Lemjabbar-Alaoui et al. (2006)[20] demonstrated that hedgehog signaling proteins are critical mediators of cigarette smoke-induced disease, such as lung cancer and chronic airway inflammatory disease, and the expression levels of hedgehog signaling proteins are modulated by HHIP. Based on our current study of HHIP polymorphisms and the Hh signaling pathway, we need to further our mechanistic research in the context of smoking. Here, HHIP is linked to lung cancer.