Neuroblastoma regression and immunity induced by transgenic expression of interleukin-12

Localized Interleukin-12 for Cancer Immunotherapy

Interleukin-12 (IL-12) is a potent, pro-inflammatory type 1 cytokine that has long been studied as a potential immunotherapy for cancer. Unfortunately, IL-12's remarkable antitumor efficacy in preclinical models has yet to be replicated in humans. Early clinical trials in the mid-1990's showed that systemic delivery of IL-12 incurred dose-limiting toxicities. Nevertheless, IL-12's pleiotropic activity, i.e., its ability to engage multiple effector mechanisms and reverse tumor-induced immunosuppression, continues to entice cancer researchers. The development of strategies which maximize IL-12 delivery to the tumor microenvironment while minimizing systemic exposure are of increasing interest. Diverse IL-12 delivery systems, from immunocytokine fusions to polymeric nanoparticles, have demonstrated robust antitumor immunity with reduced adverse events in preclinical studies. Several localized IL-12 delivery approaches have recently reached the clinical stage with several more at the precipice of translation. Taken together, localized delivery systems are supporting an IL-12 renaissance which may finally allow this potent cytokine to fulfill its considerable clinical potential. This review begins with a brief historical account of cytokine monotherapies and describes how IL-12 went from promising new cure to ostracized black sheep following multiple on-study deaths. The bulk of this comprehensive review focuses on developments in diverse localized delivery strategies for IL-12-based cancer immunotherapies. Advantages and limitations of different delivery technologies are highlighted. Finally, perspectives on how IL-12-based immunotherapies may be utilized for widespread clinical application in the very near future are offered.

In Silico Insights on GD2 : A Potential Target for Pediatric Neuroblastoma

Background:

Originating from the abnormal growth of neuroblasts, pediatric neuroblastoma affects the age group below 15 years. It is an aggressive heterogenous cancer with a high morbidity rate. Biological marker GD2 synthesised by the GD2 gene acts as a powerful predictor of neuroblastoma cells. GD2 gangliosides are sialic acid-containing glycosphingolipids. Differential expression during brain development governs the function of the GD2. The present study explains the interaction of the GD2 with its established inhibitors and discovers the compound having a high binding affinity against the target protein. Technically, during the development of new compounds through docking studies, the best drug among all pre-exist inhibitors was filtered. Hence in reference to the best docked compound, the study proceeded further.

Methodology:

The In silico approach provides a platform to determine and establish potential inhibitor against GD2 in Pediatric neuroblastoma. The 3D structure of GD2 protein was modelled by homology base fold methods using Smith-Watermans’ Local alignment. A total of 18 established potent compounds were subjected to molecular docking and Etoposide (CID: 36462) manifested the highest affinity. The similarity search presented 336 compounds similar to Etoposide.

Results:

Through virtual screening, the compound having PubChem ID 10254934 showed a better affinity towards GD2 than the established inhibitor. The comparative profiling of the two compounds based on various interactions such as H-bond interaction, aromatic interactions, electrostatic interactions and ADMET profiling and toxicity studies were performed using various computational tools.

Conclusion:

The docking separated the virtual screened drug (PubChemID: 10254934) from the established inhibitor with a better re-rank score of -136.33. The toxicity profile of the virtual screened drug was also lesser (less lethal) than the established drug. The virtual screened drug was observed to be bioavailable as it does not cross the blood-brain barrier. Conclusively, the virtual screened compound obtained in the present investigation is better than the established inhibitor and can be further augmented by In vitro analysis, pharmacodynamics and pharmacokinetic studies.

Developing preclinical models of neuroblastoma: driving therapeutic testing

Despite advances in cancer therapeutics, particularly in the area of immuno-oncology, successful treatment of neuroblastoma (NB) remains a challenge. NB is the most common cancer in infants under 1 year of age, and accounts for approximately 10% of all pediatric cancers. Currently, children with high-risk NB exhibit a survival rate of 40–50%. The heterogeneous nature of NB makes development of effective therapeutic strategies challenging. Many preclinical models attempt to mimic the tumor phenotype and tumor microenvironment. In vivo mouse models, in the form of genetic, syngeneic, and xenograft mice, are advantageous as they replicated the complex tumor-stroma interactions and represent the gold standard for preclinical therapeutic testing. Traditional in vitro models, while high throughput, exhibit many limitations. The emergence of new tissue engineered models has the potential to bridge the gap between in vitro and in vivo models for therapeutic testing. Therapeutics continue to evolve from traditional cytotoxic chemotherapies to biologically targeted therapies. These therapeutics act on both the tumor cells and other cells within the tumor microenvironment, making development of preclinical models that accurately reflect tumor heterogeneity more important than ever. In this review, we will discuss current in vitro and in vivo preclinical testing models, and their potential applications to therapeutic development.

