National Cancer Institute
Science Behind the News Understanding Cancer
A drawing of a normal cell and a cancer cell.


The first group of genes implicated in the development of cancer are damaged genes, called "oncogenes." Oncogenes are genes whose PRESENCE in certain forms and/or overactivity can stimulate the development of cancer. When oncogenes arise in normal cells, they can cause the cells to become malignant. Oncogenes contribute to the development of cancer by instructing cells to make proteins that stimulate excessive cell growth and division.

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