Methylation of CLDN6, FBN2, RBP1, RBP4, TFPI2, and TMEFF2 in esophageal squamous cell carcinoma

In the development and progression of cancer, tumor suppressor genes may be silenced by mechanisms such as methylation. Thus the discovery of new genes silenced by methylation may uncover new tumor suppressor genes, and improve our understanding of cancer biology. In this study we investigated the methylation of 19 genes in esophageal squamous cell carcinoma. Methylation was measured in 10 of these genes in esophageal squamous cell carcinoma cell lines: CDH13, CLDN6, C16orf62, FBN2, FNBP1, ID4, RBP1, RBP4, TFPI2 and TMEFF2. To determine if there was a correlation between DNA methylation and gene silencing, each cell line was cultured with or without the demethylating drug 5-aza-2'-deoxycytidine (aza-dC). For 6 genes (CLDN6, FBN2, RBP1, RBP4, TFPI2 and TMEFF2) there was an association between reduction of methylation and increase in mRNA expression in the demethylated cell lines. The frequency of the methylation of these 6 genes in esophageal squamous cell carcinoma resection specimens was also investigated. All 6 genes showed more frequent methylation in the tumor than the matched proximal resection margin of uninvolved esophagus. There was a significant difference in the frequency of methylation and in the extent of the methylation between the cancer and the margin tissues for CLDN6, FBN2, TFPI2 and TMEFF2 (P=0.0007, P=0.0048 P=0.0002 and P<0.0001, respectively). This is the first report of gene silencing by methylation of CLDN6, FBN2, RBP4, TFPI2 and TMEFF2 in esophageal squamous cell carcinoma.

Similarity of aberrant DNA methylation in Barrett's esophagus and esophageal adenocarcinoma

Background

Barrett's esophagus (BE) is the metaplastic replacement of squamous with columnar epithelium in the esophagus, as a result of reflux. It is the major risk factor for the development of esophageal adenocarcinoma (EAC). Methylation of CpG dinucleotides of normally unmethylated genes is associated with silencing of their expression, and is common in EAC. This study was designed to determine at what stage, in the progression from BE to EAC, methylation of key genes occurs.

Results

We examined nine genes (APC, CDKN2A, ID4, MGMT, RBP1, RUNX3, SFRP1, TIMP3, and TMEFF2), frequently methylated in multiple cancer types, in a panel of squamous (19 biopsies from patients without BE or EAC, 16 from patients with BE, 21 from patients with EAC), BE (40 metaplastic, seven high grade dysplastic) and 37 EAC tissues. The methylation frequency, the percentage of samples that had any extent of methylation, for each of the nine genes in the EAC (95%, 59%, 76%, 57%, 70%, 73%, 95%, 74% and 83% respectively) was significantly higher than in any of the squamous groups. The methylation frequency for each of the nine genes in the metaplastic BE (95%, 28%, 78%, 48%, 58%, 48%, 93%, 88% and 75% respectively) was significantly higher than in the squamous samples except for CDKN2A and RBP1. The methylation frequency did not differ between BE and EAC samples, except for CDKN2A and RUNX3 which were significantly higher in EAC. The methylation extent was an estimate of both the number of methylated alleles and the density of methylation on these alleles. This was significantly greater in EAC than in metaplastic BE for all genes except APC, MGMT and TIMP3. There was no significant difference in methylation extent for any gene between high grade dysplastic BE and EAC.

Conclusion

We found significant methylation in metaplastic BE, which for seven of the nine genes studied did not differ in frequency from that found in EAC. This is also the first report of gene silencing by methylation of ID4 in BE or EAC. This study suggests that metaplastic BE is a highly abnormal tissue, more similar to cancer tissue than to normal epithelium.

Methylation of TIMP3 in esophageal squamous cell carcinoma

AIM: To measure the frequency of DNA methylation of the tissue inhibitor of metalloproteinase 3 (TIMP3) promoter and relate this to any change of gene expression in esophageal squamous cell carcinoma in patients from a region of high incidence in China.

METHODS: Cancer cell lines were treated with or without the demethylating reagent 5-aza-2’-deoxycytidine. Methylation of the TIMP3 promoter was assessed in three regions by melt curve analysis and its expression was assessed by real-time RT-PCR. Tumors and proximal resection margins were obtained from 64 patients with esophageal squamous cell carcinoma from a region of high incidence in China. Methylation was assessed by melt curve analysis and expression by immunohistochemistry.

RESULTS: Methylation in one of the three promoter regions assessed correlated with gene silencing in esophageal cell lines. A degree of methylation of TIMP3 was found in only four esophageal squamous cell carcinomas, and partial loss of TIMP3 protein expression in just one.

CONCLUSION: Methylation and loss of expression of TIMP3 occurs infrequently in esophageal squamous cell carcinoma in a region of high incidence in China.

Metallothionien 3 expression is frequently down-regulated in oesophageal squamous cell carcinoma by DNA methylation

Background

Metallothionein 3 (MT3) inhibits growth in a variety of cell types. We measured MT3 gene expression by RT-PCR, and DNA methylation in the MT3 promoter by combined bisulphite restriction analysis, in four oesophageal cancer cell lines and the resected oesophagus from 64 patients with oesophageal squamous cell carcinoma (SCC).

Results

MT3 expression was not detected in one of the four oesophageal cell lines. The MT3 promoter was methylated in all of the oesophageal cell lines, but the degree of methylation was greater in the non-expressing cell line. After treatment with 5-aza-2'-deoxycytidine there was a reduction in the degree of methylation, and an increase in MT3 expression, in each of the cell lines (p < 0.01). Methylation was detected in 52% (33 of 64) of primary SCC and 3% (2 of 62) of histologically normal resection margins. MT3 expression was measured in 29 tumours, 17 of which had methylation of MT3. The expression of MT3 was significantly less in the methylated tumours compared to either the unmethylated tumours (p = 0.03), or the matched margin (p = 0.0005). There was not a significant difference in MT3 expression between the tumour and the margin from patients with unmethylated tumour. No correlations were observed between methylation of MT3 and survival time, patient age, gender, smoking or drinking history, tumour stage, volume, or lymph node involvement.

Conclusion

We conclude that MT3 expression is frequently down-regulated in oesophageal SCC, by DNA methylation, but that this is not a prognostic indicator.

Assessment of an electronic voting system within the tutorial setting: a randomised controlled trial [ISRCTN54535861]

BACKGROUND

Electronic voting systems have been used in various educational settings with little measurement of the educational impact on students. The goal of this study was to measure the effects of the inclusion of an electronic voting system within a small group tutorial.

METHOD

A prospective randomised controlled trial was run at the Royal Adelaide Hospital, a teaching hospital in Adelaide, Australia. 102 students in their first clinical year of medical school participated in the study where an electronic voting system was introduced as a teaching aid into a standard tutorial. Long-term retention of knowledge and understanding of the topics discussed in the tutorials was measured and student response to the introduction of the electronic voting system was assessed.

RESULTS

Students using the electronic voting system had improved long-term retention of understanding of material taught in the tutorial. Students had a positive response to the use of this teaching aid.

CONCLUSION

Electronic voting systems can provide a stimulating learning environment for students and in a small group tutorial may improve educational outcomes.