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Stop cancer before it starts NS 7 apr 2001

Could a weekly pill mop up the chemicals that make tumours form?

HALF of all cancers may soon be prevented simply by taking a pill once a week, say researchers working on drugs that activate our body's natural defence mechanisms.

One such drug, called oltipraz, is already being tested. Developed and approved for treating schistosomiasis, oltipraz was found to stimulate the body to make an enzyme called glutathione S-transferase. GST neutralises carcinogens such as benzene, preventing them damaging DNA and allowing the body to get rid of the by-products. Tests in animals have shown it can prevent cancer. Toxicologist Thomas Kensler of Johns Hopkins University in Maryland is carrying out trials of oltipraz in China, where as many as 1 in 10 adults die from liver cancer caused mainly by a chemical called aflatoxin, which is found in moulds growing on rice and cereal grains. Kensier gave oltipraz once a week for two months to volunteers in Qidong. They excreted over twice as much neutralised aflatoxin in their urine as volunteers given a placebo, he told a meeting in San Diego last month. "GST was boosted in these people," says Kensler. "The carcinogen interacts with GST rather than with their DNA." Kensler is now analysing the results of a longer study. If the results are good, trials will take place over many years to see if oltipraz really reduces cases of liver cancer. GST and related enzymes detoxify a broad range of carcinogens, so the approach should protect against other types of cancer too. Raymond Bergan at Northwestern University in Illinois is now enlisting volunteers for a trial to investigate whether oltipraz can protect smokers against lung cancer. People smoking more than one pack per day will take either a placebo or an oltipraz pill weekly for 3 months, to see if the drug can alter the level of carcinogens in their lungs. Clive Bates of the British anti-smoking group ASH fears the drug will give smokers an excuse not to quit. But Bergan argues the drug would help those who can't kick the habit. "What we're looking to do is decrease the side effects for people who can't quit," he says.

High-risk groups will be the first to benefit from such "chemoprotective" drugs, but the ultimate aim of researchers is to find ways to lower cancer risk for everyone. "The cancer problem can't be solved by simply devising treatments [for people who've already got it]," says pharmacologist Paul Talalay of Johns Hopkins University, who studies how enzymes such as GST work.

In the immediate future, the best general approach is likely to be a dietary one. Chemicals that boost the production of enzymes such as GST are present in vegetables such as broccoli and Brussels sprouts, so Taialay and others are developing vegetables that contain larger quantities. "Fruit and vegetables aren't just good for you because of vitamin C. It's much more profound than that," says Raymond Wolf, a researcher for the Imperial Cancer Research Fund at Dundee University. "A key difference between drugs like oltipraz and antioxidants such as vitamin C is that with agents that induce gene expression, the effects are long-lasting." Yongping Bao of the Institute of Food Research in Norwich predicts that in three years' time we will be able to use chemicals isolated from vegetables in pills or to fortify food. Changing our diet, he says, may prevent up to half of all cancers. "If we can isolate these chemicals, there is the potential for a huge impact on cancer," agrees Wolf. He also raises the tantalising possibility that protecting our DNA from damaging chemicals will not only prevent cancer but also slow the ageing process. "In animals, you can keep switching on these enzymes for life, and the only side effect is increased longevity," Wolf says. Joanna Marchant

What's the big rush? NS 7 apr 2001

Light from the oldest supemova ever seen suggests the Universe is expanding faster and faster

THE most distant supernova ever observed appears to have blown its top when the expansion of the Universe was slowing down. Ironically, this observation boosts the idea that the Universe is filled with "dark energy" that stretches space and is now making it expand faster. Adam Riess of the Space Telescope Science Institute in Baltimore and Peter Nugent of the Lawrence Berkeley National Laboratory in California spotted the explosion in Hubble Space Telescope data.

