concanavalin-a and Carcinoma--Small-Cell

We have characterized the regulation of expressed human ecto-ATPase (E-NTPDase 2), a cell surface integral membrane glycoprotein. Ecto-ATPase activity is inhibited by parameters that decrease membrane protein interaction, i.e., detergents and high temperatures. These inhibitory effects are overcome when membranes are pretreated with concanavalin A or chemical cross-linking agents that increase the amounts of ecto-ATPase oligomers. Cross-linking agents also abrogate substrate inactivation of the ecto-ATPase, a unique characteristic of the enzyme. These effects indicate that the magnitude of negative substrate regulation is dependent on quaternary structures of the protein, which likely involves interaction of transmembrane domains. The importance of transmembrane domains of ecto-ATPase in activity modulation is demonstrated further by the stimulatory effect of digitonin, a steroid glycoside that preferentially interacts with cholesterol in the membranes but does not promote oligomer formation. These results indicate that ecto-ATPase activity is regulated by a multitude of mechanisms, some of which may have physiological significance. Ecto-ATPase is also susceptible to transcriptional regulation. Ecto-ATPase gene expression is increased in a human hepatoma whereas it is undetectable in the normal liver.

Topics: Adenosine Triphosphatases; Carcinoma, Hepatocellular; Carcinoma, Small Cell; Cell Membrane; Concanavalin A; Enzyme Activation; Gene Expression Regulation, Enzymologic; Humans; Liver Neoplasms; Lung Neoplasms; Protein Conformation; Protein Structure, Quaternary; Recombinant Proteins; Transcription, Genetic; Tumor Cells, Cultured

Analysis of cell surface glycosylation not only provides information about cell properties such as their state of differentiation or histogenetic lineage. The carbohydrate chains also provide potentially functional binding sites to endogenous carbohydrate-binding proteins. This interaction can elicit consequent signalling processes. Because of the importance of neutrophils in the host defence system, we monitored the effect of the binding of such sugar receptors to their cell surface on the release of the enzymatic activities of lysozyme, elastase, and myeloperoxidase. Besides the mannose-binding lectin concanavalin A and the immunomodulatory alpha/beta-galactoside-binding lectin from Viscum album L., three preparations of human sugar receptors - beta-galactoside-binding lectin (M(r) 14 kDa) and two affinity-purified polyclonal IgG fractions from serum with the capacity to recognize alpha- or beta-galactosides, respectively - were used. Two animal lectins from chicken liver and intestine that bind beta-galactosides, as well as the lectin-like human serum amyloid P component, were included in order to assess the importance of slight differences in ligand recognition. Cytochalasin B-enhanced enzyme release was invariably seen with the two plant lectins and the chicken liver beta-galactoside-binding lectin, but the related intestinal lectin did not increase enzyme release. The mammalian homologue of these avian lectins triggered lysozyme secretion, and the lactoside-binding IgG fraction enhanced the amount of extracellular elastase activity slightly but significantly. Thus, the actual lectin, not the nominal specificity of sugar receptors, is crucial for elucidation of responses. Due to the highly stimulatory activity of the two plant lectins, neutrophils from patients with non-cancerous diseases and from patients with lung cancer were monitored for the extent of lectin-mediated enzyme release. Only the concanavalin A-mediated reactivity of the neutrophils was associated with the type of disease.

Topics: Adult; Aged; Aged, 80 and over; Agglutinins; Autoantibodies; Carbohydrate Metabolism; Carcinoma, Non-Small-Cell Lung; Carcinoma, Small Cell; Concanavalin A; Female; Galactosides; Glycosides; Humans; Immunoglobulin G; Lectins; Leukocyte Elastase; Lung Neoplasms; Male; Middle Aged; Mistletoe; Muramidase; Neutrophils; Pancreatic Elastase; Peroxidase; Plant Lectins; Plant Proteins; Plants, Medicinal; Protein Binding; Serum Amyloid P-Component

The freshly separated indicator cells (suspension of leukocytes) used in humoral leukocyte adherence inhibition test were labeled either with 14C-amino acid mixture or 3H-concanavalin A (3H-ConA). Instead of counting the adherent cells, the amount of 'adherent' radioactivity was measured by a liquid scintillation spectrometer. By the modified method, sera from 25 lung-carcinoma-bearing patients as well as serum samples from 21 healthy persons were examined in the presence of crude antigens prepared from 'normal' lung tissue or lung tumors of various histologic types. Although the results demonstrated high specificity and reproducibility of both methods, the binding of 3H-ConA to the surface of adherent cells is more expressed and assures higher levels of radioactivity.

Topics: Adenocarcinoma; Adult; Aged; Amino Acids; Carcinoma; Carcinoma, Small Cell; Carcinoma, Squamous Cell; Concanavalin A; Female; Humans; Immunologic Techniques; Indicators and Reagents; Leukocyte Adherence Inhibition Test; Lung Neoplasms; Male; Middle Aged

Serum concentrations of serum amyloid A protein (SAA), peripheral blood lymphocytes (PBL) mitogenic response to phytohemagglutinin (PHA) and Concanavalin A (Con A), numbers of circulating T- and B-lymphocytes and length of survival after diagnosis were measured in 50 patients with cancer of the lung. SAA levels were significantly elevated when compared to 50 control subjects (P less than 0.001), but did not correlate with state of tumor spread at the time of diagnosis. Mitogenic responses of PBL from the cancer patients to PHA and Con A were significantly depressed (P less than 0.001), but also did not predict state of metastatic spread. The percentage of circulating T-lymphocytes was also significantly depressed in cancer patients when compared to controls. In six patients who survived tumor-free for greater than 2.5 years, SAA serum concentrations returned to normal. Statistical analysis showed a significant correlation between SAA serum concentrations and PBL mitogenic response to Con A. In addition, both high SAA concentrations and depressed PBL responses to Con A correlated with shortened survival. Therefore, these parameters may be of value in evaluating prognosis in patients with lung cancer. In addition, serial monitoring of SAA concentrations may be of value in evaluating recurrence or cure of lung cancer.

Topics: Adenocarcinoma; Adult; Aged; Amyloid; Carcinoma; Carcinoma, Small Cell; Carcinoma, Squamous Cell; Cells, Cultured; Concanavalin A; Humans; Leukocyte Count; Lung Neoplasms; Lymphocytes; Male; Middle Aged; Phytohemagglutinins; Prognosis; Prospective Studies; Serum Amyloid A Protein