Activation Of Tumor-specific CD8 Research Articles

Abstract 4062: A novel method for generating regulated cytokine therapeutics: Safety and activity of a conditionally active cLAG3-IL2 capable of delivering IL2 to LAG3+ cells while remaining inert on LAG3- cells

Abstract IL-2 is a powerful cytokine central to the generation of an effective immune response. However, its use in cancer immunotherapy has been limited by toxicities arising from its broad activity as well as the narrow patient population in which efficacy is seen. To address these limitations, many strategies have been pursued including IL-2 attenuation and targeting of IL-2 activity. These approaches, however, retain unacceptable toxicity and/or are not targeted to the appropriate cell populations. Using a novel approach that takes advantage of the ability of an antibody to bind specifically and competitively to two distinct antigens, we have generated a conditionally active cLAG3-IL2 therapeutic that targets IL-2 to LAG3+ cells while remaining inert on IL-2Rβγ+ cells lacking LAG3 expression, even at high treatment doses. As a marker of antigen-activated and tumor-specific T cells, LAG3 is an ideal target toward which to direct IL-2 activity. In vitro, using both reporter cell lines and receptor binding assays, the regulated cLAG3-IL2 demonstrates >100 fold difference in activity in the presence or absence of LAG3. In primary immune cells, regulated cLAG3-IL2 preferentially induces IL-2 cis-signaling in activated human LAG3+ CD8 T cells compared to LAG3- T cells. In mouse syngeneic tumor models, cLAG3-IL2 inhibits tumor growth while avoiding clinical signs of IL-2-mediated toxicity at doses well above the level where the non-regulated IL2 is toxic. Additionally, cLAG3-IL2 does not induce expansion of circulating LAG3- IL-2Rβγ+ cell populations, including NK cells and LAG3- T cells. In the TME, cLAG3-IL2 drives the expansion and activation of tumor-specific CD8+ T cells. Furthermore, cLAG3-IL2 demonstrates robust combinatorial activity with anti-PD1. These results demonstrate the strength of the Bonum platform, currently applied to multiple target/effector pairs including PD1, PDL1, ATP, LRRC15 and effectors IFNα, IL12 and TGFβ inhibition, and support the clinical development of our conditionally active cLAG3-IL2. Citation Format: Justin Killebrew, Shannon Okada, Lynn Amon, David Bienvenue, Laura Carlucci, David Colby, Wendy Curtis, Kendyl Daniels, Alton Etheridge, Zane Kraft, Jamie Nguyen, Sandra Notonier, Jacqueline Pham, Megan Sprague, Kerri Thomas, Diane Hollenbaugh, John Mulligan. A novel method for generating regulated cytokine therapeutics: Safety and activity of a conditionally active cLAG3-IL2 capable of delivering IL2 to LAG3+ cells while remaining inert on LAG3- cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4062.

Intratumoral delivery of a highly active form of XCL1 enhances antitumor CTL responses through recruitment of CXCL9-expressing conventional type-1 dendritic cells.

Conventional type 1 dendritic cells (cDC1s) play a crucial role in antitumor immunity through the induction and activation of tumor-specific CD8+ cytotoxic T cells (CTLs). The chemokine XCL1 is a major chemotactic factor for cDC1s and its receptor XCR1 is selectively expressed on cDC1s. Here, we investigated the effect of intratumoral delivery of a highly active form of murine XCL1 (mXCL1-V21C/A59C) on cDC1-mediated antitumor immunity using a hydrophilic gel patch. The hydrophilic gel patch containing mXCL1-V21C/A59C increased cDC1 accumulation in the tumor masses and promoted their migration to the regional lymph nodes, resulting in enhanced induction of tumor-specific CTLs. Tumor-infiltrating cDC1s not only expressed XCR1 but also produced CXCL9, a ligand for CXCR3 which is highly expressed on CTLs and NK cells. Consequently, CTLs and NK cells were increased in the tumor masses of mice treated with mXCL1-V21C/A59C, while immunosuppressive cells such as monocyte-derived suppressive cells and regulatory T cells were decreased. We also confirmed that anti-CXCL9 treatment decreased the tumor infiltration of CTLs. The intratumoral delivery of mXCL1-V21C/A59C significantly decreased tumor growth and prolonged survival in E.G7-OVA and B16-F10 tumor-bearing mice. Furthermore, the antitumor effect of mXCL1-V21CA59C was enhanced in combination with anti-programmed cell death protein 1 treatment. Finally, using The Cancer Genome Atlas database, we found that XCL1 expression was positively correlated with tumor-infiltrating cDC1s and a better prognosis in melanoma patients. Collectively, our findings provide a novel therapeutic approach to enhance tumor-specific CTL responses through the selective recruitment of CXCL9-expressing cDC1s into the tumor masses.

