Nicotine could directly promote the development of breast cancer as it might be binding to a specific receptor in the body to promote an addiction to the substance, says a new study conducted by researchers in Taiwan.

Researchers led by Yuan-Soon Ho of the Taipei Medical University revealed that human breast cancer cells consistently over-expressed the alpha 9 subunit of the nAChR (nicotinic acetylcholine receptor). And the expression was substantially higher in advanced stages of breast cancer compared to early stages of the disease.

While several chemicals in tobacco contain carcinogens, little is known about how nicotine contributes to the growth of cancer cells. However, the current study has made it clear that nicotine binds to nAChR and promotes further smoking addiction.

As part of the study, the researchers analyzed 276 breast tumor samples to decipher whether sub-units of nAChR were in more number in breast cancer cells as compared to normal cells. It was found that breast cancer cells over-produced the alpha 9 sub-unit of nAChR and that production was higher among advanced stage cancer patients.

Further, the research team also conducted tests that found reducing levels of a9-nAChR inhibited tumor growth, while increasing levels of the subunit 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," says Yuan-Soon Ho, of the Taipei Medical University.

The results of the study have been reported online in the Journal of the National Cancer Institute. The authors have warned that more tests will be required to establish this theory as their study was limited due to its small sample size and that it only included Asian patients.