Initiation of esophageal squamous cell carcinoma (ESCC) in a murine 4-nitroquinoline-1-oxide and alcohol carcinogenesis model

Ethanol exposure exacerbates 4-nitroquinoline-1-oxide induced esophageal carcinogenesis and induces invasive carcinoma with muscularis propria infiltration in a mouse model

Esophageal squamous cell carcinoma (ESCC) is one of the most fatal cancers worldwide. Most ESCC patients are diagnosed at an advanced stage; however, current research on in vivo animal models accurately reflecting their clinical presentation is lacking. Alcohol consumption is a major risk factor for ESCC and has been used in several disease models for disease induction. In this study, we used 4-nitroquinoline-1-oxide in combination with ethanol to induce an in vivo ESCC mouse model. Esophageal tissues were stained with hematoxylin and eosin for histopathological examination and lesion scoring. In cellular experiments, cell adhesion and migration invasion ability were observed using phalloidin staining, cell scratch and transwell assays, respectively, and the expression of epithelial-mesenchymal transition-related markers was detected using quantitative reverse transcription polymerase chain reaction and western blotting. The results showed that ethanol-exposed mice lost more weight and had an increased number of esophageal nodules. Histological examination revealed that the lesion scores of the ethanol-exposed esophageal samples were significantly higher than those of the unexposed esophageal samples. Furthermore, ethanol-exposed esophageal cancer samples had more severe lesions with infiltration of tumor cells into the muscularis propria. In vitro cellular experiments showed that ethanol exposure induced cytoskeletal microfilament formation, promoted cell migration invasion elevated the expression of N-cadherin and Snail, and decreased the expression of E-cadherin. In conclusion, ethanol exposure exacerbates ESCC, promotes tumor cell infiltration into the muscularis propria, and could be an effective agent for establishing innovative models of invasive carcinoma.

ALDH2 dysfunction and alcohol cooperate in cancer stem cell enrichment

The alcohol metabolite acetaldehyde is a potent human carcinogen linked to esophageal squamous cell carcinoma (ESCC) initiation and development. Aldehyde dehydrogenase 2 (ALDH2) is the primary enzyme that detoxifies acetaldehyde in the mitochondria. Acetaldehyde accumulation causes genotoxic stress in cells expressing the dysfunctional ALDH2E487K dominant negative mutant protein linked to ALDH2*2, the single nucleotide polymorphism highly prevalent among East Asians. Heterozygous ALDH2*2 increases the risk for the development of ESCC and other alcohol-related cancers. Despite its prevalence and link to malignant transformation, how ALDH2 dysfunction influences ESCC pathobiology is incompletely understood. Herein, we characterize how ESCC and preneoplastic cells respond to alcohol exposure using cell lines, three-dimensional organoids and xenograft models. We find that alcohol exposure and ALDH2*2 cooperate to increase putative ESCC cancer stem cells with high CD44 expression (CD44H cells) linked to tumor initiation, repopulation and therapy resistance. Concurrently, ALHD2*2 augmented alcohol-induced reactive oxygen species and DNA damage to promote apoptosis in the non-CD44H cell population. Pharmacological activation of ALDH2 by Alda-1 inhibits this phenotype, suggesting that acetaldehyde is the primary driver of these changes. Additionally, we find that Aldh2 dysfunction affects the response to cisplatin, a chemotherapeutic commonly used for the treatment of ESCC. Aldh2 dysfunction facilitated enrichment of CD44H cells following cisplatin-induced oxidative stress and cell death in murine organoids, highlighting a potential mechanism driving cisplatin resistance. Together, these data provide evidence that ALDH2 dysfunction accelerates ESCC pathogenesis through enrichment of CD44H cells in response to genotoxic stressors such as environmental carcinogens and chemotherapeutic agents.

Bioinformatics and network pharmacology identify promotional effects and potential mechanisms of ethanol on esophageal squamous cell carcinoma and experimental validation

