Long-term Survival Of Mice Research Articles

Macitentan, a Dual Endothelin Receptor Antagonist, in Combination with Temozolomide Leads to Glioblastoma Regression and Long-term Survival in Mice.

The objective of the study was to determine whether astrocytes and brain endothelial cells protect glioma cells from temozolomide through an endothelin-dependent signaling mechanism and to examine the therapeutic efficacy of the dual endothelin receptor antagonist, macitentan, in orthotopic models of human glioblastoma. We evaluated several endothelin receptor antagonists for their ability to inhibit astrocyte- and brain endothelial cell-induced protection of glioma cells from temozolomide in chemoprotection assays. We compared survival in nude mice bearing orthotopically implanted LN-229 glioblastomas or temozolomide-resistant (LN-229(Res) and D54(Res)) glioblastomas that were treated with macitentan, temozolomide, or both. Tumor burden was monitored weekly with bioluminescence imaging. The effect of therapy on cell division, apoptosis, tumor-associated vasculature, and pathways associated with cell survival was assessed by immunofluorescent microscopy. Only dual endothelin receptor antagonism abolished astrocyte- and brain endothelial cell-mediated protection of glioma cells from temozolomide. In five independent survival studies, including temozolomide-resistant glioblastomas, 46 of 48 (96%) mice treated with macitentan plus temozolomide had no evidence of disease (P < 0.0001), whereas all mice in other groups died. In another analysis, macitentan plus temozolomide therapy was stopped in 16 mice after other groups had died. Only 3 of 16 mice eventually developed recurrent disease, 2 of which responded to additional cycles of macitentan plus temozolomide. Macitentan downregulated proteins associated with cell division and survival in glioma cells and associated endothelial cells, which enhanced their sensitivity to temozolomide. Macitentan plus temozolomide are well tolerated, produce durable responses, and warrant clinical evaluation in glioblastoma patients.

Mitochondria-targeted hydrogen sulfide donor AP39 improves neurological outcomes after cardiac arrest in mice

AimsMitochondria-targeted hydrogen sulfide donor AP39, [(10-oxo-10-(4-(3-thioxo-3H-1,2-dithiol-5yl)phenoxy)decyl) triphenylphosphonium bromide], exhibits cytoprotective effects against oxidative stress in vitro. We examined whether or not AP39 improves the neurological function and long term survival in mice subjected to cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). MethodsAdult C57BL/6 male mice were subjected to 8 min of CA and subsequent CPR. We examined the effects of AP39 (10, 100, 1000 nmol kg−1) or vehicle administered intravenously at 2 min before CPR (Experiment 1). Systemic oxidative stress levels, mitochondrial permeability transition, and histological brain injury were assessed. We also examined the effects of AP39 (10, 1000 nmol kg−1) or vehicle administered intravenously at 1 min after return of spontaneous circulation (ROSC) (Experiment 2). ROSC was defined as the return of sinus rhythm with a mean arterial pressure >40 mm Hg lasting at least 10 seconds. ResultsVehicle treated mice subjected to CA/CPR had poor neurological function and 10-day survival rate (Experiment 1; 15%, Experiment 2; 23%). Administration of AP39 (100 and 1000 nmol kg−1) 2 min before CPR significantly improved the neurological function and 10-day survival rate (54% and 62%, respectively) after CA/CPR. Administration of AP39 before CPR attenuated mitochondrial permeability transition pore opening, reactive oxygen species generation, and neuronal degeneration after CA/CPR. Administration of AP39 1 min after ROSC at 10 nmol kg−1, but not at 1000 nmol kg−1, significantly improved the neurological function and 10-day survival rate (69%) after CA/CPR. ConclusionThe current results suggest that administration of mitochondria-targeted sulfide donor AP39 at the time of CPR or after ROSC improves the neurological function and long term survival rates after CA/CPR by maintaining mitochondrial integrity and reducing oxidative stress.

Minimal ureagenesis is necessary for survival in the murine model of hyperargininemia treated by AAV-based gene therapy.

