By Doug Bintzler
The epigenome is an extension of the genome. Epigenetic mechanisms cause specific genes in certain cells to become inaccessible, thus causing these genes to be silenced. Cells become increasingly specialized, or differentiated, into a specialized cell during development. For example, liver cells and lung cells carry the same DNA. However, only certain genes are active in liver cells while other genes are active in lung cells. This is the result of cell differentiation. What typically happens during cellular development is regions of DNA become methylated and wrap around protein molecules called histones. Genes bound to histones are silenced. This determines how a cell will differentiate.
Changes in the Epigenome
Environmental influences can impact the epigenome. Ultraviolet light and chemicals associated with tobacco are two examples. These influences can affect factors in the epigenome as well as cause mutation. Mutation has often been thought of as the primary causative agent of many cancers. However, mutation in the region of a silenced gene should not cause cancer. A silenced gene does nothing so it is as if it is not even there. Changes to factors in the epigenome can loosen the DNA bound to histones. This can cause the silenced genes to become active. Cells that loose this control may go into a stage of rapid division, eventually developing into cancer.
New Treatments for Damage Caused by Changes in the Epigenome
Typical treatments for patients with cancer include radiation therapy and chemotherapy. Although these traditional forms of treatment are sometimes successful, cancer remission does not always happen. Plus, these treatments attack both cancerous and healthy cells. This makes them very taxing on the recipient with no guarantee of remission. In many cases these therapies are the best means of treatment. Fortunately the treatments and how they are administered are continually improving.
The problem with genetic mutations that cause cancer is that the mutation is not reversible. People who survive cancer may still carry the genetic cause. If this is the case, then they may pass the cause on to the next generation. This is one reason doctors evaluate the family's medical history. Unlike mutation, epigenetic change is reversible. Some forms of treatment currently in clinical trials use drugs to repair cancerous cells instead of destroying them. Unfortunately, much like radiation and chemotherapy, these drugs are known to cause damage to healthy cells when high doses are used. However, some success has been seen when they are administered in low dosages. Azacitidine and decitabine are currently being used in studies at John Hopkins. Studies being conducted at the University of Texas MD Anderson Cancer Center are using similar treatments with Leukemia patients with varying degrees of success.
Epigenetic research is a field that helps science understand more about the complex relationship between DNA, histones and cell differentiation. It provides a new direction for the potential treatment of patients afflicted with cancer.
Doug Bintzler is the Laboratory Director for DNA Analysis, LLC. They provide automated DNA sequencing and fragment analysis services. Reprints of this article and other education resources are available at http://www.agctsequencing.com
The epigenome is an extension of the genome. Epigenetic mechanisms cause specific genes in certain cells to become inaccessible, thus causing these genes to be silenced. Cells become increasingly specialized, or differentiated, into a specialized cell during development. For example, liver cells and lung cells carry the same DNA. However, only certain genes are active in liver cells while other genes are active in lung cells. This is the result of cell differentiation. What typically happens during cellular development is regions of DNA become methylated and wrap around protein molecules called histones. Genes bound to histones are silenced. This determines how a cell will differentiate.
Changes in the Epigenome
Environmental influences can impact the epigenome. Ultraviolet light and chemicals associated with tobacco are two examples. These influences can affect factors in the epigenome as well as cause mutation. Mutation has often been thought of as the primary causative agent of many cancers. However, mutation in the region of a silenced gene should not cause cancer. A silenced gene does nothing so it is as if it is not even there. Changes to factors in the epigenome can loosen the DNA bound to histones. This can cause the silenced genes to become active. Cells that loose this control may go into a stage of rapid division, eventually developing into cancer.
New Treatments for Damage Caused by Changes in the Epigenome
Typical treatments for patients with cancer include radiation therapy and chemotherapy. Although these traditional forms of treatment are sometimes successful, cancer remission does not always happen. Plus, these treatments attack both cancerous and healthy cells. This makes them very taxing on the recipient with no guarantee of remission. In many cases these therapies are the best means of treatment. Fortunately the treatments and how they are administered are continually improving.
The problem with genetic mutations that cause cancer is that the mutation is not reversible. People who survive cancer may still carry the genetic cause. If this is the case, then they may pass the cause on to the next generation. This is one reason doctors evaluate the family's medical history. Unlike mutation, epigenetic change is reversible. Some forms of treatment currently in clinical trials use drugs to repair cancerous cells instead of destroying them. Unfortunately, much like radiation and chemotherapy, these drugs are known to cause damage to healthy cells when high doses are used. However, some success has been seen when they are administered in low dosages. Azacitidine and decitabine are currently being used in studies at John Hopkins. Studies being conducted at the University of Texas MD Anderson Cancer Center are using similar treatments with Leukemia patients with varying degrees of success.
Epigenetic research is a field that helps science understand more about the complex relationship between DNA, histones and cell differentiation. It provides a new direction for the potential treatment of patients afflicted with cancer.
Doug Bintzler is the Laboratory Director for DNA Analysis, LLC. They provide automated DNA sequencing and fragment analysis services. Reprints of this article and other education resources are available at http://www.agctsequencing.com
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