A widely-used diabetes drug may have the ability to reverse breast cancer drug resistance, research suggests.
Scientists found that metformin, used to treat type 2 diabetes, reduced the proliferation of tumour cells in the laboratory.
It also prevented or delayed resistance to the chemotherapy drug doxorubicin.
Other laboratory experiments and tests on mice showed that metformin reversed protein markers associated with multiple drug resistance (MDR).
This meant the drug might help resistant breast cancers to start responding to treatment again, said the researchers.
The drug is thought to act through a number of pathways involving histones, proteins that package DNA and also play a role in gene regulation.