Therapy of Mesothelioma
Immune and Antitumor Effects of Transfected Interleukin-12Irina Caminschi, Eleni Venetsanakos, Clement C. Leong, Michael J. Garlepp, Bruce W. S. Robinson, and Bernadette Scott Department of Medicine, University of Western Australia; Australian Neuromuscular Research Institute,Queen Elizabeth II Medical Centre, Nedlands, Australia; and DNAX Research Institute, Palo Alto, California Malignant mesothelioma (MM) is a solid tumor of the mesothelium for which there is no curative treat- ment. MM appears to be sensitive to immunotherapeutic approaches, and one of the most powerful immu- nomodulatory cytokines with antitumor effects is interleukin (IL)-12.
We have previously shown in a mu- rine model of MM that systemic administration of recombinant IL-12 induces a potent anti-MM immune response.
The nature and accessibility of MM tumors means that they are suitable candidates for direct cy-
tokine and gene-transfer therapeutic approaches. Therefore, we undertook a study to assess the antitumor effects induced by the local production of IL-12 within MM tumors by transfecting a murine MM line with the genes for IL-12. The IL-12 transfectant (AB1–IL-12) did not produce tumors in normal mice, but did so in athymic nude mice, implicating T cells in the prevention of MM tumor growth. In mixing experi- ments, paracrine IL-12 production inhibited growth of untransfected MM cells provided that cells produc- ing IL-12 represented more than 50–80% of the inoculum. Furthermore, BALB/c mice previously chal- lenged with AB1–IL-12 were protected against rechallenge with parental AB1 tumor, indicating that the
transfectant induced long-term immunity. AB1–IL-12 induced systemic immunity that was effective at re-ducing the incidence of parental AB1 tumor at a distal site, but its effects were dose-dependent. Though both CD41 and CD81 cells infiltrated the rejecting tumor, CD81 effector cells were essential for protec-tion against development of parental AB1 tumor. This study shows that paracrine secretion of IL-12, gen-erated by gene transfer, can induce immunity against MM that can act locally and also at a distant site. In addition, there was no evidence of toxicity, which has been associated with the systemic administration of IL-12, indicating that this cytokine is a good candidate for experimental gene therapy in MM. Caminschi,
I., E. Venetsanakos, C. C. Leong, M. J. Garlepp, B. W. S. Robinson, and B. Scott. 1999. Cytokine
gene therapy of mesothelioma: immune and antitumor effects of transfected interleukin-12. Am. J. Respir. Cell Mol. Biol. 21:347–356.
Materials and Methods
Mice
BALB/c and BALB/c-nu/nu mice were obtained from the Animal Resource Center (Perth, Western Australia) and maintained under standard conditions at the animal facil- ity of the Department of Medicine, University of Western Australia.
Cell Lines
The establishment of the BALB/c mouse-derived MM tumor cell line AB1 has been described previously (23). Cell lines were maintained in RPMI 1640 medium (GIBCO, Grand Island, NY) supplemented with 5% fetal bovine serum (GIBCO), 20 mM 4-(2-hydroxyethyl)-1-piperazine-
N-2-ethanesulfonic acid, 200 mM L-glutamine (GIBCO), 0.05 mM mercaptoethanol, 100 mg/ml gentamicin, and 120 mg/ml of penicillin. Additionally, cell lines transfected with the bacterial neomycin phosphotransferase gene were maintained in medium containing G418 (Geneticin; GIBCO; 400 mg/ml). All cell cultures were grown at 378C in a 5% CO2 humidified atmosphere.
We have previously shown in a mu- rine model of MM that systemic administration of recombinant IL-12 induces a potent anti-MM immune response.
The nature and accessibility of MM tumors means that they are suitable candidates for direct cy-
tokine and gene-transfer therapeutic approaches. Therefore, we undertook a study to assess the antitumor effects induced by the local production of IL-12 within MM tumors by transfecting a murine MM line with the genes for IL-12. The IL-12 transfectant (AB1–IL-12) did not produce tumors in normal mice, but did so in athymic nude mice, implicating T cells in the prevention of MM tumor growth. In mixing experi- ments, paracrine IL-12 production inhibited growth of untransfected MM cells provided that cells produc- ing IL-12 represented more than 50–80% of the inoculum. Furthermore, BALB/c mice previously chal- lenged with AB1–IL-12 were protected against rechallenge with parental AB1 tumor, indicating that the
transfectant induced long-term immunity. AB1–IL-12 induced systemic immunity that was effective at re-ducing the incidence of parental AB1 tumor at a distal site, but its effects were dose-dependent. Though both CD41 and CD81 cells infiltrated the rejecting tumor, CD81 effector cells were essential for protec-tion against development of parental AB1 tumor. This study shows that paracrine secretion of IL-12, gen-erated by gene transfer, can induce immunity against MM that can act locally and also at a distant site. In addition, there was no evidence of toxicity, which has been associated with the systemic administration of IL-12, indicating that this cytokine is a good candidate for experimental gene therapy in MM. Caminschi,
I., E. Venetsanakos, C. C. Leong, M. J. Garlepp, B. W. S. Robinson, and B. Scott. 1999. Cytokine
gene therapy of mesothelioma: immune and antitumor effects of transfected interleukin-12. Am. J. Respir. Cell Mol. Biol. 21:347–356.
Materials and Methods
Mice
BALB/c and BALB/c-nu/nu mice were obtained from the Animal Resource Center (Perth, Western Australia) and maintained under standard conditions at the animal facil- ity of the Department of Medicine, University of Western Australia.
Cell Lines
The establishment of the BALB/c mouse-derived MM tumor cell line AB1 has been described previously (23). Cell lines were maintained in RPMI 1640 medium (GIBCO, Grand Island, NY) supplemented with 5% fetal bovine serum (GIBCO), 20 mM 4-(2-hydroxyethyl)-1-piperazine-
N-2-ethanesulfonic acid, 200 mM L-glutamine (GIBCO), 0.05 mM mercaptoethanol, 100 mg/ml gentamicin, and 120 mg/ml of penicillin. Additionally, cell lines transfected with the bacterial neomycin phosphotransferase gene were maintained in medium containing G418 (Geneticin; GIBCO; 400 mg/ml). All cell cultures were grown at 378C in a 5% CO2 humidified atmosphere.
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