A commonly prescribed abortion drug could help women who are suffering from triple-negative breast cancer, Chinese scientists have said. Their study is looking at the effects of Mifepristone on tumour growth and proliferation in transgenic mice.
What is triple-negative breast cancer?
Breast cancer is heterogeneous disease that can have different causes and require different treatments from one woman to another. A triple-negative breast cancer is characterised by the fact that three of the most common types of receptors involved in the development of most breast cancer growth − estrogen, progesterone and the HER-2 protein − are not found in the tumour.
The problem is that common treatments like hormone therapy and other drugs targeting estrogen, progesterone and HER-2 do not work because the cancer cells lack the necessary receptors. Chemotherapy is therefore the most common type of treatment used against this type of breast cancer.
About 1 in 5 women with breast cancer is diagnosed with a triple negative breast cancer. Patients are mostly young women under the age of 40.
The drug has been given to women for abortion or, at small doses, for emergency contraception, for many years now and it is seen as safe and well-tolerated.
The team published their findings in the journal Theranostics after testing Mifepristone on triple-negative cancer cells grown in the lab (cell lines) and on mice who had been transplanted with those cells.
They observed a slowed tumour growth of the cell lines and in the mice, as well as a reduction of the triple-negative stem cell populations as the drug supressed the action of KLF5, a protein responsible for cell proliferation and survival of cancer cells.
"Our findings may provide new therapeutic strategies for the treatment of triple-negative breast cancer," says Liu Rong, main author of the study.
Little evidence for human trial
However, human trials and the use of Mifepristone to treat such cancers may actually be a long way away.
"The fact that this study has only been conducted on cell lines grown in the lab and on mice limits the conclusions we can draw from it. Such tests are useful for researchers to understand how the drug works and what might be going on at a molecular level, but it doesn't guarantee that it will work on humans and it may not be enough to justify a clinical trial," Dr Kat Arney, science information manager at Cancer Research UK told IBTimes UK.
Previous trials involving women suffering from other types of breast cancer have also been carried out in the past, but have only encountered limited success. In this study, Mifepristone has only proved effective to slow tumour growth, not to destroy it.
The study also suffers from another shortcoming. Researchers have not been able to explain how the drug, which normally targets progesterone receptors, works on triple-negative cancer cells, which do not have any hormone receptors and do not normally respond to hormonal therapy.
"It is surprising that Mifepristone targets the cancer cells without hormone receptors. Since this drug is safe for women and we lack therapies for triple-negative cancer, it could be interesting but more needs to be understood about how the drug works to build the evidence to support larger trials," concludes Kat Arney.