Hereditary Cancer and Cancer Genetics

Cancer genetics has for many years focused on mutational events that have their primary effect within the cancer cell. Recently that focus has widened, with evidence of the importance of epigenetic events and of cellular interactions in cancer development. The role of common genetic variation in determining the range of individual susceptibility within the population is increasingly recognized, and will be addressed using information from the Human Genome Project. These new research directions will highlight determinants of cancer that lie outside the cancer cell, suggest new targets for intervention, and inform the design of strategies for prevention in groups at increased risk.

What is Hereditary Cancer ?

Everyone has two copies of each gene, one from each parent. Most people are born with two normal copies of each gene. Hereditary cancers occur when a person is born with changes or mutations in one copy of a damage-controlling gene which normally protects against cancer. In the majority of these cases, the changes were inherited from the mother or father.

People with an inherited gene change also have a 50% chance to pass the mutation to each of their children. These changes can increase the risk for cancers in different parts of the body. The changes do not increase the risk for every type of cancer and not everyone who is born with a gene change will develop cancer. The medical community uses the term "genetic susceptibility" to describe the increased risk for cancer that occurs in people with an inherited mutation.

Cancer is a common disease, so most families will have some members who have had cancer but that does not mean the cancer in that family is hereditary. We don't know the cause of most cancer, but experts believe that about 10% of most cancer types are due to inherited gene changes. Cancer that does not appear to be caused by inherited genes is called "sporadic cancer." It is believed that most— perhaps 90%—of all cancers are sporadic. This means even if cancer does not run in a family, a family member can still be at risk for some type of cancer in his or her lifetime.

All cancers are caused by changes to materials in our bodies called “genes.” These are units of information in every cell of our bodies. Genes tell our bodies which proteins to make based on the type of cell and its needs. Some genes tell our bodies how to fix damage accumulated over time from normal aging, environmental toxins, sun exposure, dietary factors, hormones, and other influences. These damage-controlling genes can repair cells or tell cells when to stop growing and die if there is too much damage to repair.

When genes themselves are damaged, they can develop changes called “mutations.” When mutations occur in the damage-controlling genes, cells can grow out of control and cause cancer.

For most people who develop cancer, the cancer-causing gene mutations happen over the course of a lifetime, leading to cancer later in life. Some people are born with a gene mutation that they inherited from their mother or father. This damaged gene puts them at higher risk for cancer than most people. When cancer occurs because of an inherited gene mutation, it is referred to as "hereditary cancer."