Binding nicotine to the nicotinic acetylcholine receptor not only makes smoking addictive, but may also directly contribute to the development of breast cancer, warn researchers from Taiwan in The Journal of the National Cancer Institute.
Smoking is a known risk factor for various types of cancer. Since the ingredients in cigarettes are mostly carcinogens, little is known about how nicotine itself works during the formation of cancer cells. It is known, however, that smoking increases the risk of developing breast cancer significantly.
Researchers at Taipei Medical University wanted to see how nicotine influences the development of breast cancer at the cellular level. They examined 276 samples of this tumor from anonymous patients of a hospital in Taipei and found that breast cancer cells significantly upregulated a gene encoding one of the nicotinic acetylcholine receptor (alpha9-nAchR) subunits.
Expression of the alpha-9 subunit of this receptor was the higher the more advanced the tumor stage.
Moreover, the authors found that lowering the level of the alpha 9 nAChR subunit inhibits cancer growth in the laboratory, and increasing the level of this receptor subunit or exposure of breast cells to nicotine promotes cancer development. (PAP)