‘IT’S BAD LUCK YOU GOT CANCER’
Random DNA mistakes account for most mutations in tumours, says study
WHAT causes cancer? A new study published on Thursday suggests that cells make random mistakes while dividing, accounting for most of the mutations in tumours, rather than family history or environmental factors.
The report in the journal, Science, was authored by the same team that led a controversial study in January 2015 that said random DNA mutations, or in other words just “bad luck”, was often to blame for cancer.
This time, they expanded their mathematical model based on DNA sequencing and epidemiologic data to 69 countries worldwide.
“Two-thirds of the mutations that occur in cancers are due to the mistakes that cells make when they divide,” co-author Bert Vogelstein, co-director of the Ludwig Centre at the Johns Hopkins University Kimmel Cancer Center, said.
Environment was a factor in 29 per cent of the mutations in cancer, while heredity accounted for five per cent, according to the study.
“Every time a perfectly normal cell divides, it makes several mistakes— mutations. Most of the time, these mutations are harmless. That is the usual situation and that is ‘good luck’ in our paraphrase.
“But, occasionally, they occur in a cancer-driver gene. That is ‘bad luck’,” Vogelstein said.
The goal of the study was to better understand these mutations so that better ways of detecting cancer early can be developed.
The study shines a spotlight on cancers that will occur no matter how perfect the environment, and may alleviate the guilt some patients face when they are diagnosed.
“These copying mistakes are a potent source of cancer mutations that historically have been scientifically undervalued,” said co-author Cristian Tomasetti, assistant professor of biostatistics at the Johns Hopkins Kimmel Cancer Centre.
However, he urged people to avoid known risk factors for cancer, such as smoking and too much sun exposure.
“We need to continue to encourage people to avoid environmental agents and lifestyles that increase their risk of developing cancer mutations.”
Vogelstein concurred, stressing that the latest research was “in perfect accord with epidemiological estimates that 42 per cent of cancers can be prevented, and everyone should adhere to those prevention guidelines”.
For lay people, the takeaway message is that many cases of cancer can be prevented, even though many cancerous mutations cannot.
“Despite the role of the random replication component in producing mutations, you could reduce the cancer risk hugely for many types of cancer by getting rid of the environmental and/or hereditary causes,” he said.
Lawrence Young, director of the Cancer Research Centre at the University of Warwick in England, said the study “contributes to the controversial debate”.
However, any mathematical model that attempts to account for cancer risks must take in a variety of external factors.
“So, while this study is useful in attempting to integrate epidemiological and genome sequencing data, the message is complex and does not diminish the need to focus on improved approaches to primary and secondary cancer prevention.”
Healthy cells naturally make mistakes when they multiply.