Chen et al. (2011) found that the same line xenografted in BALB/c-nu/nu mice induced cyclin D3 over-expression after exposure to nicotine, whereas silencing α9 nAChR expression in breast cancer cells reduced in vitro and in vivo cyclin D3 levels, cell proliferation, and tumorigenic potential (Chen et al., 2011). This evidence concerns the gene CCND3 and breast carcinoma.