NK cells with KIR2DS2 immunogenotype have a functional activation advantage to efficiently kill glioblastoma and prolong animal survival.

Glioblastomas (GBMs) are lethal brain cancers that are resistant to current therapies. We investigated the cytotoxicity of human allogeneic NK cells against patient-derived GBM in vitro and in vivo, as well as mechanisms mediating their efficacy. We demonstrate that KIR2DS2 immunogenotype NK cells were more potent killers, notwithstanding the absence of inhibitory killer Ig-like receptor (KIR)-HLA ligand mismatch. FACS-sorted and enriched KIR2DS2(+) NK cell subpopulations retained significantly high levels of CD69 and CD16 when in contact with GBM cells at a 1:1 ratio and highly expressed CD107a and secreted more soluble CD137 and granzyme A. In contrast, KIR2DS2(-) immunogenotype donor NK cells were less cytotoxic against GBM and K562, and, similar to FACS-sorted or gated KIR2DS2(-) NK cells, significantly diminished CD16, CD107a, granzyme A, and CD69 when in contact with GBM cells. Furthermore, NK cell-mediated GBM killing in vitro depended upon the expression of ligands for the activating receptor NKG2D and was partially abrogated by Ab blockade. Treatment of GBM xenografts in NOD/SCID mice with NK cells from a KIR2DS2(+) donor lacking inhibitory KIR-HLA ligand mismatch significantly prolonged the median survival to 163 d compared with vehicle controls (log-rank test, p = 0.0001), in contrast to 117.5 d (log-rank test, p = 0.0005) for NK cells with several inhibitory KIR-HLA ligand mismatches but lacking KIR2DS2 genotype. Significantly more CD56(+)CD16(+) NK cells from a KIR2DS2(+) donor survived in nontumor-bearing brains 3 wk after infusion compared with KIR2DS2(-) NK cells, independent of their proliferative capacity. In conclusion, KIR2DS2 identifies potent alloreactive NK cells against GBM that are mediated by commensurate, but dominant, activating signals.

Case report: extracranial metastasis from gliosarcoma--the influence of immune system.

Extracranial metastasis of malignant glioma is an extremely rare event. We report on a 67-year-old patient with a primary gliosarcoma that was treated by open resection. The concomitant radio-chemotherapy which followed induced an unusually severe and early leucocytopenia. Ten months after diagnosis, the patient presented with multiple metastases in the lung and the skeletal system. The clinical, radiological and neuropathological findings are described. In addition, we discuss the possible role of a compromised immune system in the development of extracranial glioma metastasis.

Increase in tumor size following intratumoral injection of immunostimulatory CpG-containing oligonucleotides in a rat glioma model.

The immunosuppressive environment of malignant gliomas is likely to suppress the anti-tumor activity of infiltrating microglial cells and lymphocytes. Macrophages and microglial cells may be activated by oligonucleotides containing unmethylated CpG-motifs, although their value in cancer immunotherapy has remained controversial. Following injection of CpG-containing oligonucleotides (ODN) into normal rat brain, we observed a local inflammatory response with CD8+ T cell infiltration, upregulation of MHC 2, and ED1 expression proving the immunogenic capacity of the CpG-ODN used. This was not observed with a control ODN mutated in the immunostimulatory sequence (m-CpG). To study their effect in a syngeneic tumor model, we implanted rat 9L gliosarcoma cells into the striatum of Fisher 344 rats. After 3 days, immunostimulatory CpG-ODN, control m-CpG-ODN, or saline was injected stereotactically into the tumors (day 3 group). In another group of animals (day 0 group), CpG-ODN were mixed with 9L cells prior to implantation without further treatment on day 3. After 3 weeks, the animals were killed and the brains and spleens were removed. Rather unexpectedly, the tumors in several of the animals treated with CpG-ODN (both day 0 and day 3 group) were larger than in saline or m-CpG-ODN treated control animals. The tumor size in CpG-ODN-treated animals was more variable than in both control groups. This was associated with inflammatory responses and necrosis which was observed in most tumors following CpG treatment. This, however, did not prevent excessive growth of solid tumor masses in the CpG-treated animals similar to the control-treated animals. Dense infiltration with microglial cells resembling ramified microglia was observed within the solid tumor masses of control- and CpG-treated animals. In necrotic areas (phagocytic), activation of microglial cells was suggested by ED1 expression and a more macrophage-like morphology. Dense lymphocytic infiltrates consisting predominantly of CD8+ T cells and fewer NK cells were detected in all tumors including the control-treated animals. Expression of perforin serving as a marker for T cell or NK cell activation was detected only on isolated cells in all treatment groups. Tumors of all treatment groups revealed CD25 expression indicating T cells presumed to maintain peripheral tolerance to self-antigens. Cytotoxic T cell assays with in vitro restimulated lymphocytes ((51)chromium release assay) as well as interferon-gamma production by fresh splenocytes (Elispot assay) revealed specific responses to 9L cells but not another syngeneic cell line (MADB 106 adenocarcinoma). Surprisingly, the lysis rates with lymphocytes from CpG-ODN-treated animals were lower compared to control-treated animals. The tumor size of individual animals did not correlate with the response in both immune assays. Taken together, our data support the immunostimulatory capacity of CpG-ODN in normal brain. However, intratumoral application proved ineffective in a rat glioma model. CpG-ODN treatment may not yield beneficial effects in glioma patients.

