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Cancer epigenetics comes of age
1Department of Biochemistry and Molecular Biology, University of Southern California School of Medicine, The Norris Comprehensive Cancer Center, Los Angeles 90033, USA. jones_p@froggy.hsc.usc.edu
Abstract:
The discovery of numerous hypermethylated promoters of tumour-suppressor genes, along with a better understanding of gene-silencing mechanisms, has moved DNA methylation from obscurity to recognition as an alternative mechanism of tumour-suppressor inactivation in cancer. Epigenetic events can also facilitate genetic damage, as illustrated by the increased mutagenicity of 5-methylcytosine and the silencing of the MLH1 mismatch repair gene by DNA methylation in colorectal tumours. We review here current mechanistic understanding of the role of DNA methylation in malignant transformation, and suggest Knudson's two-hit hypothesis should now be expanded to include epigenetic mechanisms of gene inactivation.
Insights
DNA methylation, a key epigenetic mechanism, silences tumour-suppressor genes in cancer. This process, involving hypermethylated promoters, contributes to malignant transformation and genetic damage, expanding cancer gene inactivation models.
Area of Science:
- Oncology
- Epigenetics
- Molecular Biology
Background:
- DNA methylation is increasingly recognized as a significant mechanism in cancer development.
- Hypermethylation of tumour-suppressor gene promoters leads to gene silencing.
- Epigenetic alterations can promote genetic instability and cancer progression.
Purpose of the Study:
- To review the current understanding of DNA methylation's role in cancer.
- To highlight how DNA methylation contributes to tumour-suppressor gene inactivation.
- To propose an expansion of existing cancer models to include epigenetic mechanisms.
Main Methods:
- Literature review of mechanistic studies on DNA methylation in cancer.
- Analysis of the link between DNA methylation, gene silencing, and genetic damage.
- Synthesis of current knowledge to inform cancer aetiology models.
Main Results:
- Numerous tumour-suppressor genes are inactivated via promoter hypermethylation.
- DNA methylation can increase mutagenicity and silence critical DNA repair genes (e.g., MLH1).
- Epigenetic events are integral to malignant transformation alongside genetic alterations.
Conclusions:
- DNA methylation is a crucial alternative pathway for tumour-suppressor inactivation in cancer.
- Epigenetic mechanisms, including DNA methylation, play a direct role in facilitating genetic damage.
- Knudson's two-hit hypothesis should be updated to incorporate epigenetic gene inactivation in cancer models.