Sema6D forward signaling impairs T cell activation and proliferation in head and neck cancer.

Immune checkpoint inhibitors (ICIs) are indicated for a diverse range of cancer types, and characterizing the tumor immune microenvironment is critical for optimizing therapeutic strategies, including ICIs. T cell infiltration and activation status in the tumor microenvironment greatly affects the efficacy of ICIs. Here, we show that semaphorin 6D (Sema6D) forward signaling, which is reportedly involved in coordinating the orientation of cell development and migration as a guidance factor, impaired the infiltration and activation of tumor-specific CD8+ T cells in murine oral tumors. Sema6D expressed by nonhematopoietic cells was responsible for this phenotype. Plexin-A4, a receptor for Sema6D, inhibited T cell infiltration and partially suppressed CD8+ T cell activation and proliferation induced by Sema6D stimulation. Moreover, mouse oral tumors, which are resistant to PD-1-blocking treatment in wild-type mice, showed a response to the treatment in Sema6d-KO mice. Finally, analyses of public data sets of human head and neck squamous cell carcinoma, pan-cancer cohorts, and a retrospective cohort study showed that SEMA6D was mainly expressed by nonhematopoietic cells such as cancer cells, and SEMA6D expression was significantly negatively correlated with CD8A, PDCD1, IFNG, and GZMB expression. Thus, targeting Sema6D forward signaling is a promising option for increasing ICI efficacy.

Selective Agonism of Intermediate-Affinity IL-2 Receptor Promotes Systemic Antitumor Responses in Combination with Radiotherapy in Metastatic Lung Cancer

<h3>Purpose/Objective(s)</h3> For immune checkpoint inhibitor-resistant patients, adding interleukin-2 (IL-2) may aid antitumor responses by stimulating effector T cells and NK cells. Unfortunately, high-dose IL-2 therapy has limited clinical utility due to adverse events and stimulation of immunosuppressive regulatory T cells (T_regs). Nemvaleukin alfa (nemvaleukin) is a novel engineered cytokine that selectively binds to the intermediate-affinity IL-2 receptor, preferentially activating and expanding antitumor CD8⁺ T and NK cells, with minimal expansion of T_regs. Thus, Nemvaleukin may be beneficial in combination with radiation therapy (RT) and immunotherapy. This study aimed to evaluate the antitumor activity and mechanism of action of the combination of RDB 1462 (the murine ortholog of Nemvaleukin, a.k.a. mNemvaleukin), RT, and immunotherapy in multiple mouse tumor models. <h3>Materials/Methods</h3> In a bilateral 344SQ lung adenocarcinoma murine model, primary tumors were treated with high-dose RT (HDRT; 12 Gy per fraction for 3 fractions), and secondary tumors were observed for evidence of abscopal effects. In another model for low absolute lymphocyte count (ALC), we used 2 Gy total body irradiation (TBI) three days before HDRT and RDB 1462. In a third MC38-gp100 mouse model, tumors were irradiated with low-dose RT (LDRT; 3 fractions of 1 Gy each) followed by pmel-1 T cell infusion after 24 hours, and RDB 1462 administration 12 hours thereafter. We performed immune phenotyping by flow cytometry; analyzed 770 immune-related genes using a multiplex analysis platform; also performed T cell receptor (TCR) repertoire analysis. Serum pro-inflammatory cytokine markers were analyzed by 23-plex kit. <h3>Results</h3> In 344SQ-parental lung adenocarcinoma, we combined HDRT with escalating doses of RDB 1462 at various timepoints, resulting in significant tumor reduction in both irradiated and unirradiated (abscopal) tumors compared with HDRT or RDB 1462 therapy alone. HDRT+RDB 1462 increased the numbers and activity of tumor-specific CD8⁺ T cells, NK cells, and memory T cells without drastically increasing T_regs, as evidenced by peripheral and tumor-infiltrating immune phenotypic and functional analyses. T cells showed increased receptor clonality and diversity in groups receiving HDRT+RDB 1462. The addition of anti-PD-1 to HDRT+RDB 1462 further increased antitumor control of both irradiated and abscopal tumors, reduced lung metastases, and prolonged survival. The antitumor effects of HDRT and RDB 1462 persisted even in mice with low ALC. The addition of LDRT contributed to increased tumor-specific T cells that were expanded by RDB 1462 with increased infiltration of Thy1.1⁺ CD8⁺ T cells. <h3>Conclusion</h3> The addition of Nemvaleukin therapy may enhance responses to RT alone and in combination with anti-PD-1 or adoptive T cell therapy.

