A bacterial strain that specifically targets tumours could soon be used as a vehicle to deliver drugs in frontline cancer therapy. The strain is expected to be tested in cancer patients in 2013, according to a scientist at the Society for General Microbiology's Autumn Conference at the University of York.
The therapy uses Clostridium sporogenes, a bacterium that is widespread in the soil. Spores of the bacterium are injected into patients and grow only in solid tumours, where a specific bacterial enzyme is produced. An anticancer drug is injected separately into the patient in an inactive pro-drug form. When the pro-drug reaches the site of the tumour, the bacterial enzyme activates the drug, allowing it to destroy only the cells in its vicinity – the tumour cells.
Researchers at the University of Nottingham and the University of Maastricht have now overcome the hurdles that have so far prevented this therapy from entering clinical trials by introducing a gene for a much-improved version of the enzyme into the C. sporogenes DNA. The improved enzyme can now be produced in far greater quantities in the tumour than previous versions, and is more efficient at converting the pro-drug into its active form.
‘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,’ explained Professor Nigel Minton, who is leading the research.
‘When Clostridia spores are injected into a cancer patient, they will grow only in oxygen-depleted environments, i.e. in the centre of solid tumours. This is a totally natural phenomenon, which requires no fundamental alterations and is exquisitely specific. We can exploit this specificity to kill tumour cells but leave healthy tissue unscathed,’ he said.
The research may ultimately lead to a simple and safe procedure for curing a wide range of solid tumours. ‘This therapy will kill all types of tumour cell,’ Professor Minton said. ‘The treatment is superior to a surgical procedure, especially for patients at high risk or with difficult tumour locations.
‘We anticipate that the strain we have developed will be used in a clinical trial in 2013 led by Jan Theys and Philippe Lambin at the University of Maastricht in the Netherlands. A successful outcome could lead to its adoption as a frontline therapy for treating solid tumours. If the approach is successfully combined with more traditional approaches this could increase our chance of winning the battle against cancerous tumours.’