Human SCID Mouse Model Research Articles

Inhibition of growth of Asian keloid cells with human umbilical cord Wharton\u2019s jelly stem cell-conditioned medium

BackgroundKeloid formation occurs in Caucasian, African, and Asian populations and is a severe psychosocial burden on patients. There is no permanent treatment for this problem as its pathogenesis is not properly understood. Furthermore, differences in keloid behavior between ethnic groups are not known. It has been hypothesized that keloids behave like benign tumors because of their uncontrolled growth. The present study evaluated the tumoricidal properties of human Wharton’s jelly stem cell-conditioned medium (hWJSC-CM) on fresh Asian keloid cells (AKCs).MethodsHuman Wharton’s jelly stem cells (hWJSCs) and AKCs were isolated based on our previous methods. hWJSCs and human skin fibroblasts (HSF) (controls) were used to collect hWJSC-CM and HSF-conditioned medium (HSF-CM). AKCs were treated with hWJSC-CM and HSF-CM in vitro and in vivo in a human keloid xenograft SCID mouse model. The inhibitory effect of hWJSC-CM on AKCs was tested in vitro using various assays and in vivo for attenuation/abrogation of AKC tumors created in a xenograft mouse model.ResultsqRT-PCR analysis showed that the genes FN1, MMP1, and VCAN were significantly upregulated in AKCs and ANXA1, ASPN, IGFBP7, LGALS1, and PTN downregulated. AKCs exposed to hWJSC-CM in vitro showed significant decreases in cell viability and proliferation, increases in Annexin V-FITC+ cell numbers, interruptions of the cell cycle at Sub-G1 and G2/M phases, altered CD marker expression, downregulated anti-apoptotic-related genes, and upregulated pro-apoptotic and autophagy-related genes compared to controls. When AKCs were administered together with hWJSC-CM into immunodeficient mice there were no keloid tumors formed in 7 mice (n = 10) compared to the untreated control mice. When hWJSC-CM was injected directly into keloid tumors created in mice there were significant reductions in keloid tumor volumes and weights in 30 days.ConclusionshWJSC-CM inhibited the growth of AKCs in vitro and in xenograft mice, and it may be a potential novel treatment for keloids in the human. The specific molecule(s) in hWJSC-CM that induce the anti-keloid effect need to be identified, characterized, and tested separately in larger preclinical and clinical studies.

An Efficient Photodynamic Therapy Treatment for Human Pancreatic Adenocarcinoma.

To date, pancreatic adenocarcinoma (ADKP) is a devastating disease for which the incidence rate is close to the mortality rate. The survival rate has evolved only 2–5% in 45 years, highlighting the failure of current therapies. Otherwise, the use of photodynamic therapy (PDT), based on the use of an adapted photosensitizer (PS) has already proved its worth and has prompted a growing interest in the field of oncology. We have developed a new photosensitizer (PS-FOL/PS2), protected by a recently published patent (WO2019 016397-A1, 24 January 2019). This photosensitizer is associated with an addressing molecule (folic acid) targeting the folate receptor 1 (FOLR1) with a high affinity. Folate binds to FOLR1, in a specific way, expressed in 100% of ADKP or over-expressed in 30% of cases. The first objective of this study is to evaluate the effectiveness of this PS2-PDT in four ADKP cell lines: Capan-1, Capan-2, MiapaCa-2, and Panc-1. For this purpose, we first evaluated the gene and protein expression of FOLR1 on four ADKP cell lines. Subsequently, we evaluated PS2’s efficacy in our cell lines and we assessed the impact of PDT on the secretome of cancer cells and its impact on the immune system. Finally, we evaluate the PDT efficacy on a humanized SCID mouse model of pancreatic cancer. In a very interesting way, we observed a significant increase in the proliferation of activated-human PBMC when cultured with conditioned media of ADKP cancer cells subjected to PDT. Furthermore, to evaluate in vivo the impact of this new PS, we analyzed the tumor growth in a humanized SCID mice model of pancreatic cancer. Four conditions were tested: Untreated, mice (nontreated), mice with PS (PS2), mice subjected to illumination (Light only), and mice subjected to illumination in the presence of PS (PDT). We noticed that the mice subjected to PDT presented a strong decrease in the growth of the tumor over time after illumination. Our investigations have not only suggested that PS2-PDT is an effective therapy in the treatment of PDAC but also that it activates the immune system and could be considered as a real adjuvant for anti-cancer vaccination. Thus, this new study provides new treatment options for patients in a therapeutic impasse and will provide a new arsenal in the fight against PDAC.

