Breast cancer cells develop resistance to aromatase inhibitors by gene amplification, according to the findings of a European research project, unveiled last night.
Researchers found the extra genes allow cells to increase production of aromatase, overwhelming the drugs.
The findings, reported in Nature Genetics, come from a project led by Imperial College, London, UK, and the European Institute of Oncology, Milan, Italy.
The findings did not apply to tamoxifen – and the researchers now plan further studies of tamoxifen resistance.
They also hope to develop a test to identify tumours that have started to increase aromatase production through amplification of the CYP19A1 gene.
Some 150 women treated for breast cancer in Milan took part in the project.
Researcher Dr Luca Magnani, from Imperial College, said: “In many cases when an aromatase inhibitor stops working in a patient, doctors will try another type of aromatase inhibitor.
"However, our research suggests that if the patient’s cancer has started to make their own aromatase, this second drug would be useless. This is why we need a test to identify these patients."
Luca Magnani et al. Acquired CYP19A1 amplification is an early specific mechanism of aromatase inhibitor resistance in ERa metastatic breast cancer Nature Genetics 23 January 2017 [abstract]
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