A simple pill may reduce the risk of side effects

The drug, mitomycin C, is used mainly to treat solid tumours in the bladder and lower bowel. It is activated by enzymes found naturally in the body.

Canadian scientists have used a natural compound to stimulate tumour cells to produce more of one of these enzymes, so the drug will work at lower doses.

The research is published in the British Journal of Cancer.

It gives us a bigger bang for our buck. Dr Asher Begleiter

Although mitomycin C (MMC) has proved to be an effective treatment for some forms of cancer it can produce severe side effects at higher doses. These can include anaemia, and a weakening of the body's ability to fight infection.

Thus any method that can reduce the dose required to provide effective treatment would be a significant breakthrough.

The researchers hope it will eventually be possible to take a pill containing the extract - which is derived from fruit and vegetables - alongside MMC.

Key target

The key enzyme targeted by the researchers, from the University of Manitoba is called NQO1.

It is usually produced at higher levels in tumours compared to normal tissues, but the Manitoba team has found that the extract stimulates production in the cancer cells still further.

As a result, tumours in mice that were fed the extract - dimethyl fumarate (DMF) - were significantly smaller than those in mice given a normal diet.

Lead researcher Dr Asher Begleiter said: "It gives us a bigger bang for our buck when using mitomycin C, which should allow us to treat patients with lower doses.

"The activating enzyme NQO1 is induced by several compounds. We chose DMF because of its natural origin and the fact that we could easily administer it in the diet, but there might be even better candidates for future clinical use."

Other possible inducing agents include extracts from vegetables such as broccoli and cauliflower.

Similarly, there are other drugs in development that, like MMC, are activated by NQO1.

If a dietary supplement is developed that successfully induces NQO1 in tumours, it is probable that it will enhance the activity of these new drugs as well.

Dr Begleiter said: "We are hoping to start clinical trials in the near future to test the potential of this therapeutic strategy.

"Given the range of potential inducers of NQO1, and the increasing number of drugs that are activated by it, there's every hope we will find a successful combination."

Dr Lesley Walker, of Cancer Research UK, said: "Mitomycin C has been used for many years to treat certain forms of cancer.

"This study shows that it may be possible to achieve the same anticancer effect with lower doses, which means fewer and less severe side effects for patients."