TIM4 expression by dendritic cells mediates uptake of tumor-associated antigens and anti-tumor responses

Acquisition of cell-associated tumor antigens by type 1 dendritic cells (cDC1) is essential to induce and sustain tumor specific CD8+ T cells via cross-presentation. Here we show that capture and engulfment of cell associated antigens by tissue resident lung cDC1 is inhibited during progression of mouse lung tumors. Mechanistically, loss of phagocytosis is linked to tumor-mediated downregulation of the phosphatidylserine receptor TIM4, that is highly expressed in normal lung resident cDC1. TIM4 receptor blockade and conditional cDC1 deletion impair activation of tumor specific CD8+ T cells and promote tumor progression. In human lung adenocarcinomas, TIM4 transcripts increase the prognostic value of a cDC1 signature and predict responses to PD-1 treatment. Thus, TIM4 on lung resident cDC1 contributes to immune surveillance and its expression is suppressed in advanced tumors.

Metabolic stress in cancer cells induces immune escape through a PI3K-dependent blockade of IFN\u03b3 receptor signaling

BackgroundT-cell mediated immunotherapy brought clinical success for many cancer patients. Nonetheless, downregulation of MHC class I antigen presentation, frequently occurring in solid cancers, limits the efficacy of these therapies. Unraveling the mechanisms underlying this type of immune escape is therefore of great importance. We here investigated the immunological effects of metabolic stress in cancer cells as a result of nutrient deprivation.MethodsTC1 and B16F10 tumor cell lines were cultured under oxygen- and glucose-deprivation conditions that mimicked the tumor microenvironment of solid tumors. Presentation of peptide antigens by MHC class I molecules was measured by flow cytometry and via activation of tumor-specific CD8 T cell clones. The proficiency of the IFNy-STAT1 pathway was investigated by Western blots on phosphorylated proteins, transfection of constitutive active STAT1 constructs and qPCR of downstream targets. Kinase inhibitors for PI3K were used to examine its role in IFNy receptor signal transduction.ResultsCombination of oxygen- and glucose-deprivation resulted in decreased presentation of MHC class I antigens on cancer cells, even in the presence of the stimulatory cytokine IFNy. This unresponsiveness to IFNy was the result of failure to phosphorylate the signal transducer STAT1. Forced expression of constitutive active STAT1 fully rescued the MHC class I presentation. Furthermore, oxygen- and glucose-deprivation increased PI3K activity in tumor cells. Pharmacological inhibition of this pathway not only restored signal transduction through IFNy-STAT1 but also improved MHC class I presentation. Importantly, PI3K inhibitors also rendered tumor cells sensitive for recognition by CD8 T cells in culture conditions of metabolic stress.ConclusionsThese data revealed a strong impact of metabolic stress on the presentation of tumor antigens by MHC class I and suggest that this type of tumor escape takes place at hypoxic areas even during times of active T cell immunity and IFNy release.

Photochemical Internalization of Peptide Antigens Provides a Novel Strategy to Realize Therapeutic Cancer Vaccination.

