All cancers are caused by a permanent change or damage that has occurred in one or more genes. Genes are present in every cell of your body and direct how each one develops, behaves and works. We’re talking about genetic mutation that occurs when there is a change in a gene. A mutation in a gene modifies the guidelines given to the body and prevents it from working properly, which can disrupt normal development or cause a medical condition. Genetic mutations create various effects on health. Their effects depend on where they occur and change of function they cause to essential proteins.
Some genes help control cell growth and play a role in the development of cancer cells. A change may, for example, occur in a gene that promotes cell growth or a gene that slows cell growth and normally protects the body against cancer (tumor suppressor gene). Mutations affecting these genes may allow the cells to grow erratically and thus contribute to cancer development.
Each cell has the ability to detect changes in DNA and repair it before they are passed on to new cells. But sometimes this repair mechanism may be lacking and the change is passed on to new cells. The cells whose DNA has been damaged are more likely to become cancerous. Several mutations are usually required before a normal cell can turn into a cancer cell.
Scientists have discovered a lot about how the changes that occur in our genes can affect our health and increase the risk of cancer.
Sporadic cancers (non-hereditary or acquired)
Some cancers are caused by genes with which we are born. Other cancers are due to genetic changes that occur over a lifetime. Sporadic cancers (acquired) are caused by mutations that occur as we age or due to age, accident or something that you have been exposed (carcinogens). Sometimes these mutations are errors that occurred during cell division. They can also appear because something has damaged the DNA of the cell. Mutations may affect the structure of a gene and prevent it from working properly. The majority of cancers are sporadic, that is to say, they are caused by acquired genetic mutations.
Only a few cancers (about 5-10 %) are caused by a certain inherited genetic mutation. We often talk then of hereditary cancer, but this term is not quite accurate. Cancer cannot be inherited. It is rather a specific genetic mutation that is hereditary. This mutation makes a person more susceptible (predisposed) to be diagnosed with cancer. Although this inherited mutation increases the risk of cancer, it does not always mean that it is certain that a person with this inherited mutation will have cancer. As is often the case of hereditary cancers, the person with cancer tends to be of a younger age than the rest of the population.
Heredity has been linked to many types of cancer and sometimes, breast cancer and colon cancer in adults and pediatric retinoblastoma are caused by hereditary cancer gene.