IL-12 treatment of endogenously arising murine brain tumors

Coixendide efficacy in combination with temozolomide in glioblastoma and transcriptome analysis of the mechanism

The purpose of this study was to explore the role of coixendide (Coix) combine with temozolomide (TMZ) in the treatment of Glioblastoma (GBM) and explore its possible mechanism. CCK-8 was used to determine the inhibitory rate of Coix group, TMZ group and drug combination group on GBM cells, and the combination index (CI) was calculated to determine whether they had synergistic effect. Then RNA was extracted from each group, transcriptome sequencing was performed, and differentially expressed genes (DEGs) were identified. The possible mechanism was analyzed by GO enrichment analysis and KEGG enrichment analysis. The CI of Coix and TMZ indicating a synergistic effect when TMZ concentration is 0.1 mg/ml and Coix concentration is 2 mg/ml. Transcriptome sequencing analysis showed that interferon (IFN) related genes were down-regulated by Coix and up-regulated by TMZ and combined drugs, however, the up-regulation induced by combined drugs was less than that of TMZ. Besides IFN related genes, cholesterol metabolism pathway were also been regulated. Coix and TMZ have synergistic effects in the treatment of GBM at certain doses. RNA-Seq results suggested that the abnormal on genetic materials caused by DNA damage induced by TMZ treatment can be sensed by IFN related genes and activates antiviral IFN signaling, causing the activation of repairing mechanism and drug resistance. Coix inhibits IFN related genes, thereby inhibits drug resistance of TMZ. In addition, the activation of ferroptosis and the regulation of DEGs in cholesterol metabolism pathway were also contributed to the synergistic effects of Coix and TMZ.

Diagnosis of human cytomegvirus association with malignant gliomas and pro- and anti-inflammatories

The study was conducted on seventy individuals of both genders who have been exposed to human cytomegalovirus, a common illness in Iraq. Total cases of human cytomegvirus associated with malignant brain tumors were detected by a real time PCR technique. This resulted in only thirty-six cases of true infection. Of these 24 cases were female, while 12 cases of male infected. The titer to assay the presence of anti- and pro-inflammatories was assessed in sera of all patients by using ELISA kits to evaluate cytokines. This indicated that the pro-inflammatory IL12, after seven days increased (1.67±0.23 pg/ml), while IL4, an anti-inflammatory, decreased to reach (0.39±0.16 pg/ml) (at p<0.05) in the plasm of the experimental patients compared with the control group.

Gene-gene interactions between interleukin-12A and interleukin-12B with the risk of brain tumor

Emerging evidence from preclinical and clinical studies has shown that interleukin-12 (IL-12) has some effectiveness against endogenously arising brain tumor. The aim of this study was to investigate interactions of IL-12A and IL-12B polymorphisms on the risk of brain tumor. We analyzed IL-12A rs2243115 and IL-12B rs3212227 polymorphisms in 170 patients with brain tumor and 222 healthy controls in a Chinese population using a polymerase chain reaction-restriction fragment length polymorphism assay and DNA sequencing method. Individuals carrying a G allele of IL-12A rs2243115 had a significantly higher risk of developing brain tumor compared with those carrying a T allele (odds ratio [OR]=2.01, 95% confidence interval [CI], 1.17-3.45). After stratification analysis according to tumor types, a similarly higher risk was detected in patients with glioma (OR=2.56, 95% CI, 1.25-5.21). When gene-gene interactions were examined, carriers at both loci rs2243115 TG/GG and rs3212227 AC/CC had a 2.62-fold increased risk of glioma compared with those with rs2243115 TT and rs3212227 AC/CC genotypes (OR=2.62, 95% CI, 1.05-6.50). This study provides evidence that IL-12A rs2243115 may be associated with the risk of brain tumor. Additionally, gene-gene interactions of IL-12A rs2243115 and IL-12B rs3212227 may contribute to brain tumor susceptibility.

