Cancer

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What is it?

A cancer is an uncontrolled proliferation of cells.
See Cancer Cells in Culture for other properties of cancer cells.

Cancer cells contain several (6–8) mutated genes. These almost always include:

Progression to Cancer

What probably happens is:

Stem cells are cells that divide to form

There is increasing evidence that most of the cells in a cancer are not able to proliferate out-of-control (and to metastasize). Only those members of the clone that retain their stem-cell-like properties can do so.

Colon Cancer: An Example

Colon cancer: Examination of the cells at the earliest, polyp, stage, reveals that they contain one or two mutations associated with cancer. Frequently these include The cells in the later stages of the disease show additional types of damage such as deletions of p53 and another tumor-suppressor gene.

Note that each of the mutations shown probably occurs in one cell of the type affected. This cell then develops into the next stage of the progression. The mutations do not necessarily occur in the order shown, although they often do.

A similar stepwise genetic progression occurs in

Cancers become more common as one gets older.

The graph shows the death rate from cancer in the United States as a function of age. The graph can best be explained by the need for an accumulation of several "hits" to genes that control the cell cycle before a cell can become cancerous.

The graph also explains why cancer has become such a common cause of death during the twentieth century. It probably has very little to do with exposure to the chemicals of modern living and everything to do with the increased longevity that has been such a remarkable feature of this century.

A population whose members increasingly survive accidents and infectious disease is a population increasingly condemned to death from such "organic" diseases as cancer.

Causes of Cancer

Cancers are caused by

Viruses and Cancer

Many viruses have been studied that reliably cause cancer when laboratory animals are infected with them. What about humans? The evidence obviously is indirect but some likely culprits are:

But note! Clearly viral infection only contributes to the development of cancer.

So again it appears that only if an infected cell is unlucky enough to suffer several other types of damage will it develop into a tumor.

Nevertheless, widespread vaccination against these viruses should not only prevent disease but lower the incidence of the cancers associated with them.
"The Causes and Prevention of Cancer" by Bruce Ames
Three cancers of special biological interest: [Burkitt's lymphoma] [ Chronic Myelogenous Leukemia] [lung cancer]
The role of the proto-oncogene BCL-2 in B-cell leukemia and lymphoma.
Estimating the risk of cancer from radiation and chemicals in the environment.
Cancer Chemotherapy
Fighting cancer with angiogenesis inhibitors.
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14 October 2005