Highly successful therapeutic vaccinations combining dendritic cells and tumor cells secreting granulocyte macrophage colony-stimulating factor.

In an attempt to induce potent immune antitumor activities, we investigated, within the rat 9L gliosarcoma model, distal therapeutic vaccinations associating three therapies: dendritic cell vaccination, intratumoral granulocyte macrophage colony-stimulating factor (GM-CSF) gene transfer, and tumor apoptosis induction. Vaccines of dendritic cells coinjected with processed GM-CSF secreting 9L cells induced systemic responses, resulting in the complete regression of distant preimplanted 9L tumor masses in, with the best strategy, 94% of male rats. All of the cured rats developed a long-term resistance to a rechallenge with parental cells. The curative responses were correlated with the detection of elevated specific cytotoxic activities and a CD4+, CD8+ T cell-, and natural killer (NK) cell-mediated IFN-gamma production. The survival rate of the rat seemed more directly linked to the amount of GM-CSF secreted by the transduced tumor cells, which in turn depended on the toxicity of the apoptosis-inducing treatment, than to the level of apoptosis induced. Unexpectedly, alive GM-CSF secreting 9L cells became apoptotic when injected in vivo. Thus we documented the positive role of apoptosis in the induction of therapeutic antitumor responses by comparing, at equal GM-CSF exogenous supply, the effects of dendritic cells coinjected with apoptotic or necrotic 9L cells. The data showed the superior therapeutic efficiency of combined vaccines containing apoptotic tumor cells. In conclusion, vaccinations with dendritic cells associated with apoptotic tumor cells secreting GM-CSF show a very high therapeutic potency that should show promise for the treatment of human cancer.

Cytokine gene therapy of gliomas: induction of reactive CD4+ T cells by interleukin-4-transfected 9L gliosarcoma is essential for protective immunity.

Tumor cells genetically modified to secrete cytokines stimulate potent immune responses against peripheral and central nervous system tumors; however, variable results on the efficacy of this strategy for therapeutic intervention against established intracranial neoplasia have been reported. We have found that vaccination with rat 9L gliosarcoma cells expressing interleukin 4 (9LmIL4) induced a specific, protective, immune response against rechallenge with parental 9L tumors. In naive rats, sham-transfected 9L (9Lneo) tumors and 9LmIL4 tumors grew at comparable rates for 12-14 days, and then 9LmIL4 tumors regressed. After regression of 9LmIL4 tumors, rats were resistant to rechallenge with parental 9L cells. To investigate the mechanism(s) responsible for 9LmIL4-induced immunity, the phenotype and function of tumor-infiltrating lymphocytes (TILs) in 9Lneo and 9LmIL4 tumors were compared. In flow cytometric analyses, it was determined that CD4+ T cells were the predominant cell type in both 9Lneo and 9LmIL4 tumors at day 10. However, at the onset of regression (day 14), 9LmIL4 tumors were infiltrated predominantly by CD8+ T cells. To investigate functional aspects of the anti-9L tumor responses, we assessed the capacity of 9LmIL4 TILs to mediate specific lytic function or production of cytokines. In response to parental 9L, TILs isolated from day 14 9LmIL4 tumors were demonstrated to produce substantially greater amounts of IFN-gamma than did TILs from 9Lneo tumors. Although freshly isolated TILs from 9LmIL4 or control tumors did not lyse 9L cells in 51Cr-release cytotoxicity assays, specific cytotoxicity was demonstrable using TILs from day 14 9LmIL4 or splenocytes from 9LmIL4-bearing rats after their restimulation for 5 days with parental 9L tumor cells in vitro. Antibody blocking studies demonstrated that cytokine production and lytic activity by TILs, or splenocytes from 9LmIL4-immunized rats, were mediated in a T-cell receptor-dependent fashion. Because interleukin-4 also promotes humoral responses, quantity and isotype of immunoglobulins in sera from 9Lneo or 9LmIL4-immunized rats were compared. The amount of IgG1 antibodies was significantly increased in sera from 9LmIL4-immunized rats compared to sera from 9Lneo-bearing rats. Experiments using sublethally irradiated, naive rats adoptively transferred with splenocytes and/or sera from 9LmIL4-immunized or naive rats demonstrated that immune cells, with or without immune sera, protected recipients from challenge with parental 9L. Immune sera provided no protection when given with lymphocytes from naive rats, and it did not enhance protection against parental 9L when given in conjunction with lymphocytes for 9LmIL4-immunized rats. In additional adoptive transfer experiments, an essential role for CD4+ T cells in immunity was observed because their depletion from among splenocytes of 9LmIL4-immunized rats eliminated the protective effective against 9L, whereas depletion of CD8+ cells resulted in a more limited effect on protection against 9L. These data suggest that strategies for inducing systemic, long-term tumor-specific reactivity among CD4+ T cells will be critical for the development of immunotherapy of gliomas.