Antitumor mechanism of recombinant murine interleukin-12 vaccine

This study was designed to establish an interleukin-12 (IL-12)-expressing murine Lewis lung carcinoma (LLC) cell vaccine (LLC/murine IL-12 [mIL-12]) and assess its antitumor efficacy and mechanism in vivo. The recombinant IL-12 plasmid was transfected into LLC cells and screened by G418, and positive clones were obtained. C57BL/6 tumor-bearing mouse model was established and tumor-bearing mice were randomly divided into three groups (n = 20), that is, treated with an intratumoral injection of phosphate-buffered solution, blank plasmid, or LLC/mIL-12 vaccine, respectively, at days 0, 7, and 14. Tumor size was measured before and after treatment. Tumor growth curve was plotted, cytolytic T lymphocyte (CTL) activity assay and natural killer (NK) cell activity assay were performed, CD4(+) and CD8(+) T lymphocyte were quantitated using flow cytometry, and the expression of interferon-gamma (IFN-gamma), IL-12, and interferon-inducible protein-10 (IP-10) in serum was detected by ELISA. Microvessel density was determined by immunohistochemistry after all mice were euthanized at day 21. The study revealed suppressed tumor growth, elevated levels of IFN-gamma, IP-10, and IL-12, augmented NK and CTL cell activities, and decreased microvessel density of tumor tissues. There were abundant CD4(+) and CD8(+) T lymphocyte infiltration in the vaccine group. This study demonstrated that the antitumor mechanism of LLC/mIL-12 vaccine was to promote IFN-gamma and IL-12 secretion, augment the NK and CTL cell activities, and decrease the microvessel density of tumors.

Prediction of human protein-protein interaction by a mixed Bayesian model and its application to exploring underlying cancer-related pathway crosstalk

Protein-protein interaction (PPI) prediction method has provided an opportunity for elucidating potential biological processes and disease mechanisms. We integrated eight features involving proteomic, genomic, phenotype and functional annotation datasets by a mixed model consisting of full connected Bayesian (FCB) model and naive Bayesian model to predict human PPIs, resulting in 40 447 PPIs which contain 2740 common PPIs with the human protein reference database (HPRD) by a likelihood ratio cutoff of 512. Then we applied them to exploring underlying pathway crosstalk where pathways were derived from the pathway interaction database. Two pathway crosstalk networks (PCNs) were constructed based on PPI sets. The PPI sets were derived from two different sources. One source was strictly the HPRD database while the other source was a combination of HPRD and PPIs predicted by our mixed Bayesian method. We demonstrated that PCNs based on the mixed PPI set showed much more underlying pathway interactions than the HPRD PPI set. Furthermore, we mapped cancer-causing mutated somatic genes to PPIs between significant pathway crosstalk pairs. We extracted highly connected clusters from over-represented subnetworks of PCNs, which were enriched for mutated gene interactions that acted as crosstalk links. Most of the pathways in top ranking clusters were shown to play important roles in cancer. The clusters themselves showed coherent function categories pertaining to cancer development.

Minocycline differentially modulates viral infection and persistence in an experimental model of Japanese encephalitis

Japanese encephalitis (JE) is caused by a neurotropic flavivirus that causes CNS damage that leads to death in acute cases or permanent neuropsychiatric sequel in survivors. The course of infection of this virus is not well defined though it is clear that it evades the host's innate immune response in the periphery. The current study was designed to investigate the time-dependent changes in the spleen and lymph node, apart from the CNS that are infected by the Japanese encephalitis virus (JEV). Our previous studies have led to the identification of minocycline, a semi-synthetic antibiotic, as a protective drug in JE. In this study we have also investigated the role of minocycline on the peripheral organs that are infected by JEV. Levels of IL-12 and MCP-1 in the organs were estimated by cytometric bead array, and immunohistochemical studies were performed on cryosections of tissue to detect CD3- or CD11b-positive cells as well as JEV antigen. We found that the levels of T cell-activating cytokine IL-12 and MCP-1 levels were significantly elevated in JEV-infected tissue samples in a time-dependent manner. Corresponding to this increase was the increase in the number of CD3- and CD11b-positive cells in the tissues of infected animals. Minocycline treatment abrogated these changes. Minocycline treatment also resulted in the gradual decrease in the number of CD11b (but not CD3) positive cells in the lymph node and spleen, even though the virus persisted in these organs. We also observed structural changes in the spleen following minocycline treatment.

