Interferon-gamma produced by interleukin-12-activated tumor infiltrating CD8+T cells directly induces apoptosis of mouse hepatocellular carcinoma.
OBJECTIVE
Interleukin-12 (IL-12), a cytokine with antitumor activity, was examined for the suppressive effect on hepatocellular carcinoma (HCC) in mouse model, and its mechanism of antitumor activity was analyzed.


METHODS
Mice implanted with MIH-2 HCC cells were treated with recombinant mouse IL-12 (500 ng/mouse). Involvement of CD4(+), CD8(+), NK cells and interferon (IFN)-gamma on tumor suppression by IL-12 was examined by treatment of mice with each antibody. Interferon-gamma (IFN-gamma) production by tumor infiltrating cells was analyzed by immunofluorescence microscopy and flow cytometric analysis. Signal transduction for apoptosis induction was examined by immunoblot analysis.


RESULTS
The growth of implanted MIH-2 tumors was significantly suppressed by IL-12 and the suppression was inhibited by depletion of CD8(+)T cells. IL-12 treatment caused numerous IFN-gamma-producing CD8(+)T cells to infiltrate into MIH-2 tumors. Antitumor activity of IL-12 was blocked by treating mice with anti-IFN-gamma mAb. CD8(+)T cells from IL-12-treated mice attached to MIH-2 cells and produced IFN-gamma in vitro. Cell attachment might be associated with intercellular adhesion molecule-1 induced by IFN-gamma. In vitro treatment with IFN-gamma induced apoptosis of MIH-2 cells via a mitochondria-dependent pathway.


CONCLUSIONS
IL-12 suppressed HCC growth in mouse model. IFN-gamma produced by IL-12-activated tumor-infiltrating CD8(+)T cells directly induced apoptosis of HCC cells.
Komita
Hideo
H
Department of Oncology, Institute of DNA Medicine, Jikei University School of Medicine, 3-25-8 Nishi-shimbashi, Minato-ku, Tokyo 105-8461, Japan.
Homma
Sadamu
S
Saotome
Hideo
H
Zeniya
Mikio
M
Ohno
Tsuneya
T
Toda
Gotaro
G
D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000276:immunology*; D053453:Caspase 9 / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D007371:Interferon-gamma / Q000378:metabolism*; D018664:Interleukin-12 / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000276:immunology*; D016246:Lymphocytes, Tumor-Infiltrating / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D023421:Models, Animal; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology
D000276:Adjuvants, Immunologic; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D018664:Interleukin-12; D007371:Interferon-gamma; D045304:Cytochromes c; D053453:Caspase 9