"Jekyll and Hyde scenario" for immune cells and breast cancer

Researchers at the University of Adelaide have shown that while the immune cells known as macrophages have a role to play in the normal function of the breast, at certain stages in the menstrual cycle they may also help to make the breast more susceptible to cancer.

In a study published in the journal Biology of Reproduction, the researchers explained that as the mammary gland “undergoes development and regression over the course of the ovarian cycle under the regulation of ovarian hormones ... macrophages are implicated as local mediators of this tissue remodelling”. But in laboratory studies analysing the mammary gland cells of mice, the role of the cells was found to change because of fluctuations in hormones during different times of the month.

“These cells should be protecting our body from cancer, but at certain times of the month it appears macrophages might be allowing cancerous cells to escape immune system detection,” said Associate Professor Wendy Ingman, the lead author of the study and Head of the Breast Biology & Cancer Unit with the University of Adelaide’s School of Medicine, the Robinson Institute and the Queen Elizabeth Hospital.

“It’s sort of a Jekyll and Hyde scenario - we need the macrophages to do their job so that the breast can function normally, but at the same time they’re giving cancerous cells the chance to survive,” she said.

The research indicates that there is a “window of risk” around the time when women have their period, said Associate Professor Ingman. “This is when levels of the hormone progesterone drop, and this affects how the breast functions. At this time, immune defences in the breast tissue are down and women could be more susceptible to the initiating factors that lead to breast cancer.”

Associate Professor Ingman said researchers have known for some time that there is a link between the number of years of menstrual cycling and breast cancer risk, but only now are they “starting to understand the cell-to-cell interactions that are impacting on this risk”.

By better understanding the biological factors that underpin breast cancer susceptibility, “we might one day be able to close these windows of risk and reduce women’s lifetime risk of breast cancer”, said Associate Professor Ingman.

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