VIPR1 (Vasoactive intestinal polypeptide receptor 1) is also known as PACAP type II receptor (pituitary adenylate cyclase activating polypeptide type II receptor). It is a receptor for both vasoactive intestinal polypeptide and pituitary adenylate cyclase activating polypeptide, and therefore more popularly known as VPAC1. VIP is a neuromodulator and growth regulator in the developing nervous system. Both VIPR1 and VIPR2 are highly expressed in central primitive neuroectodermal tumors and mediate the growth modulation of VIP in these tumors. VIPR1 gene is mapped to human 3p22-p21 where loss-of-heterozygosity is observed in small-cell lung carcinoma (SCLC) cell lines and primary tumors.