Targeting MAP3K19 prevents human lung myofibroblast activation both in vitro and in a humanized SCID model of idiopathic pulmonary fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a disease with a devastating prognosis characterized by unrelenting lung scarring. Aberrant activation of lung fibroblasts is a key feature of this disease, yet the key pathways responsible for this are poorly understood. Mitogen-activated protein kinase, kinase, kinase- 19 (MAP3K19) was recently shown to be upregulated in IPF and this MAPK has a key role in target gene transcription in the TGF-β pathway. Herein, we further investigate the role of MAP3K19 in cultured normal and IPF fibroblasts and in a humanized SCID mouse model of IPF employing both short interfering (si) RNA and novel small-molecule inhibitors directed at this kinase. Targeting MAP3K19 had significant inhibitory effects on the expression of both alpha smooth muscle actin and extracellular matrix in cultured human IPF fibroblasts. Quantitative protein and biochemical assays, as well as histological analysis, showed that MAP3K19 was required for the development of lung fibrosis in SCID mice humanized with IPF lung fibroblasts. MAP3K19 was required for IPF myofibroblast differentiation, and targeting its activity attenuated the profibrotic activity of these cells both in vitro and in an adoptive transfer SCID model of pulmonary fibrosis.

Mesenchymal stromal cell exosome–enhanced regulatory T-cell production through an antigen-presenting cell–mediated pathway

Background aimsThe immunomodulatory property of mesenchymal stromal cell (MSC) exosomes is well documented. On the basis of our previous report that MSC exosomes increased regulatory T-cell (Treg) production in mice with allogenic skin graft but not in ungrafted mice, we hypothesize that an activated immune system is key to exosome-mediated Treg production. MethodsTo test our hypothesis, MSC exosomes were incubated with mouse spleen CD4+ T cells that were activated with either anti-CD3/CD28 mAbs or allogenic antigen-presenting cell (APC)-enriched spleen CD11c+ cells to determine whether production of mouse CD4+CD25+ T cells or CD4+CD25+Foxp3+ Tregs could be induced. MSC exosomes were also administered to the lethal chimeric human-SCID mouse model of graft-versus-host disease (GVHD) in which human peripheral blood mononuclear cells were infused into irradiated NSG mice to induce GVHD. ResultsWe report here that MSC exosome–induced production of CD4+CD25+ T cells or CD4+CD25+Foxp3+ Tregs from CD4+ T cells activated by allogeneic APC-enriched CD11C+ cells but not those activated by anti-CD3/CD28 mAbs. This induction was exosome- and APC dose–dependent. In the mouse GVHD model in which GVHD was induced by transplanted human APC-stimulated human anti-mouse CD4+ T cell effectors, MSC exosome alleviated GVHD symptoms and increased survival. Surviving exosome-treated mice had a significantly higher level of human CD4+CD25+CD127low/– Tregs than surviving mice treated with Etanercept, a tumor necrosis factor inhibitor. ConclusionsMSC exosome enhanced Treg production in vitro and in vivo through an APC-mediated pathway.

Profiling of the anti-malarial drug candidate SC83288 against artemisinins in Plasmodium falciparum

BackgroundThe increased resistance of the human malaria parasite Plasmodium falciparum to currently employed drugs creates an urgent call for novel anti-malarial drugs. Particularly, efforts should be devoted to developing fast-acting anti-malarial compounds in case clinical resistance increases to the first-line artemisinin-based combination therapy. SC83288, an amicarbalide derivative, is a clinical development candidate for the treatment of severe malaria. SC83288 is fast-acting and able to clear P. falciparum parasites at low nanomolar concentrations in vitro, as well as in a humanized SCID mouse model system in vivo. In this study, the antiplasmodial activity of SC83288 against artemisinins was profiled in order to assess its potential to replace, or be combined with, artemisinin derivatives.ResultsBased on growth inhibition and ring survival assays, no cross-resistance was observed between artemisinins and SC83288, using parasite lines that were resistant to either one of these drugs. In addition, no synergistic or antagonistic interaction was observed between the two drugs. This study further confirmed that SC83288 is a fast acting drug in several independent assays. Combinations of SC83288 and artesunate maintained the rapid parasite killing activities of both components.ConclusionThe results obtained in this study are consistent with artemisinins and SC83288 having distinct modes of action and different mechanisms of resistance. This study further supports efforts to continue the clinical development of SC83288 against severe malaria as an alternative to artemisinins in areas critically affected by artemisinin-resistance. Considering its fast antiplasmodial activity, SC83288 could be combined with a slow-acting anti-malarial drug.

A complicated interpretation of a therapeutic effect with humanized mice using a novel peptide platform

In the article “Systemic delivery of tumor-targeted Bax-derived membrane-active peptides for the treatment of melanoma tumors in a humanized SCID mouse model”, Karageorgis and colleagues, cyclic RGD conjugated apoptosis-inducing peptide platform strongly inhibited the growth of melanoma tumors in humanized SCID mouse model (1).

