Simply adding a low-cost hormone to the therapy of women suffering
from breast cancer could slow tumor growth in about half of them,
according to a new study released in Nature.
After treating the cancer with progesterone in combination with the
hormonal drug Tamoxifen, researchers found that tumors were half the
size of those treated with just the drug alone.
“This important research helps explain why some breast cancer patients have a better prognosis,” explains
Dr. Jason Carroll from the University of Cambridge, who co-led the
study. “Crucially, it has provided a strong case for a clinical trial to
investigate the potential benefit of adding progesterone to drugs that
target the oestrogen receptor, which could improve treatment for the
majority of hormone-driven breast cancer.”
Scientists have already shown
that by blocking the hormone estrogen from attaching to certain types
of tumor cells that express estrogen receptors, it is possible to slow
the cancer's growth. This is in effect what the drug Tamoxifen does, putting a brake on the cell division within the tumor.
But what they didn’t know was why those women who had tumors that
express not only estrogen receptors, but also progesterone receptors –
known as “double positive” cancers – have a far better chance of
survival. It turns out that when progesterone binds to the tumor cell,
it also alters the receptor for estrogen, changing its activity and
basically putting a second brake on cell growth.
“We used state-of-the-art DNA reading technology to create maps
showing where the estrogen receptor attaches to DNA to switch on genes,”
says
Carroll. “We then compared these maps in breast cancer cells grown with
and without progesterone. This revealed how the 'switched on'
progesterone receptor redirects the estrogen receptor to different DNA
regions – switching on a different set of genes that slow down cell
growth.”
With around 1.7 million
women diagnosed with breast cancer each year, it’s thought that the new
treatment – which is simply adding the cheap and easily available
progesterone to Tamoxifen – could benefit up to half of them. But first,
it needs to go through a clinical trial.
This research was only possible because researchers at the University
of Adelaide were able to “rescue” tumor cells removed from
participating patients, and use them to test new forms of therapy. They hope
that in the future, this technique could even be used to provide
personalized treatment for women by testing out different therapies on
the cells in the lab before giving them to the patient.