A new study has found that inevitable mistakes in DNA cause nearly two-thirds of cancers. The mistakes are random, and in these cases, the cancer is not related to heredity or environmental factors, but rather to results of aleatory errors.
The mutation causes cancer to occur because a tiny error in a DNA sequence can make cells multiply out of control. The researchers wrote that the cancer mutation was thought to happen due to hereditary genes or outside factors like cigarette smoke or ultraviolet radiation. These factors can, in fact, cause cancer, but the third cause, random mutations, accounts for two-thirds of the disease.
Cancer can occur no matter how perfect the environment is
The study was published Thursday in the journal Science. Researchers explained that when a cell divides, it copies its DNA so that every new cell will have its own version of the genetic material. However, when this copying process occurs, there’s an opportunity for a mistake to take place, and sometimes these mistakes can lead to cancer.
Meaning, cancer can take place no matter how perfect the environment is. The study was led by Dr. Bert Vogelstein, a pathologist at the Sydney Kimmel Comprehensive Cancer Center at John Hopkins University, Christian Tomasetti and Lu Li, also professors at John Hopkins.
“Cancers are caused by mutations that may be inherited, induced by environmental factors, or result from DNA replication errors,” the study reads. “We studied the relationship between the number of normal stem cell divisions and the risk of 17 cancer types in 69 countries throughout the world. The data revealed a strong correlation between cancer incidence and normal stem cell divisions in all countries, regardless of the environment.”
The study found that inherited mutations caused about 5 percent of cancers, 29 percent of cancers were due to environmental factors, and nearly 66 percent were caused by random mistakes.
Random errors almost entirely cause some strains of cancer such as brain and prostate cancer, the study found. The researchers found that over 95 percent of the cancers studied for the research were due to the random mistakes.
Other types of cancer were more likely to occur due to environmental factors, such as lung cancer. In the study, they found that 65 percent of all lung cancers were caused by environmental factors, mostly related to patients that smoked. The other 35 percent of lung cancer factors was attributed to random mistakes.
Vogelstein explained that a single mutation in a cell is unlikely to cause cancer, but if a person has more mutations, it is more likely that the cells will become cancerous. Furthermore, Vogelstein noted that in some cases random mistakes are dangerous enough to cause cancer, and in other cases, the combination of random DNA mistakes plus environmental factors can lead to the cells turning cancerous.
Tomasetti illustrated the theory using typos while writing on a keyboard as an example. He says that some typos could be due to the typist being distracted or tired, which would be the environmental factors; and if the keyboard the typist is using is missing a key, that would be a hereditary factor. However, Tomasetti notes that even if the typist is working in a perfect condition and the keyboard is intact, typos will still occur, and those are the random mistakes.
“It is, of course, possible that virtually all mutations in all cancers are due to environmental factors, most of which have simply not yet been found,” the study said. “However, such a possibility seems inconsistent with the exhaustively documented fact that about three mutations occur every time a normal cell divides and that normal stem cells often divide throughout life.”
Secondary prevention is the only option for random mistakes
Researchers conclude their study stating that cancer is the most common cause of death in the world, and although the recognition of a third contributor to cancer does not reduce the importance of primary prevention, it does emphasize that not all forms of cancer can be prevented by evading environmental risk factors.
They explain that primary prevention is not the only prevention that exists. Secondary prevention can also be lifesaving, and it consists of an early detection of the cancer and intervention. They note that secondary prevention is the only option for patients with cancer attributed to random DNA mistakes.
Source: Live Science