Entry

Using a rat PAP cDNA to screen a human pancreatic cDNA library, Orelle et al. (1992) isolated the human equivalent. The predicted protein had the same size as the rat protein and showed 71% amino acid identity, the 6 half-cysteines being in identical positions. As in the rat, the protein was expressed at very low levels in control tissues and overexpressed during the acute phase of pancreatitis in humans. The protein could be immunolocalized to the apical regions of acinar cells. The protein was also quantifiable in serum with an elevation of levels in pancreatitis, suggesting its possible use as a biologic marker of the disease.

To analyze the molecular basis of the pancreatitis-specific expression of the PAP gene, Dusetti et al. (1994) isolated the genomic clone for human PAP. Dusetti et al. (1993) and others demonstrated that the PAP molecule is constitutively expressed by the epithelial cells of the small intestine.

By differentially screening a human primary liver cancer library Lasserre et al. (1994) identified a cDNA, which they designated HIP. HIP expression was markedly increased in about a quarter of human primary liver cancers. Itoh et al. (1995) observed that HIP was identical to PAP. Itoh et al. (1995) showed that at least 3 different mRNAs are transcribed from the PAP gene as a result of alternative splicing of the 5-prime exons. The relative amounts of different mRNAs varied between normal and tumor tissues and especially between gastric and liver cancers.

Rafaeloff et al. (1997) cloned hamster Pap, which they designated Ingap. Ingap was expressed during islet neogenesis, and the protein could initiate duct cell proliferation, a prerequisite for islet neogenesis.