guts, and extends lifespan. Our results establish a mechanism by which age-related chronic inflammation causes the decline of intestinal compartmentalization and microbiota dysbiosis, limiting lifespan.

Pathophysiological mechanisms linking obesity and esophageal adenocarcinoma

In recent decades there has been a dramatic rise in the incidence of esophageal adenocarcinoma (EAC) in the developed world. Over approximately the same period there has also been an increase in the prevalence of obesity. Obesity, especially visceral obesity, is an important independent risk factor for the development of gastro-esophageal reflux disease, Barrett’s esophagus and EAC. Although the simplest explanation is that this mediated by the mechanical effects of abdominal obesity promoting gastro-esophageal reflux, the epidemiological data suggest that the EAC-promoting effects are independent of reflux. Several, not mutually exclusive, mechanisms have been implicated, which may have different effects at various points along the reflux-Barrett’s-cancer pathway. These mechanisms include a reduction in the prevalence of Helicobacter pylori infection enhancing gastric acidity and possibly appetite by increasing gastric ghrelin secretion, induction of both low-grade systemic inflammation by factors secreted by adipose tissue and the metabolic syndrome with insulin-resistance. Obesity is associated with enhanced secretion of leptin and decreased secretion of adiponectin from adipose tissue and both increased leptin and decreased adiponectin have been shown to be independent risk factors for progression to EAC. Leptin and adiponectin have a set of mutually antagonistic actions on Barrett’s cells which appear to influence the progression of malignant behaviour. At present no drugs are of proven benefit to prevent obesity associated EAC. Roux-en-Y reconstruction is the preferred bariatric surgical option for weight loss in patients with reflux. Statins and aspirin may have chemopreventative effects and are indicated for their circulatory benefits.

Activity of mitogen-activated protein kinases in the esophageal epithelium of patients with Barrett's esophagus

Barrett's esophagus (BE), a complication of gastroesophageal reflux disease, is associated with an increased risk of esophageal cancer. Mitogen-activated protein kinases may play an important role in the pathogenesis of this process. We aimed to evaluate mitogen-activated protein kinases activity in esophageal mucosa of patients with BE and find possible relationship between reflux type and BE. Twenty-four patients (mean age: 59 years) with gastroesophageal reflux disease symptoms and endoscopically suspected esophageal metaplasia (ESEM) were prospectively enrolled for testing by a multichannel intraluminal impedance monitoring along with a Bilitec 2000. Endoscopic biopsies were taken from methylene blue-positive pit patterns (sites suggesting specialized intestinal metaplasia [SIM]), from 2 cm above the Z-line and from cardial parts of the stomach. The biopsies were analyzed for extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), p38 activity by Western blot. Seventeen ESEMs had histologically proven metaplasia: eight patients had SIM and nine had gastric-type epithelia (GE). Biliary reflux was more evident in SIM (P = 0.019) but not in GE (P = 0.019); non-biliary reflux was typical for GE (P = 0.005) but not for SIM (P = 0.04). Strong activations of ERK and p38 were found predominantly in SIM, but not in normal esophageal mucosa (NE) (P = 0.01 and P < 0.001 respectively). Strong signals for active JNK and p38 were detected in GE, but not in NE (P = 0.006 and P = 0.02 respectively). ERK activity was significantly higher than p38 activity in ESEM patients only with GE (P = 0.02). The strong activation of ERK, but not JNK is indicative of SIM. The presence of bile in gastroesophageal refluxate is predisposing to SIM, but not to GE in esophageal mucosa.

Dpp signaling determines regional stem cell identity in the regenerating adult Drosophila gastrointestinal tract

The gastrointestinal tract is lined by a series of epithelia that share functional requirements but also have distinct, highly specialized roles. Distinct populations of somatic stem cells (SCs) regenerate these epithelia, yet the mechanisms that maintain regional identities of these SCs are not well understood. Here, we identify a role for the BMP-like Dpp signaling pathway in diversifying regenerative processes in the adult gastrointestinal tract of Drosophila. Dpp secreted from enterocytes at the boundary between the posterior midgut and the middle midgut (MM) sets up a morphogen gradient that selectively directs copper cell (CC) regeneration from gastric SCs in the MM and thus determines the size of the CC region. In vertebrates, deregulation of BMP signaling has been associated with Barrett's metaplasia, wherein the squamous esophageal epithelium is replaced by a columnar epithelium, suggesting that the maintenance of regional SC identities by BMP is conserved.

