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Protective immune cells in breastfeeding women guard against breast cancer, research finds
Women who breastfeed develop protective immune cells that help guard against breast cancer, with effects lasting for more than 30 years, new research shows.
The study found that specialised T-cells — immune cells that fight disease — remain in breast tissue long after pregnancy and provide lasting protection, particularly against triple-negative breast cancer, one of the most aggressive forms.
Observations dating back to the 18th century, when physicians noticed nuns had some of the highest rates of breast cancer, first hinted that childbearing and breastfeeding could protect against the disease.
Modern research has confirmed this link, though the biological explanation was unclear.
Professor Sherene Loi is senior author and clinician scientist at the Peter MacCallum Cancer Centre.
The researcher said: “The key take-home messages are that pregnancy and breastfeeding will leave behind long-lived protective immune cells in the breast and the body, and these cells help to reduce risk and improve defence against breast cancer, particularly triple-negative breast cancer, but potentially other cancers as well as disease.”
Researchers from the Peter MacCallum Cancer Centre in Melbourne studied non-cancerous breast tissue from more than 260 women who had undergone breast reduction or preventive surgery.
They found that women who had given birth had more specialised immune cells called CD8⁺ T-cells — part of the adaptive immune system that targets specific threats, including cancer.
The team then tested whether these cells directly provided protection.
In mice, cancer cells implanted into breast tissue grew less in those that had pups and breastfed compared with those that had not. When the researchers removed the T-cells from the nursing mice, the protective effect disappeared.
The researchers also analysed data from more than 1,000 breast cancer patients diagnosed after childbirth with available breastfeeding records.
Women who had breastfed had better outcomes from triple-negative breast cancer than those who had not. Their tumours also contained more immune cells, suggesting ongoing immune activity against the cancer.
The study provides an explanation for why breastfeeding appears protective, and the findings could help inform new strategies for women unable to have children or breastfeed.
Understanding the underlying biology may aid development of vaccines or therapies that mimic this natural defence.
Professor Loi said: “The effects are really quite small for every individual, but population-wide the effects are large.”
She stressed that breastfeeding does not guarantee protection against breast cancer, noting it is “not a 100 per cent guarantee that they won’t get breast cancer.”
The study also explored why some breast cancers contain high numbers of specialised immune cells while others do not.
Patients with more of these cells generally had better outcomes, particularly with triple-negative breast cancer.
Professor Loi explained that T-cells react not only to viruses or bacteria but also to cancer, describing this response as “one of our very modern therapeutic weapons against cancer.”
Associate Professor Wendy Ingman from the University of Adelaide’s Medical School said longer breastfeeding duration provided greater benefits.
Each year of breastfeeding is linked to a 4 per cent lifetime reduction in the mother’s breast cancer risk.
“This study shows that having babies and breastfeeding causes long-lasting changes in immune cells that could help protect the breast from cancer,” Ingman said.
“I’m hopeful that this type of research will lead to new approaches to reduce women’s breast cancer risk.”
Small bowel microbiome differences between women and men may help explain why some conditions are more common in women, a study suggests.
The small bowel microbiome is the community of microorganisms living in this part of the digestive tract, where they play vital roles in immune function, metabolism and hormonal regulation.
Researchers found differences between women and men in the composition and organisation of these microbial communities. One bacterial community containing Granulicatella was found only in women.
The study was conducted by investigators at Cedars-Sinai Health Sciences University.
Ruchi Mathur, director of clinical research and clinical operations for the Medically Associated Science and Technology (MAST) Program at Cedars-Sinai and corresponding author of the study, said: “One intriguing finding was a bacterial community containing Granulicatella, which we found only in women.
“Bacteria in this community appear at increased levels in women with polyendocrine metabolic ovarian syndrome, formerly known as polycystic ovary syndrome.”
The researchers also identified differences between women and men in how microbes in the small bowel produce fructans, complex carbohydrates known to trigger digestive symptoms in irritable bowel syndrome (IBS).
IBS is far more common in women than men.
Mathur, who is also a professor of medicine, said: “Our findings show that biological sex is a critical variable in the small bowel microbiome.
“We must consider it as we move toward more personalised approaches to understanding and treating disease.”
An experimental cancer drug reduced bone loss and body fat in mice modelling post-menopausal changes, early research suggests.