Autologous hematopoietic stem cell transplantation for pediatric solid tumors

While advances in the treatment of pediatric cancers have increased cure rates, children with metastatic or recurrent solid tumors have a dismal prognosis despite initial transient responses to therapy. Autologous hematopoietic stem cell transplantation takes advantage of the steep dose-response relationship observed with many chemotherapeutic agents. While clearly demonstrated to improve outcomes in patients with metastatic neuroblastoma, autologous hematopoietic stem cell transplantation is also frequently used to treat patients with other high-risk diseases such as Ewing sarcoma, osteosarcoma, rhabdomyosarcoma, Wilms' tumor, retinoblastoma, germ cell tumors, lymphomas and brain tumors. Most published experience consists of retrospective, single-arm studies; randomized clinical trials are lacking, due in part to the rarity of pediatric cancers treatable by autologous hematopoietic stem cell transplantation. These published literature demonstrate that autologous hematopoietic stem cell transplantation results in most cases in equivalent or superior outcomes when compared with conventional therapies. However, patient heterogeneity, patient selection, graft characteristics and processing and the varied conditioning regimens are additional factors to consider. Since the inception of autologous hematopoietic stem cell transplantation, regimen-related toxicity has markedly decreased and the vast majority of treatment failures are now due to disease recurrence. Prospective clinical trials are needed to identify specific high-risk patient populations, with randomization (when possible) to compare outcomes of patients undergoing autologous hematopoietic stem cell transplantation with those receiving standard therapy. In addition, investigators need to better define the role of autologous hematopoietic stem cell transplantation in these solid tumors, particularly in combination with other therapeutic modalities such as immunotherapy and novel cell processing methodologies.

Preclinical evaluation of engineered oncolytic herpes simplex virus for the treatment of neuroblastoma

Despite intensive research efforts and therapeutic advances over the last few decades, the pediatric neural crest tumor, neuroblastoma, continues to be responsible for over 15% of pediatric cancer deaths. Novel therapeutic options are needed for this tumor. Recently, investigators have shown that mice with syngeneic murine gliomas treated with an engineered, neuroattenuated oncolytic herpes simplex virus-1 (oHSV), M002, had a significant increase in survival. M002 has deletions in both copies of the γ₁34.5 gene, enabling replication in tumor cells but precluding infection of normal neural cells. We hypothesized that M002 would also be effective in the neural crest tumor, neuroblastoma. We showed that M002 infected, replicated, and decreased survival in neuroblastoma cell lines. In addition, we showed that in murine xenografts, treatment with M002 significantly decreased tumor growth, and that this effect was augmented with the addition of ionizing radiation. Importantly, survival could be increased by subsequent doses of radiation without re-dosing of the virus. Finally, these studies showed that the primary entry protein for oHSV, CD111 was expressed by numerous neuroblastoma cell lines and was also present in human neuroblastoma specimens. We concluded that M002 effectively targeted neuroblastoma and that this oHSV may have potential for use in children with unresponsive or relapsed neuroblastoma.

Immunotherapy for neuroblastoma: turning promise into reality

Neuroblastoma is one of the commonest and most aggressive paediatric malignancies. The majority of children present with metastatic disease for which long-term survival remains poor despite intensive multi-modal therapies. Toxicity from current treatment regimes is already significant, and there is little room to further intensify therapy. Alternative treatment strategies are therefore needed in order to improve survival. Immunotherapy is an attractive therapeutic option for these children as it potentially offers a much more specific and less toxic treatment than conventional therapies. This review discusses the different immunotherapy strategies that may be useful in neuroblastoma, their advantages and disadvantages and the challenges that need to be overcome to successfully use them clinically.

