Pre-existing tumor-sensitized T cells are essential for eradication of established tumors by IL-12 and cyclophosphamide plus IL-12

T-cell Homing Therapy for Reducing Regulatory T Cells and Preserving Effector T-cell Function in Large Solid Tumors

Purpose: Infused autologous tumor-infiltrating lymphocytes (TIL) and tumor-targeted chimeric antigen receptor (CAR) T cells typically surround malignant lesions or penetrate small tumor nodules but fail to penetrate large solid tumors, significantly compromising their antitumor impact. Strategies to overcome this primary challenge are largely required.Experimental Design: We tested the effects of IL12 plus doxorubicin on T-cell penetration and efficacy in solid tumors in a murine lung cancer model, a murine breast carcinoma lung metastasis model, and two human xenograft tumor models bearing large tumors (>10 mm).Results: Intriguingly, this simple approach increased the numbers, the distribution, and the depth of penetration of infused CD8+ T cells in these tumors, including both TILs and CAR T cells. This combined treatment halted tumor progression and significantly extended survival time. Studies of the underlying mechanism revealed multiple effects. First, the combined treatment maintained the high ratios of immune-stimulatory receptors to immune-inhibitory receptors on infiltrated CD8+ T cells, reduced the accumulation of immunosuppressive regulatory T cells, and enhanced the numbers of T-bet+ effector T cells in the tumors. Second, doxorubicin induced chemokines CXCL9 and CXCL10, which may attract NKG2D+CD8+ T cells to tumors, and this effect was boosted by IL12-induced IFNγ accumulation in tumors, promoting the penetration of NKG2D+CD8+ T cells.Conclusions: The deep penetration of infused T cells associated with combined IL12 plus doxorubicin yielded striking therapeutic effects in murine and human xenograft solid tumors. This approach might broaden the application of T-cell therapy to a wider range of solid tumors. Clin Cancer Res; 24(12); 2920-34. ©2018 AACRSee related commentary by Berraondo et al., p. 2716.

Immunological, anti-angiogenic and clinical effects of intratumoral interleukin 12 electrogene therapy combined with metronomic cyclophosphamide in dogs with spontaneous cancer: A pilot study

The immunological, anti-angiogenic and clinical effects of metronomic cyclophosphamide and 3 consecutive intratumoral interleukin (IL)-12 gene therapy (electrogene therapy (EGT)) treatments were evaluated in 6 dogs with spontaneous cancer. In all dogs, a decrease in peripheral leukocytes 2 days after IL-12 EGT coincided with erythema and swelling of the tumor. In the tumor, a transient increase in IL-12 levels was measured, whereas a continuous increase in interferon γ (IFNγ) and thrombospondin 1 (TSP-1) were determined in contrast to a continuous decrease in vascular endothelial growth factor (VEGF). In the serum, a transient increase in IL-12 and IL-10 levels were noted in contrast to a transient decrease in VEGF and TSP-1. The treatment resulted in a significant anti-angiogenic effect. Although all primary tumors continued to progress in time, this progression was slower than before treatment according to the contrast-enhanced ultrasound data. Besides the encouraging immunostimulatory and anti-angiogenic effects observed in all dogs we also noticed in 4 out of 6 dogs clinically relevant improvements in quality of life and weight. These results hold great promise for combinatorial strategies of IL-12 EGT and metronomic chemotherapy with conventional antitumor (immuno)therapies.

Interleukin 12 shows a better curative effect on lung cancer than paclitaxel and cisplatin doublet chemotherapy

BACKGROUND

Interleukin 12 (IL-12) is a cytokine that has been reported to exhibit potent tumoricidal effects in animal tumor models. A combined approach using Paclitaxel and platinum-based doublet chemotherapy is the most commonly used backbone regimen for treating lung cancer. Despite numerous studies regarding the anti-tumor effects of IL-12 and the widespread use of conventional chemotherapy, few direct comparisons of IL-12 and conventional chemotherapy in the treatment of lung cancer have been performed.

METHODS

We compared IL-12 to paclitaxel and cisplatin doublet chemotherapy in terms of efficacy against lung cancer in mouse models. The antitumor effect was measured by survival assays, histological analyses and imaging analyses. The cytokine levels were assessed using enzyme linked immunosorbent assay (ELISA) and flow cytometry (FACS). The spleen sizes were measured. CD31, CD105 and Vascular endothelial growth factor receptor 3 (VEGFR3) were analyzed using immunofluorescence. Matrix metalloprotein-9 (MMP-9) and cadherin 1 (CDH1) transcript levels were measured by quantitative PCR. Tumor cells apoptosis were examined by Tunel assay.

