The team discovered this link by using supercomputers to compare thousands of gene sequences in cancer patients (both smokers and non-smokers) and lump them into mutational signatures, five of which are commonly linked to cancer in smokers. One signature in particular (where a DNA nucleobase changes from cytosine to adenine) was more common across smokers in general, especially those suffering from lung or larynx cancers. The mutations may not do much by themselves, but they speed up cellular 'clocks' and increase the odds that cell DNA will mutate prematurely.

This doesn't provide a complete explanation for how smoking creates cancer (or factors behind other cancer types), but it illustrates the complexity of the process. It also helps explain how smokers develop cancer even in areas that don't come into direct contact with smoke, like the bladder. And the findings you see here could get the ball rolling on preventing other, less avoidable forms of cancer -- it might indirectly save your life, even if you've never come close to a cigarette.