Effective priming and activation of tumor-specific CD8+ cytotoxic T lymphocytes (CTLs) is crucial for realizing the potential of therapeutic cancer vaccination. This requires cytosolic antigens that feed into the MHC class I presentation pathway, which is not efficiently achieved with most current vaccination technologies. Photochemical internalization (PCI) provides an emerging technology to route endocytosed material to the cytosol of cells, based on light-induced disruption of endosomal membranes using a photosensitizing compound. Here, we investigated the potential of PCI as a novel, minimally invasive, and well-tolerated vaccination technology to induce priming of cancer-specific CTL responses to peptide antigens. We show that PCI effectively promotes delivery of peptide antigens to the cytosol of antigen-presenting cells (APCs) in vitro. This resulted in a 30-fold increase in MHC class I/peptide complex formation and surface presentation, and a subsequent 30- to 100-fold more efficient activation of antigen-specific CTLs compared to using the peptide alone. The effect was found to be highly dependent on the dose of the PCI treatment, where optimal doses promoted maturation of immature dendritic cells, thus also providing an adjuvant effect. The effect of PCI was confirmed in vivo by the successful induction of antigen-specific CTL responses to cancer antigens in C57BL/6 mice following intradermal peptide vaccination using PCI technology. We thus show new and strong evidence that PCI technology holds great potential as a novel strategy for improving the outcome of peptide vaccines aimed at triggering cancer-specific CD8+ CTL responses.

A gene therapy model to treat liver-implanted tumors.

An expression vector based on the Semliki Forest Virus (SFV), an alpha virus replicating in the cytoplasm of infected cells originally discovered in the Semliki Forest in Uganda, was developed to express interleukin 12 (IL-12) and SVF-IL-12 were shown to induce potent antitumor response against liver implanted colon tumor cells in immunocompetent mice in a recent study by Jose I. Quetglas and co-investigators [J. I. Quetglas, et. al, J. of Immunology 2013]. The researchers reported that the tumor-specific CD 8+ T cells in responder mice persisted at greater numbers and for a long period of time while maintaining enhanced effector functions in contrast to those of non-responder animals. The long-lasting persistence and activity of tumor-specific CD8+ T cells from responder mice might be mediated by the production of IFN-alpha by cells infected by SFV as the replication of this virus can induce type I IFN response. We proposed a mathematical model based on a set of ordinary differential equations with an attempt to describe the SFV-IL-12 antitumor efficacy. The project was supported by NIH Grant P20GM103434 to the West Virginia IDeA Network for Biomedical Research Excellence and the West Virginia Higher Education Policy Commission Division of Science and Research SURE Grant Program.

Abstract 5020: Cooperative effects of programmed cell death-1 blockade and radiation in a model of a poorly immunogenic breast carcinoma

Abstract We have previously shown that radiation therapy (RT) converts poorly immunogenic tumors resistant to antibodies (mAbs) against the checkpoint receptor CTLA-4 into susceptible ones. Importantly, RT induced the upregulation of PDL-1 and PDL-2 on the tumor cells and infiltrating myeloid cells in the TSA mouse breast cancer, suggesting that PD-1 ligands may limit rejection of the irradiated tumor by T cells. PD-1 is a checkpoint receptor upregulated on T cells shortly after activation and expressed at high levels on exhausted T cells. To test the hypothesis PD-1 blockade can promote the ability of RT to induce effective anti-tumor immunity we employed BALB/c mice inoculated s.c. with the syngeneic poorly immunogenic TSA breast cancer cells. When tumors became palpable mice were randomly assigned to one of 4 treatment groups (N=6-7): (1) control, (2) RT, (3) anti-PD-1 mAb and (4) RT+anti-PD-1 mAb. RT was delivered exclusively to the primary tumor in 8 Gy fractions on days 13, 14 and 15 post tumor inoculation. PD-1 blocking mAb RMP1-14 was given on day 15 and every 4 days thereafter, and mice were followed for tumor growth. In a separate experiment, mice were euthanized on day 20 to characterize tumor-infiltrating lymphocytes (TILs) and development of CD8+ T cells specific for the tumor epitope AH1 by pentamer analysis. TSA tumors were resistant to PD-1 blockade. RT significantly delayed tumor growth (p&amp;lt;0.01), but tumor regression was seen only in 1 of 6 mice. In contrast, when RT was combined with anti-PD-1 mAb, all of the mice completely rejected tumors by day 25. AH1-specific CD8+ T-cells were markedly increased (5.5%) in the spleen of mice treated with RT+anti-PD-1 compared to control (1.7%) and anti-PD-1 (1.9%) or RT (3.7%) treated mice (p&amp;lt;0.01). Analysis of TILs showed a significant increase in mice treated with RT compared to control in CD8+ T cells expressing high levels of PD-1 (CD8+PD-1hi) (67% versus 36%, p&amp;lt;0.01), as detected by a mAb non-cross-reactive with RMP1-14. Interestingly, in mice receiving anti-PD-1 mAb there was a significant decrease in CD8+PD-1hi (14% RMP1-14 versus 36% control, p&amp;lt;0.01; and 30% RT+RMP1-14 versus 67% RT, p&amp;lt;0.01). In contrast, CD8+ T cells expressing activation markers CD69 and CD137 and low levels of PD-1 were increased significantly in the tumors of mice treated with RT (64%) compared to control (42%) (p&amp;lt;0.001) irrespective of the treatment with anti-PD-1. Overall, data suggest that the IgG2a anti-PD-1 mAb RMP1-14 selectively depletes CD8+PD-1hi TILs, possibly by ADCC, while enhancing the RT-elicited priming and activation of tumor-specific CD8+ T cells. We propose that this represents a novel mechanism of anti-tumor activity of anti-PD-1 mAb and supports testing its combination with radiotherapy. Supported by the Breast Cancer Alliance (Exceptional Project Award). Citation Format: Karsten Pilones, Joseph Aryankalayil, Silvia Formenti, Sandra Demaria. Cooperative effects of programmed cell death-1 blockade and radiation in a model of a poorly immunogenic breast carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5020. doi:10.1158/1538-7445.AM2014-5020

