Cigarette Smoke and Saliva Form a Toxic Mix

Researchers have found that carcinogenic components of cigarette smoke mix with saliva to create a toxic mixture that is more likely to cause cancer than the cigarette smoke alone.

Oropharyngeal cancer is the most common head and neck malignancy and accounts for 2-4% of all new cancers, meaning that nearly 400,000 new cases of the illness are diagnosed worldwide each year, with the majority in developing countries.

Investigators at the Technion-Israel Institute of Technology (Haifa, Israel; www.technion.ac.il) grew oropharyngeal cancer cells in tissue culture and exposed them to either cigarette smoke alone or in combination with saliva. Control cultures were exposed to saliva alone. They reported in the May 25, 2004, online edition of the British Journal of Cancer that both cigarette smoke and the saliva and smoke mixture caused cancer-like changes in the tissue culture cells. Furthermore, the mixture was a more potent carcinogen than the smoke alone.

The cause of the increased toxicity of the mixture was the reaction between redox active metals in saliva and low reactive free radicals in cigarette smoke, which resulted in the production of highly active hydroxyl free radicals. Previously the authors had shown that cigarette smoke destroyed various salivary components, including protective ones such as peroxidase, the most important salivary antioxidant enzyme.

Senior author Dr. Rafi Nagler, professor of oral biochemistry at the Technion, said, "We know that most cases of oral cancer are due to cigarette smoke, and--in the case of cultures like Southeast Asia--from chewing tobacco. Both the cigarette smoke and chewing tobacco are focused in the region of the oral cavity and the pharynx, and we realized the common denominator was saliva. Most people will find it very shocking that the mixture of saliva and smoke is actually more lethal to cells in the mouth than cigarette smoke alone.”




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Technion-Israel Institute of Technology