Impact of radiation therapy on the oncolytic adenovirus dl520: implications on the treatment of glioblastoma.
OBJECTIVE
Viral oncolytic therapy is emerging as a new form of anticancer therapy and has shown promising preclinical results, especially in combination with radio- and chemotherapy. We recently reported that nuclear localization of the human transcription factor YB-1 in multidrug-resistant cells facilitates E1-independent adenoviral replication. The aim of this study was to evaluate the combined treatment of the conditionally-replicating adenovirus dl520 and radiotherapy in glioma cell lines in vitro and in human tumor xenografts. Furthermore, the dependency of YB-1 on dl520 replication was verified by shRNA directed down regulation of YB-1.


METHODS
Localization of YB-1 was determined by immunostaining. Glioma cell lines LN-18, U373 and U87 were infected with dl520. Induction of cytopathic effect (CPE), viral replication, viral yield and viral release were determined after viral infection, radiation therapy and the combination of both treatment modalities. The capacity of treatments alone or combined to induce tumor growth inhibition of subcutaneous U373 tumors was tested also in nude mice.


RESULTS
Quantitative real-time PCR demonstrated that the shRNA-mediated down regulation of YB-1 is leading to a dramatic decrease in adenoviral replication of dl520. Immunostaining analysis showed that the YB-1 protein was predominantly located in the cytoplasm in the perinuclear space and less abundant in the nucleus. After irradiation we found an increase of nuclear YB-1. The addition of radiotherapy increased the oncolytic effect of dl520 with enhanced viral replication, viral yield and viral release. The oncolytic activity of dl520 plus radiation inhibited the growth of subcutaneous U373 tumors in a xenograft mouse model.


CONCLUSIONS
Radiation mediated increase of nuclear YB-1 in glioma cells enhanced the oncolytic potential of adenovirus dl520.
Bieler
Alexa
A
Institute of Experimental Oncology, Technical University of Munich, Germany.
Mantwill
Klaus
K
Holzmüller
Regina
R
Jürchott
Karsten
K
Kaszubiak
Alexander
A
Stärk
Sybille
S
Glockzin
Gabriel
G
Lage
Hermann
H
Grosu
Anca-Ligia
AL
Gansbacher
Bernd
B
Holm
Per Sonne
PS
D000256:Adenoviridae / Q000378:metabolism / Q000528:radiation effects*; D000818:Animals; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000528:radiation effects; D005909:Glioblastoma / Q000628:therapy*; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D050504:Oncolytic Viruses / Q000528:radiation effects*; D051840:Y-Box-Binding Protein 1
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human