Scientists in the US have, for the first time, identified a chemical in smokeless tobacco which causes oral cancer. Smokeless tobacco products have long been associated with certain cancers, including those of the oral cavity and oesophagus, but it is for the first time that a specific chemical present in these has been shown to induce oral cancers in animals.
A team of researchers at the Masonic Cancer Center of the University of Minnesota found that a compound called (S)-N'-nitrosonornicotine, or (S)-NNN, present in smokeless tobacco is a strong oral carcinogen. “(S)-NNN is the only chemical in smokeless tobacco known to cause oral cancer," said Silvia Balbo, a research associate at the Masonic Cancer Center. “This finding provides mechanistic underpinning for the epidemiologic observations that smokeless tobacco products cause oral cancer.”
In their findings presented at the American Association for Cancer Research Annual Meeting in Chicago, the researchers said they tested the effects of two forms of NNN – called (S)-NNN and (R)-NNN – on rats.
Two dozen rats were divided into four groups and given either (S)-NNN alone, (R)-NNN alone, a combination of both or tap water. The total dose was approximately equivalent to the amount of (S)-NNN to which a smokeless tobacco user would be exposed from chronic use of these products. At the end of one year, all rats assigned to (S)-NNN alone or the combination began losing weight after one year of exposure and died by 17 months. Rats assigned to (R)-NNN or tap water were terminated at 20 months.
All rats assigned to (S)-NNN had oesophageal tumours and demonstrated 100 per cent incidence of oral tumours including tumours of the tongue, buccal mucosa, soft palate and pharynx.
In contrast, researchers found oral tumours in only five of 24 rats given (R)-NNN and oesophageal tumors in three of 24 rats assigned to (R)-NNN. Twelve rats given the combination of (S)-NNN and (R)-NNN had 153 oesophageal tumours and 96 oral tumours.
According to Ms Balbo, the results reinforce the dangers of tobacco products. It also belies the perception that smokeless tobacco is safer than smoking.
"Measures should be taken to reduce this chemical in smokeless tobacco," Balbo said. "If it is not possible to stop the use of smokeless tobacco products, we should advocate for a reduction of this chemical in these products."
A team of researchers at the Masonic Cancer Center of the University of Minnesota found that a compound called (S)-N'-nitrosonornicotine, or (S)-NNN, present in smokeless tobacco is a strong oral carcinogen. “(S)-NNN is the only chemical in smokeless tobacco known to cause oral cancer," said Silvia Balbo, a research associate at the Masonic Cancer Center. “This finding provides mechanistic underpinning for the epidemiologic observations that smokeless tobacco products cause oral cancer.”
In their findings presented at the American Association for Cancer Research Annual Meeting in Chicago, the researchers said they tested the effects of two forms of NNN – called (S)-NNN and (R)-NNN – on rats.
Two dozen rats were divided into four groups and given either (S)-NNN alone, (R)-NNN alone, a combination of both or tap water. The total dose was approximately equivalent to the amount of (S)-NNN to which a smokeless tobacco user would be exposed from chronic use of these products. At the end of one year, all rats assigned to (S)-NNN alone or the combination began losing weight after one year of exposure and died by 17 months. Rats assigned to (R)-NNN or tap water were terminated at 20 months.
All rats assigned to (S)-NNN had oesophageal tumours and demonstrated 100 per cent incidence of oral tumours including tumours of the tongue, buccal mucosa, soft palate and pharynx.
In contrast, researchers found oral tumours in only five of 24 rats given (R)-NNN and oesophageal tumors in three of 24 rats assigned to (R)-NNN. Twelve rats given the combination of (S)-NNN and (R)-NNN had 153 oesophageal tumours and 96 oral tumours.
According to Ms Balbo, the results reinforce the dangers of tobacco products. It also belies the perception that smokeless tobacco is safer than smoking.
"Measures should be taken to reduce this chemical in smokeless tobacco," Balbo said. "If it is not possible to stop the use of smokeless tobacco products, we should advocate for a reduction of this chemical in these products."
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Times of India, 6 May 2012 |
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