Abstract
Hypermethylation associated silencing of the CpG islands of tumor suppressor genes is a common hallmark of human cancer. Here we report a functional search for hypermethylated CpG islands using the colorectal cancer cell line HCT-116, in which two major DNA methyltransferases, DNMT1 and DNMT3b, have been genetically disrupted (DKO cells). Using two molecular screenings for differentially methylated loci [differential methylation hybridization (DMH) and amplification of inter-methylated sites (AIMS)], we found that DKO cells, but not the single DNMT1 or DNMT3b knockouts, have a massive loss of hypermethylated CpG islands that induces the re-activation of the contiguous genes. We have characterized a substantial number of these CpG island associated genes with potentially important roles in tumorigenesis, such as the cadherin member FAT, or the homeobox genes LMX-1 and DUX-4. For other genes whose role in transformation has not been characterized, such as the calcium channel alpha1I or the thromboxane A2 receptor, their re-introduction in DKO cells inhibited colony formation. Thus, our results demonstrate the role of DNMT1 and DNMT3b in CpG island methylation associated silencing and the usefulness of genetic disruption strategies in searching for new hypermethylated loci.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Cadherins / genetics
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Cadherins / metabolism
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Calcium Channels / genetics
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Calcium Channels / metabolism
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Cell Transformation, Neoplastic
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Colonic Neoplasms / enzymology
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Colonic Neoplasms / genetics*
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Colony-Forming Units Assay
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CpG Islands / genetics
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DNA (Cytosine-5-)-Methyltransferase 1
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DNA (Cytosine-5-)-Methyltransferases / deficiency*
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DNA (Cytosine-5-)-Methyltransferases / genetics
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DNA Methylation
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DNA Methyltransferase 3B
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DNA, Neoplasm
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Epigenesis, Genetic / genetics*
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Female
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Gene Expression Regulation, Neoplastic
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Gene Silencing*
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Gene Targeting
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Genes, Tumor Suppressor*
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Homeodomain Proteins / genetics
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Homeodomain Proteins / metabolism
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Humans
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LIM-Homeodomain Proteins
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Male
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Nucleic Acid Hybridization
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Promoter Regions, Genetic / genetics
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
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Receptors, Thromboxane A2, Prostaglandin H2 / genetics
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Receptors, Thromboxane A2, Prostaglandin H2 / metabolism
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Transcription Factors
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Tumor Cells, Cultured
Substances
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CACNA2D1 protein, human
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Cadherins
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Calcium Channels
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DNA, Neoplasm
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DUX1 protein, human
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FAT1 protein, human
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Homeodomain Proteins
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LIM-Homeodomain Proteins
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LMX1A protein, human
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RNA, Messenger
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Receptors, Thromboxane A2, Prostaglandin H2
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Transcription Factors
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DNA (Cytosine-5-)-Methyltransferase 1
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DNA (Cytosine-5-)-Methyltransferases
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DNMT1 protein, human