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What Causes Cancer?
Just about everyone can benefit from understanding what causes cancer. Whether trying to understand the diagnosis of cancer in oneself or a loved one, or trying to improve ones health and prevent future disease, being armed with as much information as possible can only help and put one at ease.
What Causes Cancer?
Mutations: Errors in Your DNA
Cancer is a general term for a family of disorders characterized by the growth of malignant tumors in the body. These tumors arise from cells within our bodies which were once normal. However, over time they developed mutations, errors in the genetic material (DNA). If particular mutations occur together in a given cell, this can lead to the cell becoming cancerous and to begin dividing and growing uncontrollably. This type of disease can occur in just about any tissue type in the body, resulting in all the various forms of cancer which can occur (lung cancer, skin cancer, leukemia, etc.).
So what causes these errors in DNA?
Where do mutations come from?
Mutations can be caused in various ways. There are three most important sources of mutations. The first are simple errors of replication...
Errors of Replication
When normal cells divide, they must make an identical copy of their DNA, the genetic blueprint for each organism. Each time this happens, billions of base pairs, the units of DNA, must be copied. While human cells have evolved remarkable molecular machinery to accomplish this daunting task and prevent errors, errors still occur rarely. However, over the life of an individual, these errors do add up. Some of these errors do not affect the cells appreciably. Others do. Only some may contribute to cancer. This is one aspect of what causes cancer which is uncontrollable. All cells can develop some mutations by this process and they increase with age.
DNA Damage by Chemicals
Some chemical compounds cause direct damage to DNA. Some of this damage can be repaired by special proteins which exist in every cell, but some of this damage and the resulting mutations stick. There are hundreds of known chemicals that cause mutations. Termed mutagens or carcinogens ("cancer causing compounds"), some of these exist in nature and some of them are the product of man. For example, cigarette smoke contains several known carcinogens which can cause mutations in DNA. This is one askpect of what causes cancer which can be modifiable in some circumstances. For example, quiting smoking and avoiding second-hand smoke prevents exposure to many known cancer-causing chemicals.
DNA Damage by Physical Means
Physical factors, such as radiation in various forms, can also cause damage to DNA and result in mutations. The most widespread and ubiquitous form of radiation is solar radiation, sunlight. The ultraviolet rays (UV light), particularly, in sunlight is damaging to DNA and is one of the important causes of skin cancer. Other types of radiation exposure can lead to cancers as well, including environmental radon exposure, therapeutic radiation and occupational exposure to radiation. Radiation from nuclear explosions or nuclear reactor meltdowns are another potential, but thankfully very rare, source of radiation exposure and mutations. This is another aspect of what causes cancer that can be modifiable in some circumstances. Taking actions like reducing sun exposure, wearing sunscreen and reducing tanning booth use (which does cause DNA damage!) can all decrease your exposure to these physical mutagens which can be cancer-causing.
What Causes Cancer? Putting it All Together:
From Mutations to Cancer
So as described above, damage to a cells DNA causes mutations. Some of these mutations do nothing, some kill the cell, but some can lead to cancer. It takes mutations in several specific genes in a single cell to make that cell cancerous. Generally, the mutations that give the cell the ability to grow and divide uncontrollably will cause cancer. These genes, called oncogenes when they are mutated into a form that can cause cancer, are different for each type of cancer although there are many genes that contribute to many different types of cancer. When these mutations in these genes add up in the same cell, that cell may become cancerous and start growing as a malignant tumor.
When looking to reduce your risk for cancer, there are several things to consider. Each type of cancer has its own risk factors which can contribute to their development. However, there are certain lifestyle changes which can help reduce the exposure to some of the most important cancer-causing agents. Called "modifiable risk factors" these are things you can do to reduce damage to your cells and reduce the risk for cancer. For example, avoiding smoking and second-hand smoke, wearing sunscreen and reducing overall sun exposure, good general health and diet, limiting alcohol intake to moderate amounts and a diet rich in compounds known to reduce the risks of some cancers, such as anti-oxidants (found naturally in many foods, green tea, etc.). Unfortunately, no matter how healthy a lifestyle you lead there are many "unmodifiable risk factors" for cancer which you cannot control. These include increasing age, genetic and familial influences and environmental exposures, amongst other things.
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