NKR-P1+ cells localize selectively in Rat 9L gliosarcomas but have reduced cytolytic function.

To better understand immune responses to brain tumors and to develop possible approaches for immunotherapy, we have investigated the leukocyte populations infiltrating the rat 9L gliosarcoma. By immunocytochem-ical analyses of the cells infiltrating the tumor, we observed a substantial number of cells expressing natural killer cell receptor protein 1 (NKR-P1), a marker expressed only on rat lymphocytes capable of non-MHC-restricted cytotoxicity. Previous investigations have determined the existence of three populations of NKR-P1+ lymphocytes in normal rats, including NKR-P1bright/T-cell receptor (TCR)-/CD3-/CD5- (approximately 5-15%), NKR-P1dim-/TCRalphabeta+/CD3+/CD5+ (approximately 1-5%), and NKR-P1dim/TCRgammadelta+/CD3+/CD5+ (approximately 0.5-2%). By one-parameter flow cytometry, it was determined that NKR-P1+ cells constituted 30-60% of the lymphocytes in 9L tumors. Among splenic lymphocytes or peripheral blood leukocytes, NKR-P1bright cells are 1.5-4.5 times more numerous than NKR-P1dim cells. In striking contrast, NKR-p1dim cells were 4-5 times more numerous than NKR-P1bright cells among lymphocytes isolated from 9L tumors. Using quantitative analyses of laser confocal microscopic scans, we determined that NKR-P1dim cells were approximately 4 times as numerous as NKR-P1bright cells in situ, confirming flow cytometric findings. By two-color now cytometric analyses, it was observed that approximately 5-10% of the cells were NKR-p1bright/CD5-/TCR-, a phenotype representative of NK cells. Also, approximately 11-25% of the cells were NKR-P1dim/CD5+/TCR+ cells, corresponding to the T-cell subset with non-MHC-restricted lytic function. In addition, we observed a cell population among 9L-derived lymphocytes with a NKR- p1dim/CD5-/TCR- phenotype (approximately 15-25%). Cells of this phenotype have not been reported previously, and most likely represent NK cells down-modulated for expression of NKR-P1. Alternatively, they might represent cells of unknown origin or cells down-modulated for expression of T-cell markers in the microenvironment of 9L tumors. We also compared the lytic capacity of NKR-P1+ populations derived from normal animals and from 9L gliosarcomas. In these experiments, it was determined that, although cells isolated from 9L tumors had some capacity to lyse tumor target cells, they were clearly less efficient than cells isolated from normal splenocytes. Cumulatively, these data suggest that there is selective localization of cells capable of mediating antitumor responses in 9L, but that tumor-associated factors may down-regulate their function and expression of NKR-P1.

Tumor immunity within the central nervous system stimulated by recombinant Listeria monocytogenes vaccination.