Abstract 4788: Abraxane eliminates cancer stem cells in triple-negative breast cancers

Abstract Triple-negative breast cancer (TNBC) represents about 20 percent of all breast cancers, with a poorer survival rate and being associated with high-grade tumors and the least favorable prognosis. Due to the absence of hormone receptors and Her2 receptor, no targeted therapy is available and chemotherapy is the standard treatment for TNBC patient. Paclitaxel is a widely used chemotherapy drug for various cancers with severe side effects due to its solvent. Abraxane is an albumin-bound nanoparticle of paclitaxel with less severe side effects. Here we investigated whether cancer stem cells (CSCs) in TNBC response differentially to abraxane and paclitaxel both in cell culture and xenograft mouse models. Using a series of human TNBC cell lines, we showed that there is no difference between solvent-based paclitaxel and abraxane in vitro in term of efficacy and eliminating cancer stem cells using MTS assay, mammosphere formation assay, and flow analysis of cancer stem cells. Interestingly, we demonstrated that abraxane shows superior efficacy than solvent-based paclitaxel in human SUM149 xenograft NOD SCID mouse model in adjuvant treatment. More important, we demonstrated that abraxane eliminates cancer stem cells in xenograft NOD SCID mouse model in advanced treatment, while solvent-based paclitaxel increases cancer stem cells. Cell uptake assay indicated that TNBC cells take more abraxane than solvent-based paclitaxel, which partially attributes to its superior efficacy in xenograft mouse models. Taken together, our data confirmed that abraxane is superior to solvent-based paclitaxel and may be a better option for TNBC patients in adjuvant or metastatic treatment. Citation Format: Hebao Yuan, Hongwei Guo, Feng Li, Joseph Burnett, Miao He, Nathan Truchan, Ila Myers, Duxin Sun. Abraxane eliminates cancer stem cells in triple-negative breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4788. doi:10.1158/1538-7445.AM2017-4788

Systemic Delivery of Tumor-Targeted Bax-Derived Membrane-Active Peptides for the Treatment of Melanoma Tumors in a Humanized SCID Mouse Model

Melanoma is a highly metastatic and deadly form of cancer. Invasive melanoma cells overexpress integrin αvβ3, which is awell-known target for Arg-Gly-Asp-based (RGD) peptides. We developed a sophisticated method to synthetize milligram amounts of a targeted vector that allows the RGD-mediated targeting, internalization, and release of a mitochondria-disruptive peptide derived from the pro-apoptotic Bax protein. We found that 2.5μM Bax[109-127] was sufficient to destabilize the mitochondria in ten different tumor cell lines, even in the presence of the anti-apoptotic Bcl2 protein, which is often involved in tumor resistance. This pore-forming peptide displayed antitumor activity when it was covalently linked by a disulfide bridge to the tetrameric RAFT-c[RGD]4-platform and after intravenous injection in a human melanoma tumor model established in humanized immuno-competent mice. In addition to its direct toxic effect, treatment with this combination induced the release of the immuno-stimulating factor monocyte chimoattractant protein 1 (MCP1) in the blood and a decrease in the level of the pro-angiogenic factor FGF2. Our novel multifunctional, apoptosis-inducing agent could be further customized and assayed for potential use in tumor-targeted therapy.

The lncRNA HOTAIRM1 regulates the degradation of PML-RARA oncoprotein and myeloid cell differentiation by enhancing the autophagy pathway

Increasing evidence has indicated that long noncoding RNAs (lncRNAs) are of great importance in different cell contexts. However, only a very small number of lncRNAs have been experimentally validated and functionally annotated during human hematopoiesis. Here, we report an lncRNA, HOTAIRM1, which is associated with myeloid differentiation and has pivotal roles in the degradation of oncoprotein PML-RARA and in myeloid cell differentiation by regulating autophagy pathways. We first revealed that HOTAIRM1 has different variants that are expressed at different levels in cells and that the expression pattern of HOTAIRM1 is closely related to that of the PML-RARA oncoprotein in acute promyelocytic leukemia (APL) patients. We further revealed that the downregulation of HOTAIRM1 could inhibit all-trans retinoic acid (ATRA) -induced degradation of PML-RARA in APL cells and repress the process of differentiation from promyelocytic to granulocytic cells. More importantly, we found that HOTAIRM1 regulates autophagy and that autophagosome formation was inhibited when HOTAIRM1 expression was reduced in the cells. Finally, through the use of a dual luciferase activity assay, AGO2 RNA immunoprecipitation and RNA pull-down, HOTAIRM1 was revealed to act as a microRNA sponge in a pathway that included miR-20a/106b, miR-125b and their targets ULK1, E2F1 and DRAM2. We constructed a human APL-ascites SCID mouse model to validate the function of HOTAIRM1 and its regulatory pathway in vivo. This is the first report showing that a lncRNAs regulates autophagy and the degradation of the PML-RARA oncoprotein during the process of myeloid cell differentiation blockade, suggesting that lncRNAs may be the potential therapeutic targets for leukemia.