RESULTS

The results showed that IL-12 treatment inhibited lung tumor growth, resulting in the long-term survival of lung cancer-bearing mice. Further examination revealed that IL-12 rapidly activated NK cells to secrete IFN-γ, resulting in the inhibition of tumor angiogenesis. In contrast, paclitaxel and cisplatin doublet chemotherapy did not show the expected efficacy in orthotopic lung cancer models; the IFN-γ levels were not increased after this treatment, and the number of peripheral lymphocytes was reduced.

CONCLUSION

Together, these animal model data indicate that IL-12 shows a better curative effect than PTX + CDDP doublet chemotherapy.

Intratumoural interleukin 12 gene therapy stimulates the immune system and decreases angiogenesis in dogs with spontaneous cancer

Interleukin 12 (IL-12) is a powerful immunostimulatory cytokine with a strong antitumoural activity. In this work, the immunological, anti-angiogenic and clinical effects of three consecutive intratumoural IL-12 electrogene therapy (EGT) treatments were evaluated in nine dogs with spontaneous cancer. In all the dogs, tumour biopsies and blood samples were taken prior, during and after the intratumoural IL-12 EGT (on days 1, 8, 35 and 1, 3, 8, 15, 35, respectively). An initial decrease in immune cells was followed by an increase above baseline 1-3 weeks after treatment initiation. Interestingly, the decrease in peripheral leukocytes 2 days after the first intratumoural IL-12 EGT coincided with erythema and tumour swelling. Transient increases of IL-12 and interferon γ were measured in the serum and the tumour tissue, whereas IL-10 transiently increased only in the serum. The effect of intratumoural IL-12 EGT on the levels of IL-24 and vascular endothelial growth factor in the sera and tumour biopsies differed per dog. Via contrast-enhanced ultrasound (US) (on days 1, 8 and 35), we demonstrated that intratumoural IL-12 EGT resulted in a significant decrease of the relative blood volume and blood flow speed in the tumour compared with baseline. Metastases were present in two dogs. In one of these dogs, IL-12 EGT of the primary tumour caused a transient partial regression of the metastases, but not of the primary tumour. The second dog with metastases did not survive long enough to complete the entire treatment cycle. Despite encouraging immunostimulatory and anti-angiogenic effects after intratumoural IL-12 EGT, no clinically relevant outcomes were observed in this study, as persistent tumour regression could not be obtained. On the other hand, the laboratory and US results hold great promise for combinatorial strategies of intratumoural IL-12 EGT with conventional antitumour (immuno)therapies.

In situ vaccine, immunological memory and cancer cure

As surgery is able to remove primary tumors and limit metastases, the major challenge in cancer management is the prevention of post-resection recurrence and metastases. From the immune point of view, tumor resection removes the supply of tumor antigens that maintain an active concomitant antitumor immunity elicited by the primary tumor, and may also signal for deposition of immunological memory against future metastases. However, the natural course of this antitumor immunity in many cancer patients following complete tumor resection may not be favorable because protection is often lost after 1-3 years. Recent studies suggest that chemotherapy is able to activate this pre-existing antitumor immunity, and tumor resection following immune activation may lead to higher levels of immunological memory against future tumor antigens (in the form of metastases). Interleukin-12 added to chemotherapy mimics the function of a vaccine adjuvant in that it helps to enhance the antitumor immunity activated by chemotherapy and leaves a much stronger antitumor immune memory. This finding, when applied to cancer management, may help to maintain a strong and long lasting antitumor immunity following complete tumor resection, thus eliminating post-surgery recurrence and metastases.

Engineered Materials for Cancer Immunotherapy

Immunotherapy is a promising treatment modality for cancer as it can promote specific and durable anti-cancer responses. However, limitations to current approaches remain. Therapeutics administered as soluble injections often require high doses and frequent re-dosing, which can result in systemic toxicities. Soluble bolus-based vaccine formulations typically elicit weak cellular immune responses, limiting their use for cancer. Current methods for ex vivo T cell expansion for adoptive T cell therapies are suboptimal, and achieving high T cell persistence and sustained functionality with limited systemic toxicity following transfer remains challenging. Biomaterials can play important roles in addressing some of these limitations. For example, nanomaterials can be employed as vehicles to deliver immune modulating payloads to specific tissues, cells, and cellular compartments with minimal off-target toxicity, or to co-deliver antigen and danger signal in therapeutic vaccine formulations. Alternatively, micro-to macroscale materials can be employed as devices for controlled molecular and cellular delivery, or as engineered microenvironments for recruiting and programming immune cells in situ. Recent work has demonstrated the potential for combining cancer immunotherapy and biomaterials, and the application of biomaterials to cancer immunotherapy is likely to enable the development of effective next-generation platforms. This review discusses the application of engineered materials for the delivery of immune modulating agents to the tumor microenvironment, therapeutic cancer vaccination, and adoptive T cell therapy.