Hyperammonemia is less severe in arginase 1 deficiency compared with other urea cycle defects. Affected patients manifest hyperargininemia and infrequent episodes of hyperammonemia. Patients typically suffer from neurological impairment with cortical and pyramidal tract deterioration, spasticity, loss of ambulation, seizures, and intellectual disability; death is less common than with other urea cycle disorders. In a mouse model of arginase I deficiency, the onset of symptoms begins with weight loss and gait instability which progresses to development of tail tremor with seizure-like activity; death typically occurs at about two weeks of life. Adeno-associated viral vector gene replacement strategies result in long-term survival of mice with this disorder. With neonatal administration of vector, the viral copy number in the liver greatly declines with hepatocyte proliferation in the first 5 weeks of life. While the animals do survive, it is not known from a functional standpoint how well the urea cycle is functioning in the adult animals that receive adeno-associated virus. In these studies we administered [1-13C] acetate to both littermate controls and adeno-associated virus-treated arginase 1 knockout animals and examined flux through the urea cycle. Circulating ammonia levels were mildly elevated in treated animals. Arginine and glutamine also had perturbations. Assessment thirty minutes after acetate administration demonstrated that ureagenesis was present in the treated knockout liver at levels as low at 3.3% of control animals. These studies demonstrate that only minimal levels of hepatic arginase activity are necessary for survival and ureagenesis in arginase deficient mice and that this level of activity results in control of circulating ammonia. These results may have implications for potential therapy in humans with arginase deficiency.

Exploiting metabolic inhibition to eradicate residual tumors after chemo-immunotherapy

Cancer cells have long been known to exhibit metabolic reprogramming which involves a shift towards glycolysis. The enhanced glycolysis of cancer cells not only impose nutrient restriction in the tumor microenvironment, but also contribute to the acidic environment which is hostile to the invading anti-tumor immune cells. Hence, targeting the glycolysis dependency of tumor cells has been exploited for therapy. The glucose anti-metabolite, 2-deoxyglucose (2DG), a competitive inhibitor of glucose transport and glucose phosphorylation by hexokinase, has been extensively tested in various animal models and clinical trials. Although 2DG as anti-cancer agent showed a limited efficacy, its combined use with other treatment modalities, including chemotherapy and radiotherapy, has shown encouraging results. In particular, it has been shown that the combination of 2DG and cytotoxic agent etoposide resulted in enhanced antitumor immune responses, suggesting the therapeutic potential of combining chemotherapy, immunotherapy and glycolysis inhibition. We set out to study how metabolic inhibition alters the tumor microenvironment and how it can be utilized to augment the efficacy of chemo-immunotherapy. We found that glycolysis inhibition alone was detrimental to adoptive T-cell therapy (ACT). However, a rational combination of chemotherapy, ACT and 2DG led to tumor eradication and long-term survival in mice. The underlying mechanism of this synergy will be discussed.

Vitamin E-based micelles enhance the anticancer activity of doxorubicin

The purpose of this study was to develop vitamin E-based micelles loaded with Doxorubicin (DOX) (DOX–TOS–TPGS), taking advantages of the anti-cancer activity of vitamin E derivatives: Tocopherol succinate (TOS) and d-α-tocopherol polyethylene2000 succinate (TPGS). Therefore, we developed micelles consisting in a mixture of TOS (as solubilizer) and TPGS2000 (as stabilizer) (1:1). DOX–TOS–TPGS micelles exhibited a size of 78nm and a ζ potential of −7mV. High drug loading (40% w/w) was achieved. The critical micellar concentration was determined at 14μg/ml. In vitro, after 24h, DOX-TOS- TPGS micelles exhibited higher cytotoxicity than free-DOX (IC50 on MCF-7 cells, at 24h, 58 vs 5μg/ml). In vivo anti-tumor efficacy, performed on two tumor models (CT26 and MCF-7), demonstrated a 100% long-term survival of mice when treated with DOX–TOS–TPGS compared to DOX-free. Interestingly, the survival time of mice treated with unloaded TOS–TPGS micelles was similar to DOX-free, indicating an anti-cancer activity of vitamin E derivatives. Based on these results, it can be concluded that the formulations developed in this work may be considered as an effective DOX delivery system for cancer chemotherapy.

