Localization of MOC-1 cell surface antigen in small-cell lung carcinoma cell lines: an immunohistochemical and immunoelectron microscopic study.
Expression of cell surface antigens of the neural cell adhesion molecule (N-CAM) class was recently shown to be shared by both fetal and neoplastic neuroendocrine cells, including those of the lung. We investigated the expression and localization of MOC-1 antigen on small-cell (neuroendocrine) lung carcinoma cell lines with immunohistochemical methods at the light (LM) and electron microscopy (EM) level and by Western blot. At LM level, using monoclonal antibody (MAb) MOC-1 with the ABC method and immunofluorescence, positive staining was observed on surfaces of cells from all tumor lines examined. Strongest immunostaining was found on cell surfaces of pulmonary small-cell carcinoma-derived cell line NCI-H69 with the majority of cells showing positive staining. An adherent variant of NCI-H69 cell line, H69V, exhibited positive staining in about 60% of cells, whereas only occasional cells of NCI-H727 cell line derived from pulmonary carcinoid tumor were positive for MOC-1 antigen. Western blot analysis confirmed these findings, showing a strong MOC-1-specific band in cell extracts of NCI-H69, with weaker band densities for H69V and NCI-H727. Immunoelectron microscopy (IEM) revealed that MOC-1 was not uniformly distributed on the outer surface of plasma membrane; immunogold particles appeared concentrated in areas of thick cell surface "fuzz" coating, surface microvilli, and in areas of cell-cell contact. In some cells, areas of plasma membrane invaginations and a few intracytoplasmic vesicles were also labeled, suggesting endocytosis. Surface labeling for SEM confirmed the finding of more dense labeling over the microvilli, cell membrane folds, and in areas of cell-cell contact. The cell lines derived from pulmonary neuroendocrine cell tumors can provide a useful model to study the role and function of neural adhesion molecules in pulmonary neoplasia and during lung development.
Department of Pathology, Hospital for Sick Children, Toronto, Ontario, Canada.
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Speirs
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Eich-Bender
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Youngson
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Cutz
D000818:Animals; D000951:Antigens, Neoplasm / Q000032:analysis*; D000954:Antigens, Surface / Q000032:analysis*; D015153:Blotting, Western; D018288:Carcinoma, Small Cell / Q000737:chemistry* / Q000276:immunology / Q000473:pathology*; D002462:Cell Membrane / Q000737:chemistry / Q000648:ultrastructure; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000737:chemistry* / Q000276:immunology / Q000473:pathology*; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D016253:Microscopy, Immunoelectron; D008871:Microvilli / Q000737:chemistry / Q000648:ultrastructure; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D000954:Antigens, Surface