WT Hosts Research Articles

Immunoediting is not a primary transformation event in a murine model of MLL-ENL AML.

Although it is firmly established that endogenous immunity can prevent cancer outgrowth, with a range of immunomodulatory strategies reaching clinical use, most studies on the topic have been restricted to solid cancers. This applies in particular to cancer initiation, where model constraints have precluded investigations of immunosurveillance and immunoediting during the multistep progression into acute myeloid leukemia (AML). Here, we used a mouse model where the chimeric transcription factor MLL-ENL can be conditionally activated in vivo as a leukemic "first-hit," which is followed by spontaneous transformation into AML. We observed similar disease kinetics regardless of whether AML developed in WT or immunocompromised hosts, despite more permissive preleukemic environments in the latter. When assessing transformed AML cells from either primary immunocompetent or immunocompromised hosts, AML cells from all sources could be targets of endogenous immunity. Our data argue against immunoediting in response to selective pressure from endogenous immunity as a universal primary transformation event in AML.

Reduced TGF‑βR signaling results in increased T cell activation without autoinflammatory disease

Abstract Transforming growth factor-β receptor (TGF-βR) signaling is important in regulating the proliferation and differentiation of CD4+ T cells, but how modulating the level of signaling can affect T cell fate remains unclear. We have created a mouse model of Loeys-Dietz syndrome (LDS), an autosomal dominant disease caused by mutations in genes encoding the TGF-βR, by targeting a missense mutation (M318R) to the endogenous murine Tgfbr1 locus. LDS patients exhibit an increased propensity for allergic disease, but no overt immunodeficiency or autoimmune disease. A higher percentage of CD4+ T cells in Tgfbr1M318R/+ mice exhibited a memory phenotype and produced enhanced levels of cytokines including IFN-γ, IL-13, IL-17, and IL-10 upon stimulation, but no autoimmunity was observed. In contrast, mice lacking TGF-βR2 specifically in T cells demonstrate exaggerated IFN-γ production and widespread autoinflammatory disease. While naïve CD4+ T cells from Tgfbr1M318R/+ mice were less likely to upregulate Foxp3 during in vitro culture with recombinant TGF-β, paradoxically, increased percentages and numbers of suppressive Foxp3+ regulatory T cells (Tregs) were observed in vivo, which may indicate a role for increased proliferation or survival of thymically-derived Tregs. The effects of the Tgfbr1M318R/+on T cells appear to be cell intrinsic. We observed no differences in T cells derived from WT bone marrow used to reconstitute irradiated Tgfbr1M318R/+ or WT hosts, while Tgfbr1M318R/+ bone marrow co-transferred with WT bone marrow into WT hosts gave rise to more activated CD4+ T cells and a higher frequency of Foxp3+ cells. These data suggest that partially abrogated TGF-β signaling leads to unexpected effects on T cell development and function.

Abstract B06: Imaging regulatory mechanisms that limit intratumoral CTL function in a mouse melanoma model

