Plant gene kills cancer cells
Genetic material from a plant has been transferred to a virus, enabling it to kill cancer cells, in research funded over the past seven years by European Union Research, Technological development and Demonstration (RTD) programmes. Cassava is one of many plants which exhibits cyanogenesis - the manufacture of cyanide to deter grazing animals. The plant achieves this by producing a chemical called linamarin which releases hydrogen cyanide when it is broken down by linamarase, an enzyme which is also produced by the plant. By transferring genetic material from cassava to a virus and introducing it into cancer cells impregnated with linamarin, extracted from cassava, lethal amounts of hydrogen cyanide can be liberated within the target cells. The technique stems from the work of Professor Monica Hughes, a geneticist at Newcastle University, whose study of cassava has enabled her to clone some of the genes responsible for cyanogenesis. Her aim is to reduce the toxicity of the plant, a staple crop for 500 million people in Africa, Asia and South America. Thousands of people have been crippled by chronic cyanide poisoning as a result of improper processing of the plant. Because cassava is rarely grown or eaten in developed countries, it is regarded as an orphan crop and has been subject to little genetic research. A collaborating research group in Madrid modified a gene isolated from cassava in Newcastle and transferred it to a retrovirus, giving it the ability to manufacture linamarase. The Madrid team was able to eradicate a brain tumour in a rat after one week's treatment with constant local release of small doses of cyanide caused by breakdown of linamarin by linamarase. The team noted that the treatment was made more effective by a large bystander effect - the release of cyanide in one cell tended to destroy neighbouring cells. Tests on human tissue samples also look promising for certain types of tumour. European Union RTD programmes have funded the research carried out by Professor Hughes over the past seven years. This source of funding has now ended and she needs more funding to develop the project further. "My next step would be to modify the genetic material with a view to making the treatment more effective when applied to mammalian cells. I believe it would be possible to obtain higher yields of active linamarase, for example," said Professor Hughes.