Immunologic and therapeutic synergy of IL-27 and IL-2: enhancement of T cell sensitization, tumor-specific CTL reactivity and complete regression of disseminated neuroblastoma metastases in the liver and bone marrow

IL-27 exerts antitumor activity in murine orthotopic neuroblastoma, but only partial antitumor effect in disseminated disease. This study demonstrates that combined treatment with IL-2 and IL-27 induces potent antitumor activity in disseminated neuroblastoma metastasis. Complete durable tumor regression was achieved in 90% of mice bearing metastatic TBJ-IL-27 tumors treated with IL-2 compared with only 40% of mice bearing TBJ-IL-27 tumors alone and 0% of mice bearing TBJ-FLAG tumors with or without IL-2 treatment. Comparable antitumor effects were achieved by IL-27 protein produced upon hydrodynamic IL-27 plasmid DNA delivery when combined with IL-2. Although delivery of IL-27 alone, or in combination with IL-2, mediated pronounced regression of neuroblastoma metastases in the liver, combined delivery of IL-27 and IL-2 was far more effective than IL-27 alone against bone marrow metastases. Combined exposure to IL-27 produced by tumor and IL-2 synergistically enhances the generation of tumor-specific CTL reactivity. Potentiation of CTL reactivity by IL-27 occurs via mechanisms that appear to be engaged during both the initial sensitization and effector phase. Potent immunologic memory responses are generated in mice cured of their disseminated disease by combined delivery of IL-27 and IL-2, and depletion of CD8(+) ablates the antitumor efficacy of this combination. Moreover, IL-27 delivery can inhibit the expansion of CD4(+)CD25(+)Foxp3(+) regulatory and IL-17-expressing CD4(+) cells that are otherwise observed among tumor-infiltrating lymphocytes from mice treated with IL-2. These studies demonstrate that IL-27 and IL-2 synergistically induce complete tumor regression and long-term survival in mice bearing widely metastatic neuroblastoma tumors.

Effects of irradiated tumor vaccine and infusion of granulocyte-macrophage colony-stimulating factor and interleukin-12 on established gliomas in rats

PURPOSE

We investigated granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-12 (IL-12) infused into the injection site of irradiated tumor vaccine (TV) as therapy for gliomas.

METHODS

Rats with subcutaneous RT-2 gliomas were treated with irradiated TV and/or subcutaneous infusion of GM-CSF and/or IL-12 via osmotic minipump 5 days after tumor-cell inoculation. Cytotoxic T lymphocyte (CTL) and natural killer (NK) cell activity were analyzed to investigate immune responses. Rats with intracerebral gliomas were treated with irradiated TV and infused GM-CSF/IL-12 3 days after tumor-cell inoculation. Tumor growth rates and animal survival were followed. Survivors were re-challenged with wild-type RT-2 cells subcutaneously or intracerebrally to study long-term anti-tumor immunity.

RESULTS

Rats with subcutaneous gliomas treated with GM-CSF and IL-12 or TV plus GM-CSF or IL-12 did not have increased survival rate (P>0.2), but did have prolonged survival time (P<0.05); in contrast, rats treated with TV plus GM-CSF/IL-12 had increased survival rate (P<0.05) and prolonged survival time (P<0.05) compared with controls. These treatment strategies showed enhanced CTL and NK cell activities. Rats with intra-cerebral gliomas treated with TV plus GM-CSF/IL-12 did not have increased survival rate (P=0.11), but did have prolonged survival time (P<0.0001). Survivors in each group were re-challenged with wild-type RT-2 cells, and all had long-term survival.

CONCLUSIONS

Irradiated TV plus continuous localized infusion of GM-CSF/IL-12 may induce a tumor-specific anti-tumor immune response on established subcutaneous or intra-cerebral gliomas, and such a treatment strategy deserves consideration as adjuvant treatment for glioma.

Administration route- and immune cell activation-dependent tumor eradication by IL12 electrotransfer

Injection of DNA via electric pulses into targeted tissues is referred to as electrotransfer. Intratumoral electrotransfer of the IL12 gene is more effective than intramuscular electrotransfer of the same gene in the eradication of established tumors. To understand the underlying immunological mechanisms, T cell infiltration, CTL activity, inhibition of angiogenesis, and transgene expression were analyzed using immunohistochemistry, fluorescence-based CTL analysis, Northern blot, and ELISA. In addition, the therapeutic effects of IL12 gene therapy were determined in immunocompetent, immune-cell-depleted, and immunodeficient mice. We found that intratumoral, but not intramuscular, electrotransfer of the IL12 gene induces CD8+ T cell infiltration, CTL activity, and tumor eradication. Tumor eradication by intratumoral IL12 gene electrotransfer requires both NK and T cells. The absence of either cell type will abrogate the intratumoral IL12 gene therapy-induced tumor eradication. Such a requirement explains why tumors cannot be eradicated by intramuscular electrotransfer of the IL12 gene. Only NK-cell-dependent, and not T-cell-dependent, anti-tumor effects are induced by intramuscular administration. Together, these results suggest that NK cells play an important role in both administration routes, mediating tumor growth inhibition, but T cells are specifically activated by intratumoral IL12 gene electrotransfer and not by the intramuscular route.