Experimental Evidence of Bacterial Colonization of Human Coronary Microvasculature and Myocardial Tissue during Meningococcemia.

Meningococcal septic shock is associated with profound vasoplegia, early and severe myocardial dysfunction, and extended skin necrosis responsible for a specific clinical entity designated purpura fulminans (PF). PF represents 90% of fatal meningococcal infections. One characteristic of meningococcal PF is the myocardial dysfunction that occurs in the early phase of sepsis. Furthermore, hemodynamic studies have shown that the prognosis of meningococcal sepsis is directly related to the degree of impairment of cardiac contractility during the initial phase of the disease. To gain insight into a potential interaction of Neisseria meningitidis with the myocardial microvasculature, we modified a previously described humanized mouse model by grafting human myocardial tissue to SCID mice. We then infected the grafted mice with N. meningitides Using the humanized SCID mouse model, we demonstrated that N. meningitidis targets the human myocardial tissue vasculature, leading to the formation of blood thrombi, infectious vasculitis, and vascular leakage. These results suggest a novel mechanism of myocardial injury in the course of severe N. meningitidis sepsis that is likely to participate in primary myocardial dysfunction.

Chemokines CCL2, 3, 14 stimulate macrophage bone marrow homing, proliferation, and polarization in multiple myeloma.

We previously showed that macrophages (MΦs) infiltrate the bone marrow (BM) of patients with myeloma and may play a role in drug resistance. This study analyzed chemokines expressed by myeloma BM that are responsible for recruiting monocytes to the tumor bed. We found that chemokines CCL3, CCL14, and CCL2 were highly expressed by myeloma and BM cells, and the levels of CCL14 and CCL3 in myeloma BM positively correlated with the percentage of BM-infiltrating MΦs. In vitro, these chemokines were responsible for chemoattracting human monocytes to tumor sites and in vivo for MΦ infiltration into myeloma-bearing BM in the 5TGM1 mouse model. Surprisingly, we also found that these chemokines stimulated MΦ in vitro proliferation induced by myeloma cells and in vivo in a human myeloma xenograft SCID mouse model. The chemokines also activated normal MΦ polarization and differentiation into myeloma-associated MΦs. Western blot analysis revealed that these chemokines promoted growth and survival signaling in MΦs via activating the PI3K/Akt and ERK MAPK pathways and c-myc expression. Thus, this study provides novel insight into the mechanism of MΦ infiltration of BM and also potential targets for improving the efficacy of chemotherapy in myeloma.

Anti-Pneumococcal Capsular Polysaccharide Antibody Response and CD5 B Lymphocyte Subsets.

The role of CD19(+) CD5(+) and CD19(+) CD5(-) B cell subpopulations in the antibody response to pneumococcal capsular polysaccharides (caps-PSs) is controversial. In the present study, we evaluated the role of human CD19(+) CD5(+) and CD19(+) CD5(-) cell populations in the serotype-specific antibody response to caps-PS. After vaccination of 5 healthy human adults with Pneumovax (23-valent pneumococcal polysaccharide vaccine [PPV23]), IgG anti-caps-PS serotype 4 antibody-producing cells resided mainly in the CD19(+) CD5(-) B cell subset, as assessed by enzyme-linked immunosorbent spot (ELISpot) analysis. Moreover, in a humanized SCID mouse model, CD19(+) CD5(-) B cells were more effective than CD19(+) CD5(+) cells in producing IgG anti-cap-PS antibodies. Finally, an association was found between the level of IgG anti-caps-PS antibodies and the number of CD19(+) CD5(-) B cells in 33 humans vaccinated with PPV23. Taken together, our data suggest that CD5 defines a functionally distinct population of B cells in humans in the anti-caps-PS immune response.

Macrophage Migration Inhibitory Factor Regulates Multiple Myeloma Bone Marrow Homing

