Heritable breast cancer: What is the BRCA gene?- Maria Munden
Approximately 12% of women will be diagnosed with breast cancer in their lifetime, making
it the most common female cancer. Breast cancer can also occur in men, however it’s rarer,
with only 360 new cases in 2016.
Anyone can get breast cancer. However, approximately 5-10% of all breast cancer patients
carry a genetic mutation in the BRCA1 or BRCA2 gene. A gene is a short piece of
‘information’ that gives the body instructions to carry out a particular function. In the case
of the BRCA1 and BRCA2 genes, this function is to aid DNA repair, which can occur
randomly, but also increases with exposure to certain chemicals and UV light. DNA repair
helps to prevent uncontrollable cell division, reducing the risk of cancerous tumour growth.
This gives the BRCA genes the name of ‘tumour suppressor genes’, or TSGs.
Occasionally, the BRCA genes mutate (or ‘change’), which alters their function. This can
result in the inability to repair DNA, causing uncontrollable cell division, and therefore
cancerous breast tumour growth.
One in 400 people carry a mutated version of the BRCA1 or BRCA2 gene, of which is
heritable, meaning that the mutated or faulty gene can be passed on to their children (50%
chance). These mutations are much more common in Eastern European or Ashkenazi Jewish backgrounds. The reasons for this have yet to be studied in depth.
Possessing a BRCA1 mutation gives you an alarmingly high 55-65% chance of developing
breast. cancer before the age of 70 and possessing a BRCA2 mutation gives you a 45%
chance. This implies that these mutations significantly increase the risk of developing breast
cancer at a young age.
Aside from the risk of developing breast cancer, BRCA mutations also increases the risk of
developing ovarian, prostate (men) and pancreatic cancers.
If you’re diagnosed with a BRCA mutation, preventative measures can take place to reduce
the risk of developing cancers associated with these mutations. These most commonly
include mastectomies and the removal of ovaries and fallopian tubes.
However, drug treatment is rapidly becoming a more common way of reducing the risk of
developing BRCA associated cancers. An example of a drug treatment is hormone therapy
medicine, which contain compounds called SERMs (selective oestrogen-receptor
modulators). SERMs have been shown to reduce the chance of developing a particular type
of breast cancer called hormone receptor positive breast cancer.
Another, more novel way of reducing BRCA gene associated cancer risk is through the use of a drug called Olaparib. In your cells, an enzyme called ‘PARP’ (poly-ADP ribose polymerase) fixes DNA damage in both healthy and malignant (cancerous) cells. Olaparib inhibits PARP, making it more difficult for cells containing mutations to fix DNA damage, so cancerous cells are less likely to survive.
BRCA1 and BRCA2 mutant cells are 1000 times more sensitive to PARP inhibition, so this is
an effective treatment in reducing the risk of breast and other associated cancers.
In a study of 298 patients, 26.2% of cancer responded to Olaparib treatment. Although this
figure seems quite low, it’s considered a success as cancers are extremely difficult to treat.
However, uncomfortable side effects were prevalent, including nausea, vomiting and even
anaemia (low red blood cell count).
Scientists are constantly researching to develop new and more effective ways to treat
BRCA1 and BRCA2 mutations, in the hopes that one day, breast cancer incidences will
dramatically decrease, and perhaps even cure BRCA associated cancers.