intrinsic-factor and Cell-Transformation--Neoplastic

Loss of gastric parietal cells is a critical precursor to gastric metaplasia and neoplasia. However, the origin of metaplasia remains obscure. Acute parietal cell loss in gastrin-deficient mice treated with DMP-777 leads to the rapid emergence of spasmolytic polypeptide/trefoil factor family 2 (TFF2)-expressing metaplasia (SPEM) from the bases of fundic glands. We now sought to characterize more definitively the pathway for emergence of SPEM.. Emerging SPEM lineages in gastrin-deficient mice treated with DMP-777 were examined for immunolocalization of TFF2, intrinsic factor, and Mist1, and morphologically with electron microscopy. Emerging SPEM was isolated with laser-capture microdissection and RNA was analyzed using gene microarrays. Immunohistochemistry in mouse and human samples was used to confirm up-regulated transcripts.. DMP-777-induced SPEM was immunoreactive for TFF2 and the differentiated chief cell markers, Mist1 and intrinsic factor, suggesting that SPEM derived from transdifferentiation of chief cells. Microarray analysis of microdissected SPEM lineages induced by DMP-777 showed up-regulation of transcripts associated with G1/S cell-cycle transition including minichromosome maintenance deficient proteins, as well as a number of secreted factors, including human epididymis 4 (HE4). HE4, which was absent in the normal stomach, was expressed in SPEM of human and mouse and in intestinal metaplasia and gastric cancer in human beings.. Although traditionally metaplasia was thought to originate from normal mucosal progenitor cells, these studies indicate that SPEM evolves through either transdifferentiation of chief cells or activation of a basal cryptic progenitor. In addition, induction of metaplasia elicits the expression of secreted factors, such as HE4, relevant to gastric preneoplasia.

Topics: Animals; Atrophy; Basic Helix-Loop-Helix Transcription Factors; beta-Defensins; Carrier Proteins; Cell Cycle Proteins; Cell Transformation, Neoplastic; Chief Cells, Gastric; DNA-Binding Proteins; Epididymal Secretory Proteins; Fetal Proteins; Gastric Fundus; Gastric Mucosa; Gastrins; Humans; Intercellular Signaling Peptides and Proteins; Intrinsic Factor; Metaplasia; Mice; Mice, Inbred C57BL; Mice, Knockout; Microtubule-Associated Proteins; Minichromosome Maintenance Complex Component 3; Mucins; Muscle Proteins; Nuclear Proteins; Parietal Cells, Gastric; Peptides; Precancerous Conditions; Stomach Neoplasms; Trefoil Factor-2

The erbB-2 gene product, gp185erbB-2, displays a potent transforming effect when overexpressed in NIH 3T3 cells. In addition, it possesses constitutively high levels of tyrosine kinase activity in the absence of exogenously added ligand. In this study, we demonstrate that its carboxy-terminal domain exerts an enhancing effect on erbB-2 kinase and transforming activities. A premature termination mutant of the erbB-2 protein, lacking the entire carboxy-terminal domain (erbB-2 delta 1050), showed a 40-fold reduction in transforming ability and a lowered in vivo kinase activity for intracellular substrates. When the carboxy-terminal domain of erbB-2 was substituted for its analogous region in the epidermal growth factor receptor (EGFR) (EGFR/erbB-2COOH chimera), it conferred erbB-2-like properties to the EGFR, including transforming ability in the absence of epidermal growth factor, elevated constitutive autokinase activity in vivo and in vitro, and constitutive ability to phosphorylate phospholipase C-gamma. Conversely, a chimeric erbB-2 molecule bearing an EGFR carboxy-terminal domain (erbB-2/EGFRCOOH chimera) showed reduced transforming and kinase activity with respect to the wild-type erbB-2 and was only slightly more efficient than the erbB-2 delta 1050 mutant. Thus, we conclude that the carboxy-terminal domains of erbB-2 and EGFR exert different regulatory effects on receptor kinase function and biological activity. The up regulation of gp185erbB-2 enzymatic activity exerted by its carboxy-terminal domain can explain, at least in part, its constitutive level of kinase activity.

Topics: Animals; Blotting, Western; Cell Line; Cell Transformation, Neoplastic; Cells, Cultured; ErbB Receptors; Gene Expression; Genetic Vectors; Intrinsic Factor; Phosphorylation; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Signal Transduction; Transfection

Topics: Animals; Brain Neoplasms; Cell Transformation, Neoplastic; Cricetinae; Female; Follicle Stimulating Hormone; Glioma; Guinea Pigs; Intrinsic Factor; Liver; Luteinizing Hormone; Meningioma; Neuraminic Acids; Neuraminidase; Orthomyxoviridae; Rats; Serotonin; Tetanus Toxin; Uterus