Could tobacco help cure cancer?

The tobacco plant could be modified to produce a cancer-fighting drug, scientists believe.

Etoposide is a chemotherapy drug used to treat tumours in the lung, ovaries, testes as well as lymphoma.

There is currently no way to produce etoposide without one of its key ingredients, a compound called podophyllotoxin, which is found naturally in the rare Himalayan mayapple plant.

But now, scientists at Stanford University in California, believe they have managed to genetically engineer nicotiana benthamiana - the tobacco plant - to create a new extract that outperforms one of the key ingredients needed to create etoposide.

At the moment manufacturers of the drug rely on the endangered mayapple plant to extract podophyllotoxin, a vital ingredient.

But the mayapple grows very slowly and is only found in the Himalayas.

Instead researchers focused on four genes that are known in the production of podophyllotoxin, and then analysed genetic data of the mayapple to identify similar genes.

They then manipulated a tobacco plant to express new genes, and identified the resulting compounds in leaf tissue.

In total, the authors identified six new genes that, combined with the original four, produce a new ingredient for etoposide, desmethyl-epipodophyllotoxin.

Researchers said it outperforms podophyllotoxin as an ingredient for the chemotherapy drug.

Professor Elizabeth Sattely and her graduate student Warren Lau, of Stanford University, California, said podophyllotoxin, a chemical from Mayapple, is the natural precursor to etoposide, which is 'used in dozens of chemotherapy regimens for a variety of malignancies.'

They have isolated the method by which they can recreate the ingredient in tobacco plants, and hope it could be applied to other plants.

The work, published in the journal Science, may lead to a more stable supply of the drug and allow scientists to make it even safer and more effective.

Many of the drugs we take today to treat pain, fight cancer or thwart disease were originally identified in plants, some of which are endangered or hard to grow.

In many cases, those plants are still the primary source of the drug.

Professor Sattely said: 'People have been grinding up plants to find new chemicals and testing their activity for a really long time.

'What was striking to us is with a lot of the plant natural products currently used as drugs, we have to grow the plant, then isolate the compound, and that is what goes into humans.'

She said the team hope to eventually produce the drug in yeast.

'A big promise of synthetic biology is to be able to engineer pathways that occur in nature, but if we don't know what the proteins are, then we can't even start on that endeavour,' Professor Sattely added.