What is colon cancer

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In cellular model systems, cells are exposed to carcinogenic influences (chemicals, radiation). In these systems, the first signs of a cell developing into a tumor cell are:

Immortality. The usual number of cell divisions for a mammalian cell is 50-60 (cell senescence), then it ceases to divide. Tumor cells keep dividing forever.
Altered morphology.
Building of cellular clusters (Foci).
Loss of contact inhibition.
Low or no need for growth factors.

Items 2-4 (above) can sometimes be traced to mutations in genes that result in a disruption of cell adhesion. Some cell adhesion proteins are oncogenes.

The field of medicine concerned with the treatment of cancer is oncology. Cancer has become an important problem with the rise in life expectancy, as the abovementioned mutations become more likely the longer a person lives. Though great progress in treatment has been made, most cancers in advanced stages remain incurable and ultimately fatal.

Cancer is, ultimately, a disease of genes. Typically, a series of several mutations is required before a cell becomes a cancer cell. We distinguish between oncogenes, which promote cancer when "switched on" by a mutation, and tumor suppressor genes, which prevent cancer unless "switched off" by a mutation. These mutations can have various causes: radiation or chemicals called carcinogens; some inherited predisposition is not uncommon; some viruses that can cause cancer have also been described. Usually, they carry in their genome some oncogene or tumor suppressor inactivating gene. In about 15% of all cancers, viruses seem to play a role; Bacteria, like Helicobacter pylori, also induce carcinogenesis by a process of chronic inflammation. Finally, damage by free radicals, which are a natural by-product of oxygen metabolism, can cause mutations in the DNA.

Cancer Rates And Risks
Provides international incidence and mortality rates including information about risk factors. From the U.S. National Cancer Institute.
About.com: Cancer
Presents general overview information on many of the main kinds of tumors. Includes news, doctor search, glossary and access to support hotlines.
Imperial Cancer Research Fund
News and information about the prevention, diagnosis and treatment of this condition. A UK charity site.
HCA Cancer Guides
General information including treatment options.
EMedicine Health: What You Need To Know
Consumer health resource center providing general information on cancer prevention, symptoms and treatment.

What is colon cancer