Multiple myeloma (MM) is the most frequently occurring bone cancer and is characterized by malignant antibody-producing cell accumulation in bone marrow (BM). MM is still incurable, and the disease management is complicated by crosstalk between MM cells and the BM microenvironment. Why MM cells predominantly locate in bone is not well understood. The process by which MM cells are recruited into BM and reside in bone for colonization is called MM BM homing. BM homing is also critical for MM metastasis to distal BM sites. Therefore, MM BM homing is an active process throughout the disease pathogenesis. Here for the first time, we report that macrophage migration inhibitory factor (MIF) regulates MM BM homing via a mechanism that involves MM adhesion in the BM microenvironment. More importantly, we also show that MIF might be a promising target for MM treatment.MIF is an inflammatory cytokine, secreted by various human cell types. Our results here showed that BM biopsies from MM patients had significantly higher MIF expression, compared with that from healthy donors as determined by both immunohistochemistry of BM biopsies and ELISA of BM aspirates (P<0.05). Animal studies using a human MM SCID mouse model (ARP-1 in the SCID mouse) and a murine MM mouse model (5-TGM1 in the C57BL/KawRij mouse) showed that intravenously inoculated (IV) MIF knocked-down (MIF-KD) MM cells did NOT form tumors in bone, whereas control knocked-down cells did form tumors in bone, as determined by both in vivo bioluminescent assay and FACS analysis of BM cells. Unlike the previously identified SDF-1/CXCR4 axis, which regulates MM chemotaxis to BM, MIF knock-down did NOT affect MM cell migration to BM. However, MIF-KD MM cells showed decreased adhesion to BM stromal cells. A mechanistic study suggested that MIF regulation of MM BM homing was mediated by MIF and its receptor CXCR4, but was independent of its primary receptor CD74. The MIF/CXCR4 axis regulated a panel of adhesion molecules via NFκB and JNK intracellular signaling, and MIF-KD and CXCR4-KD MM cells had similar downstream cell signaling and adhesion molecule expression. In addition, exposing MM cells to a MIF inhibitor (4-IPP) down-regulated expression of those adhesion molecules. Further, in the murine MM model with established MM tumors in bone, administering 4-IPP resulted in extramedullary metastasis. Overall, the findings above suggest that MIF regulates MM cell homing to the BM.We also explored MIF-targeting therapy for MM treatment. In the human MM SCID model, IV-inoculated ctrl-KD MM cells formed tumors both in BM and outside of the bone, such as in the abdomen and lung. When tumor-bearing mice were treated with the chemotherapeutic melphalan, the extramedullary tumors regressed significantly (P<0.05), whereas the BM tumors were not sensitive to treatment, probably because the BM microenvironment conferred MM chemoresistance. In the same mouse model inoculated with MIF-KD MM cells, because the MIF-KD MM cells had impaired attachment and could NOT form tumors in bone, the tumor-bearing mice had a complete response to the drug treatment as determined by tumor burden and mouse survival (P<0.05). These encouraging results suggested that MIF might be a valid target for MM treatment. To test this hypothesis, we used the murine MM mouse model and treated the tumor-bearing mice with both melphalan and MIF inhibitor. This combined therapy significantly repressed the MM tumor growth in vivo and lengthened survival (P<0.05). Thus, MIF might be a promising target for MM treatment, in combination with conventional chemotherapy.To summarize, our findings suggest a novel function for MIF in MM BM homing regulation. MIF regulates a panel of adhesion molecules and promotes MM cell attachment within the BM. MIF inhibition disrupts the boundary between MM cells and the BM microenvironment and may raise MM cell drug sensitivity. DisclosuresNo relevant conflicts of interest to declare.

Prevention of Acute Graft-Versus-Host Disease in Human/Mouse Xenogeneic SCID Mouse Model by Humanized Anti-CD74 Monoclonal Antibody, Milatuzumab