Antitumoral efficacy of DNA nanoparticles in murine models of lung cancer and pulmonary metastasis

Polyethylenimine (PEI)-DNA complexes are nanoparticles that are able to efficiently transfer plasmids to the lungs. Interleukin-12 (IL12) gene transfer using PEI may represent an important strategy for lung cancer treatment. In this study, we evaluated the antitumoral efficacy of the administration of PEI-DNA nanoparticles carrying IL12 gene (PEI-IL12) for the treatment of lung cancer and pulmonary metastases in animal models. After inoculation of tumor cells, mice were treated intravenously with a single dose of PEI-IL12, PEI nanoparticles carrying the reporter gene beta-galactosidase (PEI-LacZ) or vehicle. Transgene expression, survival rates and immune response were analyzed in both models. Administration of PEI-LacZ and PEI-IL12 nanoparticles controlled tumor growth and prolonged survival times in both animal models. Although PEI-IL12 and PEI-LacZ administration showed similar antitumoral effects in the lung cancer model, the efficacy of PEI-IL12 was significantly superior in the inhibition of the development of pulmonary metastases. Furthermore, the administration of PEI-DNA nanoparticles results in the production of high levels of proinflammatory cytokines. Our results showed that PEI-DNA nanoparticles are an efficient vector for mediating gene transfer to the lungs, are a potent inducer of the innate immune response and represents an interesting strategy for the treatment of bronchogenic carcinoma and metastatic lung carcinoma.

Intracerebral interleukin 12 induces glioma rejection in the brain predominantly by CD8+ T cells and independently of interferon-gamma

The prognosis of gliomas is generally poor since these tumors elude established therapeutic approaches. Immunotherapy might present an effective therapy in particular because the glioma cells are diffusely dispersed in the infiltration zone of the tumor and show a strong propensity to invade the surrounding brain along white matter tracts. Although various immune therapies for brain tumors are successful in rodents, there is currently no effective therapy in humans. In the present study, we investigated the mechanisms by which intracerebral IL-12 mediates rejection of GL261 cells in a syngenic mouse glioma model. Wild type mice revealed smaller tumors as compared to mice lacking functional T and B cells indicating that considerable immune dependent tumor rejection occurs physiologically in this model. However, glioma rejection was significantly enhanced in mice expressing IL-12 in the CNS and was predominantly dependent on the presence of CD8+ T cells while CD4+ T cells had less impact. Interestingly, the rejection of tumors was independent of IFN-gamma. Our findings contrast results obtained after in vitro or systemic stimulation with IL-12 and demonstrate that successful IL-12 induced glioma rejection critically depends on the localization, duration and time of IL-12 expression.

Post-Chemotherapeutic Administration of Interleukin-12 Retards Tumor Growth and Enhances Immune Cell Function: Combination Therapy Using Paclitaxel and IL-12

The antineoplastic agent paclitaxel (TAXOL) is a potent inhibitor of tumor cell division that also suppresses lymphocyte proliferative responses. Because chemotherapy-induced immunosuppression may limit the patient's antitumor responses, we investigated the possibility that the T cell stimulatory cytokine interleukin-12 (IL-12) could be used to reverse paclitaxel-mediated lymphocyte suppression. Recognizing that IL-12 treatment following paclitaxel exposure promotes T cell responses in vitro, we evaluated the antitumor efficacy of IL-12 administration concurrent and subsequent to paclitaxel treatment. Simultaneous administration of IL-12 and paclitaxel failed to limit tumor outgrowth or extend survival beyond chemotherapy alone, although IL-12 did not manifest negative effects. In contrast, post-chemotherapeutic IL-12 significantly delayed tumor outgrowth and extended survival in tumor-burdened BALB/c mice. Correlative enhancements in ex vivo immune cell effector function were also observed following paclitaxel and temporally delayed IL-12 therapy. Collectively, these data demonstrate an immunotherapeutic efficacy of IL-12 that augments the chemotherapeutic activities of paclitaxel when delivered in the appropriate temporal sequence.

