A treatment for cancerous tumors comes from the soil. Researchers from the University of Nottingham and University of Maastricht found that an ancient strain of harmless bacteria, which is common in the soil, can be used to kill tumors by using it as a drug delivery vehicle.

Spores of the Clostridium sporogenes bacterium thrive in low oxygen environments and can grow within tumors because there is no oxygen.

Researchers have found a way to inject the Clostridium sporogenes bacterium into patients, where it grows inside solid tumors and produces a specific enzyme.

An anti-cancer drug is injected separately into the patient in an inactive pro-drug form. When the pro-drug reaches the site of the tumor, the bacterial enzyme activates the drug, allowing it to destroy only the cells in its vicinity - the tumor cells.

Scientists at Nottingham University and the University of Maastricht introduced a gene for a much-improved version of the enzyme into the C. sporogenes DNA.  This improved enzyme can now be produced in far greater quantities in the tumor than previous versions and is more efficient at converting the pro-drug into its active form.

Scientists now plan to carry out a clinical trial after successful lab tests of the technique, as reported on Monday at the conference of the Society for General Microbiology in York. The clinical trials are expected to begin in the Netherlands in 2013.

Professor Nigel Minton from the University of Nottingham, who is leading the research, said, Clostridia are an ancient group of bacteria that evolved on the planet before it had an oxygen-rich atmosphere and so they thrive in low oxygen conditions.

When Clostridia spores are injected into a cancer patient, they will only grow in oxygen-depleted environments, i.e. the centre of solid tumors.

This is a totally natural phenomenon, which requires no fundamental alterations and is exquisitely specific. We can exploit this specificity to kill tumor cells but leave healthy tissue unscathed, said Minton.

According to Minton, this procedure would be more effective than surgeries especially for patients with high risk or difficult tumor locations.

The bacterium's ability to target tumors and cancer cells while leaving healthy tissues unaffected could make it a landmark treatment for cancer.

Finding ways to target treatments to cancer cells while leaving healthy cells unharmed is a key aim of researchers around the world, said Nell Barrie, senior science information officer at Cancer Research UK, reports BBC News.

However, since the approach hasn't yet been tested in patients it would be some time before researchers will know whether it will offer real benefits, Barrie added.