Cancer may be a genetic disease—that is, cancer is caused by certain changes to genes that control the way our cells function, especially how they grow and divide.
Genes carry the instructions to form proteins, which do much of the add our cells. Certain gene changes can cause cells to evade normal growth controls and become cancer. For instance, some cancer-causing gene changes increase production of a protein that creates cells grows. Others end in the assembly of a misshapen, and thus nonfunctional, sort of a protein that normally repairs cellular damage.
Genetic changes that promote cancer are often inherited from our parents if the changes are present in germ cells, which are the reproductive cells of the body (eggs and sperm). Such changes, called germline changes, are found in every cell of the offspring. Cancer-causing genetic changes also can be acquired during one’s lifetime, because the results of errors that occur as cells divide or from exposure to carcinogenic substances that damage DNA, like certain chemicals in tobacco smoke, and radiation, like ultraviolet rays from the sun. Genetic changes that occur after conception are called somatic (or acquired) changes.
In general, cancer cells have more genetic changes than normal cells. But each person’s cancer features a unique combination of genetic alterations. A number of these changes could also be the results of cancer, instead of the cause. Because the cancer continues to grow, additional changes will occur. Even within an equivalent tumor, cancer cells may have different genetic changes.
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