Gastric reflux is an independent risk factor for laryngopharyngeal carcinoma

BACKGROUND

Gastric reflux can reach into the upper airway, inducing cellular damage in the epithelial lining. This condition is believed to be a risk factor for development of laryngopharyngeal squamous cell carcinoma (LPSCC), although the literature is conflicting.

METHODS

To better clarify this relationship, we assessed the association of self-reported heartburn history and medication use among 631 patients with LPSCCs and 1234 control subjects (frequency-matched on age, gender, and town of residence) enrolled as part of a population-based case-control study of head and neck squamous cell carcinoma in the greater Boston area.

RESULTS

After adjusting for age, gender, race, smoking, alcohol consumption, HPV16 seropositivity, education, and body mass index, subjects reporting a history of frequent heartburn and who were neither a heavy smoker nor heavy drinker had a significantly elevated risk of LPSCCs [OR, 1.78; 95% confidence interval (CI), 1.00-3.16]. Among those with a history of heartburn, there was an inverse association between antacid use and LPSCCs relative to those never taking heartburn medication (OR, 0.59; 95% CI, 0.38-0.93) that remained consistent when analyzed by smoking/drinking status, HPV16 status, or by primary tumor site.

CONCLUSIONS

Our data show that gastric reflux is an independent risk factor for squamous cancers of the pharynx and larynx. Further studies are needed to clarify the possible chemopreventive role of antacid use for patients with gastric reflux.

IMPACT

Elucidation of additional risk factors for head and neck cancer can allow for risk stratification and inform surveillance of high-risk patients.

Disturbed balance between SOX2 and CDX2 in human vitelline duct anomalies and intestinal duplications

Congenital gastric-type heteroplasia is common in intestinal duplications and anomalies, which originate from incomplete resorption of the omphalomesenteric duct during development. Two transcription factors determine the proximodistal specification of the gastrointestinal tract, SOX2, expressed exclusively in the proximal part of the primitive gut, and CDX2, expressed solely in the distal part. Aberrant expression of these factors may result in abnormal development and congenital abnormalities. Therefore, we analyzed the expression of SOX2 and CDX2 in a number of pediatric intestinal anomalies. We investigated the expression pattern of SOX2 and CDX2 in three congenital intestinal anomalies in which ectopic gastric tissue may be present, Meckel's diverticulum (N = 8), persistent ductus omphalomesentericus (N = 14), and intestinal duplications (N = 8). CDX2, but not SOX2, was detected in intestinal epithelial cells in tissue lacking gastric heteroplasia. In gastric-type heteroplasia, a reciprocal expression pattern existed between SOX2 and CDX2 in the gastric and intestinal tissues, respectively. Interestingly, patches of CDX2-positive cells were present within the gastric mucosa in a subset of Meckel's diverticula and intestinal duplications, suggesting that it is not the absence of CDX2, but rather the ectopic expression of SOX2 that leads to gastric tissue in the prospective intestinal tissue. This is in concordance with our previous mouse studies. Collectively, our data indicate that a fine balance between SOX2 and CDX2 expression in the gastrointestinal tract is essential for proper development and that ectopic expression of SOX2 may lead to malformations of the gut.

Molecular basis of esophageal cancer development and progression

This article discusses the molecular basis of esophageal cancer development and subsequent progression of disease. Differing epidemiologic factors are associated with esophageal adenocarcinoma and squamous cell carcinoma. These 2 different histologic types have differing putative underlying mechanisms of transdifferentiation from normal esophageal mucosa to malignant histologies via gene dysregulation, biochemical modifications, and altered cell signaling pathways. Our developing understanding of the molecular events underlying esophageal cancer is leading to the establishment of identifiable biomarkers and the clinical use of molecularly targeted treatment agents. The identification of driving genetic mutations and altered signaling pathways has also had favorable outcomes.

A surprise cell of origin for Barrett's esophagus

Barrett's esophagus is a metaplasia of the distal esophagus that is the only recognized precursor of esophageal adenocarcinoma. Despite a characteristic histology, the pathogenesis of Barrett's has remained obscure. A recent paper from the laboratories of Wa Xian and Frank McKeon presents evidence for a novel cell of origin of Barrett's. Their work is based on studies of mice engineered to lack the squamous epithelial stem cell survival factor p63. These mice develop a metaplasia of the proximal stomach and esophagus that harbors substantial histological and molecular features of Barrett's. The metaplasia appears to form from embryonic progenitor cells that normally persists post-natally only at the squamo-columnar junction. Moreover, in their model, the metaplasia is initiated not by mutation but by reduced competition between these cells and squamous epithelial cells.