Experimental manipulations of afferent immune responses influence efferent immune responses to brain tumors

Tumors grow more readily in the brain than in the periphery, in part due to immune privilege. Differences in both afferent and efferent components of the immune response contribute to this lower level of responsiveness. On the afferent side, despite the lack of lymphatic vessels in the brain, antigens from brain arrive in lymph nodes and spleen by several routes, and the route taken may influence the type of response generated. Work with viruses and soluble antigens in mice has shown that the intracerebral location and the volume of the inoculation influence the strength of the cytotoxic T cell response. We examined whether these factors influence the T cell response against experimental brain tumors in mice. Placement of tumor cells in the cerebral ventricles instead of the parenchyma generated an immune response sufficient to increase survival time. A large volume of an intraparenchymal infusion of tumor cells caused spread of cells to the ventricles, and resulted in longer survival time relative to a small volume infusion. Infusion of the same dose of radiolabeled tumor cells in either a small volume or a large volume allowed tracking of potential tumor antigens to the periphery. Both modes of infusion resulted in similar levels of radioactivity in blood, spleen and kidney. Unexpectedly, cells infused intraparenchymally in a small volume, compared to a large volume, resulted in (1) more radioactivity in cervical lymph nodes (parotid and deep cervical lymph nodes), (2) a greater number of CD11b+/Gr1+ myeloid suppressor cells in the tumors, and (3) fewer CD8+ cells within the tumor mass. Consistent with these observations, providing a stronger afferent stimulus by giving a concurrent subcutaneous injection of the same tumor cells infused into the brain increased CD8+ T cell infiltration of the tumor in the brain. These results suggest that the immune response elicited by antigens that drain predominantly to the cervical lymph nodes may be less effective than responses elicited at other lymph nodes, perhaps due to immunosuppressive cells. Directing therapies to the optimal peripheral sites may improve immune responses against brain tumors.

Antimetastatic effect of suicide gene therapy for mouse mammary cancers requires T-cell-mediated immune responses

These experiments were conducted to investigate whether the antimetastatic effects of HSVtk/GCV therapy involve T-cell-mediated immune responses. In the first experiment, immunocompetent syngeneic mice were inoculated with metastatic mammary cancers, then given a direct intratumoral injection of a plasmid vector containing a suicide gene (pHSVtk) or control vector once a week for 8 weeks. Gene electrotransfer treatment was applied to the tumors, and mice were administered ganciclovir (GCV) using a mini-osmotic pump. At the end of the experiment, tumor volume was significantly lower in the pHSVtk/GCV group. Macrophage accumulations were frequently observed in the peripheries of the necrotic regions in pHSVtk-transfected mice. Levels of CD4 and CD8 proteins in tumors were higher in the pHSVtk/GCV group than in the control group. Interleukin (IL)-12 mRNA levels tended to be higher in tumors in the pHSVtk/GCV group, but there were large variations. Tumor microvessel density was significantly lower in the pHSVtk/GCV group. The numbers of dilated lymphatic vessels containing intraluminal tumor cells tended to be higher in the pHSVtk/GCV group. However, vascular endothelial growth factor (VEGF)-A and VEGF-C mRNA levels in tumors were similar in the control and pHSVtk/GCV groups. In the second experiment, tumor volume and metastatic parameters were compared for immunocompetent syngeneic mice and immunodeficient athymic mice (without an intact T-cell system) given pHSVtk/GCV therapy. Although tumor volumes were significantly smaller in both syngeneic and athymic mice given pHSVtk/GCV therapy, the inhibition ratios (relative to control mice) were much greater in syngeneic mice than in athymic mice. No suppression of metastasis to the lymph nodes and lungs was observed for athymic mice given pHSVtk/GCV therapy. Our data suggest that HSVtk/GCV suicide gene therapy exerts an antimetastatic effect via a T-cell-mediated immune response.

