Nicotine, long known to be the addictive agent in tobacco products, has been reported to be a possible promoter of cancer progression in human lung cells grown in the laboratory. Phillip A. Dennis, M.D., Ph.D., and colleagues from the Center for Cancer Research, National Cancer Institute (NCI), report in the January 2003 Journal of Clinical Investigation that nicotine may contribute to lung cancer by promoting the survival of lung cells, thereby allowing them to accumulate the genetic changes necessary for full cancer formation.
Normally, when damaged by exposure to tobacco smoke, a cell repairs the damage or, if unable to do so, undergoes a protective form of suicide called apoptosis. According to Dennis and colleagues, nicotine seems to interrupt the death sequence by activating a very strong promoter of cell survival. In laboratory-grown lung cells, nicotine activated the survival pathway within minutes of exposure.
When damaged cells survive, they may be susceptible to subsequent genetic changes that are critical for lung cancer formation, according to the researchers. They also found that the survival pathway was activated in 10 out of 10 human lung cancer specimens they examined. Finding drugs that inhibit this pathway may lead to new ways to prevent and treat lung cancer.
Some news reports of Dennis' results have indicated that nicotine causes lung cancer and that nicotine used in nicotine replacement therapy (NRT) is dangerous, in spite of the fact that nicotine itself is not a known carcinogen. It is not yet known how Dennis' laboratory findings relate to the human situation. Smoking, which delivers tar, carbon monoxide, and other chemicals along with nicotine, is a major risk to health. Therefore, any potential risks of short-term use of NRT to stop smoking are far outweighed by the significant and known benefits that accrue to patients who stop smoking.
NRT includes various patches, gums, sprays, and other products to aid in the cessation of smoking. These products contain nicotine and reduce the amount of withdrawal smokers experience as they halt tobacco use. NRT, approved by the Food and Drug Administration, has been used safely and effectively by millions of people to stop smoking.
The single most important thing a smoker can do to protect his or her health is to quit smoking. There are several effective methods smokers can use to give up smoking. According to the U.S. Public Health Service, counseling, social support, and medications, including bupropion SR and NRT, all work to help smokers quit.
NCI offers smokers help in quitting smoking through its Smoking Quitline. Information specialists can provide information about social support, referrals to local smoking-cessation programs, and other resources. The toll-free line is 1-877-448-7848 (1-877-44U-QUIT).
Lung cancer, which is most frequently caused by cigarette smoking, is the leading cause of cancer-related deaths in the United States. It claimed about 155,000 lives in 2002. Death rates for this disease, unlike many other cancers, have not declined significantly. Lung cancer kills more people than cancers of the breast, prostate, colon, and pancreas combined. There are an estimated 90 million current and former smokers in the United States, all of whom are at increased risk for lung cancer.
For more information about lung cancer, go to http://cancer.gov/cancertopics/types/lung.
For material on smoking cessation, visit http://www.cancer.gov/cancertopics/factsheet/Tobacco/cessation.
For questions and answers about cigarette smoking and cancer, go to http://www.cancer.gov/cancertopics/factsheet/Tobacco/cancer.
NCI is conducting a research study for men and women at risk for lung cancer. For more information on the National Lung Screening Trial (NLST), visit http://cancer.gov/NLST.