SECRETED TYPE OF MODIFIED INTERLEUKIN-18 GENE TRANSDUCED INTO MOUSE RENAL CELL CARCINOMA CELLS INDUCES SYSTEMIC TUMOR IMMUNITY

Triple combination of oncolytic herpes simplex virus-1 vectors armed with interleukin-12, interleukin-18, or soluble B7-1 results in enhanced antitumor efficacy

Conditionally replicating herpes simplex virus-1 (HSV-1) vectors are promising therapeutic agents for cancer. Insertion of therapeutic transgenes into the viral genome should confer desired anticancer functions in addition to oncolytic activities. Herein, using bacterial artificial chromosome and two recombinase-mediated recombinations, we simultaneously created four "armed" oncolytic HSV-1, designated vHsv-B7.1-Ig, vHsv-interleukin (IL)-12, vHsv-IL-18, and vHsv-null, which express murine soluble B7.1 (B7.1-Ig), murine IL-12, murine IL-18, and no transgene, respectively. These vHsv vectors possess deletions in the gamma34.5 genes and contain the green fluorescent protein gene as a histochemical marker and the immunostimulatory transgene inserted in the deleted ICP6 locus. The vHsv showed similar replicative capabilities in vitro. The in vivo efficacy was tested in A/J mice harboring s.c. tumors of syngeneic and poorly immunogenic Neuro2a neuroblastoma. The triple combination of vHsv-B7.1-Ig, vHsv-IL-12, and vHsv-IL-18 exhibited the highest efficacy among all single vHsv or combinations of two viruses. Combining 1 x 10(5) plaque-forming units each of the three armed viruses showed stronger antitumor activities than any single armed virus at 3 x 10(5) plaque-forming units in inoculated tumors as well as in noninoculated remote tumors. Studies using athymic mice indicated that this enhancement of antitumor efficacy was likely mediated by T-cell immune responses. The combined use of multiple oncolytic HSV-1 armed with different immunostimulatory genes may be a useful strategy for cancer therapy.

Triple Gene-Deleted Oncolytic Herpes Simplex Virus Vector Double-Armed with Interleukin 18 and Soluble B7-1 Constructed by Bacterial Artificial Chromosome–Mediated System

Conditionally replicating herpes simplex virus type 1 (HSV-1) vectors are promising therapeutic agents for cancer. Certain antitumor functions may be added to oncolytic activities of recombinant HSV-1 vectors by inserting transgenes into the viral genome. Because conventional homologous recombination techniques had required time-consuming processes to create "armed" oncolytic HSV-1 vectors, we established an innovative construction system using bacterial artificial chromosome and two recombinase systems (Cre/loxP and FLPe/FRT). Using G47Delta, a safe and efficacious oncolytic HSV-1 with triple gene mutations, as the backbone, this system allowed a rapid generation of multiple vectors with desired transgenes inserted in the deleted ICP6 locus. Four oncolytic HSV-1 vectors, expressing murine interleukin 18 (mIL-18), soluble murine B7-1 [B7-1-immunoglobulin (B7-1-Ig)], both, or none, were created simultaneously within 3 months. In vitro, all newly created recombinant vectors exhibited virus yields and cytopathic effects similar to the parental G47Delta. In two immunocompetent mouse tumor models, TRAMP-C2 prostate cancer and Neuro2a neuroblastoma, the vector expressing both mIL-18 and B7-1-Ig showed a significant enhancement of antitumor efficacy via T-cell-mediated immune responses. The results show that "arming" with multiple transgenes can improve the efficacy of oncolytic HSV-1 vectors. The use of our system may facilitate the development and testing of various armed oncolytic HSV-1 vectors.

Antitumor effect of simultaneous transfer of interleukin-12 and interleukin-18 genes and its mechanism in a mouse bladder cancer model

BACKGROUND

The objectives of this study were to evaluate the antitumor effects of the simultaneous introduction of interleukin 12 (IL-12) and IL-18 genes into a mouse bladder cancer cell line (MBT2). We intended to compare these with those of either gene alone and to investigate the mechanism of the effects induced by the transfer of IL-12 and/or IL-18 genes in this model system.

METHODS

We transfected the IL-12 and/or IL-18 genes into MBT2 cells by the liposome-mediated gene transfer method. We confirmed the secretion of IL-12 and/or IL-18 by enzyme-linked immunosorbent assay. Parental (MBT2/P), IL-12-transfected (MBT2/IL-12), IL-18-transfected (MBT2/IL-18) or both IL-12- and IL-18-transfected (MBT2/Both) cells were subcutaneously or intravenously injected into syngeneic C3H mice. To analyze the mechanism of tumor rejection, these clones were subcutaneously injected into naive nude mice and those depleted with natural killer (NK) cells by antibody.

RESULTS

MBT2/IL-12, MBT2/IL-18 and MBT2/Both were completely rejected when they were injected subcutaneously or intravenously into syngeneic mice. However, MBT2/IL-12, but not MBT2/IL-18, could grow in nude mice. Moreover, the antitumor effect of MBT2/IL-18 was partially abrogated when injected into nude mice of which NK cells were depleted by antibody treatment. MBT2/Both was completely rejected in both nude mice with and without NK cells.