Inactivation of tumor‐specific CD8+ CTLs by tumor‐infiltrating tolerogenic dendritic cells

Cancer immunosurveillance failure is largely attributed to the insufficient activation of tumor-specific class I major histocompatibility complex (MHC) molecule (MHC-I)-restricted CD8+ cytotoxic T lymphocytes (CTLs). DEC-205+ dendritic cells (DCs), having the ability to cross-present, can present captured tumor antigens on MHC-I alongside costimulatory molecules, inducing the priming and activation of tumor-specific CD8+ CTLs. It has been suggested that reduced levels of costimulatory molecules on DCs may be a cause of impaired CTL induction and that some tumors may induce the downregulation of costimulatory molecules on tolerogenic DCs. To examine such possibilities, we established two distinct types of murine hepatoma cell lines, named Hepa1-6-1 and Hepa1-6-2 (derived from Hepa1-6 cells), and confirmed that they display similar antigenicities, as well as identical surface expression of MHC-I. We found that Hepa1-6-1 had the ability to grow continuously after subcutaneous implantation into syngeneic C57BL/6 mice and did not prime CD8+ CTLs. In contrast, Hepa1-6-2 cells, which display reduced levels of adhesion molecules, such as Intercellular Adhesion Molecule 1 (ICAM-1), failed to grow in vivo and efficiently primed CTLs. Moreover, Hepa1-6-1-derived factors, such as transforming growth factor (TGF)-β1, vascular endothelial growth factor (VEGF) and α-fetoprotein (AFP), converted CD11chigh MHC-IIhigh DEC-205+ DC subsets into tolerogenic cells, displaying downregulated costimulatory molecules and having impaired cross-presenting capacities. These immunosuppressive tolerogenic DCs appeared to inhibit the induction of tumor-specific CD8+ CTLs and suppress their cytotoxic functions within the tumor. Together, the findings presented here provide a new method of cancer immunotherapy using the selective suppression, depletion or alteration of immunosuppressive tolerogenic DCs within tumors.

A novel iNKT cell-mediated vaccine maneuver induces potent long-lasting anti-tumor immunity for advanced prostate cancer by boosting CD8+T cell memory and function (53.24)

Abstract iNKT cells have considerable therapeutic promise in cancer, but so far this has not been fully realized. At issue has been delivering iNKT ligand and tumor Ag to the same APC for optimal processing and presentation. Also, although tumor-infiltrating APCs express CD1d in both prostate cancer (PCa) models and patients, tumor induced tolerance and suppression leads to defective iNKT activation. Whole-cell tumor vaccines represent a promising treatment approach and prevent tumor progression in multiple models of cancer. Here, we use an optimized approach consisting of alpha-galactosylceramide (aGalCer) and the GM-CSF-based PCa vaccine, ‘GVax’ combined with IL-12. This approach was capable of breaking tumor-induced tolerance and causing dramatic and substantial tumor regression and survival in large advanced prostate tumors in TRAMP mice. Remarkably, 10/12 vaccinated &amp;gt;9 month old mice rejected tumors, 'breaking tolerance', even at this late stage of tumor growth. The vaccine induced strong immune responses capable of reversing INKT defects in tumor-bearing mice as well as in patient iNKT in vitro. Both IL-12 and aGalCer were crucial for this response. Vaccinated mice had higher levels and activation of tumor-specific CD8 T, CD4 T and iNKT cells, and greater memory CD8 T cell expansion capable of producing the effector cytokines IFN-γ and TNF-α in response to tumor. These studies shed light on how whole cell vaccines targeting iNKTs can be utilized in PCa immunotherapy.

