Clinical and biological significance of a - 73A > C variation in the CDH1 promoter of patients with sporadic gastric carcinoma

Epigenetic reprogramming in gastrointestinal cancer: biology and translational perspectives

Gastrointestinal tumors, the second leading cause of human mortality, are characterized by their association with inflammation. Currently, progress in the early diagnosis and effective treatment of gastrointestinal tumors is limited. Recent whole-genome analyses have underscored their profound heterogeneity and extensive genetic and epigenetic reprogramming. Epigenetic reprogramming pertains to dynamic and hereditable alterations in epigenetic patterns, devoid of concurrent modifications in the underlying DNA sequence. Common epigenetic modifications encompass DNA methylation, histone modifications, noncoding RNA, RNA modifications, and chromatin remodeling. These modifications possess the potential to invoke or suppress a multitude of genes associated with cancer, thereby governing the establishment of chromatin configurations characterized by diverse levels of accessibility. This intricate interplay assumes a pivotal and indispensable role in governing the commencement and advancement of gastrointestinal cancer. This article focuses on the impact of epigenetic reprogramming in the initiation and progression of gastric cancer, esophageal cancer, and colorectal cancer, as well as other uncommon gastrointestinal tumors. We elucidate the epigenetic landscape of gastrointestinal tumors, encompassing DNA methylation, histone modifications, chromatin remodeling, and their interrelationships. Besides, this review summarizes the potential diagnostic, therapeutic, and prognostic targets in epigenetic reprogramming, with the aim of assisting clinical treatment strategies.

Promotion of rs3746804 (p. L267P) polymorphism to intracellular SLC52A3a trafficking and riboflavin transportation in esophageal cancer cells

Riboflavin is an essential micronutrient for normal cellular growth and function. Lack of dietary riboflavin is associated with an increased risk for esophageal squamous cell carcinoma (ESCC). Previous studies have identified that the human riboflavin transporter SLC52A3a isoform (encoded by SLC52A3) plays a prominent role in esophageal cancer cell riboflavin transportation. Furthermore, SLC52A3 gene single nucleotide polymorphisms rs3746804 (T>C, L267P) and rs3746803 (C >T, T278M) are associated with ESCC risk. However, whether SLC52A3a (p.L267P) and (p.T278M) act in riboflavin transportation in esophageal cancer cell remains inconclusive. Here, we constructed the full-length SLC52A3a protein fused to green fluorescent protein (GFP-SLC52A3a-WT and mutants L267P, T278M, and L267P/T278M). It was confirmed by immunofluorescence-based confocal microscopy that SLC52A3a-WT, L267P, T278M, and L267P/T278M expressed in cell membrane, as well as in a variety of intracellular punctate structures. The live cell confocal imaging showed that SLC52A3a-L267P and L267P/T278M increased the intracellular trafficking of SLC52A3a in ESCC cells. Fluorescence recovery after photobleaching of GFP-tagged SLC52A3a meant that intracellular trafficking of SLC52A3a-L267P and L267P/T278M was rapid dynamics process, leading to its stronger ability to transport riboflavin. Taken together, the above results indicated that the rs3746804 (p.L267P) polymorphism promoted intracellular trafficking of SLC52A3a and riboflavin transportation in ESCC cells.

Genetic variants in the regulation region of TLR4 reduce the gastric cancer susceptibility

Gastric cancer (GC) is one of the most common cancers diagnosed in China. It has been suggested that the genetic polymorphisms of Toll-like receptors (TLRs) might be in close relation to tumorigenesis and development of gastric cancer. In this study, we performed a case-control study to investigate the genetic polymorphisms of TLR3, 4, 5, 7 with the genetic susceptibility of gastric cancer. TLRs gene polymorphisms in 471 gastric cancer (GC) patients and 471 healthy controls were analyzed by polymerase chain reaction-restrictive fragment length polymorphism (PCR-RFLP) analysis or TaqMan assays. Odds ratio (OR) and its 95% confidence interval (95%CI) were used to evaluate the association of TLR4 variants with the GC risk via unconditional logistic regression. Our results suggested that variant genotypes of TLR4 rs7869402 (OR = 0.61, 95%CI = 0.40-0.92, P = 0.02) and TLR4 rs7873784 (OR = 0.17, 95%CI = 0.09-0.33, P < 0.01) gene polymorphisms reduced the risk of GC. Stratified analysis showed that rs7869402 T-containing genotype significantly decreased the susceptibility of GC among females (OR = 0.38, 95%CI = 0.16-0.91, P = 0.03), older subjects (OR = 0.48, 95%CI = 0.26-0.87, P = 0.02), non-smokers (OR = 0.41, 95%CI = 0.23-0.71, P < 0.01) and non-drinkers (OR = 0.58, 95%CI = 0.30-0.78, P < 0.01). In case of rs7873784 polymorphism, C-containing genotype reduced the risk of GC among males (OR = 0.08, 95%CI = 0.03-0.21, P < 0.01), but not among females (OR = 0.53, 95%CI = 0.22-1.27, P = 0.15). As to the other four SNPs (TLR3 rs5743303, TLR4 rs1927914, TLR5 rs1640816 and TLR7 rs3853839), no significant correlations were found to be related to the risk of gastric carcinoma. Our research demonstrated the significance of TLRs polymorphisms in decreasing the risk of GC.