Local hyperthermia treatment of tumors induces CD8(+) T cell-mediated resistance against distal and secondary tumors

Combinatorial use of iron oxide nanoparticles (IONPs) and an alternating magnetic field (AMF) can induce local hyperthermia in tumors in a controlled and uniform manner. Heating B16 primary tumors at 43°C for 30 min activated dendritic cells (DCs) and subsequently CD8(+) T cells in the draining lymph node (dLN) and conferred resistance against rechallenge with B16 (but not unrelated Lewis Lung carcinoma) given 7 days post hyperthermia on both the primary tumor side and the contralateral side in a CD8(+) T cell-dependent manner. Mice with heated primary tumors also resisted rechallenge given 30 days post hyperthermia. Mice with larger heated primary tumors had greater resistance to secondary tumors. No rechallenge resistance occurred when tumors were heated at 45°C. Our results demonstrate the promising potential of local hyperthermia treatment applied to identified tumors in inducing anti-tumor immune responses that reduce the risk of recurrence and metastasis.

FROM THE CLINICAL EDITOR

Local heating of tumors via iron oxide NPs and an alternating magnetic field led to activation of anti-cancer CD8 T cells, which resulted in resistance against re-challenge and greater resistance to secondary tumors. Similar local heating-based strategies may become an important weapon in enhancing tumor elimination via a naturally existing but attenuated immune response.

Preexisting antitumor immunity augments the antitumor effects of chemotherapy

Efficacy of cancer chemotherapy is generally believed to be the result of direct drug killing of tumor cells. However, increased tumor cell killing does not always lead to improved efficacy. Herein, we demonstrate that the status of antitumor immunity at the time of chemotherapy treatment is a critical factor affecting the therapeutic outcome in that tumor-bearing mice that possess preexisting antitumor immunity respond to chemotherapy much better than those that do not. Enhancing antitumor immunity before or at the time of chemotherapy-induced antigen release increases subsequent response to chemotherapy significantly. By in vitro and in vivo measurements of antitumor immunity, we found a close correlation between the intensity of antitumor immunity activated by chemotherapy and the efficacy of treatment. Immune intervention with interleukin-12 during the early phase of chemotherapy-induced immune activation greatly amplifies the antitumor response, often resulting in complete tumor eradication not only at the chemo-treated local site, but also systemically. These findings provide additional evidence for an immune-mediated antitumor response to chemotherapy. Further, our results show that timely immune modification of chemotherapy-activated antitumor immunity can result in enhanced antitumor-immune response and complete tumor eradication.

Prospects of combinatorial synthetic peptide vaccine-based immunotherapy against cancer

The insight that the immune system is involved in tumor resistance is gaining momentum and this has led to the development of immunotherapeutic strategies aiming at enhancement of immune-mediated tumor destruction. Although some of these strategies have moderate clinical benefit, most stand-alone therapies fail to significantly affect progressive disease and survival or do so only in a minority of patients. Research on the mechanisms underlying the generation of immune responses against tumors and the immune evasion by tumors has emphasized that various mechanisms simultaneously prevent effective immunity against cancer including inefficient presentation of tumor antigens by dendritic cells and induction of negative immune regulation by regulatory T-cells (Tregs) and myeloid derived suppressor cells (MDSCs). Thus the design of therapies that simultaneously improve effective tumor immunity and counteract immune evasion by tumors seems most desirable for clinical efficacy. As it is unlikely that a single immunotherapeutic strategy addresses all necessary requirements, combinatorial strategies that act synergistically need to be developed. Here we discuss the current knowledge and prospects of treatment with synthetic peptide vaccines that stimulate tumor-specific T-cell responses combined with adjuvants, immune modulating antibodies, cytokines and chemotherapy. We conclude that combinatorial approaches have the best potency to accomplish the most significant tumor destruction but further research is required to optimize such approaches.

The mechanism of the anticancer function of M1 macrophages and their use in the clinic

M1-type macrophages are capable of inducing lysis in various types of cancer cells, but the mechanism of action is unclear. It has been noted that an "unknown protein" produced together with protease by activated macrophages is responsible for this action. Activated M1 macrophages have been recently reported to produce family 18 chitinases, all of which have been named chitotriosidase. Our experiments have demonstrated that family 18 chitinases work together with proteases and can damage various cancer cells both in vitro and in vivo. Thus, in this article, we suggest that the 50-kDa chitotriosidase is the reported "unknown protein". In addition, we discuss how to properly stimulate activated M1 macrophages to produce 50-kDa chitotriosidases and proteases for destroying cancer cells. Because family 19 chitinase has recently been reported to kill cancer cells, we also discuss the possibility of directly using human family 18 chitotriosidase and the humanized plant family 19 chitinase for cancer treatment.

