2 July 2004

Smoke And Saliva A Potent Cancer Mix

by Kate Melville

Normally, saliva provides a protective buffer between toxins and the lining of the mouth because it contains enzymes that neutralize harmful substances. But research published in the British Journal of Cancer suggests that the chemicals in tobacco smoke, when combined with saliva, destroy saliva's protective components, creating a corrosive mix that damages cells in the mouth and eventually turn them cancerous.

"Cigarette smoke is damaging on its own, but when mixed with saliva it turns the body against itself," says co-lead researcher Dr. Raphael Nagler of the Technion-Israel Institute of Technology. "Our study shows that when exposed to cigarette smoke, normally healthy saliva loses its beneficial qualities, turns traitor and actually aids in destroying the cells of the mouth and oral cavity."

The study recreated the effects of cigarette smoke on cancerous cells of the mouth. Half the cells were exposed to cigarette smoke only, while the other half were exposed to a saliva and cigarette smoke mixture. The researchers then studied the cells to assess whether the saliva and smoke mixture would speed up the cancer's development.

The longer the mouth cells were exposed to the contaminated saliva, the more they were damaged. The researchers also found that the cigarette smoke destroyed various salivary components, including protective ones such as peroxidase, the most important antioxidant contained in saliva. Antioxidants are molecules that help protect the body against cancer.

Nagler said the reaction between certain components of saliva and the low reactive free radicals contained in cigarette smoke results in the production of highly active hydroxyl free radicals. Free radicals, oxygen by-products created by normal cell metabolism, possess unpaired electrons. In a process called oxidation, they cause cellular damage by taking electrons from molecules in healthy cells. "These hydroxyl radicals are dangerous and lethal," notes Nagler. "They attack biological molecules in a tenth of a second." Nagler and his colleagues believe this research could open new avenues for developing better ways to prevent oral cancer.