Tumors arising within the central nervous system (CNS) present the immune system with a challenging target, given the heterogeneous nature of these neoplasms and their location within an "immunologically privileged" site. We used the lymphocytic choriomeningitis virus nucleoprotein (LCMV-NP) as a pseudotumor antigen to investigate recombinant Listeria monocytogenes as a tumor vaccine against s.c. and intracerebral challenges with a NP-expressing glioma, 9L-NP. Using Fischer 344 rats, we demonstrate that vaccination with recombinant L. monocytogenes-NP stimulates protection against s.c., but not intracerebral, 9L-NP tumor challenge in an antigen-specific, CD8(+) T-cell-dependent manner. After s.c. tumor rejection, enhanced antitumor immunity is achieved via epitope spreading that permits complete resistance against lethal intracerebral challenge with 9L-NP and with the untransfected parental 9L tumor. Unlike the CD8(+)-dependent immune responses against s.c. 9L-NP tumors, this expanded intracerebral immunity against endogenous tumor-associated antigens is dependent on both CD4(+) and CD8(+) T cells. Taken together, these results demonstrate that the mechanisms of tumor immunity within the brain are different from those elicited against non-CNS tumors. Furthermore, vaccination approaches exploiting the concept of epitope spreading may enhance the efficacy of antitumor immune responses within the immunologically privileged CNS, potentially mediating tumor cell killing through both CD4(+)- and CD8(+)-dependent effector pathways.

The human leukemic T-cell line, TALL-104, is cytotoxic to human malignant brain tumors and traffics through brain tissue: implications for local adoptive immunotherapy.

Preclinical studies with the human MHC nonrestricted cytotoxic T-cell leukemic line, TALL-104, were performed in anticipation of its use in cellular immunotherapy trials for primary malignant brain tumors. In this study, we have: (a) quantitated the in vitro brain tumor cell lysis; (b) measured the cytokine secretion upon coincubation of TALL-104 cells with brain tumor cells; (c) investigated the effect of dexamethasone on brain tumor cell cytolysis by TALL-104 cells; (d) explored the effects of lethal irradiation and cryopreservation on TALL-104 cell viability and lytic efficacy; and (e) estimated the damage TALL-104 cells induce to murine normal and tumor brain cells and their trafficking patterns in both normal and tumor-bearing rat brain upon intracranial infusion. In vitro coincubation of TALL-104 cells with human brain tumor cells, explants, and cell lines resulted in significant lysis of them, but normal brain cells were spared. Lysis of tumor at 4 h was unaffected by dexamethasone or lethal irradiation. Secretion of tumor necrosis factor-alpha, tumor necrosis factor-beta, IFN-gamma, or granulocyte/macrophage-colony stimulating factor upon TALL-104 cell coincubation with brain tumor cells variably occurred without always correlating with lysis. In vivo experiments using irradiated TALL-104 cells, placed at multiple times into normal cannulated rat brain, produced focal sterile abscesses at the instillation site but no widespread allergic encephalitic reaction. Cells morphologically consistent with TALL-104 cells specifically trafficked from the site of instillation through the neuropil, occasionally into the contralateral brain, and egressed at perivascular and leptomeningeal spaces. In vivo experiments with cannulated rats bearing 9L gliosarcoma showed a preferential localization of the TALL-104 cells in tumor compared with normal brain. Taken together, these data support the concept that TALL-104 cells can be used as a novel nontoxic and efficacious paradigm for cellular immunotherapy trials in human primary malignant brain tumors.

Glioma-associated hyaluronan induces apoptosis in dendritic cells via inducible nitric oxide synthase: implications for the use of dendritic cells for therapy of gliomas.

As a means of enhancing immunity to gliomas, we investigated local delivery of rat, bone marrow-derived dendritic cells (DCs) into rat 9L gliosarcoma tumors and into 9L tumors induced to undergo apoptosis by gamma knife radiosurgery. Contrary to other tumors, local delivery of DCs had no therapeutic effect on 9L gliomas, even when tumor apoptosis was induced via radiosurgery, which leads to efficient "loading" of the DCs with tumor antigen. To determine whether antigen-presenting cells, such as DCs, were viable in tumors, we carried out multiparametric staining of 9L tumors, using phycoerythrin-conjugated OX6 (MHC class II) or OX62 (DC specific) and FITC-labeled Val-Ala-Asp-fluoromethyl ketone (FITC-VAD-FMK; activated caspases). It was determined that DCs were undergoing apoptosis in these tumors. We therefore sought to determine which glioma cell surface receptors or components of the extracellular matrix in gliomas influenced DC viability. Hyaluronan (HA) is a major component of glioma extracellular matrix and has been found to support tumor cell migration and metastasis. However, its influence on the immune system, and particularly on DCs, via its receptor CD44 is not well documented. Using reverse transcription-PCR, Northern blot, and Western blot analyses, we determined that HA stimulated production of inducible nitric oxide synthase (iNOS) in DCs. NO production by HA-stimulated DCs was then verified biochemically. NO production was dependent on the size of HA; intermediate HA fragments had the greatest capacity to induce NO production in DC, whereas completely digested HA oligosaccharides failed to induce NO. Furthermore, N-monomethyl-L-arginine, an inhibitor of iNOS, completely blocked HA-induced NO production by DCs. Because induction of NO results in the induction of apoptosis in macrophages as well as other cells, DCs treated with HA were examined for apoptosis in terminal deoxynucleotidyl transferase (TdT)-mediated dUTP biotin nick-end labeling assays. It was demonstrated that HA induced apoptosis in DCs and that induction of apoptosis was dependent on the production of NO because it was entirely inhibited by N-monomethyl-L-arginine. Using flow cytometric analyses with FITC-VAD-FMK, which is specific for activated caspases, we also determined that induction of apoptosis in DCs with HA could be titrated. Coincubation of 9L tumor cells with DCs was found to induce apoptosis in DCs as indicated by fluorescent staining with FITC-VAD-FMK. Specificity of this reaction for CD44-HA interactions was determined by pretreatment of DCs with anti-CD44 or pretreatment of 9L tumor cells with hyaluronidase, which blocked the induction of apoptosis in DCs. These data indicate that HA expressed by gliomas may contribute to their immunosuppressive effects by promoting apoptosis among professional antigen-presenting cells such as DCs via iNOS induction after CD44-HA interactions.

