Last year saw more than 1.6 million new cancer cases diagnosed in the US. While environmental and genetic factors are known to drive cancer development, a new study by researchers from the Johns Hopkins Kimmel Cancer Center in Baltimore, MD, claims two thirds of cancer cases in adults are a result of “bad luck.”
Dr. Bert Vogelstein and Cristian Tomasetti, PhD, publish their findings in the journal Science.
According to Dr. Vogelstein, it is well established that tissue-specific stem cells make random mutations – caused by DNA errors during cell division replication – that are drivers of cancer; the more these mutations expand, the higher the cancer risk.
However, the researchers note that it was unclear as to just how much of a role these random mutations play in cancer incidence, compared with hereditary or environmental factors. This is something the team sought to find out with their study.
To reach their findings, the team used scientific literature to analyze 31 types of cancer. They evaluated the number of stem cell divisions in each cancer and compared these rates with lifetime cancer risk among the same cancer types in the American population.
Dr. Vogelstein and Tomasetti then calculated the contribution of stem cell divisions to cancer risk using statistical theory.
They found that random DNA mutations during cell division may account for around 65% of cancer incidence, while the remaining 35% may be explained by hereditary or environmental factors.
In general, the team found that the more stem cell divisions that occurred – which increased the presence of random DNA mutations – the higher the likelihood of cancer development.
“The majority [of cancer risk] is due to “bad luck,” that is, random mutations arising during DNA replication in normal, noncancerous stem cells,” the researchers explain. “This is important not only for understanding the disease but also for designing strategies to limit the mortality it causes.”
In detail, the team found that these “bad luck” mutations primarily accounted for 22 of the 31 cancer types assessed, including ovarian, pancreatic, bone, testicular and pancreatic cancers.
The remaining nine cancer types – including skin, colorectal and lung cancers – were mainly influenced by a combination of bad luck and hereditary and environmental factors – such as carcinogen exposure
“We found that the types of cancer that had higher risk than predicted by the number of stem cell divisions were precisely the ones you’d expect, including lung cancer, which is linked to smoking, skin cancer, linked to sun exposure and forms of cancers associated with hereditary syndromes,” says Dr. Vogelstein.
The researchers note, however, that while two thirds of cancer incidence may be attributed to random DNA mutations, a poor lifestyle can increase the risk of such mutations.
Dr. Vogelstein adds:
“This study shows that you can add to your risk of getting cancers by smoking or other poor lifestyle factors.
However, many forms of cancer are due largely to the bad luck of acquiring a mutation in a cancer driver gene, regardless of lifestyle and heredity factors. The best way to eradicate these cancers will be through early detection, when they are still curable by surgery.”
The team says they did not include certain cancers – including breast and prostate cancers – in their study, as they were unable to identify reliable stem cell division rates of these types.
They note, however, that they have created a statistical model that other scientists can apply to more definite rates of stem cell division.
Medical News Today recently reported on a study published in the journal Cell Metabolism in which scientists claim to shed light on how diet influences cancer development.