Oncolytic herpes simplex virus mutants are more efficacious than wild-type adenovirus Type 5 for the treatment of high-risk neuroblastomas in preclinical models

BACKGROUND

High-risk neuroblastoma (Nb) is incurable using current treatment regimens in the majority of patients. Oncolytic virotherapy is a novel approach being tested for several types of adult cancers.

OBJECTIVES

To compare the susceptibility of Nb tumor models to oncolytic adenovirus and HSV mutants and delineate the mechanisms of resistance or sensitivity.

METHODS

Human Nb cell lines were used to determine susceptibility to adenovirus type 5 wild-type and HSV1 mutant (NV1066) infection, adenovirus receptor expression, support of NV1066 replication, and induction of apoptosis. Human xenograft tumors in immunodeficient mice were evaluated for histological effects and tumor response to intratumoral injection of an oncolytic HSV mutant.

RESULTS

All eight Nb cell lines tested in culture were relatively resistant to infection with wild type and attenuated adenoviruses. Cells expressed the cocksackie-adenovirus attachment receptor (CAR) but had low or absent expression of the internalization receptors (alphavbeta3, alphavbeta5 integrins). In contrast, all cells were uniformly sensitive to infection with the attenuated HSV mutant, NV1066. Productive virus replication and induction of apoptosis were observed in HSV-infected cells. CHLA-20 and LAN-5 xenograft tumors injected with a single dose of NV1066 showed a significant antitumor response, and the animals had a prolonged survival post infection in comparison to the PBS-treated control group. HSV injected tumors showed extensive areas of necrosis and morphologic evidence of apoptosis.

CONCLUSIONS

Nb tumor models are resistant to adenovirus mediated oncolysis but highly sensitive to HSV mediated oncolysis. Further studies of HSV virotherapy as a novel treatment for Nb are warranted.

Sequential Immunogene Therapy with Interleukin-12– and Interleukin-15–Engineered Neuroblastoma Cells Cures Metastatic Disease in Syngeneic Mice

Purpose: To investigate the potential synergistic effects of Neuro2a neuroblastoma cells engineered with IL-12 and/or IL-15 genes in improving survival of syngeneic mice bearing neuroblastoma metastatic disease.

Experimental Design: Neuro2a cells engineered with interleukin (IL)-12 (Neuro2a/IL-12), IL-15 (Neuro2a/IL-15), or both cytokines (Neuro2a/IL-12/IL-15) were injected s.c. in syngeneic A/J mice challenged i.v. with Neuro2a parental cells (Neuro2apc) using different schedules of administration in either preventive or therapeutic settings.

Results: A single injection of Neuro2a/IL-12 or Neuro2a/IL-15 cells induced resistance to a subsequent i.v. Neuro2apc challenge in 45% and 28% of mice, respectively. Neuro2a/IL-12/IL-15 cells protected 28% of mice, showing no synergistic effect. However, sequential vaccination with Neuro2a/IL-12 (day −30) followed by Neuro2a/IL-15 (day −15) protected 71% of mice from subsequent challenge with Neuro2apc. A single dose of Neuro2a/IL-12 prolonged the mean survival time of mice bearing established metastatic neuroblastoma from 21 ± 3 to 46 ± 27 days but failed to cure mice, whereas Neuro2a/IL-15 or Neuro2a/IL-12/IL-15 were ineffective. However, sequential vaccination with Neuro2a/IL-12 (day +3) followed by Neuro2a/IL-15 (day +13) cured 43% of mice as assessed by histologic analysis of different organs from long-term surviving mice. CTL activity against Neuro2apc cells was observed in splenocytes from treated mice, and CD8+ T-cell depletion abrogated the therapeutic effect of vaccination.

Conclusions: Sequential vaccination with IL-12- and IL-15-engineered neuroblastoma cells induced optimal preventive and therapeutic effects, which may be related to the Th1 priming effect of IL-12 followed by the enhancement of CD8+ T-cell responses and their maintenance mediated by IL-15.

Resveratrol-induced cellular apoptosis and cell cycle arrest in neuroblastoma cells and antitumor effects on neuroblastoma in mice

BACKGROUND

The prognosis of neuroblastoma patients remains unsatisfactory. Therefore, developing an effective treatment strategy is important. Resveratrol, a natural polyphenol, possesses chemopreventive and antitumor effects. We investigated the effects of resveratrol on the proliferation, apoptosis, and cell cycle alteration of neuroblastoma cells and determined its effects on neuroblastoma tumors in mice.