Abstract Introduction: Immunotherapies that harness CTLs to eradicate solid tumors, melanoma in particular, have re-emerged as potent clinical options in recent years. Improving the dispersion and cytotoxicity of intratumoral CTLs may further benefit patients. To gain insight into the regulatory processes that limit CTL activity in melanoma we investigated the influence of PD-1 signaling and Tregs on CTL behavior. Methodology: To mimic adoptive cell therapy we transferred mice bearing B16.OVA melanoma tumors with OT-I CTLs. To study Treg-mediated regulation, we used FOXP3-GFP-LuciDTR-4 host mice, in which 95% of the cells expressing Foxp3 could be depleted using diphtheria toxin. To study PD-1 mediated regulation we injected anti PD-1 to WT host mice. Tumor rejection was monitored for 2-5 weeks. Two-photon imaging of live mice was used to follow the behavior of CTLs and Tregs within tumors. Time-lapse confocal microscopy was used to follow the influence of PD-1 signaling on the behavior of CTLs and their interaction with B16-Ova cells. Results: Tumor rejection was closely regulated by Tregs as tumors were densely infiltrated by these cells and their depletion dramatically accelerated tumor rejection. Interactions between CTLs and Tregs seemed indirect, as they did not form conjugates. Following their transfer, antigen-specific OT-I CTLs, as well as polyclonal CTLs, entered murine tumors through selected ICAM-decorated intratumoral vessels. As CTLs accumulated, Treg numbers in the tumors dropped and CTLs could be observed conjugating tumor cells and killing them. Treatment with anti PD-1 increased CTL velocities and accelerated killing of B16.OVA cells in vitro, and was mirrored in vivo by enhanced tumor rejection. Whereas CTL migration and cytolysis was limited to oxygenated tumor areas within 50 µm of flowing blood vessels, Tregs exhibited higher velocities, were not affected by the proximity of blood vessels, and penetrated deeper into avascular areas. Conclusions: Our findings suggest that regulatory mechanisms influence CTL efficiency partly by affecting their migration. CTLs, more than Tregs, depend on oxygen for intratumoral locomotion and cytolysis. This disparity allows tumor cells to escape CTL lysis in deep hypoxic tumor niches where high Treg to CTL ratios favor their survival. Thus, differential motility and dependence on oxygen among CTLs and Tregs can dictate the efficiency of CTL-based therapies of melanoma. Citation Format: Tali Feferman, Natalia G. Zabolinsky, Yoav Manaster, Anat Hutzler, Guy Shakhar. Imaging regulatory mechanisms that limit intratumoral CTL function in a mouse melanoma model. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B06.

Moesin Is a Major Regulator of Centrosome Behavior in Epithelial Cells with Extra Centrosomes

SummaryCentrosome amplification has severe consequences during development and is thought to contribute to a variety of diseases such as cancer and microcephaly. However, the adverse effects of centrosome amplification in epithelia are still not known. Here, we investigate the consequences of centrosome amplification in the Drosophila wing disc epithelium. We found that epithelial cells exhibit mechanisms of clustering but also inactivation of extra centrosomes. Importantly, these mechanisms are not fully efficient, and both aneuploidy and cell death can be detected. Epithelial cells with extra centrosomes generate tumors when transplanted into WT hosts and inhibition of cell death results in tissue over-growth and disorganization. Using SILAC-fly, we found that Moesin, a FERM domain protein, is specifically upregulated in wing discs with extra centrosomes. Moesin localizes to the centrosomes and mitotic spindle during mitosis, and we show that Moesin upregulation influences extra-centrosome behavior and robust bipolar spindle formation. This study provides a mechanistic explanation for the increased aneuploidy and transformation potential primed by centrosome amplification in epithelial tissues.

Defects in RNA polyadenylation impair both lysogenization by and lytic development of Shiga toxin-converting bacteriophages.

In Escherichia coli, the major poly(A) polymerase (PAP I) is encoded by the pcnB gene. In this report, a significant impairment of lysogenization by Shiga toxin-converting (Stx) bacteriophages (Φ24B, 933W, P22, P27 and P32) is demonstrated in host cells with a mutant pcnB gene. Moreover, lytic development of these phages after both infection and prophage induction was significantly less efficient in the pcnB mutant than in the WT host. The increase in DNA accumulation of the Stx phages was lower under conditions of defective RNA polyadenylation. Although shortly after prophage induction, the levels of mRNAs of most phage-borne early genes were higher in the pcnB mutant, at subsequent phases of the lytic development, a drastically decreased abundance of certain mRNAs, including those derived from the N, O and Q genes, was observed in PAP I-deficient cells. All of these effects observed in the pcnB cells were significantly more strongly pronounced in the Stx phages than in bacteriophage λ. Abundance of mRNA derived from the pcnB gene was drastically increased shortly (20 min) after prophage induction by mitomycin C and decreased after the next 20 min, while no such changes were observed in non-lysogenic cells treated with this antibiotic. This prophage induction-dependent transient increase in pcnB transcript may explain the polyadenylation-driven regulation of phage gene expression.

