A commonly prescribed diabetes drug also has the potential to boost the immune system's response to cancer treatments, Canadian and American researchers have found.

In studies on mice published in Wednesday's issue of the journal Nature, Prof. Yongwon Choi, a professor of pathology and laboratory medicine at the University of Pennsylvania in Philadelphia, and his colleagues found the drug metformin increases the effectiveness of an experimental anti-cancer vaccine.

'I like to think of it as an immune system booster.'— Prof. Russell Jones

Cancer and diabetes may seem quite different, but researchers are uncovering common metabolic pathways in both diseases.

Cancer vaccines aim to treat the disease rather than prevent it, by priming the immune system to recognize cancerous cells as a threat before they grow out of control.

The challenge of cancer vaccines is to get the immune system to recognize the threat posed by cancer cells and mount enough of a response to eliminate the tumour, said study co-author Russell Jones, a professor at McGill University's Goodman Cancer Centre in Montreal.

The team said they serendipitously discovered that the immune system's specialized white blood cells known as CD 8 T-cells switch from burning glucose to fatty acids following infection.

"While I definitely would stop short of saying, 'Let's take it as a prophylactic therapy' [for cancer], because I think it's more complex than that, it certainly gives hope," said Jones, who also works in McGill's pathology department.

"Essentially, I like to think of it as an immune system booster."

Causing the cells to switch to burning fatty acids using the anti-diabetes drug metformin enhanced the immunological memory of CD 8 T-cells in mice, and significantly improved how well an experimental vaccine worked against an aggressive tumour, the researchers found.

Traditionally, immunological memory is important for mounting a speedy response to bacteria or viruses after a vaccine primes the immune system to recognize the threat.

Tricking cells

Metformin is known to bring down blood sugar levels by mimicking starvation.

In the experiments, mice engineered to lack immunological memory were unable to switch from using glucose as a fuel source to using fatty acids.

Giving metformin "tricked" the T-cells into thinking they were starved, and restored their immunological memory, Jones explained.

The immunological memory of normal mice also improved.

The findings are potentially extremely important for both therapeutic and preventive vaccines, the researchers said.

The study's first author, postdoctoral fellow Erika Pearce of the University of Pennsylvania, now plans to test the immune boosting approach in humans, to determine the best time and approach to deliver it.

Human trials should proceed faster than the 15 to 20 years it normally takes to develop a drug, Jones said, since the researchers aren't starting from scratch. Metformin is reasonably well tolerated in people with Type 2 diabetes, and the team effectively gave the mice the same dose that patients receive.

The research was funded by the U.S. National Institutes of Health, Canadian Institutes of Health Research and the National Cancer Institute.