July 2, 2001 -- For smokers who try to quit using a nicotine skin patch or nicotine gum, it sounds like damned if you don't, and damned if you do. A new study in the July issue Nature Medicine suggests that nicotine by itself can stimulate the growth of new blood vessels, a key feature of both cancerous tumors and artery-clogging atherosclerosis.
But if you're struggling to stop smoking, relax (if you can): The overall benefits of kicking the habit far outweigh the theoretical risk from short-term use of replacement nicotine, emphasize experts interviewed by WebMD.
Nicotine replacement therapy is an effective way to help people quit smoking, says researcher John P. Cooke, MD, PhD. "It is so important to stop smoking that certainly this article -- which is in mice and not in men -- shouldn't dissuade people from using nicotine replacement therapy," says Cooke, associate professor of medicine and director of vascular medicine at Stanford University, in an interview with WebMD.
"However, nicotine replacement therapy should be used as directed: Short-term, which is how it is approved by the FDA." Long-term use, which is not recommended, may have unwanted side effects.
Researcher Rakesh K. Jain, PhD, who studies blood vessel growth, and who wrote an editorial accompanying Cooke's study, agrees.
"I think people should not panic here," he says, because the finding needs to be further investigated. Jain is with the division of radiation oncology at Massachusetts General Hospital in Boston and a professor of radiation oncology at Boston's Harvard Medical School.
Building on a previous study from the University of California at Davis, Cooke and colleagues studied the effects of nicotine on human blood vessel cells. In these lab studies, they found that nicotine caused a substantial increase in the number of cells and interfered with programmed cell death, a trick the body uses to get rid of old, unwanted cells. Many types of cancer cells have lost this ability to die off naturally.
In addition, when the researchers gave nicotine to mice with human lung cancer and atherosclerosis, or narrowing of the arteries, they observed that nicotine promoted new vessel growth in both the tumors and within the atherosclerotic growths -- both are signs of disease progression.
One of the most significant findings was that nicotine had these effects at concentrations found in the blood of moderate smokers. This suggests that long-term treatment with nicotine in smoking cessation programs or in experimental therapies for Alzheimer's disease and chronic pain may have hidden risks.
In his editorial, however, Jain notes that in previous studies of animals exposed to nicotine, there was no evidence that nicotine contributed to either new blood vessel growth or heart and blood vessel problems.
But both Jain and Cooke agree that there may be potential risks to patients who use nicotine-based therapies for a long time. They also caution that researchers who are considering nicotine therapies for other diseases must take into account recent evidence suggesting that certain byproducts of nicotine appear to be cancer-causing agents, and that, as Cooke and colleagues write, cancer growth and blood vessel growth "are inextricably linked."