MiR-146a and miR-155 Delineate a MicroRNA Fingerprint Associated with Toxoplasma Persistence in the Host Brain

microRNAs were recently found to be regulators of the host response to infection by apicomplexan parasites. In this study, we identified two immunomodulatory microRNAs, miR-146a and miR-155, that were coinduced in the brains of mice challenged with Toxoplasma in a strain-specific manner. These microRNAs define a characteristic fingerprint for infection by type II strains, which are the most prevalent cause of human toxoplasmosis in Europe and North America. Using forward genetics, we showed that strain-specific differences in miR-146a modulation were in part mediated by the rhoptry kinase, ROP16. Remarkably, we found that miR-146a deficiency led to better control of parasite burden in the gut and most likely of early parasite dissemination in the brain tissue, resulting in the long-term survival of mice.

Analysis of acquired resistance to metronomic oral topotecan chemotherapy plus pazopanib after prolonged preclinical potent responsiveness in advanced ovarian cancer

An alternative or follow-up adjunct to conventional maximum tolerated dose (MTD) chemotherapy now in advanced phase III clinical trial assessment is metronomic chemotherapy--the close regular administration of low doses of drug with no prolonged breaks. A number of preclinical studies have shown metronomic chemotherapy can cause long term survival of mice with advanced cancer, including metastatic disease, in the absence of overt toxicity, especially when combined with targeted antiangiogenic drugs. However, similar to MTD chemotherapy acquired resistance eventually develops, the basis of which is unknown. Using a preclinical model of advanced human ovarian (SKOV-3-13) cancer in SCID mice, we show that acquired resistance can develop after terminating prolonged (over 3 months) successful therapy utilizing daily oral metronomic topotecan plus pazopanib, an oral antiangiogenic tyrosine kinase inhibitor (TKI). Two resistant sublines were isolated from a single mouse, one from a solid tumor (called KH092-7SD, referred to as 7SD) and another from ascites tumor cells (called KH092-7AS, referred to as 7AS). Using these sublines we show acquired resistance to the combination treatment is due to tumor cell alterations that confer relative refractoriness to topotecan. The resistant phenotype is heritable, associated with reduced cellular uptake of topotecan and could not be reversed by switching to MTD topotecan or to another topoisomerase-1 inhibitor, CPT-11, given either in a metronomic or MTD manner nor switching to another antiangiogenic drug, e.g. the anti-VEGFR-2 antibody, DC101, or another TKI, sunitinib. Thus, in this case cross resistance seems to exist between MTD and metronomic topotecan, the basis of which is unknown. However, gene expression profiling revealed several potential genes that are stably upregulated in the resistant lines, that previously have been implicated in resistance to various chemotherapy drugs, and which, therefore, may contribute to the drug resistant phenotype.

Lethal Giant Larvae 1 Tumour Suppressor Activity Is Not Conserved in Models of Mammalian T and B Cell Leukaemia

In epithelial and stem cells, lethal giant larvae (Lgl) is a potent tumour suppressor, a regulator of Notch signalling, and a mediator of cell fate via asymmetric cell division. Recent evidence suggests that the function of Lgl is conserved in mammalian haematopoietic stem cells and implies a contribution to haematological malignancies. To date, direct measurement of the effect of Lgl expression on malignancies of the haematopoietic lineage has not been tested. In Lgl1−/− mice, we analysed the development of haematopoietic malignancies either alone, or in the presence of common oncogenic lesions. We show that in the absence of Lgl1, production of mature white blood cell lineages and long-term survival of mice are not affected. Additionally, loss of Lgl1 does not alter leukaemia driven by constitutive Notch, c-Myc or Jak2 signalling. These results suggest that the role of Lgl1 in the haematopoietic lineage might be restricted to specific co-operating mutations and a limited number of cellular contexts.

