IL-12 cDNA direct injection: antimetastatic effect from a single injection in a murine hepatic metastases model.
BACKGROUND
Interleukin 12 (IL-12) gene therapy is an effective antitumor agent in local and metastatic murine tumor models. We sought to evaluate the antimetastatic effect of IL-12 cDNA in a liver metastases model.


METHODS
A liver metastases model was induced by creating a "primary" splenic tumor through inoculation of 1 x 10(5) TS/A adenocarcinoma cells directly into the inferior pole of the spleen in female BALB/c mice. On day 4, 50 microg of IL-12 cDNA or control plasmid DNA was injected into splenic tumor, followed by splenectomy on day 8. Mice were sacrificed on day 25 to assess liver tumor burden. IL-12 mRNA and mIL-12 and IFN-gamma protein levels were assessed after IL-12 injection. Peripheral blood CD4+, CD8+, and NK cells were quantified on day 14 using FACS. To determine the significance of site of cytokine DNA injection, IL-12 cDNA was injected on day 4 into splenic tumor or into the non-involved spleen after isolation of the inferior and superior portions of the spleen, respectively, with surgical clips. Splenectomy was performed on day 8 and sacrifice was performed on day 25.


RESULTS
IL-12 mRNA was detected in the liver 8 h after injection, with a peak at 24 h. After splenic injection, protein levels of IL-12 and IFN-gamma were detectable in the liver and spleen 24 h after treatment. IL-12 and IFN-gamma were not detectable in control animals. In the peripheral blood, there was a marked increase in NK cells (13% of total lymphocytes versus 4%, control) and in the CD4+/CD8+ ratio (5.5 versus 1.9). At day 25, there was a marked antimetastatic effect after IL-12 injection into either splenic tumor [liver:body weight, 6.2 versus 10.9 (control), P = 0.007] or non-involved spleen (6.8 g versus 10.7 g, P = 0.005). There was no difference in the antimetastatic effect between animals injected into splenic tumor or non-involved spleen (P = 0.3).


CONCLUSIONS
Injection with a single dose of IL-12 cDNA into splenic tumor or non-involved spleen resulted in a profound antimetastatic effect. Splenic IL-12 injection results in mRNA expression in the liver, protein expression in the liver and spleen, and a marked increase in NK cells and the CD4+/CD8+ ratio in peripheral blood.
Weber
Sharon M
SM
Department of Surgery, University of Wisconsin Hospital, Madison 53792, USA. webers@surgery.wisc.edu
Qi
Chen
C
Neal
Zane
Z
Sondel
Paul
P
Mahvi
David M
DM
D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D001769:Blood / Q000378:metabolism; D016516:CD4-CD8 Ratio; D003602:Cytotoxicity, Immunologic; D018076:DNA, Complementary / Q000008:administration & dosage* / Q000494:pharmacology; D005260:Female; D007267:Injections; D007371:Interferon-gamma / Q000378:metabolism; D018664:Interleukin-12 / Q000008:administration & dosage / Q000235:genetics* / Q000378:metabolism; D007694:Killer Cells, Natural; D008099:Liver / Q000378:metabolism; D008113:Liver Neoplasms / Q000473:pathology*; D018655:Lymphocyte Count; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D012333:RNA, Messenger / Q000378:metabolism; D013154:Spleen / Q000276:immunology / Q000378:metabolism; D013160:Splenic Neoplasms / Q000517:prevention & control / Q000556:secondary*; D016042:Transplantation, Heterotopic
D000276:Adjuvants, Immunologic; D018076:DNA, Complementary; D012333:RNA, Messenger; D018664:Interleukin-12; D007371:Interferon-gamma