Yew cuttings to fight cancer

Yew hedges which have grown at St John's for over 60 years are being used to make drugs to fight cancer.

The mature hedges in the Master's garden are clipped annually to maintain their shape and promote new growth. Rather than being burned or composted, however, the clippings are now being collected and used in the manufacture of drugs for chemotherapy.

English yew (taxus baccata) contains poisonous alkaloids that prevent cell division in humans and animals. Because of their toxicity, the planting of yew trees has often been restricted due to health concerns. While deadly at high doses, research conducted in the 1990s by scientists from Leicester University and the University of Manchester showed that a particular compound extracted from yew needles can be lethal to leukaemia cells and cancerous tumours in humans, preventing them from growing and dividing.

The compound, called 10-Deacetylbaccatin III, is found at the highest concentration in the new growth needles of yews that are clipped each year. Annual trimming stimulates the production of this compound in greater quantities than can be found in old growth trees.

There are two chemotherapy drugs, docetaxel and paclitaxel, which are developed using yew tree extract. They are mostly used in the treatment of breast and ovarian cancer. Both drugs can now be made semi-synthetically in the laboratory, but fresh yew still forms an important part of the manufacturing process.

Adam Magee, the College's head gardener, said: “Instead of just cutting and letting the offcuts drop, we collect them on sheets and store them somewhere dry and cool to prevent them from decomposing so the useful compounds can be extracted from them. This year, we have collected over 365kg of usable yew clippings which will go to fight cancer. The cuttings would otherwise go to waste, so I’m glad that St John’s can help out with this very worthwhile cause”.

The yew clippings are collected by the Doncaster-based company Friendship Estates, who have been collecting yew from the gardens of stately homes, churches and universities across Britain to provide raw materials for the pharmaceutical industry since 1992.

Matthew Cooke of Friendship Estates said: “We collect yew clippings from several gardens in Cambridge and all around the country and dry them to preserve and stabilise the leaves. They are then sent to a company in Europe who isolate and extract the active compound. This is then supplied to the medical industry to make drugs to fight cancer”.

“Demand for the treatment has increased in recent years, so we are very happy to have a partnership with St John’s College to help supply the raw materials we need”.