Phase I clinical trial of mixed bacterial vaccine (Coley's toxins) in patients with NY-ESO-1 expressing cancers: immunological effects and clinical activity

PURPOSE

Mixed bacterial vaccine (MBV, Coley's toxins) is a historical, vaguely defined preparation of heat-inactivated Streptococcus pyogenes and Serratia marcescens used as nonspecific immunotherapy in the treatment of cancer. The mechanism of action is suspected to have an immunologic basis, yet it is poorly defined up to now. We developed a new, biochemically well defined and current good manufacturing practice-compliant MBV preparation, which has been investigated in patients with NY-ESO-1 expressing cancers.

EXPERIMENTAL DESIGN

Patients received MBV subcutaneously at a starting dose of 250 EU (endotoxin units) twice a week. The MBV dose was escalated in each patient until a body temperature of 38°C to 39.5°C was induced or up to the maximum dose of 547.000 EU. Changes in serum cytokine levels were determined and immune responses to NY-ESO-1 were evaluated. Tumor response was assessed according to RECIST.

RESULTS

Twelve patients were enrolled and 11 of them developed fever after the administration of MBV. Ten of 12 patients showed a consistent increase in serum IL-6 levels with the highest levels coinciding with the highest body temperature. A subgroup of patients showed increasing levels of TNF-α, IFN-γ, and IL1-β. A patient with metastatic bladder cancer showed a partial tumor response strongly correlated with MBV-induced fever and highly elevated levels of several cytokines.

CONCLUSIONS

MBV at fever-inducing dose levels can lead to a massive induction of immunoregulatory cytokines that may be involved in inducing tumor regressions. We propose to further explore the role of MBV as a potent immune modulator at higher dose levels and in conjunction with antigen-specific cancer vaccines.

Antitumor activity of mixed heat shock protein/peptide vaccine and cyclophosphamide plus interleukin-12 in mice sarcoma

Background

The immune factors heat shock protein (HSP)/peptides (HSP/Ps) can induce both adaptive and innate immune responses. Treatment with HSP/Ps in cancer cell-bearing mice and cancer patients revealed antitumor immune activity. We aimed to develop immunotherapy strategies by vaccination with a mixture of HSP/Ps (mHSP/Ps, HSP60, HSP70, Gp96 and HSP110) enhanced with cyclophosphamide (CY) and interleukin-12 (IL-12).

Methods

We extracted mHSP/Ps from the mouse sarcoma cell line S180 using chromatography. The identity of proteins in this mHSP/Ps was assayed using SDS-PAGE and Western blot analysis with antibodies specific to various HSPs. BALB/C mice bearing S180 cells were vaccinated with mHSP/Ps ×3, then were injected intraperitoneally with low-dose CY and subcutaneously with IL-12, 100 μg/day, ×5. After vaccination, T lymphocytes in the peripheral blood were analyzed using FACScan and Cytotoxicity (CTL) was analyzed using lactate dehydrogenase assay. ELISPOT assay was used to evaluate interferon γ (IFN-γ), and immune cell infiltration in tumors was examined in the sections of tumor specimen.

Results

In mice vaccinated with enhanced vaccine (mHSP/Ps and CY plus IL-12), 80% showed tumor regression and long-term survival, and tumor growth inhibition rate was 82.3% (30 days), all controls died within 40 days. After vaccination, lymphocytes and polymorphonuclear leukocytes infiltrated into the tumors of treated animals, but no leukocytes infiltrated into the tumors of control mice. The proportions of natural killer cells, CD8+, and interferon-γ-secreting cells were all increased in the immune group, and tumor-specific cytotoxic T lymphocyte activity was increased.

Conclusions

In this mice tumor model, vaccination with mHSP/Ps combined with low-dose CY plus IL-12 induced an immunologic response and a marked antitumor response to autologous tumors. The regimen may be a promising therapeutic agent against tumors.

Cancer immunoediting and "spontaneous" tumor regression

The combination of host protective and tumor-promoting actions of the immune system throughout tumor development is termed cancer immunoediting. This review briefly summarizes the currently vast evidence supporting the immune system's role in not only protecting against developing cancer, but also sculpting tumor immunogenicity and immune escape. We also briefly summarize the history of immunotherapy and discuss the immunoediting process in the context of spontaneous tumor regression and whether this observation can be utilized in future treatment regimens.

