HOW DOES CANCER PROGRESS?
Cancer does not develop all it once. It results from a gradual accumulation of mutations to genes that control the cell cycle over periods of time. The average cancerous cell carries six to eight different mutations. Cancer is more prevalent in the elderly because more time has passed for mutations to accumulate.
The Effect of Age on all Cancer Rates in Males and Females
FROM NON-CANCEROUS TO CANCEROUS
Any form of cancer can be traced back to a single cell that underwent a progressive series of changes to its DNA. Here is a general idea of how this happens.
1. A cell acquires mutations to both tumor suppressor and proto-oncogenes allowing it to divide unchecked.
The cell is not cancerous, but it now has the ability to divide uncontrolled, one feature of cancerous cells. (Since the cell cycle is so tightly controlled, this requires mutations to both types of cell cycle control genes.)
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Mutations to Proto-oncogenes can be compared to a gas petal on a car getting stuck in the “down” position. Proto-oncogenes promote cell division and when mutated, the cell divides more frequently that it is supposed to. |
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Mutations to tumor suppressor genes can be compared to the brakes on a car no longer functioning. Normal tumor suppressor genes inhibit cell division. Mutations to tumor suppressor genes prevents them from inhibiting cell division. |
2. Formation of a benign tumor as the mutated cell divides uncontrollable by mitotic division. (This also means all of the daughter cells within the tumor have the same mutations.)
3. Tumor cells accumulate more mutations. Cancerous cells develop within the tumor.
Having the initial mutations makes the cells more likely to develop more mutations. Accumulating mutations to the following genes results in malignant cells.
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P53 gene: normally detects errors in DNA and sends the cell down the apoptosis pathway, the mutated form does not do this and the cell becomes immortal. |
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Telomerase gene: normally, this gene is not expressed in somatic body cells preventing them from replacing their lost telomeric sequences so they must stop dividing, the mutated form codes for an enzyme that allows the telomeric sequences to be regenerated so the cell can divide forever. |
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Angiogenesis genes: activation of these genes encode proteins that stimulate the formation of new blood vessels so the tumor can obtain nutrients (these blood vessel will eventually aid in metastasis) |
www.omegagenesis.com
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Metastasis genes: activation of these genes allow cancerous cells to break apart from the tumor and migrate to other areas of the body |
4. The malignant cells of the tumor outcompete surrounding tissue for space and nutrients (due to rapid division and angiogenesis).
5. Malignant cells within the tumor break apart and spread (metastasize) to other parts of the body.
Cancer cell Moving down a Pore in Lab
http://wills4223.blogspot.com/2005_09_01_archive.html
To learn about how cancer is detected, click here.