Regulation of Immune Responses during Acute GvHD Via the IL-33/ST2 Axis

The IL-1 superfamily member IL-33 is produced in barrier tissues. IL-33 binds to the receptor suppression of tumorigenicity 2 (ST2), expressed on stromal cells, regulatory T cells (Tregs), myeloid derived suppressor cells (MDSCs), and macrophages. IL-33 has both anti-inflammatory and pro-inflammatory properties. It is not known if IL-33 plays a role in acute GvHD, and if so what properties it exerts. By immunohistochemistry staining of gut tissues, IL-33 production by non-hematopoietic cells was increased in mice post-conditioning and in patients during GvHD. To determine whether IL-33 could augment GvHD via a host signaling mechanism, we compared st2-/- to wildtype (wt) hosts and observed decreased GvHD lethality (Figure 1A). Additionally, IL-33-/- versus wt hosts had a marked decrease in GvHD lethality and reduced TNFα production. Conversely, IL-33 administration during the peak inflammatory response worsened GvHD. Previous studies have shown increased levels of the soluble form of ST2 (sST2) are a biomarker for steroid-refractory GvHD (Vander Lugt, NEJM, 2013). We hypothesized that sST2 acted not only as an indicator of tissue injury and biomarker of GvHD but also as an immune modulator during GvHD. In rodents, we found that ST2 was upregulated on alloreactive T cells and sST2 increased as GvHD progressed. St2-/- versus wt donor T cells had a marked reduction in GvHD lethality (Figure 1B) without compromise of graft-vs-leukemia responses. Comparable data was seen in 2 different strain combinations. Alloantigen-induced IL-18 receptor upregulation was significantly lower in the absence of ST2, which was linked to significantly reduced IFNγ production by st2-/- vs wt CD4 and CD8 T cells during GvHD. Similarly, sST2 transgenic hosts and wt recipients given exogenous sST2-Fc fusion protein infusions (Figure 1C) to block ST2/IL-33 interaction each had significantly reduced GVHD lethality, establishing the functional role of ST2 as a decoy receptor modulating GVHD. During the peak of the GvHD inflammatory response, IL-33 signalling of either donor or host cells promoted activation of donor T cells, while the use of exogenous sST2-Fc protein to prevent IL33/ST2 engagement ameliorates disease. Together, these studies point to targeting of the IL-33/ST2 axis as a novel and potent target for GvHD therapy. [Display omitted] DisclosuresWarncke:Novartis Pharma AG: Employment. Junt:Novartis Pharma AG: Employment.

Natural Killer Cells Adapt to Major Histocompatibility Complex: Implications for Hematopoietic Cell Transplantation

Natural Killer (NK) cells play several important roles in hematopoietic cell transplantation. Host NK cells can reject allogeneic transplants that lack major histocompatibility complex (MHC) molecules of the host (so-called “missing self” reactivity), whereas donor NK cells in the marrow can promote engraftment, inhibit graft versus host disease, and mediate rejection of host leukemic cells (graft versus tumor (GVT) response). Like T cells, NK cells can distinguish allogeneic cells from self-cells, and “learn” self vs. non-self so as to establish self-tolerance. This presentation will summarize current understanding of some of these processes based primarily on studies in mice, and present new data that may be relevant for the success of human bone marrow transplantation. The self-tolerance of T cells and B cells is established in large part by developmental processes that either remove or suppress self-reactive clones as the cells differentiate from hematopoietic stem cells. Studies will be presented that show that NK cell self-tolerance is regulated quite differently, by an adaptation process that occurs quite rapidly and acts on mature NK cells. NK cell reactivity against susceptible untransformed cells (e.g., cells from animals lacking MHC of the NK cell donor) is rapidly lost after transfer of such NK cells to susceptible hosts, indicating that self-tolerance is an adaptation that occurs rapidly under non-inflammatory conditions. Irradiation chimeras were employed to identify the cell types that induce tolerance of NK cells to cells from MHC-deficient mice, as one model of missing self-recognition. Stable tolerance of wild type NK cells to MHC-deficient cells was established when NK cells were exposed in chimeras to either MHC-deficient hematopoietic cells or MHC-deficient non-hematopoietic cells. Interestingly, however, tolerance induced by exposure solely to MHC-deficient hematopoietic cells was unstable in the face of inflammatory conditions arising from infections or exposures to inflammatory cytokines in vivo. Specifically, mixed chimeras consisting of WT and MHC-deficient hematopoietic cells in WT hosts were stably chimeric until the mice were exposed to viral or bacterial infections, at which time the MHC-deficient cells were rapidly eliminated. In contrast, tolerance induced by non-hematopoietic cells was much more stable. Specifically, mixed chimeras consisting of WT and MHC-deficient hematopoietic cells in MHC-deficient hosts were stably chimeric whether or not they underwent infections. These findings suggest that tolerance may be imposed by multiple mechanisms depending on the cell types that induce tolerance, with distinct properties as a result. Most importantly from a clinical perspective, the results suggest that depending on the host/donor combination, intense infections may jeopardize the stability of bone marrow transplants. Previous studies have shown that tolerance of NK cells to MHC-deficient cells is accompanied by a state of hyporesponsiveness of the NK cells, characterized by low functional responses to stimulation via crosslinking of activating receptors ex vivo. Accordingly, it has been widely accepted that hyporesponsiveness to stimulation is the mechanism of NK cell self-tolerance when NK cells lack inhibitory receptors specific for host MHC molecules. However, our recent analysis of chimeric NK cells showed that this cannot be the sole explanation. When NK cells developed in MHC+ hosts in the presence of MHC-deficient hematopoietic cells, the cells became responsive to activating receptor stimulation despite being tolerant of MHC-deficient cells. Hence, tolerance can occur even when NK cells are responsive to stimulation. In contrast, when NK cells developed in MHC-deficient hosts, they became hyporesponsive. These data suggest that non-hematopoietic cells in the host impart hyporesponsiveness. Furthermore, exposure to MHC-deficient hematopoietic cells induces tolerance by a mechanism distinct from hyporesponsiveness. The latter mechanism is relatively unstable as it can be broken as a result of infections. DisclosuresRaulet:Innate Pharma: Membership on an entity’s Board of Directors or advisory committees; Novo Nordisk: Consultancy.