Thymic Stromal Lymphopoeitin Signaling Contributes To Increased Risk Of Relapse Of Pediatric Acute Lympoblastic Leukemia Through Enhanced Survival Of Leukemic Cells That Overexpress Thymic Stromal Lymphopoeitin Receptor

Pediatric acute lymphoblastic leukemia (ALL) is the most common childhood malignancy. Although the cure rate for this disease is greater than 85%, ALL remains the number one cause of cancer-related deaths in children due to relapse of ALL. Therefore, there is a great need to identify new therapies for patients who have recurrent disease. Recently, a subset of pediatric ALL patients whose leukemic cells express high levels of thymic stromal lymphopoietin receptor (TSLPR/CRLF2) have been shown to have an increased risk of relapse and shorter disease free and poorer overall survival. Overexpression of TLSPR occurs in 8% of unscreened pediatric precursor B ALL and occurs by genomic rearrangement of the TSLPR gene, which fuses the unmutated TSLPR gene to altered transcriptional control or by other yet to be described means. The mechanism by which Thymic Stromal Lymphopoietin (TLSP) signaling contributes to increased risk of relapse is unknown. Studies have shown aberrant signaling in high TSLPR expressing ALL patient derived cell lines relying heavily on in vitro experiments. As no pre-clinical model of high TSLPR ALL has been published, we created a model of high TSLPR expressing leukemia to study TSLPR overexpressing leukemia progression. We have created a high TSLPR expressing leukemia cell line through retroviral transduction of a transplantable syngeneic mouse leukemia model in which the leukemic progression can be studied with physiologic levels of TSLP. This high TSLPR leukemia has levels of expression of TSLPR comparable to what is found on human leukemia that overexpress TSLPR. The TSLPR is functional in these cells and we see increased phosphorylation of STAT5 protein in response to IL-7 or TSLP stimulation. When we introduce the leukemia into mice and look at disease progression, we observed an 8 fold difference in the numbers of cells in the bone marrow 5 days after intravenous injection corresponding to an early stage of leukemia progression (Figure 1. high TSLPR 1.61%+/-0.95 vs. low TSLPR 0.20%+/-0.16). Interestingly we find no significant difference in long term survival of mice injected with either low or high TSLPR leukemia lines. The increased numbers of leukemic cells in the bone marrow at early stages of leukemic progression could be due to an increased rate of proliferation or better survival/engraftment. Low and high TSLPR expressing cells show no significant difference in growth rate in vitro or in vivo in dye dilution assays (Figure 2) suggesting that the increase in leukemic cells in the bone marrow is through enhanced survival. To test this, we treated low and high TSLPR leukemia lines with the steroid dexamethasone in the absence or presence of TSLP. We found that the addition of TSLP significantly reduced the Annexin V positive relative to cells not treated with TSLP in the high TSLP expressing leukemia cells, while in low TSLPR expressing cells we observed no decrease in Annexin V positive cells (Figure 3). This suggests that high TSLPR expression sensitizes leukemia cells to TSLP in the leukemia microenvironment. To confirm that this is the case we have found by gene expression analysis that we can detect TSLP in mouse bone marrow. We hypothesize that therapies targeting the TSLP signaling axis in ALL would decrease the risk of relapse. To test this hypothesis we have generated TSLPR-Fc conjugates to block TSLP signaling. We plan on using these reagents to block TSLP signaling to see if we can reverse the increased amounts of leukemia we find in mice at early stages of leukemic progression as well as the eliminate the survival advantage provided by TSLP to high TSLPR expressing leukemic cells in response to chemotherapeutic agents. [Display omitted] [Display omitted] [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Anti-PD-1 Blockade and Stereotactic Radiation Produce Long-Term Survival in Mice With Intracranial Gliomas

Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults, and radiation is one of the main treatment modalities. However, cure rates remain low despite best available therapies. Immunotherapy is a promising modality that could work synergistically with radiation, which has been shown to increase antigen presentation and promote a proinflammatory tumor microenvironment. Programmed-death-1 (PD-1) is a surface receptor expressed on activated and exhausted T cells, which mediate T cell inhibition upon binding with its ligand PD-L1, expressed on many tumor types including human GBMs. We tested the combination of anti-PD-1 immunotherapy with stereotactic radiosurgery in a mouse orthotopic GBM model. We performed intracranial implantation of mouse glioma cell line GL261 transfected with luciferase into C57BL/6 mice. Mice were stratified into 4 treatment groups: (1) control; (2) radiation only; (3) anti-PD-1 antibody only; and (4) radiation plus anti-PD-1 antibody. Overall survival was quantified. The mice were killed on day 21 after implantation to assess immunologic parameters in the brain/tumor, cervical lymph nodes, and spleen. Improved survival was demonstrated with combination anti-PD-1 therapy plus radiation compared with either modality alone: median survival was 25 days in the control arm, 27 days in the anti-PD-1 antibody arm, 28 days in the radiation arm, and 53 days in the radiation plus anti-PD-1 therapy arm (P<.05 by log-rank Mantle-Cox). Long-term survival was seen only in the combined treatment arm, with a fraction (15%-40%) of animals alive at day 180+ after treatment. Immunologic data on day 21 after implantation showed increased tumor infiltration by cytotoxic T cells (CD8+/interferon-γ+/tumor necrosis factor-α+) and decreased regulatory T cells (CD4+/FOXP3) in the combined treatment group compared with the single modality arms. The combination of PD-1 blockade and localized radiation therapy results in long-term survival in mice with orthotopic brain tumors. These studies provide strong preclinical evidence to support combination trials in patients with GBM.

Abstract 1544: Combined oncolytic virotherapy and immunotherapy for malignant mesothelioma

Abstract Introduction. Oncolytic viruses have therapeutic potential in cancer by selectively replicating within malignant cells and/or other cells in the tumor tissues, causing cell death. Vaccinia virus (VACV) with deletion of viral genes encoding for thymidine kinase and vaccinia growth factor and armed with a chemokine gene encoding CCL5 (vvDD-CCL5) has been previously shown to be safe and efficacious in a murine colon cancer model (Li J. et al., Mol Ther., 19: 650-7; 2011). Here we explored combination therapy with the use of this armed oncolytic virus and immunotherapy in a murine malignant mesothelioma model in syngeneic BALB/c mice. Methods. The viral replication and oncolysis was examined in murine AB12 mesothelioma cancer cells in vitro, and the combination of oncolytic virus, IL-2 and anti-CD25 and anti-CTLA4 antibodies, was investigated in vivo to treat a murine model of peritoneal malignant mesothelioma (PMM) derived from AB12 cells in BALB/c mice. Results. In vitro, vvCCL5 and its parental virus vvDD replicate well in AB12 cancer cells and lead to efficient cytotoxicity in these cancer cells. In vivo biodistribution analysis indicated that both viruses displayed highly tumor selective replication; however, vvDD-CCL5 replicated to a greater extent and displayed increased persistence in the tumor tissue. As a result, vvDD-CCL5 was more efficient than vvDD, working in a viral dose-dependent manner and leading to increased survival of tumor-bearing mice. Combination therapy of virus with antibodies against CD25 and CTLA4 and IL-2 was investigated. Clearly, this has been the best strategy to treat AB12 PMM, achieving the best long-term survival of mice. We are currently investigating its cellular and molecular mechanisms by this combination leading to tumor regression and long-term survival of mice. Conclusions: The chemokine gene-armed oncolytic virus (vvDD-CCL5) is effective in a PMM tumor model. The combination of this virus with an immunologic regimen of Treg depletion and IL-2 treatment has been demonstrated to be highly efficacious for PMM. Further understanding of its cellular and molecular mechanisms of this treatment strategy will facilitate the optimization of combined therapeutic regimens for PMM. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1544. doi:1538-7445.AM2012-1544

A Potent Vaccination Strategy That Circumvents Lymphodepletion for Effective Antitumor Adoptive T-cell Therapy

