Osteopontin (OPN) may facilitate metastasis by protecting cells from macrophage NO-mediated cytotoxicity: evidence from cell lines down-regulated for OPN expression by a targeted ribozyme

Osteopontin (OPN) is a GRGDS-containing phosphoglycoprotein that is capable of facilitating cell adhesion and modulating gene expression via integrin receptors. Three hammerhead ribozymes designed to target three different regions of OPN mRNA were shown to cleave the message catalytically in vitro....

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Bibliographic Details
Published in:Clinical & experimental metastasis 1995-11, Vol.13 (6), p.453-462
Main Authors: Feng, B, Rollo, E E, Denhardt, D T
Format: Article
Language:English
Subjects:
Animals
Base Sequence
Cathepsin L
Cathepsins - genetics
Cysteine Endopeptidases
Cytotoxicity, Immunologic
DNA Primers - chemistry
Down-Regulation
Endopeptidases
Genes, ras
Macrophages - physiology
Mice
Mice, Nude
Molecular Sequence Data
Neoplasm Metastasis
Neoplasms, Experimental - metabolism
Neoplasms, Experimental - pathology
Nitric Oxide - physiology
Osteopontin
RNA, Catalytic - chemistry
RNA, Catalytic - pharmacology
Sialoglycoproteins - genetics
Sialoglycoproteins - metabolism
Tumor Cells, Cultured
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Summary:Osteopontin (OPN) is a GRGDS-containing phosphoglycoprotein that is capable of facilitating cell adhesion and modulating gene expression via integrin receptors. Three hammerhead ribozymes designed to target three different regions of OPN mRNA were shown to cleave the message catalytically in vitro. Plasmid vectors that had been engineered to express the ribozymes in mammalian cells were used to generate stably transfected T24 H-ras-transformed NIH3T3 cells that normally express OPN at high levels. Northern and Western blot analyses showed that OPN mRNA and protein expression were reduced in a subset of these anti-OPN ribozyme-expressing cell lines. Cells whose ability to produce OPN had been impaired exhibited greater sensitivity to the cytotoxic action of activated RAW264.7 macrophage-like cells; they were also less effective at suppressing macrophage NO production. In agreement with previous reports, they were also less tumorigenic and metastatic in an experimental metastasis assay. These results are consistent with the hypothesis that OPN serves as a defense against NO-mediated host cell cytotoxicity and thereby augments the metastatic phenotype.
ISSN:0262-0898
1573-7276
DOI:10.1007/BF00118184