Ethanol is an important risk factor for esophageal squamous cell carcinoma (ESCC); however, the molecular mechanisms behind how ethanol promotes ESCC development remain poorly understood. In this study, ethanol-ESCC-associated target genes were constructed and screened using network pharmacology and subjected to Kyoto Encyclopedia of Genes and Genomes (KEGG) and bioinformatics analysis. A mouse ethanol-exposed esophageal cancer model was constructed with 4-nitroquinoline-1-oxide (4-NQO) to assess its survival and tumor lesion status, and the mechanism of ethanol-promoted ESCC lesions was verified by qRT-PCR and Western blotting. The results showed that 126 ethanol-ESCC crossover genes were obtained, which were significantly enriched in the PI3K/AKT signaling pathway. Bioinformatics results showed that the target genes TNF, IL6, IL1β and JUN were highly expressed in esophageal tumor samples and positively correlated with tumor proliferation and apoptosis genes, and the genetic information of these genes was mutated to different degrees. Animal model experiments showed that ethanol decreased the survival rate and aggravated the occurrence of esophageal cancer in mice. qRT-PCR showed that ethanol promoted the expression of TNF, IL6, IL1β and JUN mRNA in mouse esophageal tumor tissues, and Western blotting showed that ethanol promoted p-PI3K and p-AKT protein expression in mouse esophageal tumor tissues. In conclusion, ethanol promotes esophageal carcinogenesis by increasing the expression of TNF, IL6, IL1β and JUN and activating the PI3K/AKT signaling pathway.

IL-1β transgenic mouse model of inflammation driven esophageal and oral squamous cell carcinoma

Chronic inflammation is integral to the development of esophageal adenocarcinoma (EAC) and esophageal squamous cell carcinoma (ESCC), although the latter has not been associated with reflux esophagitis. The L2-IL-1β transgenic mice, expressing human interleukin (IL)-1β in the oral, esophageal and forestomach squamous epithelia feature chronic inflammation and a stepwise development of Barrett's esophagus-like metaplasia, dysplasia and adenocarcinoma at the squamo-columnar junction. However, the functional consequences of IL-1β-mediated chronic inflammation in the oral and esophageal squamous epithelia remain elusive. We report for the first time that in addition to the previously described Barrett's esophagus-like metaplasia, the L2-IL-1β mice also develop squamous epithelial dysplasia with progression to squamous cell carcinoma (SCC) in the esophagus and the tongue. L2-IL-1β showed age-dependent progression of squamous dysplasia to SCC with approximately 40% (n = 49) and 23.5% (n = 17) incidence rates for esophageal and tongue invasive SCC respectively, by 12-15 months of age. Interestingly, SCC development and progression in L2-IL-1β was similar in both Germ Free (GF) and Specific Pathogen Free (SPF) conditions. Immunohistochemistry revealed a T cell predominant inflammatory profile with enhanced expression of Ki67, Sox2 and the DNA double-strand break marker, γ-H2AX, in the dysplastic squamous epithelia of L2-IL-1β mice. Pro-inflammatory cytokines, immunomodulatory players, chemoattractants for inflammatory cells (T cells, neutrophils, eosinophils, and macrophages) and oxidative damage marker, iNOS, were significantly increased in the esophageal and tongue tissues of L2-IL-1β mice. Our recent findings have expanded the translational utility of the IL-1β mouse model to aid in further characterization of the key pathways of inflammation driven BE and EAC as well as ESCC and Oral SCC.

A method for scoring 4-nitroquinoline 1-oxide-induced murine esophageal squamous neoplasia

A mouse model for esophageal squamous cell carcinoma (ESCC) is induced by oral administration of the carcinogen 4-nitroquinoline 1-oxide (4-NQO). There is not an objective method for determining histopathologic severity of disease in this model. We aim to create a clearly defined and easily applied scoring system that can quantify the severity of 4-NQO-induced murine ESCC. Fifteen wild-type C57BL/6J mice were treated with 4-NQO for 8 (n = 8) or 16 (n = 7) weeks, while the rest (n = 9) were treated with vehicle, as 8 weeks of 4-NQO typically results in dysplasia and 16 weeks in carcinoma. We identified histologic abnormalities of the esophagus in this model and developed metrics to grade severity of dysplasia, papillomas, and invasion. Scores were then calculated using quantitative digitized image analysis for measuring depth and extent of each feature within the entire sample. Each feature was also assigned a weight based on its relation to cancer severity. Histology scores were significantly different in the three groups, suggesting that this method can discriminate dysplasia from carcinoma. This model can be applied to any mouse treated with 4-NQO.

