Silencing of interferon regulatory factor gene 6 in melanoma.

Yoshimasa Nobeyama,Hidemi Nakagawa

doi:10.1371/journal.pone.0184444

Yoshimasa Nobeyama, Hidemi Nakagawa

Open Access

https://doi.org/10.1371/journal.pone.0184444

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Journal: PloS one	Publication Date: Sep 6, 2017
Citations: 8	License type: CC BY 4.0

Affiliation: Jikei University School of Medicine

Abstract

BackgroundMethylation of a CpG island (CGI; a dense cluster of CpGs) located in the 5' region of a gene suppresses transcription of that gene. Interferon regulatory factor 6 (IRF6) is associated with the expression of interferon, which is used as an effective adjuvant therapy for melanoma, and is regarded as a tumor suppressor. However, little is known about the methylation status of the IRF6 gene in melanoma.ObjectiveThe purpose was to determine the methylation status of the CGI located in the 5' region of IRF6 (5' IRF6 CGI) in melanoma.MethodsQuantitative real-time methylation-specific PCR (RT-MSP) and bisulfite sequencing were performed to examine IRF6 gene methylation status. Quantitative real-time reverse transcription-PCR (RT-PCR) was performed to examine IRF6 expression.ResultsThe methylation level of the 5' IRF6 CGI was completely inversely correlated with cell sensitivity to interferon-β in eight examined melanoma cell lines. These methylation levels were high in the melanoma cell lines with suppression of IRF6 expression and were low in the cell lines with IRF6 expression. The methylation levels of the 5' IRF6 CGI ranged widely from 0.0% to 65.4% in 21 clinical melanoma samples but showed a narrow range of low levels between 0.0% to 7.2% in 24 clinical melanocytic nevus samples. These methylation levels were not associated with clinical parameters except for melanoma subtypes.ConclusionIRF6 is aberrantly silenced by DNA methylation of the 5' IRF6 CGI in melanoma. The methylation status of IRF6 is potentially associated with the sensitivity of melanoma to interferon.

Highlights

DNA methylation is a DNA modification resulting from the covalent binding of a methyl group to a DNA nucleotide such as the cytosine of a CpG dinucleotide, where a 5’ cytosine is adjacent to a 3’ guanine [1,2]
The methylation level of the 5’ Interferon regulatory factor 6 (IRF6) CpG island (CGI) was completely inversely correlated with cell sensitivity to interferon-β in eight examined melanoma cell lines
IRF6 is aberrantly silenced by DNA methylation of the 5’ IRF6 CGI in melanoma

Summary

Introduction

DNA methylation is a DNA modification resulting from the covalent binding of a methyl group to a DNA nucleotide such as the cytosine of a CpG dinucleotide, where a 5’ cytosine is adjacent to a 3’ guanine [1,2]. CpG islands (CGIs) are dense clusters of CpGs that are often located in the 5’ regions of genes. Methylation of a CGI located in the 5’ region of a gene suppresses transcription of that gene [4]. The CGIs located in the 5’ regions of most genes are unmethylated, resulting in the expression of those genes [4]. In malignant cells, a number of CGIs located in the 5’ regions of genes, including tumor-suppressor genes, may be methylated, resulting in the suppression of the transcription of those genes [4,5]. Methylation of a CpG island (CGI; a dense cluster of CpGs) located in the 5’ region of a gene suppresses transcription of that gene.

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Conclusion