"However, many people will still develop cancers due to these random DNA copying errors, and better methods to detect all cancers earlier, while they are still curable, are urgently needed", says Bert Vogelstein, M.D., co-director of the Ludwig Center at the Johns Hopkins Kimmel Cancer Center.
"These cancers will occur no matter how flawless the environment", said Dr Bert Vogelstein of the oncology department at Johns Hopkins.
Random DNA-replication mistakes account for about 77 per cent of critical mutations in pancreatic cancer, and virtually all of those in childhood cancer, they said.
Separate research has shown that roughly 42 percent of cancers are preventable by, for instance, not smoking, maintaining a healthy weight, and not being exposed to cancer-causing pollutants. "This observation provided a hint that these random mutations play a large role in cancer, but didn't provide information on how numerous mutations in colon cancer, for example, were due to environmental or hereditary factors rather than random errors made during DNA replication", Vogelstein told The Scientist. "We believe the first step is simply recognizing that these enemies exist and they're already here". These factors can, in fact, cause cancer, but the third cause, random mutations, accounts for two-thirds of the disease. Essentially, cells divide and make mistakes copying DNA. "One day, being able to say "these mutations probably came from DNA replication, and these from an environmental factor" will help us to reconstitute the history of cancer". "The fact that we see a similar correlation in all the world's countries we analyzed, to us says that this result is largely independent of the variations in environments and lifestyle factors observed across the world", Tomasetti told The Scientist.
The new analysis report was published on March 23 in the journal Science.
The new research builds on a 2015 study that highlighted the role of "bad luck" - random DNA errors - in developing cancer.
What causes cancer? High-profile culprits obviously include bum genes inherited from parents and harmful environmental and lifestyle factors, such as smoking or not wearing sunscreen.
That study was later criticised by many in the scientific community who were anxious it would prompt people to take a fatalistic approach to the disease rather than trying to reduce risk by maintaining a healthy lifestyle. Because at least three mutations must typically occur, random errors will often combine with mutations caused by eating poorly or being sedentary to push cancer development forward when it otherwise might not have happened.
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One of the new sticking points is that mutations, while necessary for cancer to develop, aren't the whole story. Occasionally, while copying itself a mistake can occur in the DNA.
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. "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". "As people age", he said, "their cells will divide more and a greater fraction of the mutations will turn out to be random replication factors".
She said that environmental causes of cancer have always been underestimated, and that estimates on their contribution to cancer will increase as more is learned.
A study in Nature in December 2015, nearly a year afterward, countered that most cases of cancer were in fact caused by environmental factors, whether from smoking or exposure to ultraviolet radiation-and not by random mutations.
"It is well-known that we must avoid environmental factors such as smoking to decrease our risk of getting cancer".
For some other cancers, however, environmental factors play a large role, the study found.
Vogelstein says his team's approach to studying cancer mutations is akin to sorting out why typos typing a 20-volume book.
Most cells copy themselves, growing and dividing into two.