Protective effects of Alda-1, an ALDH2 activator, on alcohol-derived DNA damage in the esophagus of human ALDH2*2 (Glu504Lys) knock-in mice

Alcohol consumption is the key risk factor for the development of esophageal squamous cell carcinoma (ESCC), and acetaldehyde, a metabolite of alcohol, is an alcohol-derived major carcinogen that causes DNA damage. Aldehyde dehydrogenase2 (ALDH2) is an enzyme that detoxifies acetaldehyde, and its activity is reduced by ALDH2 gene polymorphism. Reduction in ALDH2 activity increases blood, salivary and breath acetaldehyde levels after alcohol intake, and it is deeply associated with the development of ESCC. Heavy alcohol consumption in individuals with ALDH2 gene polymorphism significantly elevates the risk of ESCC; however, effective prevention has not been established yet. In this study, we investigated the protective effects of Alda-1, a small molecule ALDH2 activator, on alcohol-mediated esophageal DNA damage. Here, we generated novel genetically engineered knock-in mice that express the human ALDH2*1 (wild-type allele) or ALDH2*2 gene (mutant allele). Those mice were crossed, and human ALDH2*1/*1, ALDH2*1/*2 and ALDH2*2/*2 knock-in mice were established. They were given 10% ethanol for 7 days in the presence or absence of Alda-1, and we measured the levels of esophageal DNA damage, represented by DNA adduct (N²-ethylidene-2′-deoxyguanosine). Alda-1 significantly increased hepatic ALDH2 activity both in human ALDH2*1/*2 and/or ALDH2*2/*2 knock-in mice and reduced esophageal DNA damage levels after alcohol drinking. Conversely, cyanamide, an ALDH2-inhibitor, significantly exacerbated esophageal DNA adduct level in C57BL/6N mice induced by alcohol drinking. These results indicate the protective effects of ALDH2 activation by Alda-1 on esophageal DNA damage levels in individuals with ALDH2 gene polymorphism, providing a new insight into acetaldehyde-mediated esophageal carcinogenesis and prevention.

Retinoids induce antagonism between FOXO3A and FOXM1 transcription factors in human oral squamous cell carcinoma (OSCC) cells

To gain a greater understanding of oral squamous cell carcinoma (OSCC) we investigated the actions of all-trans-retinoic acid (RA; a retinoid), bexarotene (a pan-RXR agonist), and forkhead box (FOX) transcription factors in human OSCC-derived cell lines. RA and bexarotene have been shown to limit several oncogenic pathways in many cell types. FOXO proteins typically are associated with tumor suppressive activities, whereas FOXM1 acts as an oncogene when overexpressed in several cancers. RA and/or bexarotene increased the transcript levels of FOXO1, FOXO3A, and TRAIL receptors; reduced the transcript levels of FOXM1, Aurora kinase B (AURKB), and vascular endothelial growth factor A (VEGFA); and decreased the proliferation of OSCC-derived cell lines. Also, RA and/or bexarotene influenced the recruitment of FOXO3A and FOXM1 to target genes. Additionally, FOXM1 depletion reduced cell proliferation, decreased transcript levels of downstream targets of FOXM1, and increased transcript levels of TRAIL receptors. Overexpression of FOXO3A decreased proliferation and increased binding of histone deacetylases (HDACs) 1 and 2 at the FOXM1, AURKB, and VEGFA promoters. This research suggests novel influences of the drugs RA and bexarotene on the expression of FOXM1 and FOXO3A in transcriptional regulatory pathways of human OSCC.

Clinical and translational advances in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is among the most deadly forms of human malignancy characterized by late stage diagnosis, metastasis, therapy resistance and frequent recurrence. Clinical management of ESCC remains challenging and the disease presently lacks approved targeted therapeutics. However, emerging data from recent clinical and translational investigations hold great promise for future progress toward improving patient outcomes in this deadly disease. Here, we review current clinical perspectives in ESCC epidemiology, pathophysiology, and clinical care, highlighting recent advances with potential to impact ESCC prevention, diagnosis and management. We further provide an overview of recent translational investigations contributing to our understanding of the molecular mechanisms underlying ESCC development, progression and therapy response, including insights gained from genetic studies and various murine model systems. Finally, we discuss future perspectives in the clinical and translational realms, along with remaining hurdles that must be overcome to eradicate ESCC.