Adoptive cell therapy using tumor-reactive T lymphocytes is a promising approach for treating advanced cancer. Successful tumor eradication depends primarily on the expansion and survival of the adoptively transferred T cells. Lymphodepletion using total body irradiation (TBI) and administering high-dose interleukin (IL)-2 have been used with adoptive cell therapy to promote T-cell expansion and survival to achieve maximal therapeutic effects. However, TBI and high-dose IL-2 increase the risk for major complications that impact overall survival. Here we describe an alternative approach to TBI and high-dose IL-2 for optimizing adoptive cell therapy, resulting in dramatic therapeutic effects against established melanomas in mice. Administration of a potent, noninfectious peptide vaccine after adoptive cell therapy dramatically increased antigen-specific T-cell numbers leading to enhancement in the survival of melanoma-bearing mice. Furthermore, combinations of peptide vaccination with PD1 blockade or IL-2/anti-IL-2 antibody complexes led to complete disease eradication and long-term survival in mice with large tumors receiving adoptive cell therapy. Our results indicate that PD1 blockade and IL-2/anti-IL-2 complexes enhance both the quantitative and qualitative aspects of the T-cell responses induced by peptide vaccination after adoptive cell therapy. These findings could be useful for the optimization of adoptive cell therapy in cancer patients without the need of toxic adjunct procedures.

Long Term Survival of Mice with Hepatocellular Carcinoma after Pulse Power Ablation with Nanosecond Pulsed Electric Fields

Novel therapies are needed for treating hepatocellular carcinoma (HCC) without recurrence in a single procedure. In this work we evaluated anti-neoplastic effects of a pulse power ablation (PPA) with nanosecond pulsed electric fields (nsPEFs), a non-thermal, non-drug, local, regional method and investigated its molecular mechanisms for hepatocellular carcinoma tumor ablation in vivo. An ectopic tumor model was established using C57BL/6 mice with Hepa1-6 hepatocellular carcinoma cells. Pulses with durations of 30 or 100 ns and fast rise times were delivered by a needle or ring electrode with different electric field strengths (33, 50 and 68 kV/cm), and 900 pulses in three treatment sessions (300 pulses each session) or a single 900 pulse treatment. Treated and control tumor volumes were monitored by ultrasound and apoptosis and angiogenesis markers were evaluated by immunohistochemistry. Seventy five percent of primary hepatocellular carcinoma tumors were eradicated with 900 hundred pulses at 100 ns pulses at 68 kV/cm in a single treatment or in three treatment sessions without recurrence within 9 months. Using quantitative analysis, tumors in treated animals showed nsPEF-mediated nuclear condensation (3 h post-pulse), cell shrinkage (1 h), increases in active executioner caspases (caspase-3 > -7 > -6) and terminal deoxynucleotidyl transferase dUTP nick-end-labeling (1 h) with decreases in vascular endothelial growth factor expression (7d) and micro-vessel density (14d). NsPEF ablation eliminated hepatocellular carcinoma tumors by targeting two therapeutic sites, apoptosis induction and inhibition of angiogenesis, both important cancer hallmarks. These data indicate that PPA with nsPEFs is not limited to treating skin cancers and provide a rationale for continuing to investigate pulse power ablation for hepatocellular carcinoma using other models in pre-clinical applications and ultimately in clinical trials. Based on present treatments for specific HCC stages, it is anticipated that nsPEFs could be substituted for or used in combination with ablation therapies using heat, cold or chemicals.

P76. Imaging hematopoietic regeneration in real-time

Although we have learned a great deal about the phenotype and function of hematopoietic stem and progenitor cells, we have remained largely in the dark about the dynamic behavior of these cells in context of their native microenvironment. Here we describe a strategy that combines the use of transgenic mice with live microscopy to allow in vivo imaging of hematopoietic cell behavior in real time. The high spatial and temporal resolution of the system has allowed us to visualize the living hematopoietic tissue with exceptional clarity and track the architecture and dynamics of cell division, cell migration and cell death. Using this approach we have compared the kinetics of regeneration following two distinct forms of injury: chemotherapy and radiation. While chemotherapy led to a clear loss of hematopoietic cells, much of the microenvironment remained intact allowing for rapid recovery; in contrast, radiation exposure resulted in extensive destruction of both hematopoietic cells and the microenvironment, and was associated with delayed recovery. Imaging of the early events that occurred in each type of injury revealed an unexpected activation of myeloid cells in the bone marrow following chemotherapy, but not radiation. Importantly, ectopic delivery of these cells following radiation markedly enhanced both short-term hematopoietic recovery as well as long-term survival of mice receiving a limiting transplant dose, identifying myeloid cells as an important component of injury repair and regeneration. Thus, the development of this high-resolution in vivo imaging approach provides a unique view within the living organism and can be a powerful tool for gaining new insight into the regulation of fundamental biological processes such as homeostasis and regeneration.

