Drug resistant breast cancer may have met its match in a drug called metformin.

Dr. Terra Arnason and her team at the University of Saskatchewan took on a five-year-long study research the effects of metformin on multiple drug resistant breast cancer.

Dr. Terra Arnason

Dr. Terra Arnason is a clinician scientist and adult endocrinologist associate professor at the University of Saskatchewan. (Submitted by Dr. Terra Arnason)

The results were impressive, even to Arnason.

"If my mom got cancer, would I suggest to her she take metformin? I would, actually!" Arnason said.

Metformin is typically prescribed to treat Type 2 diabetes. Other studies have shown metformin is an effective treatment for cancer, but this study took it one step further.

The findings suggesting metformin can keep breast cancer cells from developing drug resistance, and can reverse drug resistance after it has appeared. The study was published in December in the open-access journal PLOS One

'The worst of the worst cancers'

"We're starting with the worst of the worst cancers and seeing if we could reverse it," Arnason said.

The team focused on drug-resistant breast cancer because women often successfully fight off the disease only for it to reappear later in life.

If my mom got cancer, would I suggest to her she take metformin? I would, actually! - Dr. Terra Arnason

Researchers used well-known markers for drug resistance, conducting experiments in both cell cultures and mouse models, and in both cases, the drug resistant markers reversed or disappeared when treated with metformin.

Arnason noted that there are limits to how much you can do in a test tube, though.

"We can cure diabetes 20 ways in a test tube, but we can't yet cure it in patients."

More compelling evidence

They've continued working in this line of research, partnering with the College of Veterinary Medicine to study the effects of metformin on dogs.

"Believe it or not, pet dogs get cancer. They get lymphoma, it's just like human lymphoma, and they develop resistance at a really high rate," Arnason said.

"We actually have had clear evidence that even in these dogs, the resistant markers in their tumours disappear when we give them metformin; that it's safe."

They've been working with the dogs for three years, and it will be another two or three years yet before they can publish a follow-up study that includes the research they've been doing with the dogs.

Only in Saskatoon

From the partnership with the College of Veterinary Medicine, to the collaboration with her co-author and colleague Dr. Gary Groot, Arnason said the study came together in a way that it only could have in a smaller centre like Saskatoon.

"I don't think that would happen in Toronto or Vancouver, where you don't have that proximity, and smaller campuses that are all located at the same place," she said.

She said without the collaborative work, she would not have been as confident in the results.

"Otherwise our paper would have all been in cells in tubes. We wouldn't have had the mouse study, growing the human tumour, which really gave us that confidence to make our conclusions."