AbstractAbstract 4105 Introduction:Graft-versus-host disease (GVHD) is a life-threatening complication of allogeneic hematopoietic stem cell transplantation. Prevention and treatment of GVHD remains a major challenge, because current T-cell depletion and mainstay immunosuppressive therapies compromise preexisting T-cell immunity, leading to severe infections and disease relapse. Thus, novel anti-GVHD agents that can spare protective T-cell memory are critically needed. Milatuzumab (hLL1) is a humanized anti-CD74 antagonist IgG1κ monoclonal antibody (mAb) currently under clinical investigation as a therapeutic mAb for relapsed or refractory B-cell malignancies. Since CD74 is widely expressed in both hematopoietic and non-hematopoietic antigen-presenting cells (APCs), and because host APCs, especially non-hematopoietic APCs, play an important role in initiating GVHD, whereas donor APCs contribute and are required to maximize GVHD, we reasoned milatuzumab could affect recipient or donor APCs, thereby modulating GVHD. We report herein the in vitro effect of milatuzumab on the survival and function of human blood APCs and T cells, including CMV-specific T cells, and the in vivo therapeutic efficacy on preventing acute GVHD in a humanized SCID mouse model. Methods:The effects of milatuzumab on APCs and T cells in human peripheral blood mononuclear cells (PBMCs) were assessed by multi-color flow cytometry. The effect of milatuzumab on the proliferation of T cells and T cell subsets in allogeneic mixed lymphocyte reactions (allo-MLRs) was measured by CFSE labeling of allogeneic PBMCs that were mixed to each other and cultured for 11 days before flow cytometric analysis of the proliferating cells that lost fluorescence. The impact of milatuzumab on preexisting anti-viral T-cell immunity was evaluated by intracellular staining of CD3+CD8+IFN-γ+T cells in allo-MLRs upon stimulation with HLA-A2-restricted cytomegalovirus (CMV) pp65 peptide (NLVPMVATV). The therapeutic effect of milatuzumab on acute GVHD was evaluated in a human PBMC-transplanted SCID mouse model, in which GVHD is developed and mediated by engrafted human T cells and DCs. Results:Milatuzumab moderately reduces the number of myeloid DC type 1 (mDC1), myeloid DC type 2 (mDC2), and B cells in PBMCs, but has little effect on plasmacytoid DC (pDC), monocytes, or T cells, which correlates with the level of CD74 expression on these cells. As a consequence, milatuzumab inhibits the proliferation of total T cells, CD4 and CD8 T cell subsets in allo-MLRs. In a human/mouse xenogeneic SCID mouse model, milatuzumab effectively prevents the onset and manifestations of acute GVHD, suppresses the serum levels of human interferon-g and IL-5, eliminates the infiltration of human lymphocytes in GVHD target organs (lung, liver and spleen), and significantly promotes the survival of animals (90% versus 20% for controls, P=0.0012). Furthermore, exposure to milatuzumab does not affect the number of CMV-specific, IFN-γ-producing, human CD8+ T cells in allo-MLRs. Conclusion:CD74 is a potential target for antibody-mediated mitigation of GVHD, as demonstrated by the encouraging results obtained with milatuzumab. Further exploration of milatuzumab as a new therapeutic agent for GVHD is warranted. Disclosures:Cardillo:Immunomedics, Inc: Employment. Goldenberg:Immunomedics: Employment, Equity Ownership.

T cell lessons from the rheumatoid arthritis synovium SCID mouse model: CD3‐rich synovium lacks response to CTLA‐4ig but is successfully treated by interleukin‐17 neutralization

To provide an intermediate step between classic arthritis models and clinical trials, the rheumatoid arthritis (RA) synovium SCID mouse model is a valuable tool for use during preclinical research. We undertook this study to investigate the validity of this humanized mouse model using anti-tumor necrosis factor (anti-TNF) and anti-interleukin-1 (anti-IL-1) treatment and to investigate the direct effect of T cells- and B cell-related therapies on the transplanted RA synovial tissue. CB17/SCID mice were engrafted with human RA synovial tissue and systemically treated with anti-TNF, anti-IL-1, anti-IL-17, CTLA-4Ig, anti-CD20, or isotype control antibodies. Validation of the model with anti-TNF treatment significantly reduced serum cytokine levels and decreased histologic inflammation, whereas anti-IL-1 therapy did not show any effect on the RA synovial grafts. In mice engrafted with B cell-rich synovial tissue, anti-CD20 treatment showed clear therapeutic effects. Surprisingly, CTLA-4Ig treatment did not show any effects in this transplantation model, despite prescreening of the synovial tissue for the presence of CD3+ T cells and the costimulatory molecules CD80 and CD86. In contrast, great therapeutic potential was observed for anti-IL-17 treatment, but only when CD3+ T cells were abundantly present in the RA synovial tissue. This human RA synovium SCID mouse model enabled us to show that CTLA-4Ig lacks direct effects on T cell activation processes in the synovial tissue. Further evidence was obtained that IL-17 might indeed be an interesting therapeutic target in RA patients with CD3-rich synovial tissue. Further characterization of the RA patients' individual synovial profiles is of great importance for achieving tailored therapy.

Elimination of autoreactive B cells in humanized SCID mouse model of SLE

Although the exact etiology of systemic lupus erythematosus (SLE) remains elusive, B-cell hyperactivity and production of autoantibodies directed to components of the cell nucleus are a well-established pathogenetic mechanism of the disease. Therefore, the targeted inhibition of DNA-specific B cells is a logical therapeutic approach. The complement receptor type 1 (CR1, CD35) has been shown to suppress human B-cell activation and proliferation after co-cross-linking with the BCR, and may serve as a mediator for negative signal delivery. In order to evaluate this therapeutic approach in a human-like system, we used immune-restricted SCID mice transferred with PBMCs from SLE patients. The tolerance of these humanized SCID mice to native DNA was re-established after administration of a chimeric molecule consisting of a CR1-specific mAb coupled to the decapeptide DWEYSVWLSN that mimics dsDNA. The generated protein-engineered chimera was able to co-cross-link selectively native DNA-specific BCR with the B-cell inhibitory receptor CR1, thus delivering a strong inhibitory signal.