Regulation of Secondary Antigen-Specific CD8+ T-Cell Responses by Natural Killer T Cells

The physiologic function of natural killer T (NKT) cells in adaptive immunity remains largely unknown because most studies have used NKT cell agonists. In the present study, the role of NKT cells during the secondary effector phase was investigated separately from the primary immunization phase via adoptive transfer of differentiated effector T cells into naive recipients. We found that secondary antitumor CD8(+) T-cell responses were optimal when NKT cells were present. Tumor-specific CD8(+) effector T cells responded less strongly to tumor cell challenge in NKT cell-deficient recipients than in recipients with intact NKT cells. NKT cell-mediated enhancement of the secondary antitumor CD8(+) T-cell response was concurrent with increased number and activity of tumor-specific CD8(+) T cells. These findings provide the first demonstration of a direct role for NKT cells in the regulation of antigen-specific secondary T-cell responses without the use of exogenous NKT cell agonists such as alpha-galactosylceramide (alpha-GalCer). Furthermore, forced activation of NKT cells with alpha-GalCer during the secondary immune response in suboptimally immunized animals enhanced otherwise poor tumor rejection responses. Taken together, our findings strongly emphasize the importance of NKT cells in secondary CD8(+) T-cell immune responses.

Photodynamic Therapy Elicited Adaptive Immunity is Critically Dependent on IL-17 Bioactivity (41.56)

Abstract Photodynamic therapy (PDT) is a FDA-approved local cancer treatment of early stages of cancer and palliation of advanced disease. A hallmark of PDT is the induction of acute local inflammation characterized by increased infiltration of innate immune cells into the treated tumor bed, which is dominated by CD11b+Ly-6GhiF4/80- leukocytes that morphologically resemble neutrophils. We have previously shown that enhanced anti-tumor CD8+ T cell activation following PDT is dependent upon the presence of CD11b+Ly-6GhiF4/80- leukocytes in the tumor and tumor draining lymph nodes (TDLNs). We now show that PDT promotes the differential expression of IL-23 and IL-17 within the treated tumor bed. Blocking the action of IL-17 using IL-17RA-/- mice does not diminish bone marrow release of CD11b+Ly-6GhiF4/80- leukocytes or their migration to the tumor post PDT but does abrogate accumulation of these cells in the TDLN. Furthermore, blocking IL-17 inhibits post-PDT activation of tumor specific CD8+ T cells. These findings suggest that IL-17 differentially regulates CD11b+Ly-6GhiF4/80- leukocyte migration and indicates that CD11b+Ly-6GhiF4/80- leukocyte accumulation in the TDLN is critical for induction of T cell activation. Neutrophils are capable of informing and shaping the immune response by influencing DC, monocyte, and lymphocyte activation. Understanding this behavior of neutrophils holds promise for the rationale design of PDT regimens to optimally enhance anti-tumor immunity in a clinical setting.

Human leukocyte elastase counteracts matrix metalloproteinase-7 induced apoptosis resistance of tumor cells

Matrix metalloproteinase-7 (MMP-7/Matrilysin) is a component of the tumor microenvironment associated with malignant progression. Its expression in tumors protects tumor cells from CD95-mediated apoptosis and the cytotoxic activity of tumor specific CD8 + T cells. In the present study, we show that human leukocyte elastase (HLE) secreted by polymorphonuclear leukocytes cleaves MMP-7 resulting in loss of enzymatic activity. The anti-apoptotic effect of MMP-7 is reduced in the presence of HLE for CD95-, doxorubicin- and CTL-mediated apoptosis. Our data indicates that HLE may be a natural inactivator of MMP-7 which can counteract MMP-7-induced apoptosis resistance.

