Nicotine may directly promote the development of breast cancer by binding to a certain cell receptor, says a new study.
Many chemicals in tobacco are believed to be carcinogens, but little is known about how nicotine might contribute to cancer cell growth. What is known is that when nicotine binds to the nicotinic acetylcholine receptor (nAChR), it promotes smoking addiction.
In this study, Taiwanese researchers analysed 276 breast tumour samples to determine whether subunits of nAChR were overproduced in breast cancer cells compared with surrounding normal cells.
The researchers found that breast cancer cells consistently overproduced the alpha 9 subunit of nAChR (a9-nAChR), and that production of this subunit was higher in advanced-stage breast cancer than in early-stage cancer.
They then conducted laboratory tests that showed reducing levels of a9-nAChR inhibited tumour growth, while increasing levels of the subunit or treating more normal breast cells with nicotine led to the development of cancer characteristics.
"These results imply that receptor-mediated carcinogenic signals play a decisive role in biological functions related to human breast cancer development," concluded Yuan-Soon Ho, of the Taipei Medical University, and colleagues in a news release from the Journal of the National Cancer Institute, which published the study. (August 2010)