Cytokine production and antitumor effect of a nonreplicating, noncytopathic recombinant vaccinia virus expressing interleukin-12.
BACKGROUND
Cancer gene therapy with interleukin-12 (IL-12) has generated much interest because of the potent antitumor effects of this cytokine. The purpose of this study was to construct a nonreplicating, noncytopathic recombinant vaccinia virus (irecVV) encoding murine IL-12 (ivKT0327mIL-12) and to assess its biologic activity and antitumor effects.


METHODS
ivKT0327mIL-12 was constructed by inserting the genes encoding mIL-12 into the VV genome by homologous recombination. Psoralen and long-wave ultraviolet light were used to render the virus incapable of replication or cell lysis. Cytokine production was assessed by infecting tumor cell lines and measuring mIL-12 in the culture supernatants by using a bioassay. C57BL/6 mice were injected subcutaneously in a randomized, blinded fashion with 5 x 10(5) MCA 101 fibrosarcoma cells or 5 x 10(5) PAN 02 pancreatic tumor cells infected in vitro with either ivKT0327mIL-12 or ivKT033, a control irecVV containing no cytokine genes. Emergence of tumor and tumor size were measured.


RESULTS
Tumor cells infected with ivKT0327mIL-12 produced large amounts of biologically active mIL-12 (up to 793 ng/10(6) cells/24 hr) but continued to proliferate in vitro with no cytopathic effect. Mice injected with MCA 101 infected with ivKT0327mIL-12 had significantly delayed tumor emergence (p < 0.03) and decreased tumor size (p < 0.003) compared with mice injected with ivKT033-infected MCA 101. Tumor growth was also significantly smaller in a similar experiment with PAN 02 (p < 0.01).


CONCLUSIONS
Tumor cells infected with irecVV encoding mIL-12 express high levels of biologically active mIL-12 in vitro and exhibit delayed tumor establishment, significant tumor growth inhibition, or both, in vivo.
Meko
J B
JB
Department of Surgery, Washington University School of Medicine, St. Louis, Mo. 63110, USA.
Tsung
K
K
Norton
J A
JA
D000818:Animals; D002455:Cell Division / Q000502:physiology; D002522:Chlorocebus aethiops; D016207:Cytokines / Q000096:biosynthesis*; D005354:Fibrosarcoma; D015870:Gene Expression / Q000502:physiology; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D018664:Interleukin-12 / Q000235:genetics*; D007668:Kidney / Q000166:cytology; D008325:Mammary Neoplasms, Experimental; D008545:Melanoma; D051379:Mice; D008810:Mice, Inbred C57BL; D012516:Osteosarcoma; D010190:Pancreatic Neoplasms; D011994:Recombinant Proteins / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000502:physiology; D014616:Vaccinia virus / Q000235:genetics*
D016207:Cytokines; D011994:Recombinant Proteins; D018664:Interleukin-12