Because the Universe is expanding, distant stars and galaxies recede from Earth and their light is stretched out, pushing it towards the red end of the spectrum. Hence, assuming the Universe expands predictably,

you can judge how far away a star is by the size of its red shift. Two years ago, two teams of astronomers reported that distant stellar explosions known as type la supernovae, which always have the same brightness, appeared about 25 per cent dimmer from Earth than expected from their red shifts. That implied that the expansion of the Universe has accelerated. This is because the supernovae were farther away than they ought to have been if the Universe had been expanding at a steady rate for the billions of years since the stars exploded.

'This transition is really the smoking gun for some sort of dark energy'

But some researchers have argued that other phenomena might dim distant supernovae. Intergalactic dust might soak up their light, or type la supernovae from billions of years ago might not conform to the same standard brightness they do today. This week's supernova finding seems to have dealt a severe blow to these arguments against an accelerating Universe. The new supernova's red shift implies it is I I billion light years away, but it is roughly twice as bright as it should be. Hence it must be significantly closer than it would be had the Universe expanded steadily. Neither dust nor changes in supernova brightness can easily explain the brightness of the explosion. Dark energy can, however. When the Universe was only a few billion years old, galaxies were closer together and the pull of their gravity was strong enough to overcome the push of dark energy and slow the expansion. A supernova that exploded during this period would thus be closer than its red shift suggests. Only after the galaxies grew farther apart did dark energy take over and make the Universe expand faster. So astronomers should see acceleration change to deceleration as they look farther back in time. "This transition from accelerating to decelerating is really the smoking gun for some sort of dark energy," Riess says. More data is needed to clinch the case, says Ira Wasserman of Cornell University in Ithaca, New York. "I'd be a little reluctant to put too much faith in one supernova," he says. But the lone observation is enough to rule out other ideas, says Michael Turner of the University of Chicago: "This supernova has driven a stake through the heart of more conventional explanations that try to avoid cosmic speed-up." Adrian Cho

A real roasting NS 7 apr 2001

The world condemns Bush for sabotaging climate treaty

GEORGE W. BUSH appears increasingly isolated this week following his unilateral rejection of the Kyoto Protocol to stem global warming. Even Americans who criticised the 1997 treaty are saying he's failed to think through the consequences. "Bush doesn't seem to have an alternative plan, and that is deeply problematic," says David Victor of the Council on Foreign Relations, a New York think tank, who was a prominent critic of Kyoto. Meanwhile, environment groups are considering telling their members to boycott American oil companies that do not set their own targets for reducing greenhousegas emissions. "The way to stand up to this is for companies as well as countries to make commitments to reduce their emissions of greenhouse gases," says Claude Martin, director-general of the World Wide Fund for Nature International.

The furore began last week when Bush announced that he doesn't support the Kyoto treaty. "It is not in the United States' economic best interest," he says. Bush says the US has to give priority to solving its energy crisis, which has triggered blackouts in California. And he promised a new climate policy, when it had been developed.

Bush's decision to turn his back on the Kyoto agreement has been attacked by leaders in Europe, Russia, Japan, Australia and by environment ministers from North and South America. "There is no serious possibility of negotiating an acceptable alternative," says Britain's environment minister Michael Meacher.

Efforts are now under way to save the agreement. European Union environment ministers meeting in Kiruna, Sweden, last weekend say they still intend to finalise the agreement in July, with or without the US.

But the mathematics are difficult. To come into force, the Kyoto Protocol has to be ratified by industrialised countries responsible for 55 per cent of carbon dioxide emissions in 1990 (see Chart). The EU plus Russia and Japan could bring it into force. Conversely, the US could block it with the support of Russia or the negotiating block that includes Japan, Canada and Australia. This week, Japan and Russia attacked Bush's stance, while Canada equivocated. Australia's environment minister Robert Hill says: "The Kyoto Protocol won't work without the US." Frank Loy, who was chief climate negotiator under President Bill Clinton, calls Bush's move "a total, unmitigated disaster". But even Clinton failed to rein in emissions. "Nearly half of the total increase in global CO, emissions since 1990 has come from the US-Rxceeding the combined emissions growth of China, India, Africa and Latin America," says Chris Flavin of the Worldwatch Institute in Washington DC.

