What Causes Cancer?
Cancer is a disease that occurs when genes in cells change and grow out of control. Cells usually produce more cells to replace old or damaged ones, but cancerous (malignant) cells continue to grow and divide even when they should die. Over time, they form a mass of abnormal cells called a tumor. Tumors may spread to other parts of the body through blood or lymph. They can also grow into nearby tissue and push on structures like nerves or blood vessels, causing pain and making it harder for those structures to function.
The first cancer treatments used surgery, radiation, and chemotherapy to destroy or kill cancer cells. These treatments are still the mainstays of treatment, but today we have improved ways to prevent and cure cancers by targeting specific genes that cause them.
Most cancers start because of gene changes that happen over a person’s lifetime. These changes may be caused by lifestyle habits, such as smoking or taking certain drugs, and are sometimes due to inherited genetic mutations that you get from your parents. However, inherited genes account for only about 10% of all cancers.
Other causes of cancer include exposure to certain substances, such as sunlight or chemicals, and infections that can make you more likely to develop cancer, such as hepatitis B virus, hepatitis C virus, human immunodeficiency virus, herpes simplex viruses 1 through 9, Epstein-Barr virus, and human papillomavirus. Some cancers may also be caused by a person’s environment, such as where they live and where they work.
Scientists have long wondered what causes cancer. In 1910, the discovery that a bacteria could cause a cancer in chickens led to an idea that maybe cancer is an infectious disease. Other early notions included the belief that chronic irritation of tissues could cause cancer, as well as the theory that X-rays and other forms of radiation can cause cancer by damaging DNA.
As scientists developed better ways to look at and study cells, they found that most cancers start in just a few types of genes. These genes produce proteins that direct how cells grow and behave. The proteins that are altered in cancers may do normal jobs but go awry and become cancerous by growing out of control and crowding out healthy cells.
Understanding how these genes change helps explain many long-standing observations about cancer. For example, it explains why cancers tend to occur more often with age. It also explains why cancers are not a single disease, but a process that unfolds across many years, and why some people who have precancerous cells never develop cancer. It also helps explain why, even when cancer does develop, modern treatment is able to reduce or eliminate the cancer. This is especially true for cancers that have very few genetic mutations. These cancers are very difficult to treat, but today’s methods of identifying and targeting the mutations that lead to a particular type of cancer give hope for future advances in prevention and treatment.
Cancer is a disease that occurs when genes in cells change and grow out of control. Cells usually produce more cells to replace old or damaged ones, but cancerous (malignant) cells continue to grow and divide even when they should die. Over time, they form a mass of abnormal cells called a tumor. Tumors may spread to other parts of the body through blood or lymph. They can also grow into nearby tissue and push on structures like nerves or blood vessels, causing pain and making it harder for those structures to function. The first cancer treatments used surgery, radiation, and chemotherapy to destroy or kill cancer cells. These treatments are still the mainstays of treatment, but today we have improved ways to prevent and cure cancers by targeting specific genes that cause them. Most cancers start because of gene changes that happen over a person’s lifetime. These changes may be caused by lifestyle habits, such as smoking or taking certain drugs, and are sometimes due to inherited genetic mutations that you get from your parents. However, inherited genes account for only about 10% of all cancers. Other causes of cancer include exposure to certain substances, such as sunlight or chemicals, and infections that can make you more likely to develop cancer, such as hepatitis B virus, hepatitis C virus, human immunodeficiency virus, herpes simplex viruses 1 through 9, Epstein-Barr virus, and human papillomavirus. Some cancers may also be caused by a person’s environment, such as where they live and where they work. Scientists have long wondered what causes cancer. In 1910, the discovery that a bacteria could cause a cancer in chickens led to an idea that maybe cancer is an infectious disease. Other early notions included the belief that chronic irritation of tissues could cause cancer, as well as the theory that X-rays and other forms of radiation can cause cancer by damaging DNA. As scientists developed better ways to look at and study cells, they found that most cancers start in just a few types of genes. These genes produce proteins that direct how cells grow and behave. The proteins that are altered in cancers may do normal jobs but go awry and become cancerous by growing out of control and crowding out healthy cells. Understanding how these genes change helps explain many long-standing observations about cancer. For example, it explains why cancers tend to occur more often with age. It also explains why cancers are not a single disease, but a process that unfolds across many years, and why some people who have precancerous cells never develop cancer. It also helps explain why, even when cancer does develop, modern treatment is able to reduce or eliminate the cancer. This is especially true for cancers that have very few genetic mutations. These cancers are very difficult to treat, but today’s methods of identifying and targeting the mutations that lead to a particular type of cancer give hope for future advances in prevention and treatment.