Characterization of a recombinant adenovirus vector encoding heat-inducible feline interleukin-12 for use in hyperthermia-induced gene-therapy

Interleukin-12 (IL-12) is a pro-inflammatory cytokine that has shown great promise as a therapeutic agent in experimental models of infectious disease and cancer. However, it is also a highly toxic molecule and for that reason has not been accepted readily into the clinic. A replication-deficient adenoviral vector was designed to deliver the feline interleukin-12 gene into tumour cells. The interleukin-12 gene has been placed under control of a heat inducible promoter, human heat shock promoter 70b, with the intent of spatially and temporally controlling the expression of IL-12, thus limiting its toxicity. In vitro, the transfection efficiency of the adenoviral vector, the effect of multiplicity of infection and the production of biologically active feline IL-12 were studied in the infected cells in response to a range of temperatures. This adenoviral vector will be a useful tool to examine the effects of intra-tumoural IL-12 delivery in a spontaneously occurring feline soft tissue sarcoma model.

Novel immunocompetent murine tumor model for evaluation of conditionally replication-competent (oncolytic) murine adenoviral vectors

Oncolytic adenoviral vectors that express immunostimulatory transgenes are currently being evaluated in clinic. Preclinical testing of these vectors has thus far been limited to immunodeficient xenograft tumor models since human adenoviruses do not replicate effectively in murine tumor cells. The effect of the immunostimulatory transgene on overall virus potency can therefore not be readily assessed in these models. Here, a model is described that allows the effective testing of mouse armed oncolytic adenovirus (MAV) vectors in immunocompetent syngeneic tumor models. These studies demonstrate that the MAV vectors have a high level of cytotoxicity in a wide range of murine tumor cells. The murine oncolytic viruses were successfully armed with murine granulocyte-macrophage colony-stimulating factor (mGM-CSF) by a novel method which resulted in vectors with a high level of tumor-specific transgene expression. The mGM-CSF-armed MAV vectors showed an improved level of antitumor potency and induced a systemic antitumor immune response that was greater than that induced by unarmed parental vectors in immunocompetent syngeneic tumor models. Thus, the oncolytic MAV-1 system described here provides a murine homolog model for the testing of murine armed oncolytic adenovirus vectors in immunocompetent animals. The model allows evaluation of the impact of virus replication and the host immune response on overall virus potency and enables the generation of translational data that will be important for guiding the clinical development of these viruses.

CCL21-induced immune cell infiltration

Cellular immune responses can be initiated via peptide presentation by specialized antigen presenting cells, dendritic cells (DCs), which stimulate naïve T cells. The trafficking of DCs and T cells is regulated by chemokines such as CCL21. CCL21 is normally expressed in the lymphoid organs and coordinates the interactions between DCs and T cells, thereby contributing to the initiation of T cell responses. In order to comprehend the mechanisms of CCL21 activity and to utilize CCL21 optimally in therapy, understanding the kinetics of the responses of various cell types to CCL21 would be beneficial. Therefore, in this study, we injected mice subcutaneously (s.c.) with CCL21 and examined the DC and T cell infiltration of the local draining lymph node. CCL21 injection resulted in significantly increased numbers of lymphoid and myeloid DCs and effector T lymphocytes in the local node at 4 days. Furthermore, at 4 days small lymphoid-like structures were visible in the injection areas. These results provide guidance for the optimal timing of CCL21 use in combination with vaccines.

Lessons from Coley's Toxin

The active molecule in Coley's Toxin is not tumor necrosis factor (TNF) or endotoxin (LPS), but interleukin-12 (IL-12). IL-12 holds the key to improved anti-tumor immuns response.

Cyclophosphamide augments inflammation by reducing immunosuppression in a mouse model of allergic airway disease

BACKGROUND

Allergic asthma is a TH2 cell-driven immunological disease, characterized by eosinophilic inflammation. The cytotoxic agent cyclophosphamide paradoxically augments several immune responses.

OBJECTIVE

We studied the proposal that cyclophosphamide may aggravate airway inflammation in allergic mice, and these features might result from the loss of regulatory T cells.

METHODS

BALB/c mice were immunized with ovalbumin on days 0 and 14 and challenged with aerosolized ovalbumin from days 21 to 27. Some mice also received cyclophosphamide on days -2 and 12.