A safety and efficacy study of local delivery of interleukin-12 transgene by PPC polymer in a model of experimental glioma

Interleukin-12 (IL-12) triggers an antitumoral immune response and an antiangiogenic effect against cancer. In this study, we tested a novel polymeric vehicle for IL-12 gene therapy along with adjuvant local biodegradable carmustine (BCNU) chemotherapy for the treatment of malignant glioma. Highly concentrated DNA/PPC (polyethylenimine covalently modified with methoxypolyethyleneglycol and cholesterol) complexes were used to deliver a murine plasmid encoding IL-12 (pmIL-12). For toxicity assessment, mice received intracranial injections with different volumes of pmIL-12/PPC. For efficacy, mice with intracranial GL261 glioma were treated with local delivery of pmIL-12/PPC and/or BCNU-containing polymers. Intracranial injections of 5-10 microl of pmIL-12/PPC were well tolerated and led to IL-12 expression in the brains of treated animals. Treatment with pmIL-12/PPC led to a significant increase in survival compared with untreated mice (median survival 57 days; 25% long-term survival >95 vs. 45 days for control; P<0.05). Treatment with BCNU led to a significant increase in survival compared with untreated mice, with 75% of treated mice having a long-term survival >95 days, (P<0.05). Most importantly, the combination of BCNU and pmIL-12/PPC led to a survival of 100% of the mice for 95 days after treatment (P<0.0001). This novel strategy is safe and effective for the treatment of malignant glioma. The synergy resultant from the combination of locally administered pmIL-12/PPC and BCNU suggests a role for this approach in the treatment of malignant brain tumors.

Enhancing Antitumor Immunity: Combining IL-12 With TGFβ1 Antagonism

With respect to CD8 effector T cells, interleukin-12 (IL-12) and transforming growth factor beta (TGFbeta) are 2 cytokines that exert opposing effects. IL-12 promotes antitumor immune responses by augmenting activated CD8 T-cell proliferation and interferon-gamma secretion. Conversely, TGFbeta generates a permissive environment for cancer growth, in part by antagonizing the effects of immunomodulatory cytokines, including IL-12. We demonstrate that TGFbeta-resistant T cells are capable of sustaining IL-12-induced mitogenesis and interferon-gamma secretion in a TGFbeta-rich milieu. Furthermore, in 2 murine tumor models associated with high TGFbeta1 levels in the local microenvironment, treatment with IL-12 and adoptively transferred TGFbeta-resistant T cells provided improved survival times. These results suggest that combining IL-12 with TGFbeta neutralization strategies may be effective in enhancing antitumor immune responses.

Accumulation of CD8+T Cells in Advanced-Stage Tumors and Delay of Disease Progression following Secondary Immunization against an Immunorecessive Epitope

Self-reactive T cells that survive the process of positive and negative selection during thymocyte development represent potential effector cells against tumors that express these same self-Ags. We have previously shown that CD8+ T lymphocytes (T(CD8)) specific for an immunorecessive epitope, designated epitope V, from the SV40 large T Ag (Tag) escape thymic deletion in line SV11 Tag-transgenic mice. In contrast, these mice are tolerant to the three most dominant Tag epitopes. The majority of the residual epitope V-specific T(CD8) have a low avidity for the target epitope, but a prime/boost regimen can expand higher avidity clones in vivo. Whether higher avidity T(CD8) targeting this epitope are affected by Tag-expressing tumors in the periphery or can be recruited for control of tumor progression remains unknown. In the current study, we determined the fate of naive TCR-transgenic T(CD8) specific for Tag epitope V (TCR-V cells) following transfer into SV11 mice bearing advanced-stage choroid plexus tumors. The results indicate that TCR-V cells are rapidly triggered by the endogenous Tag and acquire effector function, but fail to accumulate within the tumors. Primary immunization enhanced TCR-V cell frequency in the periphery and promoted entry into the brain, but a subsequent booster immunization caused a dramatic accumulation of TCR-V T cells within the tumors and inhibited tumor progression. These results indicate that epitope V provides a target for CD8+ T cells against spontaneous tumors in vivo, and suggests that epitopes with similar properties can be harnessed for tumor immunotherapy.

In vivo electrogene transfer ofinterleukin-12 inhibits tumor growth and lymph node and lung metastases in mouse mammary carcinomas

BACKGROUND

Human breast cancer metastasizes mainly to lymph nodes, lungs, liver, and bone; in the majority of cases, it is the development of metastases which leads to death. In order to suppress mammary cancer metastasis, we applied in vivo electrogene transfer (non-viral method) as a means of interleukin-12 (IL-12) gene therapy on highly metastatic murine mammary cancer model.

