Published in Science Advances: Adding progesterone to standard breast cancer treatments could be beneficial, according to a study co-authored by researchers from the University of Adelaide.
Current standard treatments target the receptor for estrogen, a protein in tumour cells that transmits the growth-promoting signals of estrogen hormones in the body.
Around 75-80% of breast cancers are driven by the female hormone. By contrast, a potential role of the sex hormone progesterone in the progression of breast cancer is less clear.
Progesterone is involved in the menstrual cycle, pregnancy, and the embryogenesis of humans. The new study now indicates that treatments that also aim at the progesterone receptor, a protein activated by progesterone, may prolong life in women with estrogen-driven breast cancer, beyond what can be achieved by targeting the estrogen receptor alone.
The researchers employed a special technique for modelling breast cancer developed at the University of Adelaide. This model allows researchers to test potential new treatments directly on breast cancer tissue donated by patients.
They were able to confirm that progesterone plays an important role in breast cancer. In addition, the study provides new insight into how progesterone receptors reprogram the actions of estrogen receptor, with an overall “braking effect” on tumour growth.
Previous reports suggested that progesterone used in hormonal therapy for postmenopausal women can have negative effects. But these results were based on synthetic versions of the hormone.
By contrast, the new study used natural progesterone or forms of this hormone that are biologically identical to the natural hormone.
The research paper provides a preclinical validation for clinical trials which will test progesterone in combination with current standard-of-care therapy.It also describes a new progesterone receptor targeting drug that opposes the action of estrogen in breast cancers and causes the tumours to regress. This new drug is now poised to enter the clinical trial phase.