The Signatures of Cancer

False color scanning electron micrograph showing two lung cancer cells.  Anne Weston, Wellcome Images

False color scanning electron micrograph showing two lung cancer cells. Anne Weston, Wellcome Images

The Sanger Institute has undertaken an ambitious project and the results have been published today in the journal Nature. You can read the original full text article here. In it, scientists studied genetic material from more than 7,000 different cancer samples to uncover the biological processes that cause mutations. As a result, they identified 21 distinct mutational signatures.

✤ We know that certain environmental factors are closely linked to cancer development. For example, smoking and lung cancer, exposure to UV light and skin cancer. But what about the other cancers? With breast cancer, only 20% arise due to a family history, so where do the rest of the 80% of mutations come from?

✤ The scientists used an algorithm to analyze their tumor samples. To generate a mutational signature, a single mutation from each cancer sample is entered into a mutational set aggregated from several cases of a particular cancer type (eg: breast cancer). But cancer is rarely a single-mutation disease, so multiple things go wrong within the cell (a genetic FUBAR if you will). That’s where the sequencing and the algorithm came in.

✤ The results were very interesting. For example, more than 50% of the cancer types analyzed had a mutational signature that is linked to the activity of a family of enzymes, known as the APOBECs, which are involved in our immune response to certain viruses. It appears that the well-intentioned actions of APOBECs, in protecting our cells from the viruses could make things worse for our genomic DNA by introducing mutations that eventually lead to cancer.

✤ The work offers a fascinating insight into a disease that affects 1 in 3 of us. Gaining a deeper understanding into how cancer develops in the first place is useful for finding ways to prevent and treat the disease.

✤ This video is a nice summary of the findings as explained by the scientists behind the study:

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  • Image credit: False color scanning electron micrograph showing two lung cancer cells. Anne Weston, Wellcome Images
  • E.E. Giorgi writes an awesome blog post about APOBEC enzymes here

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