Bacteria that thrive in oxygen starved environments have been used successfully to target cancer tumours, delivering gene therapy based anti-cancer treatments, according to scientists.
For about half of cancer sufferers our traditional treatments such as radiotherapy and chemotherapy are ineffective, so alternative techniques are being developed to target their tumours.
"To target a tumour with gene therapy you need three things. You need to be able to distinguish the tumour from its surrounding healthy tissue. You need to identify a therapeutic gene which will treat the problem. And you need some way of delivering the gene to the tumour," says Dr Jan Theys of Maastricht University, the Netherlands.
"The majority of solid tumours contain regions of low oxygen or dead tissue. This environment encourages the growth of certain bacteria such as the Clostridium family, making them an ideal agent to deliver anti-cancer treatments," says Dr Theys. "We have now shown that genetically engineered clostridia can successfully treat tumours in animals."
Although some notorious clostridia are responsible for causing serious illnesses such as tetanus and botulism, most of them don't cause any diseases in people. They are all anaerobic bacteria, but most can form highly resistant spores which allow them to survive even in oxygen-rich conditions, although they cannot grow or multiply there. But once they meet favourable conditions, such as the dead areas inside tumours, the spores can germinate and the bacteria thrive, making them ideal to target cancers.
The scientists from Maastricht, collaborating with researchers at Nottingham University to speed up progress by sharing technology and knowledge, have proved that using these bacteria to target cancer tumours is effective.
"Our important findings are that if clostridial spores are injected into an animal with cancer they spread throughout the body, but only spores that reach an oxygen starved area of a tumour will germinate, multiply and become active," says Dr Theys. "We know we can genetically engineer clostridia to express essentially any type of therapeutic gene. We have now shown that it is possible to use clostridia to deliver gene therapy safely in experimental animals. And finally, we have demonstrated effective anti-tumour results using these genetically engineered clostridia in animals with tumours."
The research is an important advance in the fight against cancer because clostridia are most effective in the oxygen starved areas of tumours, and it is precisely these areas which are the most difficult to reach with current cancer therapies such as radiotherapy and chemotherapy. The Maastricht scientists believe that a substantial number of patients could benefit from their new treatment strategy.
"For example, only about one third as many lethal DNA disruptions are caused by normal radiotherapy in low oxygen cancer cells as in high oxygen areas. This means that the cancer may not die. By using our gene therapy technique in combination with conventional treatments, we hope to increase the effectiveness of cancer treatments. The next step is to evaluate our technique in a Phase 1 clinical trial of human patients," says Dr Jan Theys of Maastricht University.
Dr Theys presented the paper 'Anaerobic bacteria in cancer treatment' on 06 September 2007 in the Anaerobe 2007 session of the 161st Meeting of the Society for General Microbiology at the University of Edinburgh.
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