Cancer: Origin

Cancer: origin

Cancer diseases arise through complex mechanisms that lead to an uninhibited proliferation of degenerated cells. Changes in the genetic code, the DNA, can be caused by disturbed endogenous processes, e.g. faulty repair of the DNA or by external carcinogens (cancer-causing factors). Most cancers are sporadic. However, there are familial mutations in cancer genes. In five to ten percent of cases, the genetic changes are hereditary. Almost all types of cancer originate in a single cell. According to recent research, multiple mutations must occur in a cell in order to result in a malignant change.

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• About oncogenes and tumor suppressor genes
• Family background
• The role of viruses
• The human genome project
• Influence of environmental factors & lifestyle

About oncogenes and tumor suppressor genes

Tumors tend to spread to neighboring tissue and in the body, and also to form daughter tumors (metastases) in distant organs. Although modern research has achieved great successes in terms of cancer research in the last few decades, many questions remain unsolved. It is only gradually that science is discovering the origins of malignant diseases and new ways of healing.

There are two main classes of cancer genes: the oncogenes and the tumor suppressor genes. Both directly influence cell growth and cell division. Normally, oncogenes are kept in check by healthy cells and tumor suppressor genes - to put it simply - ensure the suppression of cancer triggers. In cancer cells, on the other hand, oncogenes mutate and are difficult or impossible to control, and tumor suppressor genes lose their function. During the development of cancer, cells multiply differently, but this does not always automatically lead to progression of the malignant development. There are also ways in "dead ends". For most tumors, it is not known how many changes have to take place for a malignant tumor to develop.

Family background

A small proportion of cancers occur with hereditary predisposition. Approximately 100 familial cancer syndromes have been discovered to date. Most of them are rare. These include familial adenomatous polyposis, familial melanoma or hereditary breast and ovarian carcinoma. According to the current state of research, it is possible that genes causing hereditary tumor diseases can also appear mutated in sporadic (non-hereditary) tumors. Most hereditary cancers are based on a mutation of tumor suppressor genes. Even if there is a family history, environmental factors play an important role in many tumor diseases.

Genetic tests: human genetic counseling is important

It is possible to carry out genetic tests for cancer syndromes in order to assess the familial cancer risk. Negative genetic tests mean that the risk of developing cancer is no higher than in families who are not hereditary. This result can be very relieving. However, if the result of the genetic test is positive, this can result in optimized cancer prevention and early detection, but it can also lead to anxiety or depression. Genetic tests should always be accompanied by genetic counseling prior to any examination and a detailed discussion of the findings. A correct interpretation of the genetic tests is only possible with the appropriate specialist knowledge. Genetic tests are carried out, for example, if there is a suspected genetic predisposition to hereditary breast cancer or familial melanoma. However, these tests are not suitable for the general public. Internet tests without personal advice and support are to be viewed as dubious.

The role of viruses

There are types of cancer that are associated with viruses:

• Cervical carcinoma (cervical cancer) - human papillomavirus, HPV
• Burkitt lymphoma - Epstein-Barr virus
• hepatocellular carcinoma - hepatitis virus
• T-cell leukemia - retroviruses

Viruses alone do not cause cancer, but they can bring about decisive changes in the complex development process of cancer.

The human genome project

In 1990 the Human Genome Project (HPG) began - with the aim of deciphering all of the human genetic information: 3.2 billion base pairs of the DNA of the 22 chromosome pairs, as well as the X and Y chromosomes. Starting from America, many countries around the world took part in the project. Since 2003 the human genome has been considered completely deciphered. The follow-up project is called ENCODE (ENCyclopedia of DNS Elements) and determines the identity and exact location of all genes in the genome. In addition, all functional elements related to the human genome should be researched. The Cancer Genome Project analyzes changes in tumors in order to be better equipped for the prevention, diagnosis and therapy of cancer in the future.

Influence of environmental factors & lifestyle

Anything that can cause DNA breaks or other damage to DNA can potentially lead to cancer. It has been proven that the following environmental factors can cause cancer:

• Electromagnetic rays,
• certain chemicals, including those found in tobacco smoke,
• chronic infections.

Nutritional factors and obesity also play a role. For more information, see Diet and Cancer. Excessive alcohol consumption can also contribute to the development of cancer - especially in cancer of the esophagus, the pancreas, the gastrointestinal tract, as well as the female breast and liver.