Immunization with an antigen identified by cytokine tumor vaccine-assisted SEREX (CAS) suppressed growth of the rat 9L glioma in vivo.

We have reported previously that s.c. immunization of rats with IL-4 transduced 9L gliosarcoma cells (9L-IL-4) induced a potent antitumor immunity against intracranial, parental 9L tumors. Subcutaneous implantation of 9L-IL-4 influenced the systemic humoral response, which was demonstrated by Th2-type isotype-switching and the induction of cellular immune responses, which played a critical role in the rejection of tumors. Serological analyses of recombinant cDNA expression libraries (SEREX), has recently emerged as a powerful method for serological identification of tumor-associated antigens (TAAs) and/or tumor rejection antigens (TRAs). Because IL-4 is known to activate B cells and to promote humoral responses, and inasmuch as induction of humoral responses by central nervous system tumors has been reported to be minimal, we investigated whether the induction of a potent humoral immune response against 9L TAAs or TRAs in rats immunized s.c. with 9L-IL4 could be demonstrated. Screening of 5 x 10(5) independent clones of 9L-expression cDNA library for the presence of reactive antibodies in the serum from a 91-IL-4 immunized rat led to the identification of three different TAAs. One 9L TAA (clone 29) was demonstrated to be calcyclin, a member of the S-100 family of calcium-binding proteins. The second 9L TAA (clone 37) was demonstrated to be the rat homologue of the J6B7 mouse immunomodulatory molecule. The third TAA (clones 158 and 171) was determined to be the rat homologue of the mouse Id-associated protein 1 (MIDA1), a DNA-binding, protein-associated protein. Northern blotting demonstrated that message for calcyclin was overexpressed in 9L cells. Message encoding MIDA1 was highly expressed in parental 9L cells and thymus and, to a lesser degree, in testis, suggesting that MIDA1 was comparable with the cancer/testis category of TAAs. Sera obtained from animals bearing 9L-IL-4 were found to have a higher a frequency and titer of antibodies to these antigens when compared with sera obtained from rats bearing sham-transduced 9L (9L-neo) cells. To determine whether immunization with these TAAs induced antitumor immunity, animals were immunized by intradermal injection with expression plasmids encoding calcyclin or MIDA1. Subsequent challenge of rats with parental 9L resulted in significant suppression of tumor growth in animals immunized with MIDA1, but not with calcyclin. These results indicate that MIDA1 is an effective 9L TRA and will be useful for the investigation of specific antitumor immunity in this glioma model. Furthermore, these results suggest that this approach, termed "cytokine-assisted SEREX (CAS)," may serve as an effective strategy for identification of TRAs for in animal-glioma models of cytokine gene therapy, and potentially in humans undergoing cytokine gene therapy protocols as well.

Induction of immunity in peripheral tissues combined with intracerebral transplantation of interleukin-2-producing cells eliminates established brain tumors.

