We have recently cloned the mouse activity-dependent neuroprotective protein (ADNP). Here, we disclose the cloning of human ADNP (hADNP) from a fetal brain cDNA library. Comparative sequence analysis of these two ADNP orthologs indicated 90% identity at the mRNA level. Several single nucleotide polymorphic sites were noticed. The deduced protein structure contained nine zinc fingers, a proline-rich region, a nuclear bipartite localization signal, and a homeobox domain profile, suggesting a transcription factor function. Further comparative analysis identified an ADNP paralog (33% identity and 46% similarity), indicating that these genes belong to a novel protein family with a nine-zinc finger motif followed by a homeobox domain. The hADNP gene structure spans ϳ40 kilobases and includes five exons and four introns with alternative splicing of an untranslated second exon. The hADNP gene was mapped to chromosome 20q12-13.2, a region associated with aggressive tumor growth, frequently amplified in many neoplasias, including breast, bladder, ovarian, pancreatic, and colon cancers. hADNP mRNA is abundantly expressed in distinct normal tissues, and high expression levels were encountered in malignant cells. Down-regulation of ADNP by antisense oligodeoxynucleotides up-regulated the tumor suppressor p53 and reduced the viability of intestinal cancer cells by 90%. Thus, ADNP is implicated in maintaining cell survival, perhaps through modulation of p53.Mouse activity-dependent neuroprotective protein (mADNP), 1 a novel vasoactive intestinal peptide (VIP)-responsive gene, was recently cloned (1). The relative enrichment of mADNP transcripts in the cerebellum, cortex, hippocampus, medulla, and midbrain and the increases found in the presence of VIP, an established neuroprotective substance (2), implied a potential function in brain metabolism. Specifically, mADNP mRNA increased 2-3-fold in astroglial cells incubated for 3 h in the presence of nanomolar amounts of VIP (1). Another tissue containing increased mADNP transcripts is the mouse testis, a highly proliferative tissue, suggesting the involvement of ADNP in cell division.As deregulation of oncogenes has been associated with neurodegeneration (3), pathways that regulate neuronal survival may impinge upon cancer proliferation. VIP regulates both neuronal survival and cell division (2). A system whereby labeled VIP is suggested as a tumor marker has been proposed, localizing in vivo tumors of patients with gastrointestinal neuroendocrine cancers as well as pancreatic and colonic adenocarcinomas (4). Other studies have identified a very high incidence of VIP receptor binding in breast, ovarian, endometrial, prostate, bladder, lung, esophageal, colonic, and pancreatic tumors as well as in neuroendocrine and brain tumors (5). However, the VIP effect on cancer growth depends on the specific tumor and may be stimulatory (6, 7) or inhibitory (8). In view of the high incidence of tumors containing VIP receptors, a potential intervention in tumor growth may employ a gene downstr...