Irradiation, cisplatin, and 5-azacytidine upregulate cytomegalovirus promoter in tumors and muscles: implementation of non-invasive fluorescence imaging.
OBJECTIVE
The cytomegalovirus (CMV) promoter is one of the most commonly used promoters for expression of transgenes in mammalian cells. The aim of our study was to evaluate the role of methylation and upregulation of the CMV promoter by irradiation and the chemotherapeutic agent cisplatin in vivo using non-invasive fluorescence in vivo imaging.


METHODS
Murine fibrosarcoma LPB and mammary carcinoma TS/A cells were stably transfected with plasmids encoding CMV and p21 promoter-driven green fluorescent protein (GFP) gene. Solid TS/A tumors were induced by subcutaneous injection of fluorescent tumor cells, while leg muscles were transiently transfected with plasmid encoding GFP under the control of the CMV promoter. Cells, tumors, and legs were treated either by DNA methylation inhibitor 5-azacytidine, irradiation, or cisplatin. GFP expression was determined using a fluorescence microplate reader in vitro and by non-invasive fluorescence imaging in vivo.


RESULTS
Treatment of cells, tumors, and legs with 5-azacytidine (re)activated the CMV promoter. Furthermore, treatment with irradiation or cisplatin resulted in significant upregulation of GFP expression both in vitro and in vivo.


CONCLUSIONS
Observed alterations in the activity of the CMV promoter limit the usefulness of this widely used promoter as a constitutive promoter. On the other hand, inducibility of CMV promoters can be beneficially used in gene therapy when combined with standard cancer treatment, such as radiotherapy and chemotherapy.
Kamensek
Urska
U
Department of Experimental Oncology, Institute of Oncology Ljubljana, Zaloska 2, SI-1000 Ljubljana, Slovenia.
Sersa
Gregor
G
Vidic
Suzana
S
Tevz
Gregor
G
Kranjc
Simona
S
Cemazar
Maja
M
D000818:Animals; D001374:Azacitidine / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D003587:Cytomegalovirus / Q000235:genetics*; D019175:DNA Methylation; D005260:Female; D017781:Genes, Immediate-Early; D017930:Genes, Reporter; D007259:Infrared Rays; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D009132:Muscles / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D015854:Up-Regulation / Q000187:drug effects / Q000528:radiation effects
D001374:Azacitidine; D002945:Cisplatin
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