Cytokine gene therapy for the induction of potent immune responses against central nervous system tumors has proven to have significant potential. However, this strategy needs improvement in the process of antigen presentation and/or insufficient recruitment of immunocompetent cells to achieve successful eradication of established brain tumors. We investigated the therapeutic potential of induced systemic immunity in peripheral tissues combined with interleukin-2 (IL-2) production in the vicinity of brain tumors to treat established brain tumors. Sequential magnetic resonance image monitoring showed that the combinatory therapy consisting of intracerebral (i.c.) transplantation of IL-2-producing rat gliosarcoma 9L (9L/IL-2) cells and s.c. vaccination using irradiated 9L or 9L/IL-2 cells could cure 9L-bearing rats, whereas either the i.c. injection of 9L/IL-2 cells or the s.c. vaccination produced little or marginal antitumor effects, respectively. Xenogeneic murine neuroblastoma cells secreting IL-2 could substitute for 9L/IL-2 cells, producing significant antitumor effects in the vaccinated rats. Tumor-specific cytotoxic activity was induced in the vaccinated rats but not fully in the rats treated only with i.c. injection of 9L/IL-2 cells. Immunohistochemical analysis revealed that a number of CD4(+) and CD8(+) T cells infiltrated into the brain tumors which were treated with the combinatory therapy. The level of cell infiltration was similar to that found in s.c. 9L/IL-2 tumors which were subsequently rejected. In contrast, the brain tumors treated with either i.c. transplantation of 9L/IL-2 cells or the s.c. vaccination showed only moderate infiltration of T cells. The combinatory strategy, i.c. grafting of IL-2-producing cells, and s.c. immunization of irradiated whole tumor cell vaccine, is, thus, effective for recruiting activated T cells into the brain tumor site and could be a potential therapy for brain tumors.

Magnetic labeling of activated microglia in experimental gliomas.

Microglia, as intrinsic immunoeffector cells of the central nervous system (CNS), play a very sensitive, crucial role in the response to almost any brain pathology where they are activated to a phagocytic state. Based on the characteristic features of activated microglia, we investigated whether these cells can be visualized with magnetic resonance imaging (MRI) using ultrasmall superparamagnetic iron oxides (USPIOs). The hypothesis of this study was that MR microglia visualization could not only reveal the extent of the tumor, but also allow for assessing the status of immunologic defense. Using USPIOs in cell culture experiments and in a rat glioma model, we showed that microglia can be labeled magnetically. Labeled microglia are detected by confocal microscopy within and around tumors in a typical border-like pattern. Quantitative in vitro studies revealed that microglia internalize amounts of USPIOs that are significantly higher than those incorporated by tumor cells and astrocytes. Labeled microglia can be detected and quantified with MRI in cell phantoms, and the extent of the tumor can be seen in glioma-bearing rats in vivo. We conclude that magnetic labeling of microglia provides a potential tool for MRI of gliomas, which reflects tumor morphology precisely. Furthermore, the results suggest that MRI may yield functional data on the immunologic reaction of the CNS.

The role of microglia and tumor-primed lymphocytes in the interaction between T lymphocytes and brain endothelial cells.

We investigated the role of IFN-gamma activated microglia in the passage of T lymphocytes across a monolayer of brain endothelial cells (EC) in vitro. Microglia isolated from Fisher 344 (F344) newborn rats were stimulated with IFN-gamma (100 U/ml) for 48 h. T lymphocytes primed with glioma cells were 51Cr-labeled, and added to the monolayer of F344 brain EC. In the adhesion assay, when EC were cultured in medium containing the supernatant of reactive microglia before the assay was carried out, the number of T lymphocytes adhering was increased. In addition, this adhesion was blocked by the addition of anti-ICAM-1 mAb to the EC. In the migration assay, performed using the double chamber system, when reactive microglia adhered to the other side of EC, the number of T lymphocytes migrating to the underwell was also increased. When T lymphocytes were primed to tumor cells in vivo, both their adhesion and migration were enhanced. These results suggest that some soluble factors from reactive microglia are capable of enhancing the expression of ICAM-1 on the brain EC. As a consequence, large numbers of tumor-primed T lymphocytes can adhere to EC and migrate across the EC monolayer.

Cell surface expression of MHC molecules in glioma cells infected with herpes simplex virus type-1.

9L glioma cells consistently expressed major histocompatibility complex (MHC) class I but not class II molecules. Herpes simplex type-1 virus (HSV-1) infection significantly reduced the expression of MHC I on the cell surface. Recombinant interferons could enhance the cell-surface expression of MHC I but had no effect on MHC II. This enhancement was partially inhibited by HSV-1 infection. HSV-1 mutants with deletions in ICP4, ICP6, ICP27, ICP47 and UL41 genes do not affect the infection induced inhibition, suggest that a different mechanism may be employed in the inhibition of cell-surface expression of MHC molecules.

