By Science Online’s Anna Salleh
A key signal that triggers the growth of breast stem cells has been identified, helping scientists to better understand how breast cancer develops.
The research was carried out by Associate Professor Jane Visvader and colleagues at the Walter and Eliza Hall Institute of Medical Research (WEHI) in Melbourne and will be published in the journal Nature.
Co-author, Associate Professor Geoffrey Lindeman, says it is an exciting finding.
“What’s exciting is that it helps spotlight some of the mechanisms that may be involved in very early stages of breast cancer,” he said.
“By identifying the signals, it might help highlight some of the methods that could be used to help either treat, or perhaps even better, prevent, breast cancers.”
The female hormones progesterone and oestrogen are involved in the development of normal breasts and in the development of breast cancer.
But researchers have noticed that increased exposure to these hormones, for example through early periods, late menopause, hormone replacement therapy, or, in the short term, pregnancy, can increase the risk of breast cancer.
Associate Professor Lindeman says that until now, scientists have not been sure which cells were involved in breast cancer, but breast stem cells have been suspected because they are long-lived and probably have time to develop the mutations linked to cancer.
But he and colleagues previously discovered that breast stem cells in mice and humans do not have receptors, or sensors, for progesterone and oestrogen.
For this latest study post-doctoral researcher, Dr Marie-Liesse Asselin-Labat, carried out laboratory research on mouse mammary stem cells (MaSCs), which Associate Professor Lindeman says bear a “striking resemblance” to human breast stem cells.
The study found that MaSCs are highly responsive to steroid hormone signalling.
“Despite lacking the sensors [for oestrogen and progesterone], the stem cell is exquisitely sensitive to hormone manipulation,” he said.
In the study, the number of MaSCs increased with pregnancy and with oestrogen and progesterone treatment, but decreased when ovaries were removed or anti-oestrogen treatments were given.
Associate Professor Lindeman says one of the study’s key findings is that cells lining the breast ducts play a kind of “middle man” role between the hormones and the stem cells.
He says these cells, which have oestrogen and progesterone sensors, respond to the hormones and then release a chemical signal, called RANK, which tells the MaSCs what to do.