METHODS

Cytotoxic effects, cellular apoptosis, and alterations in the cell cycle were determined in neuro-2a neuroblastoma cells exposed for varying lengths of time to a series of resveratrol concentrations. Expression of associated cell cycle regulatory proteins, cyclin E and p21, was detected by Western blot analysis, and the antitumor effects of resveratrol were investigated by treating subcutaneous neuroblastoma tumors with intraperitoneal injections of 40 mg/kg resveratrol daily for 28 days.

RESULTS

Resveratrol exerted cytotoxic effects on neuroblastoma cells. After resveratrol treatment, the apoptosis rate of the neuroblastoma cells significantly increased, a significant accumulation of cells occurred at the S phase of the cell cycle, p21 was downregulated, and cyclin E was upregulated. In addition, resveratrol treatment suppressed the growth rate of subcutaneous neuroblastomas, resulting in 70% long-term survival.

CONCLUSION

Resveratrol caused significant cytotoxicity and increased apoptosis and S-phase accumulation of neuroblastoma cells. S-phase accumulation was related to the down-regulation of p21 and up-regulation of cyclin E. In addition, resveratrol exerted antitumor effects on neuroblastomas in mice. Thus, resveratrol shows promise for the treatment of neuroblastoma.

Functional and molecular characterization of interleukin-2 transgenic Ewing tumor cells for in vivo immunotherapy

BACKGROUND

Interleukin-2 (IL-2) is a potent cytokine with potential activity against several tumors including Ewing tumors (ET). Side effects of systemic IL-2 can be circumvented by the use of transgenic tumor cells. However, in vitro manipulation may change the overall gene expression profile of tumor cells unfavorably. Therefore, we assessed gene expression profiles, safety, and immunomodulatory efficacy of IL-2 transgenic (IL-2-tg) ET cells in vitro and in NOD/scid mice.

PROCEDURE

Viable wild type A673 tumor cells were co-cultured together with irradiated IL-2-tg or mock-transfected cells and HLA matched peripheral blood mononuclear cells. Activation of T and NK cells was assessed by FACS analysis. The effect of irradiated IL-2-tg cells on tumor growth in vivo was investigated by using NOD/scid mice. Gene expression profiles of wild type and transfected cells were analyzed with Affymetrix HG-U95A microarrays.

RESULTS

IL-2-tg cells activated and increased the number of T cells and NK cells in vitro. Co-culture with IL-2-tg but not with mock-transfected cells almost completely suppressed wild type tumor cell growth in vitro. Cell depletion experiments indicated a major contribution of NK cells to this tumor cell suppression. Co-transfer of irradiated IL-2-tg cells significantly reduced wild type tumor growth in NOD/scid mice. Side effects in the treated animals were not observed and no tumor growth was observed after injection of irradiated IL-2-tg cells alone. Gene expression profiling revealed a substantial degree of homogeneity of gene expression in transfected and wild type cells and suggests that transfection and selection procedures had no major impact on the gene expression profile.

CONCLUSIONS

Next to a high degree of homogeneity between transgenic and wild type cells, our data suggest that irradiated IL-2-tg ET cells can activate cytolytic effector cells. These cells may have therapeutic potential for ET patients.

Cellular mechanisms of interleukin-12-mediated neuroblastoma regression

BACKGROUND/PURPOSE

Interleukin-12 (IL-12) is a proinflammatory cytokine with potent antitumor effects. Previous studies from the authors laboratory showed regression of established neuroblastoma in mice vaccinated with IL-12 transduced dendritic cells (DC). Although regression was associated with intense T cell infiltration, the precise role of T cells is unknown. The purpose of this work is to study the cellular mechanisms in IL-12-mediated tumor regression.

METHODS

Three groups of mice (n = 12) received subcutaneous inoculation with 1 x 10(6) murine neuroblastoma cells (TBJ). Anti-CD4 (T helper), anti-CD8 (T cytotoxic), or antiasialo-GM1 (natural killer) antibodies were injected intravenously at 3-day intervals to deplete various immune effector cell populations. Mice in each depletion group and the control (nondepleted) group were injected intratumorally on day 7 with 1 x 10(6) DC IL-12-transduced DC. Tumors were harvested for morphometry and immunohistochemistry at 21 days.

RESULTS

CD4 depletion had no effect on tumor growth in either control or IL-12-vaccinated animals. In contrast, CD8-depleted animals treated with IL-12-transduced DC underwent initial regression followed by progressive tumor growth (P <.01). These tumors were smaller in size at the same time-point. However, NK cell depletion (antiasialo GM1) completely abrogated the antitumor effects of IL-12-transduced DC, leading to progressive tumor growth from the outset. There was no difference between the control and treated animals in this group.