The compound, CADD522, appeared to strengthen bones and help the animals stay leaner after surgery designed to mimic hormonal changes seen after menopause.
The treatment remains at an early experimental stage and has so far only been tested in animals.
The study, led by the University of East Anglia, investigated CADD522, which was originally developed to block a protein involved in the growth and spread of several cancers.
Mice treated with the compound for eight weeks showed significant improvements in bone health. Scans found increased bone volume and better preservation of the honeycomb-like structures inside bones that are crucial for strength and resilience.
Blood tests suggested the treatment stimulated new bone growth without interfering with the body’s normal process of breaking down and rebuilding bone.
Dr Darrell Green, lead researcher from UEA’s Norwich Medical School, said: “Osteoporosis affects around one in three women over the age of 50, leaving sufferers vulnerable to painful fractures that can seriously impact quality of life.
“Current treatments exist, but many are plagued by side effects, safety concerns or inconvenient dosing schedules that make long-term use difficult.”
The researchers also found that mice receiving CADD522 weighed less than untreated mice despite eating the same amount of food.
They had less body fat and fewer fat deposits in their bone marrow, a process commonly seen after menopause and linked to declining bone health.
The team also examined brain tissue and found that the drug appeared to reverse several menopause-related changes in fatty acids.
Levels of omega-3 fats including DHA remained largely intact, while several other lipid abnormalities shifted back towards healthier patterns.
Green said: “We didn’t directly test for memory or thinking ability, but our work raises questions about whether this drug could one day help address wider menopause-related health problems.”
Safety experiments in mice, rats and dogs found that CADD522 could be taken orally and was well tolerated.
The compound also appeared to be metabolised more slowly in human tissue than in rodents, potentially improving its performance in people.
“This is still in the early stages and has so far only been tested in animals but we hope that the benefits will translate to humans to ultimately reduce fracture rates,” added Green.
The research was led by UEA in collaboration with the University of Maryland, the Scintillon Research Institute in San Diego and the University of Stirling.
Safety testing was funded by The Sir William Coxen Trust as part of the development of CADD522 as a childhood cancer treatment.
Weight loss surgery was linked to more regular periods and fewer polyendocrine metabolic ovarian syndrome (PMOS) symptoms in women aged 18 to 45 living with obesity in a recent study.
The researchers recommend that women undergoing the procedure have access to preconception care and reproductive counselling to support their reproductive health.
Researchers at the University of Surrey analysed data over 24 months from 84 women who underwent bariatric surgery and 18 women living with obesity who did not have surgery.
Of those who underwent surgery, 49 had gastric bypass procedures and 35 had gastric sleeve surgery.
Women who underwent metabolic bariatric surgery lost more than 30kg on average at 12 and 24 months after the procedure.
Among women with polycystic ovaries, the condition persisted in only 10 per cent after 24 months.
Women also reported a resolution of clinical hirsutism, or excess body hair, by 12 months.
Women who had previously experienced irregular periods reported more regular menstrual cycles after surgery.
Professor Martin Whyte, co-author of the study and professor of metabolic medicine at the University of Surrey, said: “A large proportion of those undergoing bariatric surgery are women of reproductive age, who may be planning a pregnancy in the coming years.
“So much remains unknown about the impact of this type of surgery on women who are planning to have children.
“This raises the question of when the ideal time after surgery is to conceive.”
Women have a higher prevalence of obesity than men, with 57 per cent of women in the UK classified as overweight and 27 per cent living with obesity, which can affect fertility and the health of an unborn baby.
The researchers said 17 women had healthy pregnancies following surgery.
Although this was not specifically examined in the study, no difference in birth weight was observed between babies conceived within or after the first year.
Dr Kathryn Hart, co-author of the study and associate professor in nutrition and dietetics at the University of Surrey, said: “What we have found is that bariatric surgery positively affects the reproductive health of women living with obesity and can improve the likelihood of them having a healthy pregnancy after surgery.
“Dysregulated hormone levels, irregular periods and conditions such as polycystic ovaries are affected by obesity.
“By reducing this, what we have seen is that it can lead to improvements without the need for medication.
“We would suggest that clinicians consider medical intervention for obesity to treat irregularities in the menstrual cycle and issues with fertility.”
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