| Carcinogenesis is the creation of a cancer. | | | | ceases to divide. Tumor cells keep dividing forever. |
| Cancer is, ultimately, a disease of genes. Typically, a | | | | Altered morphology. |
| series of several mutations is required before a cell | | | | Building of cellular clusters (Foci). |
| becomes a cancer cell. We distinguish between | | | | Loss of contact inhibition. |
| oncogenes, which promote cancer when "switched | | | | Low or no need for growth factors. |
| on" by a mutation, and tumor suppressor genes, | | | | Metastasis |
| which prevent cancer unless "switched off" by a | | | | Cancers are capable of spreading through the body |
| mutation. These mutations can have various causes: | | | | by two mechanisms: local invasion and distant |
| radiation or chemicals called carcinogens; some | | | | metastasis. Invasion refers to the direct migration |
| inherited predisposition is not uncommon; some | | | | and penetration by cancer cells into neighboring |
| viruses that can cause cancer have also been | | | | tissues. Metastasis refers to the ability of cancer cells |
| described. Usually, they carry in their genome some | | | | to penetrate into lymphatic and blood vessels, |
| oncogene or tumor suppressor inactivating gene. In | | | | circulate through the bloodstream, and then invade |
| about 15% of all cancers, viruses seem to play a role. | | | | normal tissues elsewhere in the body. Cancer is most |
| Finally, damage by free radicals, which are a natural | | | | deadly when it metastasizes. |
| by-product of oxygen metabolism, can cause | | | | Forms of cancer |
| mutations in the DNA. | | | | The term cancer is very broad and covers many |
| For most of the cancers, it cannot be told which | | | | different illnesses including: |
| event was the initial cause. However, with molecular | | | | Bladder cancer |
| biology, it is possible to characterize the mutations | | | | Bone cancer |
| within a tumor, and to a certain extent to predict its | | | | Brain tumor |
| behavior. For example, about half of the tumors are | | | | Breast cancer |
| deficient in the tumor suppressor gene p53, also | | | | Cervical cancer |
| known as "the guardian of the genome". This is | | | | Colorectal cancer (includes colon, rectum, anus, and |
| associated with poor prospects for the patient, since | | | | appendix) |
| those tumor cells are unlikely to go into apoptosis | | | | Cancer of the esophagus |
| (programmed cell death) after they are damaged by | | | | Hodgkin's disease |
| therapy. There are more mutations that make a | | | | Kidney cancer |
| tumor more malignant. Telomerase mutations enable | | | | Cancer of the larynx |
| a tumor cell to divide indefinitely. Other mutations | | | | Leukemia |
| enable the tumor to grow new blood vessels to feed | | | | Liver cancer |
| it, or to detach from the surrounding tissue, | | | | Lung cancer |
| spreading to other parts of the body. | | | | Lymphoma |
| Malignant tumors such as carcinoma or sarcoma, | | | | Melanoma |
| lymphoma or leukemia originate from a cell or a group | | | | Moles and dysplastic nevi |
| of cells in a multicellular organism that have several | | | | Multiple myeloma |
| distinct properties:increased cell division ratenot | | | | Muscular Cancer |
| controllable by growth factors anymorealtered | | | | Non-Hodgkin's lymphoma |
| differentiation (specialization) abilityno ability for | | | | Oral cancer |
| contact inhibitionability to invade neighbouring | | | | Ovarian cancer |
| tissueability to build metastasesability to promote | | | | Cancer of the pancreas |
| blood vessel growth | | | | Prostate cancer |
| A cell that degenerates into a tumor cell does usually | | | | Skin cancer |
| not acquire all these properties at once, but its | | | | Stomach cancer |
| daughter cells are selected to build them. This | | | | Testicular cancer |
| process is called cellular evolution. A first step in the | | | | Teratoma |
| development of a tumor cell is usually a small change | | | | Thyroid cancer |
| in the DNA, often a point mutation, which leads, | | | | Cancer of the uterus |
| among other things, to a genetic instability of the cell. | | | | Clinical aspects |
| The instability increases to a point where the cell | | | | The field of medicine concerned with the treatment |
| loses whole chromosomes, or has double ones. Also, | | | | of cancer is oncology. |
| the DNA methylation pattern of the cell changes, | | | | Cancer has become an important problem with the |
| activating and deactivating genes more or less at | | | | rise in life expectancy, as the above mentioned |
| random. Cells that divide at a high rate, such as stem | | | | mutations become more likely the longer a person |
| cells, show a higher risk of becoming tumor cells than | | | | lives. Though great progress in treatment has been |
| those which divide less or not at all, for example, | | | | made, most cancers in advanced stages remain |
| neurons. If the initial tumor cell (or group of tumor | | | | incurable and ultimately fatal. |
| cells) is not removed by the immune system, it will | | | | Treatment of cancer typically involves surgery to |
| develop into cancer. | | | | remove tumors and nearby lymph nodes to which |
| In cellular model systems, cells are exposed to | | | | the cancer may have spread, combined with radiation |
| carcinogenic influences (chemicals, radiation). In these | | | | therapy and/or chemotherapy. The latter two target |
| systems, the first signs of a cell developing into a | | | | cells in the body that are rapidly dividing. This includes |
| tumor cell are : | | | | the cancer cells but also certain healthy ones, which is |
| Immortality. The usual number of cell divisions for a | | | | the reason for the severe side effects of these |
| mammalian cell is 50-60 (cell senescence), then it | | | | treatments. |