Epigenetic regulation (DNA methylation, histone modifications) of the 11p15 mucin genes (MUC2, MUC5AC, MUC5B, MUC6) in epithelial cancer cells

Abstract

The human genes MUC2, MUC5AC, MUC5B and MUC6 are clustered on chromosome 11 and encode large secreted gel-forming mucins. The frequent occurrence of their silencing in cancers and the GC-rich structure of their promoters led us to study the influence of epigenetics on their expression. Pre-and post-confluent cells were treated with demethylating agent 5-aza-2 0 -deoxycytidine and histone deacetylase (HDAC) inhibitor, trichostatin A. Mapping of methylated cytosines was performed by bisulfite-treated genomic DNA sequencing. Histone modification status at the promoters was assessed by chromatin immunoprecipitation assays. Our results indicate that MUC2 was regulated by site-specific DNA methylation associated with establishment of a repressive histone code, whereas hypermethylation of MUC5B promoter was the major mechanism responsible for its silencing. DNA methyltransferase 1 was identified by small interfering RNA approach as a regulator of MUC2 and MUC5B endogenous expression that was potentiated by HDAC2. MUC2 and MUC5B epigenetic regulation was cellspecific, depended on cell differentiation status and inhibited their activation by Sp1. The expression of MUC5AC was rarely influenced by epigenetic mechanisms and methylation of MUC6 promoter was not correlated to its silencing. In conclusion, this study demonstrates the important role for methylation and/or histone modifications in regulating the 11p15 mucin genes in epithelial cancer cells.

Expression of MUC2, MUC5AC, MUC5B, and MUC6 mucins in colorectal cancers and their association with the CpG island methylator phenotype

“…Several studies have examined the expression of various mucin genes in relation to the nature and extent of CpG island methylation, and have found that MUC2 and MUC5B in particular, show strong correlations between promoter methylation and suppression of mucin protein synthesis. 23,[54][55][56][57] There is currently little or no evidence of methylation-induced silencing of either MUC5AC or MUC6. 23 Furthermore, MUC17, a transmembrane mucin gene, is regulated by promoter CpG island methylation and histone H3-K9 acetylation in pancreatic ductal adenocarcinomas, where promoter hypomethylation is associated with MUC17 expression.…”

“…23,[54][55][56][57] There is currently little or no evidence of methylation-induced silencing of either MUC5AC or MUC6. 23 Furthermore, MUC17, a transmembrane mucin gene, is regulated by promoter CpG island methylation and histone H3-K9 acetylation in pancreatic ductal adenocarcinomas, where promoter hypomethylation is associated with MUC17 expression. 58 In this study, we have shown increased expression of MUC proteins in CIMPpositive colorectal cancers, which suggests the counter intuitive finding of increased protein expression in an environment that methylates (and silences) gene promoters.…”

“…[18][19][20][21] CIMP colorectal cancers also exhibit significant mucinous differentiation, suggesting that one or more gel-forming mucins are overexpressed in CIMP. Several regulatory mechanisms governing mucin gene expression have been demonstrated, including promoter CpG island methylation 22,23 and activation of the EGFR-RAS-RAF signal transduction pathway. 24 In addition, the regulation of mucin gene expression by various transcription factors such as Sp1, AP-1, and CDX2 has been explored in a range of tissues (reviewed by Andrianifahanana et al 25 ).…”

GLI1 facilitates the migration and invasion of pancreatic cancer cells through MUC5AC-mediated attenuation of E-cadherin

“…Indeed, Vincent et al reported that MUC2 and MUC5B expressions were epigenetically regulated in gastrointestinal cancer cells and in PDA cells. They also showed that MUC5AC expression was rarely influenced by epigenetic mechanisms (Vincent et al, 2007); however, the possibility remains that MUC5AC is epigenetically silenced in other cell types, such as those previously used for GLI1 target gene identification.…”

218 The Regulation of the Intestinal Mucin MUC2 Expression By Short Chain Fatty Acids: Implications for Epithelial Protection

“…This bivalent profile has already been described for embryonic stem cell genes as well as DNA-hypermethylated genes which were reexpressed by demethylation [40]. We previously showed that MUC2 is regulated by a complex combination of DNA (de)methylation and establishment of a (de)repressive histone code [41]. The changes of global epigenetic profile stated at MUC2 promoter may thus be partly responsible for the increase in MUC2 expression level induced by low concentration of butyrate.…”