Minn. researchers find 'smoking gun' link between nicotine and cancer

Researchers at the University of Minnesota have detected two substances in tobacco smoke that directly cause lung cancer, and they say the finding may help one day predict which smokers will develop the disease.

The U of M studied two large populations of people. One group, called the Shanghai Cohort Study, enrolled more than 18,000 men. The other, the Singapore Chinese Health Study, included 63,000 men and women.

Researchers followed both groups for 10 years. During that time, 246 smokers developed lung cancer.

"This is the marker we are thinking down the road can be used as a tool for screening higher-risk smokers."

The U of M team took urine samples from those smokers, and compared them with other smokers in the study who didn't develop the disease.

They discovered that the smokers with lung cancer had much higher levels of a nicotine byproduct called NNAL.

Those with the highest levels of the compound, and another byproduct called cotinine, had a nearly nine-fold increased risk of developing lung cancer compared to smokers with the lowest levels of the compounds.

Dr. Jian-Min Yuan, who led the study, says individuals differ in the way they metabolize the chemicals in cigarette smoke. Slow metabolizers appear to have a greater risk of bad chemicals causing problems in their cells.

But he says smokers haven't had any way of knowing whether they're slow or fast metabolizers, which he hopes to change.

"This is the marker we are thinking down the road can be used as a tool for screening higher-risk smokers," he said.

Yuan says it could be years before there is a test smokers can use to assess their risk of lung cancer.

He says even then, the information shouldn't be used by low-risk smokers as a reason to continue smoking. He says there are many other deadly conditions, including heart disease, that are linked to smoking.

Dr. Stan Glantz, a cardiologist and tobacco researcher at the University of California, agrees.

"Just because you happen to be in a group which is at a relatively lower risk of lung cancer, that doesn't mean that you're not going to be at increased risk of, say, heart disease because of the smoking," said Glantz.

Glantz calls the U of M study interesting, and he says it probably is useful to have a test that could measure a smoker's risk of lung cancer. He says doctors could use that information to make a stronger case against smoking.

But Glantz also thinks the university's study is a little overhyped.

"I think it's an overstatement to say this is the first time people have made a direct link," he said.

Glantz says researchers have known for a long time that some carcinogens in cigarette smoke do very specific damage to cells that ordinarily would stop tumor growth. He believes that research was the first direct link that proved tobacco smoke causes lung cancer.

But semantics aside, Glantz and others say the research has the potential to save lives.

"It's a very promising story because there are so few methods of detecting," said Bob Moffitt with the American Lung Association of Minnesota. "We've really not been able to find any practical way to screen for lung cancer early, like we have for other forms of cancer. So if we could ever find this, this will really be the magic bullet that might be able to help save a lot of lives."

But there's another tactic Moffit thinks might work even better -- raising the cigarette tax. He says higher cigarette taxes are a proven way of reducing smoking rates.

Moffitt says he thinks the recent 60-cent-per-pack hike in the national cigarette tax is already working, based on the number of calls his organization has received on its tobacco cessation hotline.

"A 34 percent increase since the federal tax increase on tobacco products began on April 1. So there are many, many people who are calling us, looking for ways to quit, they've decided it just cost too much to smoke," said Moffitt. "They know it's bad for their health. They've wanted to quit for a long time. And the higher cost is just giving added incentive for them to do so."

Minnesota DFL lawmakers unveiled a bill today that increases the state tax on cigarettes by an additional 54 cents per pack.

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