Mystery of the missing breast cancer genes
Researchers from the University of Adelaide are hoping to better understand why the mutated genes for breast and ovarian cancer are not passed on more frequently from one generation of women to the next.
That’s despite a documented link between breast cancer genes and increased fertility in women.
Dr Jack da Silva from the University’s School of Molecular & Biomedical Science says that because women who carry breast cancer genes are more fertile, in theory they have a greater chance of passing these genes on to future generations.
“A recent study in the United States found that mutations in the breast cancer genes BRCA1 and BRCA2 were directly linked with a 50% increase in the fertility of women, which is a huge number,” Dr da Silva says.
“With such an increased fertility rate, you would expect to see a high frequency of these cancer-causing genes in modern populations, but in fact that is not the case - the frequencies are relatively low.”
In a paper being published today in the Proceedings of the Royal Society B, he argues that the so-called “grandmother effect” may in part be the reason behind this phenomenon.
“In an earlier study, researchers found that post-menopausal women create a ‘grandmother effect’ - that is, the longer they live, the more they are able to support their daughters and their grandchildren, thereby creating an environment in which more grandchildren are born.
Breast Cancer Myths
Myth: Only women with a family history of breast cancer are at risk.
Reality: Roughly 70% of women diagnosed with breast cancer have no identifiable risk factors for the disease. But the family-history risks are these: If a first-degree relative (a parent, sibling, or child) has had or has breast cancer, your risk of developing the disease approximately doubles. Having two first-degree relatives with the disease increases your risk even more.
Wearing an underwire bra increases your risk of getting breast cance
Reality: Claims that underwire bras compress the lymphatic system of the breast, causing toxins to accumulate and cause breast cancer, have been widely debunked as unscientific. The consensus is that neither the type of bra you wear nor the tightness of your underwear or other clothing has any connection to breast cancer risk.
Most breast lumps are cancerous.
Reality: Roughly 80% of lumps in women’s breasts are caused by benign (noncancerous) changes, cysts, or other conditions. Doctors encourage women to report any changes at all, however, because catching breast cancer early is so beneficial. Your doctor may recommend a mammogram, ultrasound, or biopsy to determine whether a lump is cancerous.
Myth: Exposing a tumor to air during surgery causes cancer to spread.
Reality: Surgery doesn’t cause breast cancer and it doesn’t cause breast cancer to spread, as far as scientists can tell from the research so far.
Your doctor may find out during surgery that your cancer is more widespread than previously thought, however. And some animal studies have shown that removing the primary tumor sometimes enables metastatic cancers to grow, but only temporarily; this has not been demonstrated in humans.
Myth: Breast implants can raise your cancer risk.
Reality: Women with breast implants are at no greater risk of getting breast cancer, according to research. Standard mammograms don’t always work as well on these women, however, so additional X-rays are sometimes needed to more fully examine breast tissue.
All women have a 1-in-8 chance of getting breast cancer.
Reality: Your risk increases as you get older. A woman’s chance of being diagnosed with breast cancer is about 1 in 233 when she’s in her 30s and rises to 1 in 8 by the time she’s reached 85.
Wearing antiperspirant increases your risk of getting breast cancer.
Reality: The American Cancer Society pooh-poohs this rumor, but admits that more research is needed. One small study did stumble on traces of parabens in a tiny sample of breast cancer tumors.
Parabens, used as preservatives in some antiperspirants, have weak estrogen-like properties, but the study in question made no cause-and-effect connection between parabens and breast cancer, nor did it conclusively identify the source of the parabens found in tumors.
Small-breasted women have less chance of getting breast cancer.
Reality: There’s no connection between the size of your breasts and your risk of getting breast cancer. Very large breasts may be harder to examine than small breasts, with clinical breast exams- and even mammograms and MRIs - more difficult to conduct. But all women, regardless of breast size, should commit to routine screenings and checkups.
“The reverse of this is that women who die earlier - such as from breast or ovarian cancer, which are usually post-menopausal - will no longer be able to support their daughters and grandchildren. This has the effect of limiting the number of grandchildren born, and therefore the chances of passing on the mutated genes from one generation to the next is also limited,” Dr da Silva says.
However, the “grandmother effect” does not entirely negate the increased fertility caused by breast cancer genes, he says.
“Our change to today’s industrial and technological age has been relatively rapid in human history. For most of our existence, we have been hunter-gatherers. During this time, female fertility was limited, and this may have reduced the increase in fertility caused by mutations of these genes.”
Dr da Silva says further studies examining modern-day hunter-gatherer societies might shed more light on how and why the spread of these genetic mutations occurs across generations.
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Dr. Jack da Silva
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61-883-138-083
University of Adelaide