How are genes involved in cancer?

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Genes don’t cause cancer, but genetic mutations can. Our cells have about 22,000 genes, which consist of DNA packed into chromosomes inside the cell nucleus. These genes control a wide range of functions, including cell growth and division. When the genes misbehave or mutate, cancer can develop.

Sometimes these mutations are inherited. In that case, they are called germline mutations, and they are found in almost every cell of the body.

You’re probably familiar with the idea that cancer can run in families. For example, if your mother had breast cancer, you might be at risk for developing it one day. Of course, having a higher risk due to a germline mutation doesn’t mean you will develop cancer.

“You inherit two copies of most genes in your body: one from your mother and one from your father,” explains Judy Garber, MD, MPH, director of the Center for Cancer Genetics and Prevention at Dana-Farber.  “If you have a germline mutation in one copy of a particular gene, the other copy would usually be normal.”

Mutations are generally required in both copies for cancer to occur.  People born with a mutation in one copy are likely to acquire a mutation in the other more quickly – much as a baseball batter with one strike will probably reach a two-strike count faster than a batter with no strikes.

Scientists have discovered a variety of gene mutations that are more susceptible to cancer, such as BRCA1 and BRCA2, which are involved in the development of breast cancer. Being able to identify such genes allows specialists to screen people with a family history of cancer to find out if they carry mutations in these genes.

However, only about 5-10 percent of all cancers are the result of these germline (hereditary) mutations. Somatic mutations, on the other hand, occur in otherwise healthy cells. When a cell acquires enough mutations, it may become cancerous, meaning it is now able to grow and divide without control.  These mutated genes exist only within the cancer itself, not the rest of the body.

They make excellent targets for so-called “smart” drugs that take aim at specific mutations. Smart drugs are able to attack cancer cells with less harm to normal cells than traditional chemotherapy.

The Profile research project, launched last year by Dana-Farber and Brigham and Women’s Hospital, is concerned with both types of mutations. Adult patients can have their leftover tumor tissue screened for nearly 500 somatic mutations suspected of being involved in cancer. They can also donate normal cells – from a simple cheek swab or blood draw – for germline studies of genes that may predispose them to developing certain cancers.

If you are concerned about a history of cancer in your family, you can make an appointment at Dana-Farber’s Center for Cancer Genetics and Prevention. To reduce your general risk of developing cancer, don’t smoke, follow a healthy diet, get the right cancer screenings, and exercise regularly. Learn more about taking control of your cancer risk.

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