METHODS

Metastatic mammary tumors induced by inoculation in BALB/c female mice were treated by intratumoral injections of either a plasmid vector containing IL-12 or empty vector and then subjected to in vivo electrogene transfer once a week for 8 weeks.

RESULTS

Treatment with IL-12 resulted in elevation of both IL-12 and IFNgamma levels in mammary tumors and in serum and intratumoral levels of CD4 and CD8 proteins were also increased. Tumor volumes and lymphatic and pulmonary metastases were significantly reduced. The histopathological changes induced by IL-12 characteristically included marked inflammation, increased apoptosis, decreased DNA synthesis, peripheral influx of significantly greater numbers of active macrophages, and reduced blood microvessel density, and apoptotic vascular endothelial cells were frequently seen. Western blotting showed decreases in VEGFR-3 of tumors exposed to IL-12 gene therapy. In adjuvant immunofluorescence studies, the CD31-positive endothelial cells of microvessels showed decreased VEGFR-3 expression in IL-12-treated tumors. However, apparent alterations in VEGFR-3 expression of podoplanin-positive lymphatic endothelial cells were not observed in IL-12-treated tumors. Although recombinant IL-12 did not inhibit tubular formation of human umbilical vein endothelial cells in a Matrigel assay, recombinant IFNgamma did completely suppress the tubular formation.

CONCLUSIONS

In vivo electrogene transfer of IL-12 exerts strong anti-tumorigenic and anti-metastatic effects likely due to T-cell-mediated immune responses as well as anti-angiogenic action.

Immunotherapy for malignant glioma: current approaches and future directions

Traditional therapies for the treatment of malignant glioma have failed to make appreciable gains regarding patient outcome in the last decade. Therefore, immunotherapeutic approaches have become increasingly popular in the treatment of this cancer. This article reviews general immunology of the central nervous system and the immunobiology of malignant glioma to provide a foundation for understanding the rationale behind current glioma immunotherapies. A review of currently implemented immunological treatments is then provided with special attention paid to the use of vaccines, gene therapy, cytokines, dendritic cells and viruses. Insights into future and developing avenues of glioma immunotherapy, such as novel delivery systems, are also discussed.

Cytokines in cancer immunity and immunotherapy

The concept that the immune system recognizes and controls cancer was first postulated over a century ago, and cancer immunity has continued to be vigorously debated and experimentally tested. Mounting evidence in humans and mice supports the involvement of cytokines in tumor initiation, growth, and metastasis. The idea that the immune system detects stressed, transformed, and frankly malignant cells underpins much of the excitement currently surrounding new cytokine therapies in cancer treatment. In this review, we define the contrasting roles that cytokines play in promoting tumor immunity, inflammation, and carcinogenesis. We also discuss the more promising aspects of clinical cytokine use in cancer patients.

Parallel imaging for NMR microscopy at 14.1 Tesla

Parallel imaging techniques using arrays of mutually decoupled coils have become standard on almost all clinical imaging systems. Such techniques also have great potential for high-field magnetic resonance (MR) microscopy, where measurement times are usually long and susceptibility artifacts can be severe. However, it is technically very challenging to design efficient high-frequency phased arrays for small-diameter, vertical-bore magnets, especially since standard decoupling methods, such as impedance mismatched preamplifiers, cannot be easily integrated. A four-coil phased array was constructed for microimaging at 600 MHz, and sensitivity encoding (SENSE) and generalized autocalibrating partially parallel acquisitions (GRAPPA) reconstructions of spin-echo and echo-planar images of the mouse brain were performed to reduce imaging time and susceptibility artifacts, respectively.

Detection and volume determination of colonic tumors in Min mice by magnetic resonance micro-imaging

We applied MRI to the in vivo detection of spontaneous colorectal tumors in a unique mouse model, the Fox Chase Cancer Center (FCCC) ApcMIN mouse. Unlike other Min (multiple intestinal neoplasia) strains, FCCC ApcMIN animals develop an appreciable number of tumors in the large intestine, which makes them an appropriate mouse model for colon cancer in humans. We describe a method for marking the colon on MRI data sets that involves a bowel-cleansing procedure and the insertion of a polyurethane tube (filled with an MRI contrast agent) fully into the colon. We found that tumors as small as 1.5 mm in diameter can be consistently identified from MRI datasets with a voxel size of 0.1 mm x 0.133 mm x 0.133 mm. Tumor volumes were determined from the MRM data sets with the use of a novel approach to planimetry in 3D data sets. We observed a correlation between tumor volume (as measured from the MRI datasets) and tumor weight of 0.942, and a P-value of 0.008, based on Spearman's test. These data show that MRI can be used to accurately monitor tumor growth in mouse models of colorectal carcinogenesis.

