Gastrin-releasing peptide receptor (GRPR) is a Bombesin Receptor. In addition to its involvement in autism and mental retardation, GRPR may also play a role in the progression of cancer. Nicotine exposure induces an increase in GRPR expression in the lung Shriver et al. (2000). GRPR has been reported in brain, breast, colon, lung, lymph node, ovary, placenta, prostate, stomach, and uterus. It has also been shown to be expressed in several cancers, including those in breast, colon, lung, ovary, pancreas, and prostate.