RESULTS

In the lungs of cyclophosphamide-treated animals, pronounced worsening of inflammatory features was noted, including increased eosinophil infiltration, epithelial thickness, mucus occlusion, and eosinophil numbers in bronchoalveolar lavage fluid. There was also increased total and ovalbumin-specific serum IgE, increased IL-4 and IL-5 secretion by peritracheal lymph node cells, and reduced lung mRNA expression of IL-10 and TGF-beta in animals treated with cyclophosphamide. The expression of FoxP3, a marker of regulatory T cells, was significantly reduced in lymphoid organs after the second injection of cyclophosphamide, and in the lung tissue after allergen challenge in cyclophosphamide-treated mice. Lung IL-10+CD4+ T cells and cytotoxic T lymphocyte-associated antigen 4+CD4+ T cells were reduced after allergen challenge in cyclophosphamide-treated mice.

CONCLUSION

Cyclophosphamide worsened features of allergic pulmonary inflammation in this model, in association with increased production of IgE and TH2 cytokines. The reduced expression of FoxP3 and immunosuppressive cytokines by cyclophosphamide is consistent with the possibility that toxicity to regulatory T cells may contribute to the increased inflammation.

Inhibition of host signal transducer and activator of transcription factor 6 results in cure with cyclophosphamide and interleukin 12 immunotherapy

BACKGROUND

Interleukin (IL)-12 immunotherapy is highly effective against established immunogenic tumors. However, nonimmunogenic tumors fail to respond to IL-12 therapy. Analysis of tumor rejection of the immunogenic tumors shows that a preexisting antitumor immune response is required for an effective IL-12 response. It is not known whether this lack of a preexisting host antitumor immune response is a limiting factor for the lack of response to IL-12 therapy by nonimmunogenic tumors.

METHODS

Experiments were done using the spontaneously arising nonimmunogenic metastatic murine breast 4T1 carcinoma in normal and STAT6 knockout BALB/c mice.

RESULTS

4T1 is nonimmunogenic in normal mice, and established subcutaneous tumors are resistant to immunotherapy with cyclophosphamide (Cy) plus IL-12. However, in STAT6 knockout mice, 4T1 becomes immunogenic, and established 4T1 tumors are eradicated by Cy plus IL-12. Adoptive transfer of spleen cells from normal mice into STAT6 knockout mice before tumor inoculation reduces both the immunogenicity and response to Cy plus IL-12 immunotherapy of 4T1 in the recipient mice.

CONCLUSIONS

Cy plus IL-12 immunotherapy can eradicate nonimmunogenic tumors as long as a preexisting immunity is established in the tumor-bearing host. Furthermore, the STAT6 pathway is likely involved in the suppression of the development of host antitumor immunity.

An immunocompromised BALB/c mouse model for respiratory syncytial virus infection

Background

Respiratory syncytial virus (RSV) infection causes bronchiolitis in infants and children, which can be fatal, especially in immunocompromised patients. The BALB/c mouse, currently used as a model for studying RSV immunopathology, is semi-permissive to the virus. A mouse model that more closely mimics human RSV infection is needed. Since immunocompromised conditions increase risk of RSV infection, the possibility of enhancing RSV infection in the BALB/c mouse by pretreatment with cyclophosphamide was examined in this study. BALB/c mice were treated with cyclophosphamide (CYP) and five days later, they were infected with RSV intranasally. Pulmonary RSV titers, inflammation and airway hyperresponsiveness were measured five days after infection.

Results

CYP-treated mice show higher RSV titers in their lungs of than the untreated mice. Also, a decreased percentage of macrophages and an increased number of lymphocytes and neutrophils were present in the BAL of CYP-treated mice compared to controls. The CYP-treated group also exhibited augmented bronchoalveolar and interstitial pulmonary inflammation. The increased RSV infection in CYP-treated mice was accompanied by elevated expression of IL-10, IL-12 and IFN-γ mRNAs and proteins compared to controls. Examination of CYP-treated mice before RSV infection showed that CYP treatment significantly decreased both IFN-γ and IL-12 expression.

Conclusions

These results demonstrate that CYP-treated BALB/c mice provide a better model for studying RSV immunopathology and that decreased production of IL-12 and IFN-γ are important determinants of susceptibility to RSV infection.