Vaccine-Stimulated, Adoptively Transferred CD8+ T Cells Traffic Indiscriminately and Ubiquitously while Mediating Specific Tumor Destruction

It has been suggested that antitumor T cells specifically traffic to the tumor site, where they effect tumor destruction. To test whether tumor-reactive CD8(+) T cells specifically home to tumor, we assessed the trafficking of gp100-specific pmel-1 cells to large, vascularized tumors that express or do not express the target Ag. Activation of tumor-specific CD8(+) pmel-1 T cells with IL-2 and vaccination with an altered peptide ligand caused regression of gp100-positive tumors (B16), but not gp100-negative tumors (methylcholanthrene 205), implanted on opposing flanks of the same mouse. Surprisingly, we found approximately equal and very large numbers of pmel-1 T cells (>25% of all lymphocytes) infiltrating both Ag-positive and Ag-negative tumors. We also found evidence of massive infiltration and proliferation of activated antitumor pmel-1 cells in a variety of peripheral tissues, including lymph nodes, liver, spleen, and lungs, but not peripheral blood. Most importantly, evidence for T cell function, as measured by production of IFN-gamma, release of perforin, and activation of caspase-3 in target cells, was confined to Ag-expressing tumor. We thus conclude that CD8(+) T cell-mediated destruction of tumor is the result of specific T cell triggering at the tumor site. The ability to induce ubiquitous homing and specific tumor destruction may be important in the case of noninflammatory metastatic tumor foci.

Murine Melanomas Expressing High Levels of SDF-1 Repel and Escape Control by Tumor Specific T-Cells.

Most antigenic tumors are able to evade the immune system despite T cell recognition of tumor specific antigens. The chemokine, stromal derived factor- 1 (SDF-1 or CXCL12) is constitutively expressed by both normal and neoplastic tissues and is involved in tumor growth, metastasis and modulation of the anti-tumor immune response. We have previously shown that human T cells are repelled by the chemokine SDF-1, in a concentration-dependent and CXCR4 receptor-mediated manner. We proposed that the repulsion of tumor-specific T cells from a tumor expressing SDF-1 may represent a novel mechanism of immune evasion. B16 melanoma cells stably expressing OVA were genetically modified to constitutively express SDF-1 using a bicistronic MSCV2.2 retroviral transfer vector encoding murine SDF-1α and EGFP. SDF-1 generated by transduced cells was 58 ± 28.5 ng/ml/1x106 cells/24 hours as measured by ELISA. Immunization of mice with irradiated B16/OVA cells lead to destruction of B16/OVA.MSCV control tumors but not tumors expressing high levels of SDF-1 (p=0.0001). Failure to reject B16/OVA.SDF-1 tumors was associated with a reduction of T cell infiltration compared to control B16/OVA.MSCV (p=0.001). Similarly, early recruitment of adoptively-transferred OVA-specific CD8+ T cells into B16/OVA.SDF-1 tumors was significantly reduced in comparison to B16/OVA.MSCV control tumors as demonstrated by immunohistochemistry and real-time magnetic resonance imaging of nanoparticle labeled CTLs (p=0.018). Transferred memory OVA-specific CD8+ T-cells demonstrated antitumor activity against B16/OVA.MSCV control tumors but not against B16/OVA-SDF-1 tumors (p=0.04). Isolation and FACS analysis of tumor-infiltrating lymphocytes showed a 4-fold reduction of T cells in B16/OVA.SDF-1 compared to B16/OVA.MSCV control tumors (p=0.005). The in-vitro killing activity of tumor specific CD8+ T cells against B16/OVA.SDF-1 tumors was significantly reduced compared to B16/OVA.MSCV control tumors when measured in 51Cr release assay performed in a flat-bottom well system where cytotoxicity was dependent on effector cell migration (p=0.0004). Preincubation of OT-I CD8+ T cells with the CXCR4 antagonist AMD3100 restored their cytolytic activity against B16/OVA.SDF-1 cells (p=0.045). These data support the thesis that the active movement of tumor-specific T cells away from SDF-1, termed fugetaxis, may provide a novel mechanism by which a tumor evades challenge by immune effector cells and raises the possibility of the development of a novel immunotherapeutic approach to cancer.