Effects of adenovirus-mediated SV5 fusogenic glycoprotein expression on tumor cells.
BACKGROUND
The fusogenic (F) membrane glycoprotein of the paramyxovirus SV5 allows virus to enter host cells and mediates fusion between neighboring cells, which leads to cell death. F glycoprotein is synthesized as an inactive precursor (F(0)) that is cleaved by cellular protease furine to form the active heterodimer F(1) + F(2). The active protein can induce syncytium formation in the absence of another integral glycoprotein (HN), a property that appears to be unique among paramyxoviruses.


METHODS
We constructed a non-replicative adenovirus to express SV5 F protein in tumor cells, and its fusion capacity was analyzed by fluorescent and confocal microscopy. Cell viability and bystander effect were compared with the thymidine kinase/ganciclovir suicide gene therapy. The structure of F-expressing cells was studied using electron microscopy.


RESULTS
F glycoprotein expression induced syncytium formation to a maximum at 72 h, after which syncytia progressively lost viability and detached. The cell membrane was disrupted while nuclear structure was preserved. Over-expression of SV5 F protein in tumor cells led to high cytotoxicity comparable with that associated with the thymidine kinase/ganciclovir. A potent bystander killing effect was detected until the ratio of F-transduced to non-transduced cells was 1 : 100.


CONCLUSIONS
These results indicate that the fusogenic glycoprotein of the paramyxovirus SV5 could be used to eliminate tumor cells and may encourage studies aimed at modifying its selectivity and combining its expression with other cytotoxic strategies to improve their efficacy.
Gómez-Treviño
A
A
Department of Microbiology, University of Barcelona, 08028 Barcelona, Spain.
Castel
S
S
López-Iglesias
C
C
Cortadellas
N
N
Comas-Riu
J
J
Mercadé
E
E
D000256:Adenoviridae / Q000235:genetics* / Q000302:isolation & purification; D024201:Bystander Effect; D002294:Carcinoma, Squamous Cell / Q000648:ultrastructure; D045744:Cell Line, Tumor; D005260:Female; D015774:Ganciclovir / Q000494:pharmacology; D015967:Gene Expression Regulation, Viral; D015726:Giant Cells / Q000473:pathology; D006801:Humans; D016253:Microscopy, Immunoelectron; D009369:Neoplasms / Q000473:pathology / Q000628:therapy* / Q000648:ultrastructure; D013937:Thymidine Kinase / Q000494:pharmacology; D014161:Transduction, Genetic; D014760:Viral Fusion Proteins / Q000235:genetics* / Q000378:metabolism
D014760:Viral Fusion Proteins; D013937:Thymidine Kinase; D015774:Ganciclovir