CONCLUSIONS

Contrary to our hypothesis that IL-12 DC primarily function to stimulate a T cell-mediated response, these data suggest that NK cells are essential for the initial antitumor response of animals treated with IL-12-transduced DC. CD8+ T cells appear to be necessary effector cells for complete rejection of tumor and possibly memory. NK cells are responsible for the early immune response. Furthermore, CD4+ (T helper) cells did not play any role in IL-12-induced regression. These results imply that for DC to generate an effective antitumor response against neuroblastoma both acquired and innate effector cells are required.

Effects of irradiated tumor vaccine and continuous localized infusion of granulocyte-macrophage colony-stimulating factor on neuroblastomas in mice

BACKGROUND/PURPOSE

Immunomodulatory treatment has been proposed as a feasible strategy for neuroblastoma treatment. In this study, the antitumor effects of a continuous localized subcutaneous infusion of granulocyte-macrophage colony-stimulating factor (GM-CSF) into the injection site of irradiated tumor vaccine used as a source of tumor antigens on mouse neuroblastoma were investigated.

METHODS

A/J mice were inoculated subcutaneously with wild type neuro-2a neuroblastoma cells and then treated with 5 doses of irradiated tumor vaccine or continuous localized infusion of GM-CSF (1 ng/d or 10 ng/d) via an osmotic minipump. Survival rates and survival times were compared among the groups. Tumor growth rates and animal survival times were followed and compared among different groups. Histologic and immunohistochemical analyses were performed to observe the immune response induced by various treatment strategies.

RESULTS

Tumor growth rates were reduced significantly and survival times prolonged significantly by the treatment using tumor vaccine and continuous infusion of 10 ng/d of GM-CSF when compared with the control group (P <.05). One mouse treated with tumor vaccine and a 10 ng/d infusion of GM-CSF showed tumor regression and long-term survival, and no tumor growth was noted after rechallenge with wild-type neuro-2a cells. In contrast, using tumor vaccine only, or tumor vaccine combined with a 1 ng/d infusion of GM-CSF was less effective than tumor vaccine combined with a 10 ng/d infusion of GM-CSF (P <.05). Infusion of GM-CSF alone had no antitumor effects. Immunohistologic analyses showed significant CD4+ and CD8+ T cell infiltration of the tumor in the mice treated with tumor vaccine and a 10 ng/d infusion of GM-CSF.

CONCLUSIONS

The results suggest that an irradiated tumor vaccine combined with continuous localized infusion of GM-CSF may induce a tumor-specific antitumor immune response that can suppress tumor growth and prolong survival. Such a treatment strategy deserves consideration as a possible adjuvant treatment for neuroblastoma.

Effective gene therapy for medullary thyroid carcinoma using recombinant adenovirus inducing tumor-specific expression of interleukin-12

No satisfactory treatment of metastatic medullary thyroid carcinoma (MTC) is available. Cell-specific gene therapy offers a new approach. We have constructed a recombinant replication-defective adenoviral vector expressing murine interleukin-12 (mIL-12), driven by a modified CALC-I promoter (TCP). This vector (AdTCPmIL-12) includes two separate cassettes encoding mIL-12 p35 or p40 subunit controlled by TCP inserted in the E1 region of adenovirus type 5. In vitro and in vivo reporter gene expression using TCP revealed its cell-specific activity. AdTCPmIL-12-infected rat MTC (rMTC) cells produced high amounts of functional mIL-12 cells in vitro, while other cell lines infected with AdTCPmIL-12 did not. AdTCPmIL-12-transduced rMTC cells completely lost their tumorigenicity in syngenic WAG/Rij rats. Direct injection of 1 x 10(9) plaque forming units of AdTCPmIL-12 into subcutaneous rMTC tumors in WAG/Rij rats caused tumor regression in over 60% of animals within 20 days. Rats cured of tumors did not develop tumors after re-injection of naive rMTC cells, demonstrating lasting immunity. Treatment with AdTCPmIL-12 of one tumor resulted in regression of an established tumor at a distant site. Moreover, intratumoral or intravenous injection of AdTCPmIL-12 did not induce evident toxicity. These results indicate AdTCPmIL-12 can contribute to effective and less toxic gene therapy of MTC.