IL-33/ST2 axis promotes mast cell survival via BCLXL.

Mast cells (MC) are potent innate immune cells that accumulate in chronically inflamed tissues. MC express the IL-33 receptor IL-1 receptor-related protein ST2 at high level, and this IL-1 family cytokine both activates MC directly and primes them to respond to other proinflammatory signals. Whether IL-33 and ST2 play a role in MC survival remains to be defined. In skin-derived human MC, we found that IL-33 attenuated MC apoptosis without altering proliferation, an effect mediated principally through the antiapoptotic molecule B-cell lymphoma-X large (BCLXL). Murine MC demonstrated a similar mechanism, dependent entirely on ST2. In line with these observations, St2(-/-) mice exhibited reduced numbers of tissue MC in inflamed arthritic joints, in helminth-infected intestine, and in normal peritoneum. To confirm an MC-intrinsic role for ST2 in vivo, we performed peritoneal transfer of WT and St2(-/-) MC. In St2(-/-) hosts treated with IL-33 and in WT hosts subjected to thioglycollate peritonitis, WT MC displayed a clear survival advantage over coengrafted St2(-/-) MC. IL-33 blockade specifically attenuated this survival advantage, confirming IL-33 as the relevant ST2 ligand mediating MC survival in vivo. Together, these data reveal a cell-intrinsic role for the IL-33/ST2 axis in the regulation of apoptosis in MC, identifying thereby a previously unappreciated pathway supporting expansion of the MC population with inflammation.

Pathogenicity of autoreactive Th17 cells is dependent on T-bet expression in non-T-helper cells in experimental autoimmune encephalomyelitis (BA13P.117)

Abstract Experimental autoimmune encephalomyelitis is a murine model for multiple sclerosis in which autoreactive CD4+ T-helper cells infiltrate the central nervous system (CNS) and initiate autoimmune inflammation. Previous studies have shown that EAE induction via the adoptive transfer of CNS antigen-specific Th17 cells requires T-cell-intrinsic expression of the transcription factor T-bet, but the potential pathogenic role of T-bet expression in non-T-helper cells remains unclear. Using T-bet-ZsGreen reporter mice, we confirmed that multiple non-T-helper cell populations express T-bet in the CNS during active EAE. To assess the pathogenic contribution of T-bet in non-Th cells, we transferred 2D2-transgenic (expressing a CNS antigen-specific TCR) T-bet-/- or WT Th17 cells into T-bet-/- or WT recipient mice. Consistent with previous reports, 2D2 T-bet-/- Th17 cells did not induce significant levels of EAE disease in either T-bet-/- or WT recipient mice, supporting the role for T-bet in CD4+ Th cells. Surprisingly, WT Th17 cells, while fully pathogenic in WT hosts, were unable to induce EAE in T-bet-/- hosts. Our preliminary data suggest that 2D2 WT Th17 cells were unable to breach the blood-brain barrier and infiltrate the CNS parenchyma due to ineffective local re-activation of 2D2 WT cells in the CNS of T-bet-/- recipients. Ongoing studies will seek to identify the role of T-bet expression in non-Th cell populations and their interactions with 2D2 Th17 cells in EAE induction.

