Nicotine May Directly Promote Development Of Breast Cancer

Scientists have discovered that when nicotine binds to nAchRs (nicotinic acetylcholine receptors), it may not only promote addiction, but breast cancer as well. We know that non-nicotine components of smoking are carcinogens, however, very little is known about how nicotine acts on cells to encourage cancer growth, the scientists explain.

While previous studies have linked smoking to increased breast cancer risk, they have not been accompanied by molecular biology studies to determine why. In this present study, scientists reveal a link between nicotine itself and breast cancer risk - not just the other non-nicotine components of smoking.

You can read about this study in The Journal of the National Cancer Institute, August 23rd (2010) issue.

Yuan-Soon Ho, Ph.D., Taipei Medical University, and team examined 276 breast tumor samples from anonymous donors to Taipei Medical University Hospital. They wanted to determine whether subunits of the nicotinic acetylcholine receptor were overexpressed in breast cancer cells compared with other normal cells.

They found that the alpha 9 subunit nAChR (α9-nAchR) was overexpressed in human breast cancer cells. Expression was significantly higher in advanced stage breast cancer than in its early stages.

The investigators reveal that when α9-nAchRs were reduced, tumor growth in the laboratory was inhibited. The opposite promoted cancer growth - if α9-nAchRs was increased, or when treating more normal breast cells with nicotine, the development of cancer characteristics grew.

The researchers wrote:
These results imply that receptor-mediated carcinogenic signals play a decisive role in biological functions related to human breast cancer development.

The authors stress that theirs was a small study with only Asian patients involved. Breast cancer incidence in Taiwan is low.

Ilona Linnoila, M.D., of the Center for Cancer Research at the National Cancer Institute, in an accompanying editorial, writes that 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.

Better understanding of the molecular mechanisms of the cholinergic pathways will lead to more opportunities for intervention and prevention of tobacco toxicity

"Overexpression and Activation of the {alpha}9-Nicotinic Receptor During Tumorigenesis in Human Breast Epithelial Cells"
Chia-Hwa Lee, Ching-Shui Huang, Ching-Shyang Chen, Shih-Hsin Tu, Ying-Jan Wang, Yu-Jia Chang, Ka-Wai Tam, Po-Li Wei, Tzu-Chun Cheng, Jan-Show Chu, Li-Ching Chen, Chih-Hsiung Wu, Yuan-Soon Ho
JNCI (Journal of the National Cancer Institute), doi:10.1093/jnci/djq300

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