The external factors like smoking and the Sun can harm the DNA by causing some mutations, a process that happens in bursts and spurts. This process is not limited to environmental triggers: as the cells grow and split, the internal factors can cause the cell to constantly generate mutations at a steady rate. These mutations that happen in a “clock-like” manner, correspond to the age of a person. The older a person is, the more mutations the person can acquire.
The researchers have found out not 1, but 2 of these clocks-like processes of mutation, and calculated the rate at which they tick. This ticking can be responsible for different kinds of cancer, and may even have an important role in aging. Also, it lends to the chance that if the clock can be slowed, then so can the risk of getting cancer.
Dr. Ludmin Alexandrov, the co-author of the paper published in the Nature Genetics, said that this is a big exciting discovery as it solves the longstanding question. Not just has this study confirmed that the mutational molecular clocks really exist, also it has shown that there are 2 different clock processes that are repeatedly degrading the DNA. How fast the clocks tick in the cell might well determine both the likelihood for the cell to become cancerous and the ageing.
The researchers began by examining at the DNA sequences of more than 10,000 individual samples of cancer, which showed 36 types of this disease. They found out from this more than 30 different mutational stretches or “signatures” of the DNA showing different patterns of mutation, and that led to forming of the cancer. Also, 2 of these had that “clock-like” features. They showed a connection between the number of mutations, and the age of the patient from which it was taken, and have been called “signature 5” and “signature 1.”
Because of the steady rate at which these mutations have been gathered, the researchers effectively looked back to the time when the cell was healthy and count the speed at which those “clocks” ticked. While they discovered that the signatures one and five acquired mutations at a steady rate, the rate was not just different between these two signatures, but also between the cell types. As an example, the speed at which that clock ticked, and the rate of the mutation, was highest for the 1 signature in colorectal and stomach cells, but lowest in the breast cells.
The researchers should discover if these mutation clocks are able to tick at the same rate for all people. But in theory, if the doctors can count the rate at which the mutations are ticking, they will be able to predict the time when we may get cancer. Not just that, but this also raises the chance that the clock can be slowed.