ABSTRACT
Gastric gland mucin secreted from the lower portion of the gastric mucosa contains unique O-linked oligosaccharides (O-glycans) having terminal α1,4-linked N-acetylglucosamine residues (αGlcNAc). Previously, we identified human α1,4-N-acetylglucosaminyltransferase (α4GnT), which is responsible for the O-glycan biosynthesis and characterized αGlcNAc function in suppressing Helicobacter pylori in vitro. In the present study, we engineered A4gnt(-/-) mice to better understand its role in vivo. A4gnt(-/-) mice showed complete lack of αGlcNAc expression in gastric gland mucin. Surprisingly, all the mutant mice developed gastric adenocarcinoma through a hyperplasia-dysplasia-carcinoma sequence in the absence of H. pylori infection. Microarray and quantitative RT-PCR analysis revealed upregulation of genes encoding inflammatory chemokine ligands, proinflammatory cytokines, and growth factors, such as Ccl2, Il-11, and Hgf in the gastric mucosa of A4gnt(-/-) mice. Further supporting an important role for this O-glycan in cancer progression, we also observed significantly reduced αGlcNAc in human gastric adenocarcinoma and adenoma. Our results demonstrate that the absence of αGlcNAc triggers gastric tumorigenesis through inflammation-associated pathways in vivo. Thus, αGlcNAc-terminated gastric mucin plays dual roles in preventing gastric cancer by inhibiting H. pylori infection and also suppressing tumor-promoting inflammation.
Subject(s)
Gastric Mucins/metabolism , Stomach Neoplasms/metabolism , Adenocarcinoma/metabolism , Adenoma/metabolism , Aged , Aged, 80 and over , Animals , Cell Proliferation , Disease Progression , Helicobacter pylori/metabolism , Humans , Inflammation , Mice , Mice, Transgenic , Middle Aged , Models, Biological , N-Acetylglucosaminyltransferases/metabolism , Neovascularization, Pathologic , Oligonucleotide Array Sequence AnalysisABSTRACT
Two members of the N-acetylglucosamine-6-O-sulfotransferase (GlcNAc6ST) family, GlcNAc6ST-1 and GlcNAc6ST-2, function in the biosynthesis of 6-sulfo sialyl Lewis X-capped glycoproteins expressed on high endothelial venules (HEVs) in secondary lymphoid organs. Thus, both enzymes play a critical role in L-selectin-expressing lymphocyte homing. Human GlcNAc6ST-1 is encoded by a 1593-bp open reading frame exhibiting two 5' in-frame methionine codons spaced 141 bp apart. Both resemble the consensus sequence for translation initiation. Thus, it has been hypothesized that both long and short forms of GlcNAc6ST-1 may be present, although endogenous expression of either form has not been confirmed in humans. Here, the authors developed an antibody recognizing amino acid residues between the first two human GlcNAc6ST-1 methionines. This antibody specifically recognizes the long form of the enzyme, a finding validated by Western blot analysis and immunofluorescence cytochemistry of HeLa cells misexpressing long and/or short forms of human GlcNAc6ST-1. Using this antibody, the authors carried out immunofluorescence histochemistry of human lymph node tissue sections and found endogenous expression of the long form of the enzyme in human tissue, predominantly in the trans-Golgi network of endothelial cells that form HEVs.
Subject(s)
Endothelium, Vascular/enzymology , Sulfotransferases/metabolism , Venules/enzymology , Amino Acid Sequence , Antibodies , Base Sequence , Blotting, Western , Endothelium, Vascular/ultrastructure , Fluorescent Antibody Technique , Golgi Apparatus/enzymology , HeLa Cells , Humans , Lymph Nodes/blood supply , Molecular Sequence Data , Sulfotransferases/immunology , Venules/ultrastructure , Carbohydrate SulfotransferasesABSTRACT
PURPOSE: To evaluate reconstructive changes in foveal microstructures and identify a correlation with visual outcomes in eyes with surgically closed macular holes (MHs). DESIGN: Retrospective, consecutive, observational case series. PARTICIPANTS: Forty eyes (40 patients) with surgically closed MHs. METHODS: Spectral-domain optical coherence tomography (SD-OCT) was performed to assess the foveal microstructural changes 3 and 12 months postoperatively. The correlation between the postoperative best-corrected visual acuity (BCVA) and the integrity of the foveal photoreceptor layer was evaluated. MAIN OUTCOME MEASURES: The integrity of the back-reflection lines from the photoreceptor inner segment (IS) and outer segment (OS) junction and the external limiting membrane (ELM) on SD-OCT images and the BCVA measured on the same day. RESULTS: The integrity of the foveal photoreceptor layer was the only postoperative SD-OCT finding significantly associated with the 3-month BCVA (r=0.483; P=0.002). The eyes were categorized into 3 groups according to restoration of the IS/OS junction and ELM signals: 6 eyes (15%) in group A with complete restoration of the IS/OS junction and the ELM; 26 eyes (65%) in group B with a disrupted IS/OS junction and intact ELM; and 8 eyes (20%) in group C with disruption or loss of the IS/OS junction and the ELM. Although the baseline BCVA did not differ significantly (P=0.137) among groups, the mean 3-month BCVA values in groups A and B, both with reconstructed ELM with or without a restored photoreceptor IS/OS, were significantly better than in group C (P<0.05); the difference between groups A and B was not significant (P>0.05). Groups A (P=0.029) and B (P<0.001) had significant visual improvement at 12 months; group C did not have marked visual recovery. Fourteen eyes (54%) in group B had subsequent realignment of the foveal photoreceptor IS/OS; no eyes in group C had a restored IS/OS at 12 months. The presence of the ELM at 3 months is a critical structural feature significantly correlated with the BCVA at 12 months (r=0.832, P<0.001). CONCLUSIONS: Reconstruction of the foveal ELM in the early postoperative period helps predict subsequent restoration of the foveal photoreceptor layer and the potential for better visual outcomes.
