Anti-tumor effects of pNEgr-mIL-12 recombinant plasmid induced by X-irradiation and its mechanisms.
OBJECTIVE
To study the effect of gene radiotherapy combining injection of recombinant plasmid pNEgr-mIL-12 with local X-irradiation on cancer growth and to elucidate the mechanisms of tumor inhibition.


METHODS
Alkaline lysis was used to extract the plasmid and polyethylene glycol 8000 (PEG 8000) was applied for further purification of plasmids. Enzyme-linked immunosorbent assay (ELISA) was used to detect the expression of IL-12 protein. C57BL/6J mice were subcutaneously inoculated with B16 melanoma cells and the plasmid was injected directly into the tumor. Gene-radiotherapy combining pNEgr-mIL-12 recombinant plasmid with X-irradiation was given three times to C57BL/6J mice bearing B16 melanoma. Changes in immunologic parameters of tumor-bearing mice were detected with relevant immunologic assays.


RESULTS
Results showed a significant decrease in tumor growth rate (P<0.05-0.001) after 3 times of gene-radiotherapy with IL-12 and X-irradiation. Immunologic studies showed a significant increase in CTL and NK cytolytic activity (P<0.05-0.001) and an up-regulated secretion of IFN-gamma and TNF-alpha (P<0.01-0.001). Moreover, the expression of mIL-12 in B16 melanoma cells of the treated tumor-bearing mice was found to be higher than that of control.


CONCLUSIONS
pNEgr-mIL-12 plasmid combined with X-irradiation can increase tumor control and the mechanism of increased tumor inhibition is related to the enhancement of anticancer immunity in tumor-bearing mice.
Yang
Ying
Y
Immunology Laboratory, Ministry of Health, Changchun 130021, Jilin, China.
Liu
Shu-Zheng
SZ
Fu
Shi-Bo
SB
D000818:Animals; D003131:Combined Modality Therapy; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D015316:Genetic Therapy; D007371:Interferon-gamma / Q000276:immunology; D018664:Interleukin-12 / Q000096:biosynthesis / Q000235:genetics* / Q000627:therapeutic use; D007694:Killer Cells, Natural / Q000276:immunology; D008264:Macrophages / Q000276:immunology; D008546:Melanoma, Experimental / Q000276:immunology* / Q000532:radiotherapy* / Q000628:therapy*; D051379:Mice; D008810:Mice, Inbred C57BL; D010957:Plasmids; D013154:Spleen / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology; D014965:X-Rays
D014409:Tumor Necrosis Factor-alpha; D018664:Interleukin-12; D007371:Interferon-gamma