AsianScientist (Jun. 30, 2016) – Researchers from Australia and the US have shown the potential benefit of adding the female hormone, progesterone, to standard breast cancer treatments.
Published in Science Advances, the study reports that treatments aimed at the progesterone receptor, a protein activated by progesterone, could prolong life in women with estrogen-driven breast cancer beyond current standard treatments which target the estrogen receptor alone.
“About 75-80 percent of breast cancers are driven by the female hormone, estrogen,” said lead author Professor Wayne Tilley, director of the Dame Roma Mitchell Cancer Research Laboratories at the University of Adelaide (UA).
“One of the first clues pathologists look for in tissue from a newly-diagnosed breast cancer patient is the estrogen receptor, a protein in tumor cells that transmits the growth-promoting signals of estrogen hormones in the body. They also look for the presence of progesterone receptors, primarily to confirm that the estrogen receptor is active.”
The role of estrogen in driving tumor growth in breast cancers is well established, but the role of progesterone is the topic of much controversy. According to Tilley, this is because of past studies showing some negative effects of synthetic versions of progesterone used in hormonal therapy for postmenopausal women.
“We have known for some time that the progesterone receptor plays an important role in breast cancer, but gaps in our knowledge of the function of this receptor in breast tumors have limited the potential to develop new treatments,” explained Tilley.
“In our studies, we are using natural progesterone, or forms of this hormone that are biologically identical to the natural hormone, and testing it on breast cancer tissue taken from women with cancer.”
The present study employed a special breast cancer modeling technique that was developed by the UA group, which allowed them to test potential new treatments directly on breast cancer tissue donated by patients. It confirmed that progesterone receptors reprogram the actions of estrogen receptor, with an overall ‘braking effect’ on tumor growth.
The researchers also identified a new progesterone receptor-targeting drug that not only opposed the action of estrogen in breast cancers to halt tumor growth, but actually caused the tumors to regress. This new drug is now poised to enter clinical trials.
The article can be found at: Singhal et al. (2016) Genomic agonism and phenotypic antagonism between estrogen and progesterone receptors in breast cancer.
Source: University of Adelaide; Photo: Shutterstock.
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