Radiosensitizing effect of intratumoral interleukin-12 gene electrotransfer in murine sarcoma.
BACKGROUND
Interleukin-12 (IL-12) based radiosensitization is an effective way of tumor treatment. Local cytokine production, without systemic shedding, might provide clinical benefit in radiation treatment of sarcomas. Therefore, the aim was to stimulate intratumoral IL-12 production by gene electrotransfer of plasmid coding for mouse IL-12 (mIL-12) into the tumors, in order to explore its radiosensitizing effect after single or multiple intratumoral gene electrotransfer.


METHODS
Solid SA-1 fibrosarcoma tumors, on the back of A/J mice, were treated intratumorally by mIL-12 gene electrotransfer and 24 h later irradiated with a single dose. Treatment effectiveness was measured by tumor growth delay and local tumor control assay (TCD(50) assay). With respect to therapeutic index, skin reaction in the radiation field was scored. The tumor and serum concentrations of cytokines mIL-12 and mouse interferon γ (mIFNγ) were measured. Besides single, also multiple intratumoral mIL-12 gene electrotransfer before and after tumor irradiation was evaluated.


RESULTS
Single intratumoral mIL-12 gene electrotransfer resulted in increased intratumoral but not serum mIL-12 and mIFNγ concentrations, and had good antitumor (7.1% tumor cures) and radiosensitizing effect (21.4% tumor cures). Combined treatment resulted in the radiation dose-modifying factor of 2.16. Multiple mIL-12 gene electrotransfer had an even more pronounced antitumor (50% tumor cures) and radiosensitizing (86.7% tumor cures) effect.


CONCLUSIONS
Single or multiple intratumoral mIL-12 gene electrotransfer resulted in increased intratumoral mIL-12 and mIFNγ cytokine level, and may provide an efficient treatment modality for soft tissue sarcoma as single or adjuvant therapy to tumor irradiation.
Department of Experimental Oncology, Institute of Oncology Ljubljana, Ljubljana, Slovenia.
Ales
A
Sedlar
Simona
S
Kranjc
Tanja
T
Dolinsek
Maja
M
Cemazar
Andrej
A
Coer
Gregor
G
Sersa
D000818:Animals; D004307:Dose-Response Relationship, Radiation; D018274:Electroporation; D005260:Female; D005354:Fibrosarcoma / Q000097:blood / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D007371:Interferon-gamma / Q000097:blood; D018664:Interleukin-12 / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D013997:Time Factors; D047368:Tumor Burden
D018664:Interleukin-12; D007371:Interferon-gamma