Interleukin-12 transduced dendritic cells induce regression of established murine neuroblastoma

BACKGROUND/PURPOSE

Interleukin 12 (IL-12) is a potent proinflammatory cytokine that enhances cytotoxic T lymphocytes (CTL) and natural killer (NK) cell activity. The goal of these experiments was to assess whether adenoviral-mediated IL-12 expression by dendritic cells (DC) could induce an antitumor immune response in a murine model of neuroblastoma.

METHODS

Syngeneic A/J mice were inoculated subcutaneously with 1 x 10(6) cells from a murine neuroblastoma-derived cell line (TBJ). Murine DC were transduced in vitro with adCMV-mIL-12, and 1 x 10(6) cells were injected intratumorally. Tumor growth in these mice was compared with control animals injected with enhanced green-filled protein (EGFP) transduced DC or saline. The role of CTL was evaluated through cytotoxicity assays. Immunohistochemical analysis of tumor, spleen, and lymph node was performed to characterize the behavior and fate of various populations of immune effector cells in these tissues.

RESULTS

The tumors of mice injected with adIL-12 transduced DC all underwent complete regression over a 3-week period. Splenocytes isolated from mice 7 days after intratumoral injection of adIL-12 DC showed increased cytolytic activity relative to control animals in vitro. Immunohistochemistry of tumor and lymph tissue showed increased amounts of DC and T lymphocyte infiltration and a slight decrease in apoptosis relative to the control groups.

CONCLUSIONS

Increased IL-12 production by DC induced a significant antitumor response in a poorly immunogenic murine neuroblastoma model. These results show the vital role of DC in the immunobiology of the disease, and that protection of these cells from tumor induced apoptosis is a critical aspect for immunotherapies treating this aggressive tumor.

Murine models for experimental therapy of pediatric solid tumors with poor prognosis

Novel therapeutic strategies are required for pediatric solid tumors with poor prognosis such as metastasizing neuroblastoma, rhabdomyosarcoma and Ewing's sarcoma. A prerequisite for the development of such new therapies is the availability of murine models. To be useful for therapeutic studies, these models should not only recapitulate the genetic alterations characteristic of the human disease but should also mimic the metastatic process and the response to current therapy, both of which ultimately determine the fate of children with these tumors. This review scrutinizes the utility of existing murine models of neuroblastoma, rhabdomyosarcoma and Ewing's sarcoma for investigating novel therapies. Much experience has been gained with both syngeneic and xenogeneic transplantable models of these tumors, while transgenic and knockout mice are just beginning to be available for therapeutic investigations. Modeling the genetic aberrations characterizing these tumors may provide faithful models for therapeutic studies in the future.

Large nontransplanted hepatocellular carcinoma in woodchucks: treatment with adenovirus-mediated delivery of interleukin 12/B7.1 genes

BACKGROUND

Cytokine-based gene therapy strategies efficiently stimulate immune responses against many established transplanted tumors, leading to rejection of the tumor. In this study, we investigated the therapeutic potential of cancer immunotherapy in a clinically more relevant model, woodchucks with primary hepatocellular carcinomas induced by woodchuck hepatitis virus.

METHODS

Large (2-5 cm), established intrahepatic tumors were given an injection once with 1 x 10(9) plaque-forming units of AdIL-12/B7.1, an adenovirus vector carrying genes for murine interleukin 12 and B7.1, or of AdEGFP, the control virus, and regression of the tumors was then monitored. Five animals were used in total.

RESULTS

In four tumor-bearing animals, the antitumor response was assessed by autopsy and histologic analysis within 1-2 weeks after treatment. In all animals treated with AdIL-12/B7.1 therapy versus AdEGFP therapy, we observed substantial tumor regression (P =.006; two-sided unpaired Student's t test) accompanied by a massive infiltration of T lymphocytes. These tumors also contained increased levels of CD4(+) and CD8(+) T cells and interferon gamma (IFN gamma). In continuously growing tumor nodules given an injection of the control virus or in nontumoral liver, no such effects (i.e., tumor regression and increased levels of CD4(+) and CD8(+) T cells and IFN gamma) were detected. In the fifth animal, monitored for long-term antitumor efficacy by magnetic resonance imaging (MRI) after intratumoral vector administration by MRI guidance, the tumor was almost completely eliminated (> or = 95%) 7 weeks after treatment.

CONCLUSION

Adenovirus vector-based immunotherapy appears to be an effective treatment of large nontransplanted (orthotopic) tumors that acquire malignant characteristics in a stepwise process, reflecting the real-world scenario of hepatocellular carcinoma in humans.