Therapeutic effect of dendritic cells loaded with a fusion mRNA encoding tyrosinase-related protein 2 and enhanced green fluorescence protein on B16 melanoma

Dendritic cells (DCs) loaded with messenger RNA (mRNA) have been proposed to be useful for inducing specific cytotoxic T lymphocytes against tumor antigens. It is now also apparent that tumor antigen-specific T cell tolerance limits the efficacy of active immunotherapy. To improve the efficacy of mRNA-loaded DCs, we constructed a fusion mRNA encoding tyrosinase-related protein 2 (TRP2), which has a late endosomal/lysosomal sorting signal and enhanced green fluorescence protein (EGFP), and evaluated its effect in a murine melanoma model. C57BL/6 mice were challenged subcutaneously (s.c.) with 3 x 10(5) B16 tumor cells, and 3 and 10 days later, 3 x 10(5) DCs loaded with mRNA (DC/mRNA) were injected s.c. in the vicinity of the tumor site. Treatment with DC/TRP2 mRNA or DC/TRP2-EGFP mRNA significantly inhibited tumor growth compared to DC/PBS on day 17 after B16 challenge (DC/PBS vs. DC/TRP2 mRNA, p = 0.0411; DC/PBS vs.DC/TRP2-EGFP mRNA, p = 0.0253), whereas no antitumor effect was observed in mice treated with DC/EGFP mRNA or DC/TRP2 peptide. Moreover, the survival rate in mice immunized with DC/TRP2 mRNA or DC/TRP2-EGFP mRNA was significantly improved as compared with that in mice receiving DC/PBS (DC/PBS vs. DC/TRP2 mRNA, p = 0.0228; DC/PBS vs. DC/TRP2-EGFP mRNA, p = 0.0049). Depletion of CD4+ T cells or CD8+ T cells with antibody administration completely abrogated the therapeutic effectiveness of DC/TRP2-EGFP mRNA, suggesting the induction of a T cell immune response against the B16 tumor.

Gene therapy of anaplastic thyroid carcinoma with a single-chain interleukin-12 fusion protein

Anaplastic thyroid carcinoma is the most aggressive type of thyroid malignancy with a mean survival time of less than 8 months. No effective therapeutic approach is currently available, making the development of novel treatments necessary. Interleukin (IL)-12 is a proinflammatory heterodimeric cytokine with strong antitumor activity. In the present study, we investigated the potential of IL-12 gene therapy for anaplastic thyroid carcinoma in BALB/c (nu/nu) nude mice. A single-chain IL-12 fusion protein construct was created to assure equal expression of its p35 and p40 subunits. Human anaplastic thyroid carcinoma cell line ARO was stably transfected with an IL-12 expression plasmid under the control of cytomegalovirus (CMV) promoter (scIL-12/CMVpDNA). High levels of functional IL-12 (26.78 +/- 4.11 ng/ml per 10(6) cells per 48 hr) were produced by scIL-12-transfected ARO cells (ARO/IL-12). Tumorigenicity in nude mice was completely lost in scIL-12-transfected ARO cells, as demonstrated by the lack of tumor formation after subcutaneous injection of 2 x 10(6) ARO/IL-12 cells, even though there was no difference in cell proliferation between ARO and ARO/IL-12 cells. Tumor growth was observed after challenge with ARO tumor cells, indicating that protective immunity had not developed against the parental cells. Furthermore, the growth rate of established subcutaneous ARO tumors was significantly reduced by either subcutaneous injection of 2 x 10(6) ARO/IL-12 cells weekly or intramuscular injection of 50 microg scIL-12/CMVpDNA twice weekly. The antineoplastic activity of ARO/IL-12 cells was, however, abrogated by intraperitoneal injection of anti-natural killer (NK) cell antibody. Moreover, significantly higher number of ARO/IL-12 cells and ARO cells were killed by splenocytes from nude mice previously treated with ARO/IL-12 compared to those treated with ARO cells (32% vs. 9% when ARO were used as target cells, 43% vs. 17% when ARO/IL12 were used as target cells; p < 0.01) in an in vitro cytotoxicity assay. Again, tumor cell killing was neutralized by the addition of anti-NK cell antibody in the assay. In conclusion, we have demonstrated successful gene therapy with a scIL-12 fusion protein against anaplastic thyroid carcinoma in an in vivo model. The immune response against ARO/IL-12 cells is mediated by NK cells. These results may set the stage for clinical application of IL-12 gene therapy for poorly differentiated thyroid carcinoma.

Antitumor immunity induced by dendritic cell-based vaccination is dependent on interferon-γ and interleukin-12

BACKGROUND

This study was conducted to determine whether dendritic cells (DCs) pulsed with a tumor cell lysate can effectively vaccinate against tumor cells and to establish which cytokines are necessary.

MATERIALS AND METHODS

Each wild-type mouse received two subcutaneous immunizations (days 14 and 7) with either saline, tumor lysate, DCs, or tumor-lysate-pulsed DCs. Gamma-interferon (gamma-IFN), knock-out (KO), and interleukin-12 (IL-12) KO mice were also used in immunizations. A tumor challenge was given at day 0. Splenocytes were assayed for gamma-IFN production.

