Numerous studies have demonstrated the link between the gut microbiome and disease. There have also been many studies that reveal how high dietary intake of animal products, processed foods, alcohol, and sugar support a gut microbiome that encourages inflammation and poor health. Now, new research by scientists at Wake Forest School of Medicine shows that diet, including fish oil supplements, can not only alter the breast microbiome, but also breast cancer tumors.
Their findings are published in the journal Cancer Research in a paper titled, “Diet alters entero-mammary signaling to regulate the breast microbiome and tumorigenesis.”
“Obesity and poor diet often go hand-in-hand, altering metabolic signaling and thereby impacting breast cancer risk and outcomes,” wrote the researchers. “We have recently demonstrated that dietary patterns modulate mammary microbiota populations. An important and largely open question is whether the microbiome of the gut and mammary gland mediates the dietary effects on breast cancer. To address this, we performed fecal transplants between mice on control or high-fat diets (HFD) and recorded mammary tumor outcomes in a chemical carcinogenesis model.”
Previous studies have reported how disrupting the microbiome of mice caused hormone receptor-positive breast cancer to become more aggressive and spread more quickly. In this current study, researchers undertook a multi-prong approach to study both animal models and breast cancer patients to understand the relationship between microbiome, diet, and cancer risk.
Mice susceptible to breast cancer were first fed either a high-fat or low-fat diet. The researchers observed that mice consuming the high-fat diet had more tumors, which also developed more quickly and were larger than the tumors in the group receiving the low-fat diet.
The researchers then performed fecal transplants to study the microbiome. Mice consuming the low-fat diet received the high-fat diet microbiome transplant, and mice consuming the high-fat diet received the low-fat diet microbiome transplant. To their surprise, researchers observed that the mice that consumed the low-fat diet and received a high-fat diet microbiome had about the same amount of breast tumors as mice that had consumed the high-fat diet.
“Simply replacing the low-fat diet gut microbiome to the microbiome of high-fat diet consuming animals was enough to increase breast cancer risk in our models,” explained Katherine L. Cook, PhD, assistant professor in the surgery-hypertension and cancer biology departments at Wake Forest School of Medicine. “These results highlight the link between the microbiome and breast health.”
The researchers also conducted a double-blind placebo-controlled clinical trial with breast cancer patients. Patients either received placebo or fish oil supplements for approximately two to four weeks before lumpectomy or mastectomy.
Fish oil supplementation significantly modified the breast microbiome in both non-cancerous and malignant breast tissue. Researchers also found decreased proportional abundance of Bacteroidales and Ruminococcus microbes in the breast tumors of patients taking the supplements, but the significance is unknown.
“This study provides additional evidence that diet plays a critical role in shaping the gut and breast microbiomes,” Cook added.
Looking toward the future, the researchers are conducting additional studies on whether probiotic supplements can affect microbiome populations in mammary glands and in breast tumors.
“This study demonstrates a link between the gut and breast that mediates the effect of diet on cancer,” concluded the researchers. Their findings highlight the potential dietary interventions may have in reducing breast cancer risk.