Antitumor and antimetastatic activity of IL-23

The structure and T cell stimulatory effects of the recently discovered cytokine IL-23 are similar to, but distinct from, those of IL-12. Although the antitumor activities of IL-12 are well characterized, the effect of IL-23 on tumor growth is not known. In this study, murine CT26 colon adenocarcinoma and B16F1 melanoma cells were engineered using retroviral vectors to release single-chain IL-23 (scIL-23) to evaluate its antitumor activity. In BALB/c mice, scIL-23-transduced CT26 cells grew progressively until day 26 to an average size of 521 +/- 333 mm(3), then the tumors started to regress in most animals, resulting in a final 70% rate of complete tumor rejection. scIL-23 transduction also significantly suppressed lung metastases of CT26 and B16F1 tumor cells. In addition, mice that rejected scIL-23-transduced tumors developed a memory response against subsequent wild-type tumor challenge. Compared with scIL-12-expressing CT26 cells, scIL-23-transduced tumors lacked the early response, but achieved comparable antitumor and antimetastatic activity. These results demonstrated that IL-23, like IL-12, provided effective protection against malignant diseases, but it probably acted by different antitumor mechanisms. As a first step in identifying these antitumor mechanisms, tumor challenge studies were performed in immunocompromised hosts and in animals selectively depleted of various lymphocyte populations. The results showed that CD8(+) T cells, but not CD4(+) T cells or NK cells, were crucial for the antitumor activity of IL-23.

Cytotoxicity in glioma cells due to interleukin-12 and interleukin-18-stimulated macrophages mediated by interferon-gamma-regulated nitric oxide

OBJECT

Interleukin (IL)-12 and IL-18 synergistically mediate antitumor responses through the production of interferon-gamma (IFNgamma) by T and natural killer (NK) cells. Recently, it has been reported that macrophages stimulated with these cytokines also produce IFNgamma, which led the authors to investigate the antiglioma activity of macrophages stimulated by the combination of these cytokines in vitro.

METHODS

Dish-adherent peritoneal exudate cells, which had been elicited in thioglycollate broth as a source of macrophages, were used in the experiment. The murine glioma cell lines VM-glioma and 203G were labeled with [3H]thymidine for a cytotoxicity assay of macrophages. In response to the combined stimulation by IL-12 and IL-18, macrophages expressed potent cytotoxic activity against glioma cells in association with increasing production of IFNgamma and nitric oxide (NO). Inhibitors of NO abrogated the cytotoxic activity of the macrophages, which had been induced by IL-12 and IL-18, despite the increase in IFNgamma production. Neutralization of IFNgamma or use of macrophages obtained from IFNgamma gene-knockout mice markedly reduced not only cytotoxic activity, but also NO production. Depletion of T and NK cells from the macrophage population, which was achieved using antibody plus complement treatment, slightly reduced macrophage activities, suggesting that these are the main effector cells, although T and NK cells may partially participate in this cytotoxicity.

CONCLUSIONS

Macrophages stimulated with IL-12 and IL-18 produced IFNgamma and NO, which in turn mediated the antiglioma response. Therefore, macrophages as well as T and NK cells play an important role in antitumor responses stimulated by IL-12 and IL-18.

MR microscopy and high resolution small animal MRI: applications in neuroscience research

The application of magnetic resonance (MR) imaging in the study of human disease using small animals has steadily evolved over the past two decades and strongly established the fields of "small animal MR imaging" and "MR microscopy." An increasing number of neuroscience related investigations now implement MR microscopy in their experiments. Research areas of growth pertaining to MR microscopy studies are focused on (1). phenotyping of genetically engineered mice models of human neurological diseases and (2). rodent brain atlases. MR microscopy can be performed in vitro on tissue specimens, ex vivo on brain slice preparations and in vivo (typically on rodents). Like most new imaging technologies, MR microscopy is technologically demanding and requires broad expertise. Uniform guidelines or "standards" of a given MR microscopy experiment are non-existent. The main focus therefore of this review will be on biological applications of MR microscopy and the experimental requirements. We also take a critical look at the biological information that small animal (rodent) MR imaging has provided in neuroscience research.

