Apoptosis of Tumor Cells
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Apoptosis Overview
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Apoptosis is also known as programmed cell death. Apoptosis can occur when a cell becomes too damaged to survive but is still able to die in a controlled way (to prevent inflammation and the release of proteins that could damage other cells). It can also occur in healthy cells in accordance with certain chemical signals. One example of this form of apoptosis is in the disappearance of the skin cells that initially connect human fingers together to form "webbed" hands, or how a tadpole's tail disappears when it turns into a frog. Apoptosis is generally started by certain chemical cues, among them the presence of a protein called cytochrome c, and then uses the action of specific proteins called caspases. Each cell has a number of chemical signals that can either promote or inhibit the process of apoptosis.
Apoptosis and Cancer
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One of the things that will trigger apoptosis is genetic mutations. Because cells become cancerous due to multiple genetic mutations, cancerous cells have to be resistant to this apoptotic trigger. Another stimulus that can trigger apoptosis is changes to the cell or unusual cell growth. Because these are things that happen to cancer cells, in order to survive and grow into tumors, cancer cells must be naturally resistant to apoptosis. Cancer cells can become resistant to apoptosis by activating proteins that protect the cell from apoptosis, by mutating proteins that cause apoptosis or by developing the ability to ignore apoptotic signals.
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Examples
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According to CR magazine, in the early 1990s researchers discovered one way in which cancer cells can evade apoptosis. They discovered that one form of lymphoma, which is a cancer of the immune system, often develops a genetic abnormality that causes a protein called Bcl-2 to become overactive. This protects the cell from apoptosis. Another study, published by Dr. Yang in the Journal of Cancer Research in 2003 found that some kinds of lung cancer are able to suppress something called the apoptosome, which is the group of proteins which carries out apoptosis.
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