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Human DNA methyltransferase gene DNMT1 is regulated by the APC pathway
1Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada H3G 1Y6.
Abstract:
Epigenomic changes in DNA methylation patterns are evident in a variety of cancers, including colorectal cancer (CRC). In addition, a large proportion of CRC tumors and cell lines harbor genetic mutations in the APC/beta-catenin/TCF transcription activation pathway. While several target genes have been proposed, a causal downstream agent between APC mutation and cancer has not been fully established. Because previous work implicates DNA methyltransferase (DMNT1) as a critical point in tumorigenesis and recent studies suggest that familial CRC also exhibits epigenetic alterations, we sought to investigate whether this gene might be regulated by APC in CRC. Reconstitution of wild type APC in HT-29 CRC cell lines reduced the expression of both a reporter gene driven by the minimal DNMT1 promoter and DNMT1 mRNA that is independent of cell growth stasis. We also provide evidence for a causal role of DNMT1 in CRC by demonstrating that antisense-driven reduction of DNMT1 mRNA inhibits anchorage-independent growth, an indicator of tumorigenesis, of CRC cells. These data support future consideration of DNMT1 as a target in the treatment of CRC.
Insights
Researchers found that the APC gene regulates DNA methyltransferase 1 (DNMT1) in colorectal cancer (CRC). Reducing DNMT1 inhibits CRC cell growth, suggesting DNMT1 as a potential therapeutic target for CRC.
Area of Science:
- Oncology
- Molecular Biology
- Epigenetics
Background:
- Epigenomic DNA methylation changes are common in colorectal cancer (CRC).
- Mutations in the APC/beta-catenin/TCF pathway are frequent in CRC, but downstream effectors remain unclear.
- DNA methyltransferase 1 (DNMT1) is implicated in tumorigenesis and epigenetic alterations in familial CRC.
Purpose of the Study:
- To investigate the regulation of DNMT1 by APC in colorectal cancer.
- To establish a causal role for DNMT1 in CRC tumorigenesis.
Main Methods:
- Reconstitution of wild-type APC in HT-29 CRC cell lines.
- Reporter gene assays using the minimal DNMT1 promoter.
- Quantification of DNMT1 mRNA levels.
- Assessment of anchorage-independent growth following antisense-mediated DNMT1 reduction.
Main Results:
- Wild-type APC reconstitution decreased DNMT1 promoter activity and DNMT1 mRNA expression.
- DNMT1 reduction via antisense inhibition suppressed anchorage-independent growth of CRC cells.
- These effects were independent of cell growth stasis.
Conclusions:
- APC regulates DNMT1 expression in colorectal cancer.
- DNMT1 plays a causal role in CRC cell tumorigenesis.
- DNMT1 represents a potential therapeutic target for colorectal cancer treatment.