Immunomodulation of glioma cells after gene therapy: induction of major histocompatibility complex class I but not class II antigen in vitro.

OBJECTIVE: Acquired immunity has been demonstrated in Fischer rats bearing syngeneic 9L tumors after herpes simplex virus (HSV) thymidine kinase (TK) gene transfection and ganciclovir treatment. The nature of this immunity in rats and its relevance to the HSV TK/ganciclovir protocol for human subjects remain to be determined. In this study, levels of major histocompatibility complex (MHC) Class I and II antigen expression were measured before and after HSV TK transfection, in an effort to document immunomodulatory changes caused by gene therapy. METHODS: Tumor cells from the 9L gliosarcoma cell line, three primary human glioma cultures, and the human glioma cell line U87 MG were transduced with HSV TK vector-containing supernatant from fibroblast-producing cells (titer of 5 x 10(6) colony-forming units/ml) and selected in G418 medium for neomycin resistance. Clones were pooled or individually selected for cell-killing assays with ganciclovir, to confirm TK expression (10(3) cells/well in a 96-well dish). Northern analyses using MHC Class I and Class II complementary deoxyribonucleic acid probes were performed on blots containing total ribonucleic acid from wild-type tumor cells and HSV TK transfectants. A beta-actin complementary deoxyribonucleic acid probe served as an internal control. Cell surface expression was confirmed with flow cytometry. The induction of MHC Class I was tested for cycloheximide and genistein sensitivity. RESULTS: All cell cultures exhibited increases in MHC Class I but not MHC Class II expression, as determined by Northern analysis densitometry and flow cytometry. Cycloheximide treatment did not diminish the up-regulation of MHC Class I after retroviral transfection, implicating a signal transduction pathway that does not require ongoing protein synthesis. Genistein pretreatment of cell cultures did diminish the up-regulation of MHC Class I, implicating a tyrosine kinase in the signaling cascade. CONCLUSION: Induction of MHC Class I in rat and human glioma cells after HSV TK retroviral gene therapy is a primary effect that is dependent on tyrosine kinase activity. Specific immune responses generated after transfection may represent an important general side effect of gene therapy protocols. Elucidation of the mechanism of immunomodulation after gene therapy will likely yield safer and more effective clinical protocols.

Paracrine delivery of IL-12 against intracranial 9L gliosarcoma in rats.

OBJECT: Interleukin-12 (IL- 12) has potential for the treatment of tumors because it can stimulate an antitumor immune response and possesses antiangiogenic properties. In the study reported here, the authors investigated the therapeutic role of locally delivered IL-12 in a malignant brain tumor model. METHODS: After genetically engineering 9L gliosarcoma cells to express IL-12 (9L-IL12 cells), the authors used these cells as a source of locally delivered cytokine. First, they investigated the behavior of these cells, which were implanted with the aid of stereotactic guidance into the rat brain, by using serial magnetic resonance imaging and histopathological examination. Second, they assessed the antitumor efficacy of proliferating, as well as nonproliferating (irradiated), 9L-IL12 cells by implanting these cells in animals challenged by wild-type 9L gliosarcoma (9Lwt) cells. The IL-12 expression in brain regions injected with 9L-IL12 was confirmed by reverse transcription-polymerase chain reaction. Last, the authors explored whether animals treated with 9L-IL12 cells developed an antitumor immunological memory by rechallenging the survivors with a second injection of 9Lwt cells. The authors demonstrated that local delivery of IL-12 into the rat brain by genetically engineered cells significantly prolongs survival time in animals challenged intracranially with a malignant glioma. CONCLUSIONS: These findings support continued efforts to refine local delivery systems of IL-12 in an attempt to bring this therapy to clinical trials.

Time course analysis and modulating effects of established brain tumor on active-specific immunotherapy.

OBJECT: There have been numerous attempts to establish an effective immunotherapy for the treatment of brain tumors. To date, reliable methods to manipulate the immune system for promoting brain tumor regression have been disappointing. Generation of active immune responses in most of these studies was only possible in the absence of viable tumor cells, suggesting that immunotherapy can only be used as preventive therapy. In few studies the investigators have demonstrated success in using immunotherapy to treat a preestablished intracranial tumor. Using the 9L intracranial glioma model, the authors sought to delineate the underlying mechanisms for these observations. METHODS: In animals vaccinated with irradiated 9L glioma cells and interferon-gamma 14 and 7 days prior to intracranial tumor cell challenge, a significant increase in survival was shown. In contrast, vaccinations applied 3 days prior to, at the time of (Day 0) or 7 days after intracranial tumor cell challenge failed to influence survival. Histological examination of brain tissue specimens obtained in animals vaccinated before or after tumor cell challenge showed no difference in the degree of peritumoral mononuclear cell infiltration. When activated spleen cells obtained obtained from these animals were assayed for cytotoxicity and proliferative capacity, only those spleen cells derived from animals vaccinated prior to intracranial tumor cell challenge showed enhanced activity. CONCLUSIONS: These data support the presence of a strong modulatory effect of tumor on local and systemic antitumoral immune response. This immunosuppression appears to be secondary to a direct effect on T-cell function. Reversal of this immunosuppression may be a useful adjunct to tumor vaccine therapy.

