Cancer and Evolution
Cancer is a disease that happens when cells grow and divide faster than they should. This overgrowth leads to the formation of new, abnormal cells that can invade and destroy healthy tissues. Cancer can also spread to other parts of the body through blood and lymph systems. The cause of most cancers is unknown. But some cancers develop because of changes (mutations) in genes that control how fast cells grow and divide. These mutations can be inherited from our parents or can happen over time. Some types of cancer can be caused by lifestyle factors, such as smoking or sun exposure. Some cancers are linked to certain infections, like HIV, hepatitis B and C, herpes viruses, and the Epstein-Barr virus and Kaposi’s sarcoma-associated herpesvirus.
All cells have a natural life cycle. Normally, cells grow, divide, and die in a controlled way. If a cell is damaged or unhealthy, it will eventually stop growing and start to die. These damaged or unhealthy cells can form a mass of cells called a tumor. Cancer can be either benign or malignant, depending on whether the cells are able to invade surrounding tissue and spread throughout the body.
The earliest cancer cells are similar to unicellular organisms. They have a genetically distinct genome and an observable phenotype that sets them apart from normal cells. This unique set of properties makes it possible to recognize cancer as a species in its own right and is the driving force behind cancer’s evolutionary characteristics, including resistance to therapy.
The process of cancer initiation and progression is characterized by the forces of evolution, both natural and artificial, that act on heritable and accumulating mutations. This is a feature of cancer that must be included in any general definition of the disease.
A key principle of evolution is that the environment exerts a selection pressure on the population to favor certain traits. This selection pressure can be stabilizing, directional, or disruptive, depending on the environmental conditions and the range of variation in the population. Cancer cells have evolved to resist apoptosis and evade the immune system, thus increasing their likelihood of survival and proliferation. The resulting intratumoral heterogeneity contributes to cancer’s resistance to treatment and its ability to spread.
Cancers are often named after the organ or site where they first formed. For example, leukemia is cancer of the blood and sarcoma is cancer of a muscle or bone. But, in reality, most cancers are not specific to any one organ or site. In fact, most cancers have multiple causes.
Researchers have studied many things that may increase the risk of developing cancer. These are called cancer risk factors. Some of these factors are inherited, such as a family history of cancer or the type of cancer that a person’s mother had when she was young. Other factors are related to lifestyle choices, such as drinking too much alcohol or smoking. Smoking is the cause of about 22% of all cancers. Improvements in cancer detection and the decline in smoking have led to a steady decrease in cancer diagnosis and death rates.
Cancer is a disease that happens when cells grow and divide faster than they should. This overgrowth leads to the formation of new, abnormal cells that can invade and destroy healthy tissues. Cancer can also spread to other parts of the body through blood and lymph systems. The cause of most cancers is unknown. But some cancers develop because of changes (mutations) in genes that control how fast cells grow and divide. These mutations can be inherited from our parents or can happen over time. Some types of cancer can be caused by lifestyle factors, such as smoking or sun exposure. Some cancers are linked to certain infections, like HIV, hepatitis B and C, herpes viruses, and the Epstein-Barr virus and Kaposi’s sarcoma-associated herpesvirus. All cells have a natural life cycle. Normally, cells grow, divide, and die in a controlled way. If a cell is damaged or unhealthy, it will eventually stop growing and start to die. These damaged or unhealthy cells can form a mass of cells called a tumor. Cancer can be either benign or malignant, depending on whether the cells are able to invade surrounding tissue and spread throughout the body. The earliest cancer cells are similar to unicellular organisms. They have a genetically distinct genome and an observable phenotype that sets them apart from normal cells. This unique set of properties makes it possible to recognize cancer as a species in its own right and is the driving force behind cancer’s evolutionary characteristics, including resistance to therapy. The process of cancer initiation and progression is characterized by the forces of evolution, both natural and artificial, that act on heritable and accumulating mutations. This is a feature of cancer that must be included in any general definition of the disease. A key principle of evolution is that the environment exerts a selection pressure on the population to favor certain traits. This selection pressure can be stabilizing, directional, or disruptive, depending on the environmental conditions and the range of variation in the population. Cancer cells have evolved to resist apoptosis and evade the immune system, thus increasing their likelihood of survival and proliferation. The resulting intratumoral heterogeneity contributes to cancer’s resistance to treatment and its ability to spread. Cancers are often named after the organ or site where they first formed. For example, leukemia is cancer of the blood and sarcoma is cancer of a muscle or bone. But, in reality, most cancers are not specific to any one organ or site. In fact, most cancers have multiple causes. Researchers have studied many things that may increase the risk of developing cancer. These are called cancer risk factors. Some of these factors are inherited, such as a family history of cancer or the type of cancer that a person’s mother had when she was young. Other factors are related to lifestyle choices, such as drinking too much alcohol or smoking. Smoking is the cause of about 22% of all cancers. Improvements in cancer detection and the decline in smoking have led to a steady decrease in cancer diagnosis and death rates.