The receptor for advanced glycation end products (RAGE) affects T cell differentiation in OVA induced asthma.

The receptor for glycation end products (RAGE) has been previously implicated in shaping the adaptive immune response. RAGE is expressed in T cells after activation and constitutively in T cells from patients with diabetes. The effects of RAGE on adaptive immune responses are not clear: Previous reports show that RAGE blockade affects Th1 responses. To clarify the role of RAGE in adaptive immune responses and the mechanisms of its effects, we examined whether RAGE plays a role in T cell activation in a Th2 response involving ovalbumin (OVA)-induced asthma in mice. WT and RAGE deficient wild-type and OT-II mice, expressing a T cell receptor specific for OVA, were immunized intranasally with OVA. Lung cellular infiltration and T cell responses were analyzed by immunostaining, FACS, and multiplex bead analyses for cytokines. RAGE deficient mice showed reduced cellular infiltration in the bronchial alveolar lavage fluid and impaired T cell activation in the mediastinal lymph nodes when compared with WT mice. In addition, RAGE deficiency resulted in reduced OT-II T cell infiltration of the lung and impaired IFNγ and IL-5 production when compared with WT mice and reduced infiltration when transferred into WT hosts. When cultured under conditions favoring the differentiation of T cells subsets, RAGE deficient T cells showed reduced production of IFNγ but increased production of IL-17. Our data show a stimulatory role for RAGE in T activation in OVA-induced asthma. This role is largely mediated by the effects of RAGE on T cell proliferation and differentiation. These findings suggest that RAGE may play a regulatory role in T cell responses following immune activation.

Host B7-H4 Regulates Antitumor T Cell Responses through Inhibition of Myeloid-Derived Suppressor Cells in a 4T1 Tumor Transplantation Model

B7-H4, a member of the B7 family of T cell immunomodulatory proteins, has been shown to inhibit T cell responses and neutrophil expansion during bacterial infections. However, the role of B7-H4 in the immune response during tumor growth has been unclear. In this study, we examined the host immune responses in B7-H4-deficient (knockout [KO]) or sufficient (wild-type [WT]) BALB/cJ mice upon transplantation of murine 4T1 carcinoma cells that had little B7-H4 expression. We reveal that host B7-H4 not only dampens the antitumor Th1 responses, but also inhibits the protumor function of myeloid-derived suppressor cells (MDSC). We observed increased expression of both antitumor immune effectors and protumor MDSC-associated transcripts in 4T1 tumors grown in B7-H4 KO mice compared with those grown in WT hosts. Consistently, MDSCs derived from B7-H4 KO mice suppressed T cell proliferation more potently than their WT counterparts. Although the primary growth of 4T1 tumors in B7-H4 KO hosts was similar to that in WT mice, tumors that had grown in B7-H4 KO hosts grew much slower than those from WT mice when subsequently transplanted into WT hosts. Importantly, this differential tumor growth during the secondary transplantation was abrogated when recipient mice lacked T cells, indicating that the immune environment in B7-H4 KO hosts allowed outgrowth of 4T1 tumors with reduced immune-evasive capacities against T cells. Thus, B7-H4 can inhibit both antitumor T cells and protumor MDSCs, influencing the immune-evasive character of the outgrowing tumors. These factors should be considered if B7-H4 blockade is to be used for cancer immunotherapy.