DNA Methylation and SNPs in VCX are Correlated with Sex Differences in the Response to Chronic Hepatitis B

The study was conducted to explore the mechanisms of sex differences in the response to chronic hepatitis B (CHB) in terms of DNA methylation, SNP genotype, and gene expression. Genomic DNA was isolated from peripheral blood mononuclear cells (PBMCs) of CHB patients and healthy controls and evaluated using the Human Methylation 450 K Assay. The DNA methylation level at hg37 chromosome (CHR) X: 7810800 was further validated using pyrosequencing. SNP genotypes, VCX mRNA expression of PBMCs, and plasma VCX protein concentration were further examined using SNaPshot, RT-qPCR, and Western blot, respectively. Results showed that a total of 5529 CpG loci were differentially methylated between male and female CHB patients. DNA methylation level and CC + CT frequency at CHR X: 7810800, VCX mRNA expression of PBMCs, and plasma VCX protein concentration were higher in female than in male CHB patients. The CHR X: 7810800 locus was hypermethylated in CHB patients with CC + CT genotypes in comparison with those with the TT genotype. In cases of CC + CT genotypes, VCX mRNA expression was negatively correlated with the DNA methylation level. CHB patients with higher levels of HBV DNA, AST, and GGT or higher GPRI scores exhibited lower VCX expression. In conclusion, SNPs and DNA methylation at the CHR X: 7810800 locus cooperatively regulate VCX expression in CHB. The upregulated VCX expression in female CHB patients might represent a mechanism of protection from more severe liver dysfunction and extensive fibrosis, as observed in male CHB patients.

CDH1 somatic alterations in Mexican patients with diffuse and mixed sporadic gastric cancer

BACKGROUND

Diffuse gastric cancer (DGC) is associated with the reduction or absence of the expression of the cell adhesion protein E-cadherin (encoded by the CDH1 gene). Molecular characteristics are less well described for mixed gastric cancer (MGC). The main somatic alterations that have been described in the CDH1 gene are mutations, loss of heterozygosity (LOH) and promoter methylation. The aim was to analyze CDH1 somatic alterations in Mexican patients with diffuse and mixed gastric cancer.

METHODS

We searched for mutations in the CDH1 gene in tumor DNA from DGC (n = 13) and MGC (n = 7) patients by next generation sequencing (NGS). Validation of findings was performed using Sanger sequencing. LOH was analyzed using dinucleotide repeat markers surrounding the CDH1 gene, and methylation was investigated by DNA bisulfite conversion and sequencing. E-cadherin protein deficiency was analyzed by immunohistochemistry.

RESULTS

Seventeen point variants were identified by NGS, 13 of them were validated by Sanger sequencing. Only 1/13 had not been previously reported (c.-137C > A), and 12/13 were already reported as polymorphisms. Two DGC cases presented LOH at the locus 16q22.1 (13.3%). CDH1 promoter methylation was positive in (7/11) 63.6% and (4/6) 66.6% of the cases with DGC and MGC, respectively. E-cadherin protein deficiency was observed in 58.3% of DGC cases while 100% in MGC cases.

CONCLUSIONS

While no pathogenic somatic mutations were found that could explain the diffuse histology of gastric cancer in DGC and MGC, methylation was the most common somatic inactivation event of the CDH1 gene, and LOH was rare. The previously unreported c.-137C > A variant modify the CDH1 gene expression since it alters the binding sites for transcription factors.