Abstract 1931: Impact of bortezomib-induced proteasome inhibition in vivo on antitumor T cell responses

Abstract Inhibition of cellular proteasome function crucial for protein turn-over is a recent approach to overcome the resistance of tumors to cell death, a major clinical problem. Bortezomib (also known as Velcade/PS-341), a specific and reversible proteasome inhibitor, has been shown to sensitize some mouse and human tumors to apoptosis induced by the TNF-related apoptosis-inducing ligand (TRAIL) or its receptor (DR5) agonist monoclonal antibody (mAb). In established mouse renal cell (Renca) and breast (4T1) tumor models, the administration of DR5 agonist mAb to tumor-bearing mice pre-treated with bortezomib reduced experimental lung metastases. The combination of bortezomib and DR5 agonist mAb also significantly increased long-term survival of mice bearing Renca tumors compared with either agent alone. The therapeutic effects of bortezomib on tumor metastases and survival of tumor-bearing mice occurred in the absence of overt toxicity. However, little is known concerning the effects of bortezomib on specific immune responses. We thus analyzed the effects of proteasome inhibition on anti-tumor T cell responses in vivo. In mice with established Renca-HA tumor expressing influenza virus hemagglutinin (HA) as a surrogate tumor antigen, we evaluated the antigen-specific proliferation of adoptively transferred monoclonal HA-specific MHC class I or II restricted T cells following various schedules of bortezomib administration. No inhibition of T cell proliferation or cytolytic function in vivo was observed following bortezomib treatments. Nor was there any evidence of defective dendritic cell maturation in bortezomib-treated mice. However, a significant decrease in total T cell yield was noted in the tumor-draining LNs of mice treated with bortezomib. Thus, bortezomib-inhibitory effects on T cell responses seem quantitative rather than qualitative. The basis for this decrease in T cell number is under further investigation. The findings imply that, with an appropriate scheduling, it may be possible to combine bortezomib-induced sensitization of tumors to apoptosis with tumor-specific T cell immunotherapy regimens for increased therapeutic benefit in cancer. Funded in part by NCI Contract # N01-CO-12400 and HHSN261200800001E. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1931.

Anti-melanoma immunity promoted by cutaneous genetic immunizations requires agonistic signaling via the nerokinin-1 receptor (131.6)

Abstract In spite of initial enthusiasm provided by melanoma immunizations, the incidence of melanoma has increased in the past decade. To improve current melanoma vaccines is imperative that we understand the mechanisms involved in effective immunity to self-melanocyte Ags. The pro-inflammatory and immune functions of the skin are ideal for administration of cancer vaccines able to bias anti-tumor type-1 immunity. Pro-inflammatory neuropeptides that signal via the neurokinin-1 receptor (NK1R) expressed in skin cells, promote CD4+Th1 and CD8+Tc1 immunity to foreign Ag. Here, we analyzed the effects of signaling the NK1R during a skin genetic vaccination for melanoma. We utilized the gene gun to deliver plasmid DNA encoding murine TRP-2 with or without the NK1R agonist [Sar9Met O2)11]-SP (SarSP) to C57BL/6 mice. The need of the NK1R for anti-melanoma immunity was addressed by administration of our vaccine to NK1R-/- mice. GG immunizations in the presence of SarSP promoted TRP-2 immunity including short term-effector-, central- and effector- memory Th1 and CTLs resulting in the prevention of melanoma growth and long term survival of mice. Administration of TRP-2 vaccines to NK1R-/- mice showed an impaired ability to initiate anti-TRP-2 immunity. Our results shed light on the mechanisms involved in induction of self-Ag specific immune responses capable of overcoming tumor growth, and provide the foundation for the development of an effective melanoma vaccine.