Dek overexpression in murine epithelia increases overt esophageal squamous cell carcinoma incidence

Esophageal cancer occurs as either squamous cell carcinoma (ESCC) or adenocarcinoma. ESCCs comprise almost 90% of cases worldwide, and recur with a less than 15% five-year survival rate despite available treatments. The identification of new ESCC drivers and therapeutic targets is critical for improving outcomes. Here we report that expression of the human DEK oncogene is strongly upregulated in esophageal SCC based on data in the cancer genome atlas (TCGA). DEK is a chromatin-associated protein with important roles in several nuclear processes including gene transcription, epigenetics, and DNA repair. Our previous data have utilized a murine knockout model to demonstrate that Dek expression is required for oral and esophageal SCC growth. Also, DEK overexpression in human keratinocytes, the cell of origin for SCC, was sufficient to cause hyperplasia in 3D organotypic raft cultures that mimic human skin, thus linking high DEK expression in keratinocytes to oncogenic phenotypes. However, the role of DEK over-expression in ESCC development remains unknown in human cells or genetic mouse models. To define the consequences of Dek overexpression in vivo, we generated and validated a tetracycline responsive Dek transgenic mouse model referred to as Bi-L-Dek. Dek overexpression was induced in the basal keratinocytes of stratified squamous epithelium by crossing Bi-L-Dek mice to keratin 5 tetracycline transactivator (K5-tTA) mice. Conditional transgene expression was validated in the resulting Bi-L-Dek_K5-tTA mice and was suppressed with doxycycline treatment in the tetracycline-off system. The mice were subjected to an established HNSCC and esophageal carcinogenesis protocol using the chemical carcinogen 4-nitroquinoline 1-oxide (4NQO). Dek overexpression stimulated gross esophageal tumor development, when compared to doxycycline treated control mice. Furthermore, high Dek expression caused a trend toward esophageal hyperplasia in 4NQO treated mice. Taken together, these data demonstrate that Dek overexpression in the cell of origin for SCC is sufficient to promote esophageal SCC development in vivo.

KLF4 transcriptionally activates non-canonical WNT5A to control epithelial stratification

Epithelial differentiation and stratification are essential for normal homeostasis, and disruption of these processes leads to both injury and cancer. The zinc-finger transciption factor KLF4 is a key driver of epithelial differentiation, yet the mechanisms and targets by which KLF4 controls differentiation are not well understood. Here, we define WNT5A, a non-canonical Wnt ligand implicated in epithelial differentiation, repair, and cancer, as a direct transcriptional target that is activated by KLF4 in squamous epithelial cells. Further, we demonstrate functionally that WNT5A mediates KLF4 control of epithelial differentiation and stratification, as treatment of keratinocytes with WNT5A rescues defective epithelial stratification resulting from KLF4 loss. Finally, we show that the small GTPase CDC42 is regulated by KLF4 in a WNT5A dependent manner. As such, we delineate a novel pathway for epithelial differentiation and stratification and define potential therapeutic targets for epithelial diseases.

ALDH2 modulates autophagy flux to regulate acetaldehyde-mediated toxicity thresholds

A polymorphic mutation in the acetaldehyde dehydrogenase 2 (ALDH2) gene has been epidemiologically linked to the high susceptibility to esophageal carcinogenesis for individuals with alcohol use disorders. Mice subjected to alcohol drinking show increased oxidative stress and DNA adduct formation in esophageal epithelia where Aldh2 loss augments alcohol-induced genotoxic effects; however, it remains elusive as to how esophageal epithelial cells with dysfunctional Aldh2 cope with oxidative stress related to alcohol metabolism. Here, we investigated the role of autophagy in murine esophageal epithelial cells (keratinocytes) exposed to ethanol and acetaldehyde. We find that ethanol and acetaldehyde trigger oxidative stress via mitochondrial superoxide in esophageal keratinocytes. Aldh2-deficient cells appeared to be highly susceptible to ethanol- or acetaldehyde-mediated toxicity. Alcohol dehydrogenase-mediated acetaldehyde production was implicated in ethanol-induced cell injury in Aldh2 deficient cells as ethanol-induced oxidative stress and cell death was partially inhibited by 4-methylpyrazole. Acetaldehyde activated autophagy flux in esophageal keratinocytes where Aldh2 deficiency increased dependence on autophagy to cope with ethanol-induced acetaldehyde-mediated oxidative stress. Pharmacological inhibition of autophagy flux by chloroquine stabilized p62/SQSTM1, and increased basal and acetaldehyde-mediate oxidative stress in Aldh2 deficient cells as documented in monolayer culture as well as single-cell derived three-dimensional esophageal organoids, recapitulating a physiological esophageal epithelial proliferation-differentiation gradient. Our innovative approach indicates, for the first time, that autophagy may provide cytoprotection to esophageal epithelial cells responding to oxidative stress that is induced by ethanol and its major metabolite acetaldehyde. Defining autophagymediated cytoprotection against alcohol-induced genotoxicity in the context of Aldh2 deficiency, our study provides mechanistic insights into the tumor suppressor functions of ALDH2 and autophagy in alcohol-related esophageal carcinogenesis.