How is cancer linked to DNA?

Around 19 million people worldwide were diagnosed with cancer in 20201. Prevention could increasingly help in bringing this number down. Part of this prevention is knowing your genetic predisposition to take the right personalised action to avoid the disease. Let’s explore what cancer is and how it comes to be.

What do cancer and DNA have to do with each other?

Cancer is essentially cells dividing too quickly and abnormally creating a lump that can travel to other parts of the body. Uncontrolled division of cells can happen anywhere (breast, lung, blood…) which is why there are so many different types of cancer. 

These abnormal cell divisions are linked to changes in the DNA sequence. Changes, also known as mutations, are normally repaired and cause no issue. However, in the case of cancer, an accumulation of mutations in specific genes can lead to dangerous cancer developments. Cancer is therefore a genetic disease.

How does DNA cause cancer?

To make it simple, it is the accumulation of mutations in a cell’s DNA that causes cancer. Some changes to this DNA can have no effect on the cell whilst others can impact it more or less severely. Overall, these mutations affect the growth and division of cells leading them to create lumps and behave abnormally. 

To have a higher likelihood to develop cancers, mutations need to occur in three types of genes. The first type is genes encouraging cell division, the second is genes controlling and repressing cell division, and the last type is genes that participate in the repair of DNA errors. 

Cancer is linked to different types of mutations

The first type of mutation is the one encouraging cell division. Mutations in these genes can increase their activity making cell division happen more frequently. 

The second is related to genes controlling and repressing cell division. Mutations in these genes can deactivate them, likely allowing cell division in an uncontrolled manner. Cell division leads to more frequent DNA mutations as there is no more time to make sure there is no error in the DNA. 

The third type of mutation relates to genes that fix DNA errors. Mutations also deactivate them, leading to less repair, and more errors staying. The more mutations there are, the more genes activities are changing, and the more abnormally will a cell behave. It is essentially a vicious circle. 

For any cancer, no single mutation can cause the sickness by itself. It is the addition of all the mutations that crosses a threshold and leads to the development of the disease. However, some mutations are more severe and bring the cells closer to this threshold more quickly than others. 

Could I prevent cancer by knowing early?

The usual prevention measures for cancer are lifestyle changes such as not smoking, eating healthy, exercising, putting sunscreen on… However, through scientific advances, it is now possible to identify genetic predispositions with DNA tests. These can tell you more about your increased risk of developing a type of cancer. Following the information extracted from your DNA, we can now establish personalised prevention. These can either be through an increased rate of screening and diagnostic tests, preventive surgeries, or preventive treatment. 

For example, to detect potential colorectal cancers, screenings usually start around the age or 50 and are repeated every 2, 5, or 10 years depending on the country. If a genetic predisposition to this type of cancer has been identified, regular screening can start at an earlier age and be more frequent. This will help to detect the cancer more quickly to treat it more easily. 

Preventive measures are possible

In extreme cases, surgeries are available for people with a high risk for a cancer type. If a woman has severe genetic predispositions to breast cancer, she may choose to remove her breasts to reduce the risk of developing the disease. Furthermore, people with very high risk may also choose to engage in preventive treatments with the help of their medical doctor as a preventive measure. 

In most cases, only people with a strong enough family history of cancer have access to genetic testing. Through commercialised DNA tests, it is now possible for everyone to have access to this information. Nevertheless, a genetic counsellor and a doctor are the only ones that can help you with any medical decision following your DNA test results. They will be able to advise you as to what the next best step is for your specific case.

How can having a genetic predisposition to cancer affect my family?

Parents can only pass the mutation on to their children if the mutation affects germ cells (sperm cells and egg). Notorious mutations that are passed down from generation to generation are the mutations in the BRCA1 and BRCA2 genes that increase the risk of breast and ovarian cancer. These genes normally make sure that the cells do not divide too often. A parent with this mutation can pass it on to their children and also increase their risk of developing cancer.

Once you know you have this mutation, you can take preventive actions such as extra screening, tests and reducing other risk factors. If you have children, they can get a DNA test to check whether they inherited the mutations and take preventive measures in accordance. In terms of siblings or extended family, if you have a genetic predisposition to a type of cancer, their chances of having the same predisposition increases. Again, DNA tests are useful to check for its presence in each person. You can find more information on the process of a DNA test by clicking here

Overall, it may not be possible to fully prevent and stop the development of cancer, but it is possible to reduce the risk. With this, it is possible to live longer, but also live healthier.

1. Ferlay J, Ervik M, Lam F, Colombet M, Mery L, Piñeros M, et al. Global Cancer Observatory: Cancer Today. Lyon: International Agency for Research on Cancer; 2020 (, accessed July 2021).
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