In vitro synergism between LFA-1 targeting leukotoxin (Leukothera™) and standard chemotherapeutic agents in leukemia cells

Leukotoxin (Leukothera™; LtxA) is a bacterial protein and experimental therapeutic that binds leukocyte function antigen (LFA-1) on white blood cells (WBCs) and induces cell death via apoptosis or necrosis. We previously found that LtxA preferentially targets WBCs with high levels of activated LFA-1, which is characteristic of many leukemias and lymphomas, and showed that LtxA exhibits significant anti-leukemia activity in vivo using the humanized SCID mouse model. In this report, we demonstrate that LtxA induces very rapid (1h) apoptosis in acute monocytic leukemia THP-1 cells characterized by binding of annexin V to cells, loss of mitochondrial membrane potential, depletion of cellular ATP, and fragmentation of chromosomal DNA. We tested the activity of LtxA in combination with the standard chemotherapeutic agents, etoposide, mitoxantrone, daunorubicin, busulfan, and imatinib against several leukemia cell lines, including THP-1, GDM-1, HL-60, and KU-812 cells. LtxA exhibited synergism with all the drugs, and the levels of synergy were dependent on the doses used and cell lines examined. In general, the greatest level of synergy was observed with LtxA and etoposide or imatinib. Combination index (CI) values were less than 0.1 for many of the combinations, indicating very strong synergism. In addition, LtxA alone was cytotoxic to primary cells from newly diagnosed, relapsed, and refractory patients with different hematological malignancies. Thus, LtxA is highly effective at inducing rapid apoptosis both as a single agent and in combination with approved leukemia therapies.

IL-21 Promotes Skin Recruitment of CD4+ Cells and Drives IFN-γ–Dependent Epidermal Hyperplasia

Psoriasis is a chronic inflammatory disorder of the skin characterized by epidermal hyperplasia and infiltration of leukocytes into the dermis and epidermis. T cell-derived cytokines, such as IFN-γ and IL-17A, play a major role in the psoriasis-associated epidermal hyperplasia, even though factors/mechanisms that regulate the production of these cytokines are not fully understood. We have recently shown that IL-21 is synthesized in excess in psoriatic skin lesions and causes epidermal hyperplasia when injected intradermally in mice. Moreover, in the human psoriasis SCID mouse model, neutralization of IL-21 reduces both skin thickening and expression of inflammatory molecules, thus supporting the pathogenic role of IL-21 in psoriasis. However, the basic mechanism by which IL-21 promotes skin pathology remains unknown. In this study, we show that CD4(+) cells accumulate early in the dermis of IL-21-treated mice and mediate the development of epidermal hyperplasia. Indeed, IL-21 fails to induce skin damage in RAG1-deficient mice and CD4(+) cell-depleted wild-type mice. The majority of CD4(+) cells infiltrating the dermis of IL-21-treated mice express IFN-γ and, to a lesser extent, IL-17A. Studies in cytokine knockout mice show that IFN-γ, but not IL-17A, is necessary for IL-21-induced epidermal hyperplasia. Finally, we demonstrate that IFN-γ-producing CD4(+) cells infiltrating the human psoriatic plaque express IL-21R, and abrogation of IL-21 signals reduces IFN-γ expression in cultures of psoriatic CD4(+) cells. Data indicate that IL-21 induces an IFN-γ-dependent pathogenic response in vivo, thus contributing to elucidate a mechanism by which IL-21 sustains skin-damaging inflammation.

Disruption of DEPTOR/mTORC1/mTORC2 Signaling Cascade Using a Novel Selective mTOR Kinase Inhibitor AZD8055 Results In Growth Arrest and Apoptosis In Multiple Myeloma Cells