Victor accuses the Bush administration of making policy on the hoof. 'They don't even have the full complement of people in place at the State Department to make decisions on global warming,' he says. He thinks Bush will be forced to backtrack, and introduce domestic emissions controls before the 2004 election, as opposition to his environmental isolationism grows.

Flavin says the Kyoto Protocol is the best way to encourage companies to develop new technologies, and that Bush is making .a costly economic mistake" by not joining it. 'Those countries that address climate change earliest will dominate the massive new energy technology markets of the new ce y-and create millions of jobs in the pr s," says Flavin.

Even in California, scene of the recent blackouts, they may have glimpsed that future. Sales of solar panels have rocketed as households try to obtain power independently of the grid. "This is going to be the year of solar," says state energy official Sanford Miller. "By the end of the year there's going to be a lot of houses with solar in them." Fred Pearce

Gold ftom the heavens NS 7 apr 2001

Neutron star collisions may have forged the Earth's precious metals

WHAT made the gold and platinum in your favourite jewellery? The answer may lie in some of the most violent events in the Universe: collisions between superdense neutron stars. "Probably many of the heavy elements we're familiar with on Earth were made in this way," says Stephan Rosswog of the University of Leicester.

Shortly after the big bang, the Universe contained only the light elements hydrogen and helium. When these materials later formed stars, heavier elements such as carbon and oxygen were forged in the stars' nuclear furnaces. And even heavier elements were created when very massive stars exploded as supernovae. Such explosions also blast debris into space where another generation of stars and planets form.

But when it comes to the heaviest elements, such as gold and platinum, astronomers are not sure that supernovae can create enough of them. Most of these metals must be made in a nuclear reaction called the 'reprocess", in which a nucleus consumes many neutrons in quick succession. 'You would need much more extreme conditions than you get in supernova simulations," says Rosswog. He suspected the r-process might flourish during collisions between neutron starsthe collapsed remains of stellar cores left behind after some supernova explosions. Sometimes two neutron stars orbit each other, and they can spiral ever closer together before eventually merging in a violent explosion. These mergers are rare, probably happening about once every 100,000 years in our Galaxy.

To test the idea, Rosswog's team simulated the collision of two neutron stars on a supercomputer at the University of Leicester, taking account of everything from the laws of quantum physics to Einstein's theory of general relativity. The merged stars collapsed to form a black hole, but in the process they spewed out quantities of very' hot, dense, neutron-rich ash in which the r-process could thrive.

Rosswog told the National Astronomy Meeting in Cambridge this week that neutron star mergers could easily produce the amount of heavy elements we see. 'Right now, they're the best candidate for these elements," he says. He plans to look at the distribution of the heaviest elements in old populations of stars. Because neutron star collisions are so rare, there should be an uneven distribution of these heavy elements in the early Universe. "There should be some clumpiness," says Rosswog. Stan Woosley of the University of California at Santa Cruz doesn't think it's a closed case yet. "People still don't know just how and where the r-process happens," he says. "The new calculations make merging neutron stars more attractive but will not put the issue to rest." Woosley favours an alternative scenario in which, under the right conditions, supernova explosions could leave behind neutron stars that spout jets of neutrons into space. These might fuel enough r-process reactions to build up the amounts of heavy elements we see. Hazel Muir

Victory for Monsanto NS 7 apr 2001

If modified plants contaminate your crops it could cost you dear

A CANADIAN farmer must pay Monsanto for the genetically modified crops found growing in his fields even if the seeds blew there from neighbouring fields and he never intended to grow them in the first place, a federal court ruled last week.

"Basically, the judge is saying that it does not matter how it got into your field, it's Monsanto's property. But how does a farmer know if he's got a genetically altered seed that belongs to Monsanto?' asks the farmer, Percy Schmeiser of Bruno, Saskatchewan.

