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Definition of Tumor suppressor gene
Medically reviewed by Min Clinic Staff | Updated: January 2026
Tumor suppressor gene: A protective gene that normally limits the growth of tumors. When a tumor suppressor gene is mutated (altered), it may fail to keep a cancer from growing.
BRCA1, an example of a tumor suppressor gene, was the first breast cancer gene to be identified; mutated forms of this gene are responsible for some cases of inherited breast cancer, especially those that occur in younger women.