Published on 26 March 2015

Researchers in Japan have found that the risk of developing cancer could be reduced by more than a third in people taking the drug metformin.

The study by scientists at Okayama University found that metformin, used to treat type 2 diabetes, helps towards the rejection of tumours by supporting immune cells.

The results were recently published in the report Immune-mediated antitumour effect by type 2 diabetes drug, metformin in the journal PNAS (Proceedings of the National Academy of Sciences in the United States of America).

Type 2 diabetes drug could help prevent cancer tumours from developing

For people taking metformin the decrease in the risk of cancer was found to be 30 to 40%. This figure is in striking contrast with people taking insulin-based diabetes treatments, linked to increases in developing cancer. However, the causes for metformin’s anti-cancer effects has so far not been well understood.

Heiichiro Udono and colleagues at Okayama University and Kawasaki University in Japan looked to explain these anti-cancer responses in a report investigating the drug’s effects on the immune system’s T cells (a type of white blood cell that plays a key role in the immune system). 

The researchers tested the effects of dissolving metformin in the drinking water of mice injected with leukaemia cells and confirmed complete rejection of the tumours. When the mice were subsequently re-injected with twice the amount of cancer cells, no tumours formed as cells that have encountered a disease or cancer can respond more quickly when faced with the same pathogen a second time. This improved ‘memory response’ on second encounter was observed in the metformin study. 

Renal (kidney) and skin cancers also responded to the treatment and low doses similar to diabetes prescription treatments were still effective for tumour rejection. Further experiments with mice lacking certain cell types showed that the influence of metformin on other cells for the anti-cancer effects. 

The paper authors said: “These findings provide novel insights into anti-cancer immunity.”

They added that further work is needed to study the effects on different types of tumours and to clarify the specific cellular and molecular mechanisms involved. 

The purpose of metformin is to reduce hyperglycaemia (high blood sugar levels), and the drug helps stop insulin resistance.

Dr Mayank Patel, Consultant Physician in Diabetes at University Hospital Southampton, NHS Foundation Trust, and DRWF leaflet author, said: “The potential for metformin to reduce the risk for developing cancer has been remarked upon for a little while now in the medical community. Whilst the observations of this study are very interesting, it has to be remembered that this was animal based research and as acknowledged by the authors, further work is needed before directly extrapolating these mechanisms for the observed effects to humans.”

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