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Known Genetic Breast Cancer Factors


Our genes create a unique fingerprint for how our cells behave. They make proteins within our cells, and it is these proteins which influence both healthy or damaging cell activity. If particular gene or protein functions mutate, this can cause cells to grow out of control. Through genetic screening, researchers can pinpoint the genes which make us susceptible to cancers or which might be targeted by specific treatments.


These genes are involved in producing proteins that repair and manage damaged DNA. If one of these genes isn’t functioning correctly, then our safeguards against uncontrolled cell growth are potentially failing. Specific inherited mutations in BRCA1 and BRCA2 have been shown to increase the risk of female breast and ovarian cancers. Breast cancers associated with mutations in these genes usually develop at a younger age.

Breast cancers occurring in BRCA1 mutation carriers are more likely to be oestrogen receptor negative (ER-), progesterone receptor–negative, and HER2 receptor-negative (triple-negative breast cancers). BRCA2 mutations are more likely to be present in oestrogen receptor positive (ER+) breast cancer.

HER2-positive breast cancers

Between 20-25% of cancers have too much of the growth-promoting protein HER2 (also known as HER2/neu), which is produced by the HER2 gene. HER2 proteins are receptors on breast cells which play a role in managing cell growth, division and repair.

When there is an excess of HER2 proteins in the breast cells, the cells divide and spread abnormally. These cancers tend to spread quickly. Treatments that target this activity are currently available.

Hormone receptor-positive breast cancers

Oestrogen (estrogen) and progesterone are hormones which play a role in the growth of breast cells. Cancer cells may contain either, none, or both of these receptors and the presence of these receptors will help inform whether treatment with certain hormone therapy drugs will be effective.

Triple-negative breast cancers

These cancers are classified by a lack of both oestrogen and progesterone receptors on the breast cancer cell, as well as a low number of HER2 proteins. They are more common in younger women and tend to grow and spread more quickly than other types of breast cancer.

Treatments which would usually be used on HER2 positive cancers, and hormone receptor positive cancers will not be affective for triple-negative breast cancers. About 10-20% of breast cancers are found to be triple-negative and there is significant interest in finding new treatments for this type of cancer across the globe.

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