CONCLUSION

The results of the present study indicate that T cells and NK cells seem to play important roles in the antitumor effects by the secretion of IL-12 and IL-18, respectively, and MBT2/Both possesses both mechanisms.

Inhibition by interleukin-18 of the growth of Dunn osteosarcoma cells

To examine the usefulness of interleukin-18 (IL-18) in the treatment of osteosarcomas, the effect of IL-18 on the growth of Dunn osteosarcoma cells was investigated. Daily intraperitoneal (i.p.) injection of mouse recombinant IL-18 (2 microg/mouse) suppressed the growth of Dunn osteosarcoma cells transplanted subcutaneously (s.c.) into syngeneic C3H mice. This IL-18-induced suppression was not affected by simultaneous treatment with anti-asialo GM1 serum, which inactivates natural killer (NK) cells. However, IL-18 failed to suppress the growth of Dunn osteosarcoma cells transplanted into BALB/c-nude mice devoid of T lymphocytes or C3H-gld/gld mice deficient in functional Fas ligand (FasL). IL-18 also failed to suppress the growth of Dunn osteosarcoma cells in vitro, although expression of IL-18 receptor mRNA and MyD88 mRNA as well as Fas mRNA was detected by reverse transcriptase-polymerase chain reaction (RT-PCR). On the other hand, antimouse Fas antibody showed cytotoxicity against Dunn osteosarcoma cells in a dose-dependent manner in vitro. In addition, treatment of C3H mice with IL-18 enhanced the cytotoxic activity of CD8(+) T lymphocytes against Dunn osteosarcoma cells. These results indicate that IL-18 inhibits the growth of Dunn osteosarcoma cells in vivo by enhancing the cytotoxic activity of CD8(+) T lymphocytes through the FasL-Fas system.

Efficient induction of T helper type 1-mediated immune responses in antigen-primed mice by anti-CD3 single-chain Fv/interleukin-18 fusion DNA

Two types of T helper (Th) cells - Th1 and Th2 - play different roles in protection and immunopathology. The Th1 cell-mediated immune response plays an important role in inducing the host defence against intracellular bacteria and also in cancer immunotherapy. To effectively induce Th1 immune responses, we constructed a mammalian expression plasmid (pAnti-CD3sFv/IL-18) carrying a fusion gene in which anti-CD3 single-chain Fv (sFv) cDNA, the smallest unit of antibody recognizing the CD3 epsilon moiety of the T-cell receptor, was covalently linked to mature interleukin (IL)-18 cDNA. Intramuscular injection of ovalbumin (OVA)-sensitized BALB/c mice with pAnti-CD3sFv/IL-18 DNA efficiently increased the production of both OVA-specific interferon-gamma and anti-OVA immunoglobulin G2a, compared to injection with pAnti-CD3sFv DNA. In addition, pAnti-CD3sFv/IL-18 was more efficient than a mixture of pAnti-CD3sFv + pIL-18 in inducing OVA-specific, Th1 immune responses and also in inhibiting OVA-specific, IL-4 production. These studies indicate that vaccination with pAnti-CD3sFv/IL-18 fusion DNA efficiently induces the Th1 immune response in antigen-sensitized mice.

Continuous release of interleukin 12 from microencapsulated engineered cells for colon cancer therapy

AIM: To explore the anti-tumor immunity against CT26 colon tumor of the microencapsulated cells modified with murine interleukine-12 (mIL-12) gene.

METHODS: Mouse fibroblasts (NIH3T3) were stably transfected to express mIL-12 using expression plasmids carrying mIL-12 gene (p35 and p40), and NIH3T3-mIL-12 cells were encapsulated in alginate microcapsules for long-term delivery of mIL-12. mIL-12 released from the microencapsulated NIH3T3-mIL-12 cells was confirmed using ELISA assay. Transplantation of the microencapsulated NIH3T3-mIL-12 cells was performed in the tumor-bearing mice with CT26 cells. The anti-tumor responses and the anti-tumor activities of the microencapsulated NIH3T3-mIL-12 cells were evaluated.

RESULTS: Microencapsulated NIH3T3-mIL-12 cells could release mIL-12 continuously and stably for a long time. After the microencapsulated NIH3T3-mIL-12 cells were transplanted subcutaneously into the tumor-bearing mice for 21 d, the serum concentrations of mIL-12, mIL-2 and mIFN-γ, the cytotoxicity of the CTL from the splenocytes and the NK activity in the treatment group were significantly higher than those in the controls. Moreover, mIL-12 released from the microencapsulated NIH3T3-mIL-12 cells resulted in a significant inhibition of tumor proliferation and a prolonged survival of tumor-bearing mice.

CONCLUSION: The microencapsulated NIH3T3-mIL-12 cells have a significant therapeutic effect on the experimental colon tumor by activating anti-tumor immune responses in vivo. Microencapsulated and genetically engineered cells may be an extremely versatile tool for tumor gene therapy.