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BACKGROUND AND AIM: Aberrant DNA methylation has been found in various cancer types including gastric cancer, yet the genome-wide DNA methylation profile of gastric cardia cancer (GCC) remains unclear. Therefore, we aimed to profile the DNA methylation pattern of GCC and identify promising diagnostic epigenetic biomarkers. METHODS: We investigated the genome-wide DNA methylation pattern in eight pairs of GCC and adjacent normal tissues using Illumina 850K microarrays. Subsequently, bisulfite-pyrosequencing and quantitative real-time PCR were performed on eight pairs of GCC-adjacent normal tissues for validation. Finally, we performed immunohistochemistry to examine ADHFE1 expression on 126 pairs of GCC-adjacent normal samples. RESULTS: DNA methylome analysis showed global hypomethylation and local hypermethylation of promoter cytosine-phosphate-guanine (CpG) islands (CGIs) in GCC tissues compared with gastric cardia normal mucosa (P < 2.2 × 10-16 ). Differential methylation analysis identified a total of 91 723 differentially-methylated probes (DMPs), and the candidate gene with the largest average DNA methylation difference mapped to ADHFE1 (mean Δß = 0.53). Subsequently, three DMPs in the ADHFE1 promoter were validated by pyrosequencing. Notably, the mean methylation level of the three candidate DMPs (ADHFE1_cg08090772, ADHFE1_cg19283840, and ADHFE1_cg20295442) was negatively associated with ADHFE1 mRNA expression level (Spearman rho = -0.64, P = 0.01). Moreover, both mRNA (P = 0.0213) and protein (P < 0.0001) expression of ADHFE1 were significantly decreased in GCCs compared with the adjacent normal tissues. CONCLUSIONS: Our results reveal DNA methylation aberrations in GCC and that ADHFE1 gene DNA methylation contributes to the risk of GCC, thus providing novel mechanistic insights into gastric cardia cancer carcinogenesis.
Assuntos
Metilação de DNA , Neoplasias Gástricas , Humanos , Cárdia , RNA Mensageiro , Ilhas de CpG , Regulação Neoplásica da Expressão GênicaRESUMO
Background: Gastric cardia cancer (GCC) arises in the area of the stomach adjoining the esophageal-gastric junction and has unique risk factors. It was suggested that the involvement of Helicobacter pylori is associated with GCC from high-risk population. Myeloid differentiation factor 88 (MyD88) is a crucial adaptor molecule in Toll-like signaling pathway recognizing H. pylori. Its role in GCC has not been elucidated yet. In this study, our purpose is to investigate the expression and significance of MyD88 in GCC tissue. Methods: Expression of MyD88 and nuclear factor κB (NF-κB) p105/p50 and infection of H. pylori were detected by immunohistochemistry in gastric cardia tissue. The correlation of MyD88 expression to NF-κB p105/p50 expression, H. pylori infection, and clinicopathologic characteristics in gastric cardia tissue was analyzed. The involvement of MyD88 in patient prognosis was also analyzed. Results: Our data showed that the expression of MyD88 elevated from normal mucosa to inflammation (p = 0.071). The expression of MyD88 was enhanced in GCC tissues by contrast to non-malignant cardia mucosa (p = 0.025). What's more, overexpression of MyD88 was detected in intestinal-type adenocarcinoma with inflammation. Patients with high MyD88 staining revealed a better differentiation (p = 0.02). MyD88 also positively correlated with NF-κB p105/p50 expression (p = 0.012) in cancer tissue. Expression of MyD88 was increased but not significantly in biopsies with H. pylori infection compared with non-infected biopsies. Multivariate analyses revealed lymph node metastasis but not MyD88 expression was an independent predictor for patient survival. Conclusion: These findings provide pathological evidence that upregulating MyD88 and inducing inflammation might be involved in gastric cardia carcinogenesis in high-risk population. MyD88 plays a role in gastric cardia carcinogenesis with NF-κB pathway activation. Higher MyD88 expression is not a major prognostic determinant in GCC, but it may relate to the tumor cell differentiation.
RESUMO
The incidence of gastric cardia cancer (GCC) is high in China. However, the clinicopathological characteristics and the carcinogenesis of GCC are unclear. Toll-like receptor 4 (TLR4) is an important innate immunity receptor and has a role in non-GCC (NGCC). We compared the clinicopathological characteristics of GCC patients from a high-risk area in China to esophageal cancer (EC) patients. Immunohistochemistry for TLR4 was performed in 201 histological samples of normal gastric cardia mucosa (n = 11), gastric cardia inflammation (n = 87), and GCC (n = 103). We included 84 patients with EC and 99 with GCC. GCC tissue was more poorly differentiated than EC tissue and more invasive, with more histomorphologic variation. Lymph node metastasis was more frequent in GCC than in EC. The Helicobacter pylori infection rate was higher but not significantly with GCC than EC. Survival was shorter with lymph node metastasis. We found a statistically significant trend for progressive increase of TLR4 expression from normal mucosa to inflammation in GCC. GCC in this high-risk area displays clinicopathologic characteristics different from those of EC and different from those of gastroesophageal junction carcinomas in other countries, although this was not analyzed statistically. Increased TLR4 expression in gastric cardia lesions may be associated with GCC tumorigenesis.