AbstractAbstract 791Targeting PI3K/Akt/mTOR signaling is among one of the promising therapeutic strategies in multiple myeloma (MM), since it facilitates MM cell survival and development of drug resistance in the context of the bone marrow microenvironment. Specifically, regulation of PI3K activity, which mediates MM cell growth and drug resistance, by mTOR complex 1 (mTORC1) provides the rationale for use of rapamycin analogs for MM treatment. However, rapamycin alone fails to overcome bone marrow-induced proliferation of MM cells, at least in part, because of the mTORC1-dependent feedback loops which activate PI3K/Akt. More recently, extensive studies of the mTOR network have identified mTORC2 as a “rapamycin-insensitive” complex. Sharing mTOR kinase as a common catalytic subunit, mTORC1 and mTORC2 mediate two distinct pathways: mTORC1 controls cell growth by phosphorylating key regulators of protein synthesis S6 kinase 1 (P70S6K) and the eIF-4E-binding protein 1 (4E-BP1); mTORC2 modulates cell survival and drug resistance by phosphorylating target proteins including Akt and serum/glucocorticoid regulated kinase 1(SGK1)/N-myc downstream regulated 1 (NDRG1). Moreover, studies have also revealed overexpression of a novel mTOR-interacting protein DEP domain containing 6 (DEPTOR), which can modulate mTOR activity and promote PI3K/mTORC2 signaling in primary MM tumor cells and in MM cell lines while mTORC1 remains silenced. We therefore hypothesized that targeting mTOR may disrupt DEPTOR/mTOR interaction and silence mTORC1/mTORC2 signaling, thereby overcoming mTOR resistance in MM cells. To confirm this idea, we used AZD8055, an orally bioavailable selective ATP-competitive mTOR kinase inhibitor, in our MM preclinical models. AZD8055- treatment of MM.1S inhibited phosphorylation of both mTORC1 and mTORC2 substrates: P70S6K; 4E-BP1 including the rapamycin-resistant T37/46 – downstream targets of mTORC1; as well as Akt and NDRG1 – effectors of mTORC2 refractory to rapamycin. Interestingly, AZD8055-mediated mTORC1/mTORC2 downregulation was associated with DEPTOR upregulation, which is consistent with the finding that DEPTOR expression is negatively regulated by mTORC1 and mTORC2. Moreover, inhibition of mTORC1 alone by rapamycin resulted in reduction of DEPTOR, associated with Akt activation. Furthermore, we observed that DEPTOR expression was decreased in MM.1S cells cultured with IL-6, IGF-1 or bone marrow stromal cells (BMSCs), which stimulate PI3K/Akt/mTOR signaling, evidenced by enhanced P70S6K and Akt phosphorylation. Unlike rapamycin, AZD8055 reversed those effects and inhibited MM.1S proliferation, even in the presence of these cytokines or BMSCs. AZD8055-induced growth inhibition was associated with apoptosis, evidenced by caspase-9, -3 and PARP cleavage in a time-dependent fashion (80% apoptotic cells at 72 hour culture as detected by Annexin V/PI staining). Moreover, AZD8055 induced cytotoxicity even in rapamycin resistant MM cell lines and primary patient MM cells. Finally, AZD8055 demonstrated significant anti-MM activity in an in vivo human MM cell xenograft SCID mouse model. Taken together, our data show that disruption of DEPTOR/mTORC1/mTORC2 cascade in MM cells results in significant anti-tumor effects, providing the framework for future clinical trials of AZD8055 to improve patient outcome in MM. Disclosures:Guichard:AstraZeneca: Employment, Shareholder AstraZeneca. Anderson:Millenium: Consultancy; Celgene: Consultancy; Novartis: Consultancy; Onyx: Consultancy; Merck: Consultancy; BMS: Consultancy; Acetylon: Membership on an entity's Board of Directors or advisory committees, Ownership interest (inc stock options) in a Start up company. Raje:AstraZeneca: Research Funding; Acetylon: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees.

Abstract 5781: ITRI-260, a new azaazulenone class kinase inhibitor, induces complete tumor regression and prolongs survival in AML mice

Abstract The FMS-like tyrosine kinase-3 (FLT3) is a receptor tyrosine kinase with important roles in hematopoietic stem/progenitor cell survival and proliferation. FLT3 is over-expressed in the majority of acute myeloid leukemia (AML) and the presence of FLT3 active mutations is associated with poor prognosis, implicating FLT3 as a potential target for AML treatment. ITRI-260 is a new azaazulenone class kinase inhibitor that inhibited FLT3-ITD-dependent MV4-11 cell growth with IC50 of 21 nM and cellular phosphorylation with IC50 of 17 nM. In in vivo PK study, ITRI-260 showed favorable oral PK profiles. The maximum concentration of ITRI-260 was 700 nM after a single 100 mg/kg oral dosing in mice, with dose proportional exposure from 10 to 150 mg/kg. ITRI-260 showed therapeutic efficacy in a human AML orthotopic SCID mouse model, following a 100 mg/kg/qd oral dosing regimen. The treatment group showed 100% survival of animals at day 90 after tumor cell inoculation, while the vehicle control group showed 100% mortality. In the other study, ITRI-260 also increased survival in primary tumor cell engraftment model inoculated with cells isolated from sunitinib- and sorafenib-resistant AML patient. Through hERG assay with patch clamp technology, we found higher IC50 of ITIR-260 compared with sunitinib and MLN-518, which indicates that ITRI-260 might arise less cardiotoxic concern. In a 14-day subchronic toxicology study in mice, ITRI-260 was generally tolerated at 300 mg/kg/qd. The most prominent adverse effect appeared at 600 mg/kg/qd group is starry sky appearance in spleen, which is moderate and reversible. No specific clinical signs or body weight loss were attributed to the test article. In conclusion, the in vitro/in vivo PK/PD/toxicology studies have provided the basis for the clinical developmental potential of ITRI-260 in AML. The bridge studies from discovery to development such as CMC, GLP toxicology/safety pharmacology and pre-formulation are now in progress. 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 5781.