Breast cancer is also the most common cancer among females in the United States, which is parallel to skin cancer.
Two-thirds of breast cancer tumors are sensitive to hormones like estrogen and progesterone, indicating that the tumors cells have receptors that use the hormones as a fuel to grow.
Breast cancer, known as estrogen receptor-positive (ER+), is the most common type of cancer.
However, research suggests that the breasts'' unique microbiome changes with diet or the appearance of tumors.
Probiotics, according to scientists at Wake Forest University in Winston-Salem, Canada, might increase the anticancer effect of the breast cancer medication tamoxifen, which is a common endocrine-targeted therapy.
At the Endocrine Society''s annual conference in June, lead researcher Katherine L. Cook presented the teams findings. Dr. Cook is an associate professor in the Department of Surgery and Cancer Biology at Wake Forest University School of Medicine.
Dr. Parvin Peddi, a medical oncologist and director of breast medical oncology at the Margie Petersen Breast Center at the Providence Saint Johns Health Center in Santa Monica, California, was not involved in the study.
Normal breast tissue responds to the fluctuating hormones in a woman''s body, as every woman knows with periods and menstrual cycles or if someone has been pregnant. [When] there are changes in the hormone level, breast tissue has so-called receptors for estrogen inside the cells, and they are basically these keyholes.
Most breast cancer tumors are triggered by this mechanism, according to Dr. Peddi, to increase estrogen receptors.
The breast microbiome
A microbiome is a collection of microorganisms (such as bacteria, viruses, and fungi) that inhabit a particular environment. Distinct microbiomes exist in and within the human body.
The gut microbiome is the most common and well-known, but the breast also has its own microbiome.
Researchers at Wake Forest wondered if endocrine-targeted therapies used to prevent ER+ breast cancer recurrence might have a similar effect.
What is endocrine-targeted therapy?
Endocrine-targeted therapy, also known as hormone therapy, is prescribed to help reduce estrogen levels or prevent its effects. Tamoxifen is a medication commonly used to help lower the risk of breast cancer in high-risk individuals and prevent recurrence after surgical removal. Other examples include fulvestrant and aromatase inhibitors, such as exemestane.
Peddi said that endocrine therapy is generally well-tolerated with moderate side effects: [Endocrine therapy is] not like chemo that you use a big hammer and try to kill cancer that way. [Its] a slow removal of the estrogen, [a] slow dying option with cancer cells.
The studys methods
Three sub-studies were conducted by Dr. Cook and her Wake Forest team to examine how tamoxifen, a breast cancer medication, and other endocrine-targeted therapies affect the breast microbiome in the treatment of ER+ tumors.
A mouse model was fed a Mediterranean-style or a Western, high-fat diet during the first preclinical exercise and was given tamoxifen for three months.
Animals given tamoxifen developed elevated levels of Lactobacillus in their breast tissue. Lactobacillus is a Gram-positive bacteria known for probiotic anti-inflammatory properties.
The researchers then transplanted Lactobacillus into the mammary glands of mice that were engineered to develop breast tumors. These animals showed less breast tumor formation and proliferation.
Large animal populations had been removed from the ovaries in order to simulate menopause in the second phase of this study.
These subjects were given tamoxifen for 2.5 years, and these animals also had elevated levels of Lactobacillus in their breast tissue.
Dr. Cook and her colleagues studied tissue from ER+ breast tumors from women receiving neoadjuvant endocrine therapy. This therapy included the administration of aromatase inhibitors or Faslodex.
Samples from women with high levels of Gram-positive bacteria in their tumors showed decreased levels of cancer cell growth.
Dr. Cook enlisted the help of his father John Cook.
The fact that we have identified this potential population in the breast tissue that is regulated by most cancer therapies and that this population does have a potential anticancer indication [indicates] the conclusion that the breast has its own unique bacterial microbiome that can be modified by diet and drug administration and that it might be a novel targetable factor to prevent breast cancer risk and reoccurrence.
Directions for future research
This work is subject to some limitations as a preclinical study.
Dr. Cook said that it is necessary to understand whether or not [the findings] would be applicable in clinical trials.
As Dr. Peddi said, the study does not establish the causality.
Dr. Cook stated that her team is currently contemplating utilizing over-the-counter probiotics combined with endocrine-targeted medications to improve outcomes.
This research phase focused only on the effect of Lactobacillus on the breast microbiome. Dr. Cook said her team is now looking at whether all antibiotics may alter the breast microbiome.