The Cancer reference article from the English Wikipedia on 24-Jul-2004
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Cancer

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There is also a constellation named Cancer: see Cancer (constellation).

Cancer is a disease where some of the body's own cellss repeatedly divide without control as the result of a mutation. The new cells may form a malignant tumor (a neoplasm) or propagate throughout the body.

Cancer has become an important problem with the rise in life expectancy, as the mutations become more likely the longer a person lives. Though great progress in treatment has been made, many cancers reach advanced stages remain incurable and ultimately fatal. Thankfully for patients with incurable cancer, the last 20 years have seen the widespread availability of palliative care.

Cancer is treated by an oncologist, a doctor specialized in the treatment of malignant disease.

Table of contents
1 Prevention and early detection
2 Forms of cancer
3 Treatment
4 Biology of malignant tumors
5 Cancer research agencies and funding bodies
6 See also
7 External links

Prevention and early detection

Because of the difficulty treating advanced cancer prevention and early detection of cancer remain important strategies to reduce cancer related illness and death.

Proven methods of decreasing the risk of cancer include smoking cessation and avoiding other known carcinogens such as sunlight, genital warts.

Accepted early detection strategies include:

Genetic screening is likely to gain increasing prominence over the next decade

Both white and Green tea have been shown to help in preventing cancer in rats, but the significance of this in humans is unknown.

Forms of cancer

There are many forms of cancer and they grouped according to either their cell type or their location.

Cell types include:

Majors cancers, by body location:

Treatment

Treatment of cancer typically involves surgery to remove tumors and nearby lymph nodes to which the cancer may have spread, combined with radiation therapy and/or chemotherapy. The latter two target cells in the body that are rapidly dividing. This includes the cancer cells but also certain healthy ones, which is the reason for the severe side effects of these treatments.

Biology of malignant tumors

Carcinogenesis

Carcinogenesis (lit.: creation of cancer) is the process of derangement of the rate of cell division.

Cancer is, ultimately, a disease of genes. Typically, a series of several mutations is required before a cell becomes a cancer cell. The process involves both oncogenes and tumor suppressor genes. Oncogenes promote cancer when "switched on" by a mutation, whereas tumor suppressor genes prevent cancer unless "switched off" by a mutation. Chromosomal translocation, such as the Philadelphia chromosome, is special type of mutation and may involve oncogenes or tumor suppressor genes.

Mutations can have various causes:

Viruses play a role in about 15% of all cancers. Tumor viruses usually carry some oncogene or tumor suppressor inactivating gene in their genome.

It is impossible to tell the initial cause for most of the cancers.

However, with molecular biology, it is now possible to characterize the mutations within a tumor, and to a certain extent predict its behavior. For example, about half of the tumors are deficient in the tumor suppressor gene p53, also known as "the guardian of the genome". This mutation is associated with poor prognosis, since those tumor cells are less likely to go into apoptosis (programmed cell death) when damaged by therapy. There are more mutations that make a tumor more malignant. Telomerase mutations enable a tumor cell to divide indefinitely. Other mutations enable the tumor to grow new blood vessels to feed it, or to detach from the surrounding tissue, spreading to other parts of the body.

Malignant tumors cells, such as in carcinoma, sarcoma, lymphoma or leukemia, have distinct properties:

A cell that degenerates into a tumor cell does usually not acquire all these properties at once, but its descendant cells are selected to build them. This process is called cellular evolution. A first step in the development of a tumor cell is usually a small change in the DNA, often a point mutation, which leads, among other things, to a genetic instability of the cell. The instability increases to a point where the cell loses whole chromosomes, or has double ones. Also, the DNA methylation pattern of the cell changes, activating and deactivating genes more or less at random. Cells that divide at a high rate, such as stem cells, show a higher risk of becoming tumor cells than those which divide less, for example neurons. If the initial tumor cell (or group of tumor cells) is not removed by the immune system, it becomes a cancer.

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:

  1. 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.
  2. Altered morphology.
  3. Building of cellular clusters (foci).
  4. Loss of contact inhibition.
  5. 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 tumor suppressor genes.

Metastasis

Cancers are capable of spreading through the body by either local invasion or distant metastasis. Invasion is the direct migration and penetration by cancer cells into neighboring tissues. Metastasis is the process of cancer cells penetrating into lymphatic and blood vessels, circulating through the bloodstream, and then invading normal tissues elsewhere in the body. Cancer is most dangerous when it metastasizes. When malignant tissue is surgically removed, some local lymph nodes are typically removed and dissected to give an idea of if and how much the cancer is spreading.

Cancer research agencies and funding bodies

Below is a list of some well-known institutions dedicated to funding cancer research:

See also

List of cancer patients -- Oncology -- Terminal illness -- Palliative care

External links