OAC researchers aim to determine sustainability of harvesting Canada yew trees as source of cancer drug
BY COLLEEN DOHERTY AND MITCH RITTER SPARK PROGRAM
A U of G researcher is pointing to Canada's hardwood forests as a potential source of a critical and expensive component of one cancer-fighting drug.
Prof. Glenn Fox, Agricultural Economics and Business, is working to determine the economic, environmental, commercial and social sustainability of perennially harvesting Canada yew trees because they're an important source of paclitaxel, a drug that has been effective in treating several types of cancer by stopping or slowing cancer cell growth. If the trees can be grown in large enough quantities and an effective harvest process is created, the drug's price could fall dramatically, he says.
Paclitaxel sold commercially as Taxol is an especially important tool in the fight against breast cancer, a disease that will strike more than 20,000 Canadian women this year alone. But the supply of paclitaxel is limited, and it can cost thousands of dollars to treat a single patient.
The Ontario Woodlot Association (OWA) sees potential for farmers and other landowners to get involved in yew farming. It's happening elsewhere in the United States, taxane products (those that inhibit cell growth, such as paclitaxel) registered $4.2 billion US in sales worldwide in 2003, says the OWA, and the demand grows.
There's concern, however, that if the yew tree isn't managed properly, the increased interest in its harvest may ultimately lead to its demise, says Fox. Before scientists knew the yew tree produced paclitaxel, it was basically ignored, making the number of available yew trees that can easily be harvested quite sparse. Now, it's a controlled species.
Fox notes, for example, that extracting paclitaxel from the yew requires the tree to be pruned, but it's not known how much pruning the plant can take and survive. The OWA recommends pruning three years' worth of growth any more and the trees may die. In addition, harvest time is crucial to maximize the taxane yield. It will generally be higher when the tree is dormant.
These are all management issues that would have an impact on a Canadian yew industry, Fox says. At the end of the day, researchers are working to set guidelines for the pruning and management of Canada yew.
He and graduate student Susan Robertson are trying to determine the pros and cons of creating plantations where Canada yew can be grown in a sustainable manner. Robertson's research has shown that growing yew in plantations would be financially viable.
Fox's research group works closely with other researchers at the Ontario Ministry of Natural Resources and at Royal Roads University in British Columbia. His work is funded by the Sustainable Forest Management Network, headquartered at the University of Alberta.
