Location-specific epigenetic regulation of the metallothionein 3 gene in esophageal adenocarcinomas.

Abstract

BACKGROUND:

Metallothionein 3 (MT3) maintains intracellular metal homeostasis and protects against reactive oxygen species (ROS)-induced DNA damage. In this study, we investigated the epigenetic alterations and gene expression of the MT3 gene in esophageal adenocarcinomas (EACs).

METHODS AND RESULTS:

Using quantitative bisulfite pyrosequencing, we detected unique DNA methylation profiles in the MT3 promoter region. The CpG nucleotides from -372 to -306 from the transcription start site (TSS) were highly methylated in tumor (n = 64) and normal samples (n = 51), whereas CpG nucleotides closest to the TSS (-4 and +3) remained unmethylated in all normal and most tumor samples. Conversely, CpG nucleotides in two regions (from -139 to -49 and +296 to +344) were significantly hypermethylated in EACs as compared to normal samples [FDR<0.001, -log10(FDR)>3.0]. The DNA methylation levels from -127 to -8 CpG sites showed the strongest correlation with MT3 gene expression (r = -0.4, P<0.0001). Moreover, the DNA hypermethylation from -127 to -8 CpG sites significantly correlated with advanced tumor stages and lymph node metastasis (P = 0.005 and P = 0.0313, respectively). The ChIP analysis demonstrated a more repressive histone modification (H3K9me2) and less active histone modifications (H3K4me2, H3K9ace) in OE33 cells than in FLO-1 cells; concordant with the presence of higher DNA methylation levels and silencing of MT3 expression in OE33 as compared to FLO-1 cells. Treatment of OE33 cells with 5-Aza-deoxycitidine restored MT3 expression with demethylation of its promoter region and reversal of the histone modifications towards active histone marks.

CONCLUSION:

In summary, EACs are characterized by frequent epigenetic silencing of MT3. The choice of specific regions in the CpG island is a critical step in determining the functional role and prognostic value of DNA methylation in cancer cells.

• Authors: Dunfa Peng, Tian-Ling Hu, Aixiang Jiang, Mary Kay Washington, Christopher A Moskaluk, Regine Schneider-Stock, Wael El-Rifai
• Journal: PloS one (PLoS One) Vol. 6 Issue 7 Pg. e22009 ( 2011) ISSN: 1932-6203 [Electronic] United States
• PMID: 21818286 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Histones
• Metallothionein 3
• Nerve Tissue Proteins
• Repressor Proteins
• Azacitidine

Topics

• Adenocarcinoma (genetics, pathology)
• Adult
• Aged
• Aged, 80 and over
• Azacitidine (pharmacology)
• Cell Line, Tumor
• CpG Islands (genetics)
• DNA Methylation (drug effects)
• Down-Regulation (drug effects, genetics)
• Epigenesis, Genetic (drug effects)
• Esophageal Neoplasms (genetics, pathology)
• Gene Expression Regulation, Neoplastic (drug effects)
• Genes, Neoplasm (genetics)
• Histones (metabolism)
• Humans
• Lymphatic Metastasis (genetics)
• Metallothionein 3
• Middle Aged
• Neoplasm Staging
• Nerve Tissue Proteins (genetics)
• Promoter Regions, Genetic (genetics)
• Protein Processing, Post-Translational (drug effects)
• Repressor Proteins (metabolism)