RESULTS

All saline-injected mice (n = 19) and all mice injected with tumor lysate (n = 9) developed tumors. Six of nine mice immunized with DCs alone and 6/24 mice treated with lysate-pulsed DCs developed a tumor. Splenocytes from both the saline- and lysate-immunized groups produced undetectable levels of gamma-IFN, while those from mice immunized with either DCs or pulsed DCs produced high levels of gamma-IFN. Four of five gamma-IFN KO mice developed tumors after immunization with tumor-lysate-pulsed DCs. None of four IL-12 KO mice developed a tumor after immunization with wild-type pulsed DCs and 1/10 wild-type mice developed tumor after immunization with IL-12 KO pulsed DCs. Three of four IL-12 KO mice developed tumors after immunization with IL-12 KO pulsed DCs.

CONCLUSIONS

Tumor-lysate-pulsed DCs can initiate an effective antitumor immune response. The presence of gamma-IFN in the host is essential for antitumor protection. In contrast, tumor protection is observed if IL-12 is present in either the host or the DCs.

Human CD4+ T cells present within the microenvironment of human lung tumors are mobilized by the local and sustained release of IL-12 to kill tumors in situ by indirect effects of IFN-gamma

By implanting nondisrupted pieces of human lung tumor biopsy tissues into SCID mice, it has been possible to establish viable grafts of the tumor, as well as the tumor-associated microenvironment, including inflammatory cells, fibroblasts, tumor vasculature, and the extracellular matrix. Using this xenograft model, we have evaluated and characterized the effects of a local and sustained release of human rIL-12 (rhIL-12) from biodegradable microspheres. In response to rhIL-12, the human CD45+ inflammatory cells present within the xenograft mediate the suppression or the complete arrest of tumor growth in SCID mice. Analysis of the cellular events reveals that human CD4+ and CD8+ T cells are induced by rhIL-12 to produce and secrete IFN-gamma. Serum levels of human IFN-gamma in mice bearing rhIL-12-treated tumor xenografts correlate directly with the degree of tumor suppression, while neutralizing Abs to human IFN-gamma abrogate the IL-12-mediated tumor suppression. Gene expression profiling of tumors responding to intratumoral rhIL-12 demonstrates an up-regulation of IFN-gamma and IFN-gamma-dependent genes not observed in control-treated tumors. Genes encoding a number of proinflammatory cytokines, chemokines (and their receptors), adhesion molecules, activation markers, and the inducible NO synthase are up-regulated following the introduction of rhIL-12, while genes associated with tumor growth, angiogenesis, and metastasis are decreased in expression. NO contributes to the tumor killing because an inhibitor of inducible NO synthase prevents IL-12-induced tumor suppression. Cell depletion studies reveal that the IL-12-induced tumor suppression, IFN-gamma production, and the associated changes in gene expression are all dependent upon CD4+ T cells.

Production of interferon-gamma by tumor-sensitized T cells is essential for interleukin-12-induced complete tumor eradication

BACKGROUND

Interferon-gamma (IFN-gamma) is essential for eradication of established large tumors by interleukin-12 (IL-12), but the critical source of IFN-gamma has not been defined. Adoptive transfer of T cells into T cell-deficient mice allows for evaluation of the role of T cells and T cell production of IFN-gamma in the antitumor immune response.

METHODS

Wild-type C57BL/6, IL-12 receptor-beta1 knockout (IL-12Rbeta1 KO), IFN-gamma knockout (IFN-gamma KO), and IFN-gamma receptor-alpha knockout (IFN-gammaRalpha KO) mice were immunized and used as donors for adoptive transfer. Transfer of either splenocytes or CD90(+) T cells was performed into recipient T cell receptor-beta knockout (TCRbeta KO) and IFN-gamma/TCRbeta double knockout mice bearing 14-day subcutaneous MCA207 tumors. Half of the mice were treated with IL-12, and cure rates were compared.

RESULTS

Transfer of either 1/4 immunized spleen equivalent or 10(7) immunized T cells into both TCRbeta KO and IFN-gamma/TCRbeta KO mice resulted in 80% to 100% cure when given with IL-12. However, transfer of 10(7) immunized T cells from IFN-gamma KO mice into TCRbeta KO mice was ineffective with or without IL-12. T cell response to IL-12, but not IFN-gamma, was required for tumor regression.

CONCLUSIONS

Production of IFN-gamma by IL-12-responsive tumor-sensitized T cells is both necessary and sufficient for complete tumor eradication induced by IL-12. T cells are the source, but not the target, of IFN-gamma during tumor regression.