A new vector system with inducible E2a cell line for production of higher titer and safer adenoviral vectors

Adenoviral vectors have been used in gene therapy and for vaccination. The major concerns with using adenoviral vectors are the pathogenic potential of the virus backbone and the generation of replication-competent adenovirus that may replicate in an uncontrolled manner, especially in immunocompromised patients. It is important to develop new vectors that are safer for clinical trials while maintaining high titer and efficient transduction. A new adenovirus vector production system was developed, which includes several vector backbone plasmids deleted for E2a and a new cell line expressing both E1 and E2a. The new cell line with the tTA-inducible E2a expression cassette can significantly increase the titer of E1/E2a-deleted vectors by four to five orders of magnitude upon withdrawal of tetracycline. Furthermore, there is no sequence overlap between the vector and the cellular DNA within the E2a open reading frame and downstream, making the generation of virus with wild-type E2a through homologous recombination substantially less likely. The new vector system may improve the safety of vectors for vaccination and cancer therapy and may also provide safer backbones for further vector development, such as helper-dependent and hybrid vectors.

Neuroblastoma

Neuroblastoma is a malignant tumor of neural crest origin that may arise anywhere along the sympathetic ganglia or within the adrenal medulla. The median age of diagnosis is 2 years; however occurrence is skewed toward younger children, with nearly 35% of cases occurring under 1 year of age and the remainder under 10 years of age. Seventy-five percent of neuroblastomas originate within the abdomen or pelvis, and half of these occur within the adrenal medulla, whereas 20% originate within the posterior mediastinum and 5% within the neck.

Genetic immunotherapy of established tumours with adenoviral vectors transducing murine interleukin-12 (mIL12) subunits in a rat medullary thyroid carcinoma model

OBJECTIVE

Interleukin-12 (IL12) is a heterodimeric cytokine that plays an important role in the development of cellular immunity. Studies have demonstrated antitumour activity after systemic administration of recombinant IL12. As with other cytokines, with increasing dosage and longer exposure, systemic toxicity is observed. To reduce systemic toxicity and obtain local production of IL12, we developed a replication defective adenovirus transducing two subunits of the murine IL12 (AdCMVmIL12) gene.

DESIGN

Two separate cassettes, expressing the p35 or p40 subunit of mIL12, under the control of human cytomeglavirus immediate early promoter, were inserted into the early1 (E1) region of adenovirus 5. Biological activity of virally expressed mIL12 was demonstrated in vitro through its ability to induce proliferation of mouse ConA blast cells.

RESULTS

Rat medullary thyroid carcinoma (MTC) cells infected with AdCMVmIL12 lost their tumorigenicity in their syngenic WAG/Rij rat hosts. Efficient antitumour activity was found after direct injection of the AdCMVmIL12 vector into rMTC tumours. After intratumoural treatment with AdCMVmIL12, 86% of tumour bearing animals were apparently cured, and almost all remaining tumours were stabilized. Challenge studies showed that most animals cured after the first treatment remained tumour free after reinjection of wild type rMTC cells, indicating that long-term antitumour immunity developed.

CONCLUSIONS

This study demonstrates the construction of an adenoviral vector expressing a functional heterodimeric mIL12 and its efficient antitumour activity after in vivo delivery in an animal model of medullary thyroid carcinoma.

Antitumor activity of interleukin-12 against murine bladder cancer

PURPOSE

We investigated the antitumor activity of interleukin-12 (IL-12) against MBT-2, a murine bladder carcinoma, to clarify whether or not IL-12 is effective against urothelial tumors.

MATERIALS AND METHODS

MBT-2, a murine carcinogen-induced, poorly differentiated transitional cell carcinoma of C3H/He origin, was used. Three or 10 days after the subcutaneous administration of MBT-2 cells, C3H/He mice were injected intraperitoneally with IL-12 five times per wk. for 2 wk. Tumor growth was measured twice weekly. Spleen cells from the C3H/He mice that had rejected MBT-2 after the IL-12 treatment were examined for MBT-2-specific cytolytic T lymphocytes (CTL) activity and cytokine production.

RESULTS

Tumor growth and acceptance was obviously suppressed when C3H/He mice were treated with IL-12 from 3 days after the tumor inoculation. In the spleen cells from the C3H/He mice that had rejected MBT-2, MBT-2-specific CTL activity and secretion of IL-2 and interferon (IFN)-gamma were clearly detected. However, the established MBT-2 tumor cells were not rejected when C3H/He mice were given IL-12 from 10 days after the tumor inoculation, although the tumor growth was transiently suppressed during the IL-12 treatment.

CONCLUSION

These data demonstrate that IL-12 is considerably effective against murine bladder cancer and suggest the clinical application of IL-12 against human bladder cancer.