LONDON — Cancer in most cases might be the result of the random division of stem cells making people more vulnerable to mutations, rather than genes or environmental factors, according to a new study by Johns Hopkins University.
A formula that plotted the number of stem-cell divisions over a lifetime against the risk of cancer showed a correlation and explained two-thirds of cases, according to a research paper published this week in the journal Science.
The study, conducted by mathematician Cristian Tomasetti and geneticist Bert Vogelstein of Johns Hopkins, hinges on previously published cancer statistics.
The research might bolster arguments that cancer often can’t be prevented. That would support focusing more resources on diagnosing the disease in early stages and on treatments to reduce mortality rates.
The researchers cautioned that the study isn’t a license to engage in unhealthy behavior. For instance, don’t start smoking or stop using sunblock.
Tissue types that have more stem-cell divisions are more prone to mutations that can lead to cancers, Vogelstein and Tomasetti said in their paper. They suggest that only one-third of the variation in cancer risk might be due to environmental factors or inherited predispositions.
The researchers focused on stem cells because they live longer, with divisions of the self-renewing cells maintaining the tissue’s stability while also having the capacity to initiate a tumor. Random mutations — or bad luck — occurring during the replication of noncancerous stem cells, which typically account for a small number of the total cells in tissue, can lead to the disease.
Acknowledged risk factors that can lead to cancer include smoking, alcohol consumption, ultraviolet light and human papilloma virus, as well as genetic variations.
Some cancers, including breast and prostate, weren’t included in the report because reliable stem-cell division rates haven’t been determined, according to the study.
