In cancer cells, vote for growth, division and destruction of the cell structure is suspended. Regulatory signals are not recognized or not performed because most of the genetic code required for this is faulty.
Approximately 5,000 of the 25,000 human genes are responsible for the safe conservation of the genetic code of a cell generation to the next. These so-called proto-oncogenes and tumor suppressor genes control the correct sequence of base pairs in the DNA after each reduplication decide on the need of repair operations that adhere to the cell cycle until repairs are made, and when appropriate, initiate a programmed cell death (apoptosis) if the repair is not leads to success.
After today's most plausible theory of cancer development (carcinogenesis), the primary disease event a change in one of these "guardian genes', either by copying a rare inborn error or by a mutation. This gene can be monitored by the sub-step is no longer accompany him correctly, so that it can come in the next generation of cells to other defects. Is a second Wächtergen affected, the effect multiplies continuously. Although apoptosis genes (eg p53) are affected, which would trigger in such a situation, the programmed cell death, these cells are immortal.
Further changes in the DNA, the cell can develop additional features that make the treatment of cancer, including the ability to survive under oxygen deficiency, it builds its own blood supply (angiogenesis) or to emigrate from the association and in foreign tissue such as bone, lung or locate brain (metastasis). Only with this ability gains the power of his deadly cancer 90% of cancer patients in whom the disease starts deadly, do not die at the primary tumor, but at its sequelae of metastases or tumor metastasis.
The immune system basically tries to fight the uncontrolled growth of cells. Since these same but in many ways normal body cells, defensive measures are usually not sufficient to control the tumor.
Cancer cells are often aneuploid, that is, have they changed a number of chromosomes. It is the subject of research, whether the aneuploidy of cancer cells cause or consequence of disease. This also raises the theory that the development of cancer is not due or not only on the mutation of individual genes but on the change of the complete set of chromosomes.