Therapeutic efficacy of antitumor dendritic cell vaccinations correlates with persistent Th1 responses, high intratumor CD8+ T cell recruitment and low relative regulatory T cell infiltration.

Despite the increasing number of immunotherapeutic strategies for the treatment of cancer, most approaches have failed to correlate the induction of an anti-tumor immune response with therapeutic efficacy. We therefore took advantage of a successful vaccination strategy-combining dendritic cells and irradiated GM-CSF secreting tumor cells-to compare the immune response induced against 9L gliosarcoma tumors in cured rats versus those with progressively growing tumors. At the systemic level, the tumor specific cytotoxic responses were quite heterogeneous in uncured vaccinated rats, and were surprisingly often high in animals with rapidly-growing tumors. IFN-gamma secretion by activated splenic T cells was more discriminative as the CD4+ T cell-mediated production was weak in uncured rats whereas high in cured ones. At the tumor level, regressing tumors were strongly infiltrated by CD8+ T cells, which demonstrated lytic capacities as high as their splenic counterparts. In contrast, progressing tumors were weakly infiltrated by T cells showing impaired cytotoxic activities. Proportionately to the T cell infiltrate, the expression of Foxp3 was increased in progressive tumors suggesting inhibition by regulatory T cells. In conclusion, the main difference between cured and uncured vaccinated animals does not depend directly upon the induction of systemic cytotoxic responses. Rather the persistence of higher CD4+ Th1 responses, a high intratumoral recruitment of functional CD8+ T cells, and a low proportion of regulatory T cells correlate with tumor rejection.

Synergy of gene-mediated immunoprophylaxis and microbeam radiation therapy for advanced intracerebral rat 9L gliosarcomas.

PURPOSE: Microbeam radiation therapy (MRT), a novel experimental radiosurgery that largely spares the developing CNS and other normal tissues, is tolerated well by developing animals and palliates advanced 9LGS tumors. This report, to our knowledge, is the first demonstration that gene-mediated immunotherapy (GMIMPR) enhances the efficacy of MRT for advanced 9LGS tumors. METHODS: Seventy-six male Fischer 344 rats were implanted ic with 10(4)9LGS cells on d0. By d14, the cells had generated approximately approximately 40 mm3 ic 9LGS tumours, experimental models for therapy of moderately aggressive human malignant astrocytomas. Each of the 14 untreated (control) rats died from a large (>100 mg) ic tumor before d29 (median, d21). On d14, the remaining 62 rats were given deliberately suboptimal microbeam radiation therapy (MRT) by a single lateral exposure of the tumor-bearing zone of the head to a 10.1 mm-wide, approximately approximately 11 mm-high array of 20-39 microm-wide, nearly parallel beams of synchrotron wiggler-generated radiation (mainly approximately 50-150 keV X-rays) that delivered 625 Gy peak skin doses at approximately approximately 211 microm ctc intervals in approximately approximately 300 ms either without additional treatments (MRT-only, 25 rats), with post-MRT GMIMPR (MRT+GMIMPR, 23 rats: multiple sc injections of irradiated (clonogenically-disabled) GM-CSF gene-transfected 9LGS cells), or with post-MRT IMPR (MRT+IMPR, 14 rats: multiple sc injections of irradiated (clonogenically-disabled) 9LGS cells. RESULTS: The median post-implantation survivals of rats in the MRT-only, MRT+GMIMPR and MRT+IMPR groups were over twice that of controls; further, approximately approximately 20% of rats in MRT-only and MRT+IMPR groups survived >1 yr with no obvious disabilities. Moreover, over 40% of MRT+GMIMPR rats survived >1 yr with no obvious disabilities, a significant (P<0.04) increase over the MRT-only and MRT+IMPR groups. SIGNIFICANCE: These data suggest that the combination of MRT+GMIMPR might be better than MRT only for unifocal CNS tumors, particularly in infants and young children.