The decision is an important one for Monsanto, which says it has to stop farmers stealing its property. Farmers in Canada and the US must sign agreements with Monsanto sa@'ng they will buy new GM seed each year instead of saving seeds from the previous year's harvest.

Others are dismayed. 'I think it's an incomprehensible decision, reflecting an ignorance of basic reproductive plant biology and agronomic practices. I'm completely at a loss to imagine what the judge was thinking," says Ann Clark, a plant biologist at the University of Guelph.

Investigators from Monsanto found the company's glyphosate-resistant oilseed rape, or canola, growing in Schmeiser's fields in 1998. Schmeiser says seeds probably blew off a passing truck into one field in 1997. After spraying a ditch for weeds and noticing some canola survived, Schmeiser then sprayed about three adjoining acres with glyphosate, killing off all but the resistant rapeseed. He says these GM seeds from these plants must have been accidentally mixed up with the seeds he planted in 1998.

Judge W. Andrew MacKay said he wasn't convinced, noting that 90 per cent of the rapeseed in Schmeiser's fields was glyphosate-resistant. But even if the explanation is true, he said, it was Schmeiser's duty to destroy the rapeseed once he realised it was a GM strain. MacKay rejected Schmeiser's claim that Monsanto was at fault for failing to stop the crop spreading.

Schmeiser says he had no reason to steal the rapeseed, since he did not usually apply glyphosate to his crop. But MacKay ruled it didn't matter whether Schmeiser made use of the GM plant's glyphosate resistance or not. He was infringing Morisanto's licence simply by leaving the crop to grow. The judge ordered Schmeiser to pay Monsanto C$15,450 (E6930) for the plants that grew in his fields.

'It's an Incomprehensible decision, reflectingan ignoance of plant biology'

Trishjordan, a spokeswoman for Monsanto Canada in Winnipeg, says the company tries to prevent the accidental spread of its resistant canola. Monsanto will not sue farmers whose fields are accidentally contaminated, she says, only those it suspects of growing the crop intentionally.

Schmeiser says he may appeal. He is also pursuing a counter suit against Monsanto, claiming that contamination by the glyphosate-resistant rapeseed forced him to destroy a variety that he had been developing for the past 50 years. Kurt Kleiner, Toronto

Ideal homes NS 7 apr 2001

Only certain addresses in the Galaxy are suitable for life

WANT to know where in the Galaxy you might find extraterrestrial life? Help is at hand from astronomers who have mapped out a "galactic habitable zone", a narrow region of the Milky Way where suitable terrestrial planets are most likely to exist.

Astronomers already map out the habitable zone around individual stars, which they define as the region where a rocky planet could retain enough liquid water to support life. Now Guillermo Gonzalez and colleagues at the University of Washington in Seattle have widened their sights to define a habitable zone for the entire Galaxy.

To do this, the researchers looked at the composition of the clouds of dust and gas from which stars and planets form. They'reasoned that these clouds must have the right mixture of heavy and metallic elements if they are going to create Earth-like worlds. If this "metallicity" is too low, any rocky planets that formed would be small and would cool down quickly, developing a crust that was too thick for plate tectonics to occur. The movement of tectonic plates plays an important role

in controlling atmospheric temperatures. Also, the gravity of a small planet would be too weak to retain a viable atmosphere. The composition of the clouds depended on their location in the Galaxy. Gonzalez's team found that suitable Earth-making material was concentrated in a thin ring-which contains our Sun-centred on the galactic core. Stars further out are metal deficient, and those nearer the core have too high a metallicity. Also, as you get nearer to the centre of the Galaxy the stars are closer together, and planets there would have to endure supernovae fallout and bursts of gamma rays from the core which would kill life.

Gonzalez believes that his team's analysis narrows down the places where life might arise to around 1 per cent of the Milky Way's stars. Seth Shostak of the SETI Institute in Mountain View, California, says such an analysis may affect SETI searches. But, he adds, the current programme is only targeting Sun-like stars within 150 light years, well inside the habitable zone. Mark A. Gartick More at: