The substance that makes cigarettes addictive may also cause the growth of cancer tumours, scientists revealed today.

It is the first time nicotine has been implicated as one of the chemicals in cigarettes that can trigger the development of breast cancer.

The findings, published in The Journal of the National Cancer Institute, could be a major blow to makers of nicotine-based products that help smokers to quit.

Normal cigarettes are known to contain at least 60 cancer-causing substances including carbon monoxide, tar and arsenic, but until now nicotine had not been on the list.

Researchers from Taipei Medical University looked looked at both breast cancer cells and normal cells to see if nicotine promoted tumour growth at a cellular level.

Dr Yuan-Soon Ho and his team found that when normal cells were treated with nicotine in the laboratory it promoted the development of cancer characteristics. Likewise reducing the level of nicotine inhibited tumour growth.

  The research could have a negative impact on companies that make nicotine gum, patches and electronic cigarettes that are promoted as a ‘healthy alternative’ for smokers.

The authors said their study was limited by its small sample size, which looked at just a few hundred Asian patients and further study was needed.

In an accompanying editorial Dr Ilona Linnoila of the Center for Cancer Research at the National Cancer Institute, said: ‘The study suggests not only that smoking could be causally related to breast carcinogenesis but also that nicotine could directly contribute to the molecular mechanism of carcinogenesis in addition to indirectly contributing by promoting addiction to smoking.’

She added: ‘Better understanding of the molecular mechanisms of the cholinergic pathways will lead to more opportunities for intervention and prevention of tobacco toxicity.’

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By Claire Bates
Daily Mail