Interleukin-12 in anti-tumor immunity and immunotherapy

Interleukin-12 (IL-12) has an essential role in the interaction between the innate and adaptive arms of immunity by regulating inflammatory responses, innate resistance to infection, and adaptive immunity. Endogenous IL-12 is required for resistance to many pathogens and to transplantable and chemically induced tumors. In experimental tumor models, recombinant IL-12 treatment has a dramatic anti-tumor effect on transplantable tumors, on chemically induced tumors, and in tumors arising spontaneously in genetically modified mice. IL-12 utilizes effector mechanisms of both innate resistance and adaptive immunity to mediate anti-tumor resistance. IFN-gamma and a cascade of other secondary and tertiary pro-inflammatory cytokines induced by IL-12 have a direct toxic effect on the tumor cells or may activate potent anti-angiogenic mechanisms. The stimulating activity of IL-12 on antigen-specific immunity relies mostly on its ability to determine or augment Th1 and cytotoxic T lymphocyte responses. Because of this ability, IL-12 has a potent adjuvant activity in cancer and other vaccines. The promising data obtained in the pre-clinical models of anti-tumor immunotherapy have raised much hope that IL-12 could be a powerful therapeutic agent against cancer. However, excessive clinical toxicity and modest clinical response observed in the clinical trials point to the necessity to plan protocols that minimize toxicity without affecting the anti-tumor effect of IL-12.

Control of advanced choroid plexus tumors in SV40 T antigen transgenic mice following priming of donor CD8(+) T lymphocytes by the endogenous tumor antigen

Mouse models in which tumors arise spontaneously due to the transgenic expression of an oncoprotein provide an opportunity to test approaches that target the immune-mediated control of tumor progression. In this report we investigated the role of SV40 Tag-specific CD8(+) T cells in the control of advanced choroid plexus tumor progression using large tumor Ag (Tag) transgenic mice. Since mice of the SV11 line are tolerant to the immunodominant SV40 Tag-derived CTL epitopes, mice with advanced stage tumors were reconstituted with naive C57BL/6 spleen cells following a low dose of gamma-irradiation. This led to the priming of CTLs specific for the H2-K(b)-restricted epitope IV by the endogenous Tag and a significant increase in the life span of Tag transgenic mice. Epitope IV-specific CD8(+) T cells accumulated and persisted in the brains and tumors of SV11 mice, as determined by analysis with epitope-specific MHC class I tetramers. Brain-infiltrating epitope IV-specific T cells were capable of producing IFN-gamma as well as lysing syngeneic Tag-transformed cells in vitro. In addition, the adoptive transfer of spleen cells from Tag-immune C57BL/6 mice resulted in a dramatic increase in the control of tumor progression in SV11 mice and was associated with the accumulation of CD8(+) T cells specific for multiple Tag epitopes in the brain. These results indicate that the control of advanced stage spontaneous choroid plexus tumors is associated with the induction of a strong and persistent CD8(+) T cell response to Tag.

Strategies using the immune system for therapy of brain tumors

Phase II immunotherapy and gene therapy studies should be pursued because of encouraging results in many phase I studies. Future testing in this field may consider modifications of some of the above-mentioned combined strategies. For instance, in the immunization and adoptive transfer studies performed by Holladay et al and by Plautz et al, the systemic adoptive transfer could be altered to intratumoral placements of effector cells. This permutation may be more efficacious because local adoptive immunotherapy approaches involve placement of effector cells where they are needed. Additionally, new avenues of gene therapy are being explored that may offer added beneficial effects for immunization, local or systemic adoptive immunotherapy, or combined chemotherapy and adoptive immunotherapy of tumors. With new genetic tools, such as microarray analyses, SEREX, and creation of cDNA libraries from tumor cells, significant progress in the treatment of neoplasms in the immunologically privileged brain should be forthcoming.