hymecromone and dansyl-fluoride

Dansyl fluoride (Dan-F), an active site directed fluorescent inhibitor of guanidinobenzoatase (GB), has been used for the location of tumour cells in frozen sections of human squamous cell carcinoma and colonic carcinoma tissues. The tumour cell surfaces having active GB bind Dan-F and fluoresce blue. The surrounding normal epithelial lung cell surfaces fail to bind Dan-F and hence lack fluorescence, whilst the normal colon cell surfaces have another isoenzymic form of GB, bind Dan-F and fluoresce blue. Kinetic studies have shown that Dan-F is an irreversible inhibitor of GB, and Dan-GB complexes are not dissociated with SDS and high salt concentration. However hydroxylamine (1 M) can dissociate Dan-GB complexes in the presence of 0.1% SDS, both on membrane-bound and in free solution. These studies suggest that Dan-F is a potent inhibitor of GB, and in very low concentration (3 x 10(-8) M) can be used as a novel fluorescent probe for the location of tumour cells in histological sections of human tissues.

Topics: Aminacrine; Binding Sites; Carboxylic Ester Hydrolases; Colonic Neoplasms; Coloring Agents; Dansyl Compounds; Endopeptidases; Enzyme Activation; Histocytochemistry; Humans; Hydroxylamine; Hydroxylamines; Hymecromone; Isoenzymes; Lung Neoplasms; Microscopy, Fluorescence; Serine Proteinase Inhibitors; Sodium Dodecyl Sulfate; Spectrometry, Fluorescence

Pentosan polysulphate (PPS), a highly negatively charged polysaccharide, is a significant inhibitor of an isoenzymic form of a cell surface protease referred to as guanidinobenzoatase GB, associated with colonic carcinoma tissues in frozen sections and free GB in solution, in a concentration-dependent manner. However PPS failed to recognise and bind to the isoenzymic form of GB associated with normal colon epithelial cell surfaces. Texas red labelled PPS (TR-PPS) binds to the tumour cell surfaces of colonic carcinoma and colonic polyps and these cells fluoresce red, whilst the normal colon cell surfaces failed to bind the TR-PPS, and hence lacked red fluorescence. Polysulphonated suramin also selectively recognised and inhibited the colonic carcinoma GB isoenzyme. The kinetic data indicated that this inhibition was not caused by a mere polyanionic effect, since highly sulphated heparin failed to show a significant inhibition of colonic carcinoma GB, however trypan blue did show 50% inhibition. Kinetic studies have also shown that PPS is a non-competitive, reversible inhibitor of colonic carcinoma GB, with an apparent Km 6.8 x 10(-7) M. Gel analysis has shown that PPS binds to another site, distinct from the active centre, and after binding PPS changed the conformation of GB. These studies suggest that TR-PPS is a potent inhibitor of colonic carcinoma GB, and can be used as a novel fluorescent probe for the location of tumour cells in frozen sections of human colon tissues. PSS could also have potential as a vehicle for the transport of cytotoxic compounds to carcinoma cells of the colon.

Topics: Carboxylic Ester Hydrolases; Cell Membrane; Chromatography, Affinity; Colonic Neoplasms; Dansyl Compounds; Electrophoresis, Polyacrylamide Gel; Endopeptidases; Fluorescent Dyes; Heparin; Humans; Hymecromone; Isoenzymes; Kinetics; Microscopy, Fluorescence; Pentosan Sulfuric Polyester; Protease Inhibitors; Protein Conformation; Suramin; Trypan Blue; Xanthenes