Tumor Suppressor Genes
Tumor suppressor genes can be gene mutations that cause cancer when they are not functioning properly. These genes are normal and they repair DNA mistakes, slow down the division of cells, and tell cells when they need to die. When these genes are not working correctly, cancer can result due to cells growing out of control. Several different tumor suppressor genes have been discovered, including BRCA1, APC, p53, BRCA2, and RB1. These genes result in cancer when they become inactivated, or turned off, which makes them different from oncogenes which cause cancer when they are activated, or turned on.
Inherited tumor suppressor gene mutations result in certain cancers running in families. For example, familial adenomatous polyposis is caused by a defective APC gene. Most mutation associated with these genes are not inherited, but acquired. For example, more than 50 percent of cancers in humans have a p53 gene abnormality present. Acquired mutations of this gene is present in a variety of cancers, such as colorectal cancer, lung cancer, and breast cancer.