The cyclo-oxygenase 2 promoter is induced in nontarget cells following adenovirus infection, but an AU-rich 3'-untranslated region destabilization element can increase specificity.
BACKGROUND
Cyclo-oxygenase 2 (Cox-2) is expressed in many types of tumors, but typically undetectable in normal tissues. However, Cox-2 is known to be induced following infection by many microbial agents, which might threaten the tumor selectivity of the Cox-2 promoter in the context of virotherapy or viral gene delivery. Cox-2 expression is regulated in part post-transcriptionally by stimulation or inhibition of mRNA degradation by 3'-untranslated region (3'-UTR) AU-rich elements. In the present study, we investigated the induction of the Cox-2 promoter both in normal and tumor cells after adenovirus infection and explored the utility of AU-rich elements for regaining promoter selectivity.


METHODS
Nontumor and tumor cells were transfected in vitro and in vivo with plasmids containing the Cox-2 or cytomegalovirus immediate early promoter driving luciferase (with or without 3'-UTR elements) followed by adenoviral infection. Selectivity and activity of the promoters and 3'-UTR elements were analysed by luciferase assay and in-vivo imaging.


RESULTS
The Cox-2 promoter was induced in both normal and tumor cells following infection with E1 containing replicative adenoviruses but not in the absence of E1. Utilization of AU-rich elements counteracted promoter induction in vitro and in vivo in nonmalignant cells but not in cancer cells, thus increasing the selectivity of the approach ten-fold without loss of potency.


CONCLUSIONS
Adenoviral infection induces the Cox-2 promoter in normal and tumor cells, which might compromise specificity of the promoter. Utilization of AU-rich destabilization elements can rescue the tumor selectivity of the promoter.
Särkioja
Merja
M
Cancer Gene Therapy Group, Molecular Cancer Biology Program and Transplantation Laboratory, University of Helsinki, Helsinki, Finland.
Hakkarainen
Tanja
T
Eriksson
Minna
M
Ristimäki
Ari
A
Desmond
Renee A
RA
Kanerva
Anna
A
Hemminki
Akseli
A
D020413:3' Untranslated Regions / Q000378:metabolism; D000258:Adenovirus Infections, Human / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D051546:Cyclooxygenase 2 / Q000235:genetics*; D017931:DNA Primers / Q000235:genetics; D005786:Gene Expression Regulation / Q000235:genetics*; D006801:Humans; D008156:Luciferases; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014162:Transfection
D020413:3' Untranslated Regions; D017931:DNA Primers; D008156:Luciferases; D051546:Cyclooxygenase 2