Cancer and Genetic Testing – Gene Mutations Explained

If you have cancer, you may be tested for genetic mutations that you were either born with or acquired throughout life. The following is a basic explanation of the types of mutations that genetic testing will seek.

Bare with me, this gets a little scientific.

Acquired Gene Mutations – most common with cancer

Acquired mutations are the most common cause of cancer. These occur from damage to genes during a person’s life.  They are not passed from parent to child. Factors such as tobacco, ultraviolet (UV) radiation, viruses and age cause these mutations. Cancer that occurs because of acquired mutations is called sporadic cancer.

Many of the genes that contribute to the development of cancer fall into broad categories:

Tumor Suppressor Genes

Tumor suppressor genes are protective genes. Normally, they limit cell growth by monitoring how quickly cells divide into new cells, repairing mismatched DNA, and controlling when a cell dies. When a tumor suppressor gene is mutated, cells grow uncontrollably and may eventually form a mass called a tumor. BRCA1BRCA2, and p53 are examples of tumor suppressor genes. The most commonly mutated gene in people who have cancer is p53. In fact, more than 50% of all cancers involve a missing or damaged p53 gene. Most p53 gene mutations are acquired mutations.

Oncogenes

Oncogenes turn a healthy cell into a cancerous cell. Mutations in these genes are not inherited. Two common oncogenes are:

  • HER2, which is a specialized protein that controls cancer growth and spread, and it is found on some cancer cells, such as breast and ovarian cancer cells
  • The ras family of genes, which make proteins involved in cell communication pathways, cell growth, and cell death.

DNA Repair Genes

DNA repair genes fix mistakes made when DNA is copied. But if a person has an error in a DNA repair gene, these mistakes are not corrected. And then they become mutations, which may eventually lead to cancer. This is especially true if the mutation occurs in a tumor suppressor gene or oncogene. Mutations in DNA repair genes can be inherited or acquired.

Germline Mutations – less common with cancer

Germline mutations, which are less common, are passed directly from a parent to a child. In these situations, the mutation can be found in every cell of a person’s body, including the reproductive sperm cells in a boy’s body and egg cells in a girl’s body. Because the mutation affects reproductive cells, it passes from generation to generation.

MMMT – Genetic or Acquired?

Cancer caused by germline mutations is called inherited cancer, and it makes up about 5% to 10% of all cancers. Presently, most Malignant Mixed Müllerian Tumors (MMMT) or GCS are thought to occur by chance without an association to a genetic predisposition.  However, there have been rare reports of MMMT of the uterus developing in individuals with Lynch syndrome, an inherited condition in which individuals have a genetic predisposition to develop certain cancers including uterine cancer.  Germline mutations in BRCA1 or BRCA2 genes increase a woman’s risk of developing hereditary breast or ovarian cancers.

Cancers are mostly linked to multiple gene mutations

Despite all that is known about the different ways cancer genes work, many cancers cannot be linked to a specific gene. Cancer likely involves multiple gene mutations. Some evidence also suggests that genes interact with their environment, further complicating genes’ role in cancer.

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