α7-nAChR enhances colorectal cancer cell migration via nicotine-nitrosated derivative of NNK (Wei et al., 2009); parasympathetic nerves might promote CRC (colorectal cancer) progression through α9-nAChR; α9-nAChR is overexpressed in smoking-associated breast cancer and plays an crucial role in nicotine-induced transformation of normal human mammary epithelial cells (Lee et al., 2010). Here, CHRNA7 is linked to breast cancer.