Immunologic and Therapeutic Synergy of IL-27 and IL-2: Enhancement of T Cell Sensitization, Tumor-Specific CTL Reactivity and Complete Regression of Disseminated Neuroblastoma Metastases in the Liver and Bone Marrow

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

IL-21 Enhances Antitumor Responses without Stimulating Proliferation of Malignant T Cells of Patients with Sézary Syndrome

IL-21, a common gamma-chain cytokine secreted by activated CD4+ T cells, influences both humoral and cell-mediated immune responses through the regulation of T, B, dendritic, and natural killer (NK) cells. Sézary syndrome is an advanced form of cutaneous T-cell lymphoma, a clonally derived malignancy of CD4+ T cells that is characterized by profound defects in host cellular immune function. As a modulator of both innate and adaptive immune responses, IL-21 could play an important role in augmenting cell-mediated immunity in these patients. Normal donor and Sézary syndrome patient peripheral blood mononuclear cells were cultured with IL-21 and tested for CD8+ T- and NK-cell activation, NK-cell cytotoxicity, and tumor cell proliferation and apoptosis. IL-21 resulted in a modest increase in CD8+ T- and NK-cell activation, associated with a marked increase in cytolytic activity against both K562 and malignant CD4+ T-cell targets. Although IL-21 failed to demonstrate pro-apoptotic effects on the malignant CD4+ T cells, it is noteworthy that it had no demonstrable proliferative effects on these cells. Thus, IL-21 may play an important role in enhancing the host immune response of Sézary syndrome patients through the increased cytolytic activity of T and NK cells.

Modulation of NK cell activity by CpG oligodeoxynucleotides

Oligodeoxynucleotides (ODN) with hypomethylated CpG motifs have been found to be potent stimulators of various aspects of innate and adaptive immunity. One of their major effects is the activation of natural killer (NK) killing activity in vitro and in vivo. There are several categories of CpG classified as type A, type B, and type C, although another category with inhibitory activity is being characterized further. CpG type A (CpG-A) is the most potent at activating NK cells. Examination of the cells and soluble mediators involved in this activation has led to an understanding of an interesting cascade of events. It appears that CpG activates dendritic cells (DC) which in turn activate NK-cells. This is not surprising since NK-cells do not seem to express TLR9, the CpG receptor. Of the various cytokines involved in NK-cell activation, it appears that type 1 interferon plays a pivotal role. Having activated NK-cells, DC themselves appear to become susceptible to lysis by the NK-cells they activated but with a delayed time kinetic. CpG ODN have been examined as monotherapeutic agents in murine tumor models. In one model, B16 melanoma, CpG ODN were very effective and NK cells were both necessary and sufficient for that effect. In another model, EL4 lymphoma, NK cells were necessary but not sufficient. Moreover, CpG were able to induce long-term survival in mice with established tumor. Studies in humans show similar results with potent activation in vitro. In a limited Phase I dose escalation study it also appeared that CpG ODN induce NK cell activation in humans in vivo.

Proteasome inhibition promotes tumor cell apoptosis by exogenous TRAIL without blocking anti-tumor immune effectors in vivo (50.6)

Abstract The resistance of tumors to cell death poses a major clinical problem. Bortezomib (Velcade/PS-341), a specific and reversible proteasome inhibitor, sensitized renal (Renca) and mammary (4T1) mouse carcinomas to apoptosis induced by the TNF family ligand TRAIL or its receptor (DR5) agonist antibody. The molecular basis of the tumoritoxicity of the combination of bortezomib and TRAIL seemingly involved amplification of the extrinsic cell death pathway as increased expression of DR5, activation of caspase-8 and -3, and decreased apoptosis inhibitory proteins cFLIP, cIAP-1 and XIAP were observed in bortezomib-treated tumors. In an established tumor setting, anti-DR5 administration to mice pre-treated with bortezomib not only reduced lung metastases of Renca and 4T1 tumors but also significantly increased long-term survival in mice bearing Renca as compared to either agent alone. Encouragingly, no evidence of any overt tissue damage was noted in the treated mice. This provides the first experimental evidence that proteasome inhibition can be combined with DR5 agonist antibody for successful cancer therapy. Moreover, bortezomib administration 24 hours prior to adoptive transfer of T cells did not block their anti-tumor effector function. This suggests that tumor sensitization with bortezomib may also be combined with tumor-specific T cell immunotherapy of cancer. Funded in part by NCI contract N01-CO-12400.