What causes cancer?
The more we can learn about what causes cancer, the more likely we are to find ways to prevent it. In the laboratory, scientists explore possible causes of cancer and try to determine exactly what happens in cells when they become cancerous. Researchers also study patterns of cancer in the population to look for risk factors, conditions that increase the chance that cancer might occur. They also look for protective factors, things that decrease the risk. Even though doctors can seldom explain why one person gets cancer and another does not, it is clear that cancer is not caused by an injury, such as a bump or bruise. In addition, although being infected with certain viruses may increase the risk of some types of cancer, cancer is not contagious; no one can “catch” cancer from another person. Cancer develops over time. It is a result of a complex mix of factors related to lifestyle, heredity, and environment. A number of factors that increase a person’s chance of developing cancer have
Cancer can be caused by anything that damages the DNA in a cell. This includes certain chemicals, ionizing radiation, some types of viruses, genetics, and other external factors. Naturally occurring mutations in the cell’s chromosomes or aging of the cell may also lead to the development of a cancer. The process by which cancers may develop in a particular individual is not fully understood and appears to be quite complicated.
For cells to turn cancerous, some of their genes must be damaged through mutation. People may inherit mutations that predispose them to cancer, but damage to genes happens during life too – when cells are exposed to carcinogens such as tobacco, for example. But cells do not easily turn cancerous: at least three “hits”, or different types of damage or mutation, are usually needed. Three main gene groups are involved in changes that lead to cancer. Firstly, proto-oncogenes normally instruct cells to grow and divide. If these are mutated, they can turn into oncogenes that instruct cells to continue dividing when they should not – imagine a car with the accelerator jammed down. Secondly, tumour-suppressor genes normally stop cells from multiplying. If they are damaged however, like a car brake failing, cell division goes unchecked. The third gene group normally helps in the repair of damaged DNA, but if they fail in their task, cells will copy damaged DNA into their daughter cells as they
Cancer cells develop because of damage to DNA, a substance in every cell that directs all activity of the cell. Usually when DNA becomes damaged, the body is able to repair it; however, sometimes it is not repaired and the cell becomes abnormal. Scientists are working to better understand what causes DNA to become damaged. Some people inherit damaged DNA, which accounts for inherited cancers. More often, though, a person’s DNA becomes damaged by environmental factors or individual behaviors such as smoking.
A. Cancer cells develop because of damage to DNA, a substance in every cell that directs all activity of the cell. Usually when DNA becomes damaged, the body is able to repair it; however, sometimes it is not repaired and the cell becomes abnormal. Scientists are working to better understand what causes DNA to become damaged. Some people inherit damaged DNA, which accounts for inherited cancers. More often, though, a person’s DNA becomes damaged by environmental factors or individual behaviors such as smoking.
