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Hum Gene Ther. 2000 Apr 10;11(6):817-26.

A hyperfusogenic gibbon ape leukemia envelope glycoprotein: targeting of a cytotoxic gene by ligand display.

Author information

1
Hematology and Molecular Medicine, Mayo Clinic, Rochester, MN 55902, USA.

Abstract

An important goal in cancer gene therapy is the development of novel targeted cytotoxic genes. The observation that transfection of a GaLV envelope glycoprotein lacking an R peptide into human cells results in considerable cell-cell fusion and subsequent cell death prompted us to explore the potential for using this fusogenic membrane glycoprotein (FMG) as a targeted cytotoxic gene. As proof of principle, we therefore displayed epidermal growth factor (EGF) on the N terminus of GaLV envelope glycoproteins both with and without an R peptide (GaLV R+ and GaLV R-). Transfection of the GaLVR+ envelope expression plasmids did not cause cell-cell fusion. The GaLV R+ envelopes were incorporated into retroviral vectors whose infectivity was investigated on EGF receptor-positive and -negative cells. The vector incorporating an N-terminally unmodified envelope was able to infect all human cell lines tested. Infectivity of the vector incorporating an envelope on which EGF was displayed was restricted on EGF receptor-positive cells (but not on EGF receptor-negative cells) and could be restored by protease cleavage of the displayed domain or competition with exogenous ligand. The cell-cell fusion capacity of the GaLV R- envelope glycoproteins (N-terminally unmodified and with N-terminal display of both EGF and insulin-like growth factor I [IGF-I]) was investigated by plasmid DNA transfection. While the N-terminally unmodified GaLV R- fused all human cell types tested, fusogenicity of GaLV R- on which EGF or IGF-I was displayed was considerably restricted on receptor-positive cells. "Reciprocal" competition experiments showed that fusogenicity could be restored by competition only with the relevant exogenous ligand. Thus the specificity of cell-cell fusion by a hyperfusogenic GaLV envelope glycoprotein can be regulated by N-terminal display of growth factor ligands. There is therefore significant potential for further development of the targeting of the cell-killing capability of this fusogenic viral glycoprotein by using strategies similar to those we have developed for the targeting of retroviral vectors.

PMID:
10779159
DOI:
10.1089/10430340050015437
[Indexed for MEDLINE]

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