Chemotaxis of bone marrow derived eosinophils in vivo: A novel method to explore receptor‐dependent trafficking in the mouse

Here, we describe a novel method via which ex vivo cultured mouse bone marrow derived eosinophils (bmEos) can be adoptively transferred into recipient mice in order to study receptor-dependent recruitment to lung tissue in vivo. Intratracheal instillation of recombinant human eotaxin-2 (hCCL24) prior to introduction of bmEos via tail vein injection resulted in an approximately fourfold increase in Siglec F-positive/CD11c-negative eosinophils in the lungs of eosinophil-deficient ΔdblGATA recipient mice compared with controls. As anticipated, bmEos generated from CCR3-gene-deleted mice did not migrate to the lung in response to hCCL24 in this model, indicating specific receptor dependence. BmEos generated from GFP-positive BALB/c mice responded similarly to hCCL24 in vitro and were detected in lung tissue of BALB/c WT as well as BALB/c ΔdblGATA eosinophil-deficient recipient mice, at approximately fourfold (at 5 h post-injection) and approximately threefold (at 24 h postinjection) over baseline, respectively. Comparable results were obtained with GFP-positive C57BL/6 bmEos responding to intratracheal hCCL24 in C57BL/6 ΔdblGATA recipient mice. The use of ex vivo cultured bmEos via one or more of these methods offers the possibility of manipulating bmEos prior to transfer into a WT or gene-deleted recipient host. Thus, this chemotaxis model represents a novel and robust tool for pharmacological studies in vivo.

Allergic Conjunctivitis Renders CD4+ T Cells Resistant to T Regulatory Cells and Exacerbates Corneal Allograft Rejection

Allergic diseases rob corneal allografts of immune privilege and increase immune rejection. Corneal allograft rejection in BALB/c allergic hosts was analyzed using a short ragweed (SWR) pollen model of allergic conjunctivitis. Allergic conjunctivitis did not induce exaggerated T-cell responses to donor C57BL/6 (B6) alloantigens or stimulate cytotoxic T lymphocyte (CTL) responses. Allergic conjunctivitis did affect T regulatory cells (Tregs) that support graft survival. Exogenous IL-4, but not IL-5 or IL-13, prevented Treg suppression of CD4(+) effector T cells isolated from naïve mice. However, mice with allergic conjunctivitis developed Tregs that suppressed CD4(+) effector T-cell proliferation. In addition, IL-4 did not inhibit Treg suppression of IL-4Rα(-/-) CD4(+) T-cell responses, suggesting that IL-4 rendered effector T cells resistant to Tregs. SRW-sensitized IL-4Rα(-/-) mice displayed the same 50% graft survival as nonallergic WT mice, that was significantly less than the 100% rejection that occurred in allergic WT hosts, supporting the role of IL-4 in the abrogation of immune privilege. Moreover, exacerbation of corneal allograft rejection in allergic mice was reversed by administering anti-IL-4 antibody. Thus, allergy-induced exacerbation of corneal graft rejection is due to the production of IL-4, which renders effector T cells resistant to Treg suppression of alloimmune responses.

T cell intrinsic NOD2 is dispensable for CD8 T cell immunity.

NOD2 is an intracellular pattern recognition receptor that provides innate sensing of bacterial muramyl dipeptide by host cells, such as dendritic cells, macrophages and epithelial cells. While NOD2's role as an innate pathogen sensor is well established, NOD2 is also expressed at low levels in T cells and there are conflicting data as to whether NOD2 plays an intrinsic role in T cell function. Here we show that following adoptive transfer into WT hosts, NOD2−/− OT-I T cells show a small decrease in the number of OVA-specific CD8 T cells recovered at the peak of the response to respiratory influenza virus infection. On the other hand, no such defect was observed upon intranasal immunization with a replication defective adenovirus carrying the OVA epitope recognized by OT-I, or when OVA was delivered with LPS subcutaneously, or when influenza-OVA was delivered intraperitoneally. Thus we observed a selective defect in NOD2-deficient T cell responses only during a live viral infection. Moreover, there was no apparent defect when NOD2−/− OT-I T cells were stimulated in vitro. Finally, this selective defect in recovery of NOD2-deficient CD8 T cells was not observed in a non-transgenic respiratory infection model in which mixed bone marrow chimeras were used such that the NOD2−/− T cells were allowed to develop and respond in a NOD2-sufficient host. Taken together our data indicate that T cell intrinsic NOD2 is not required for CD8 T cell responses to antigen delivered under a variety of conditions in vitro and in vivo. However, CD8 T cells that have developed in the absence of NOD2 show a selective and modest impairment in their response to live respiratory influenza infection.

NOD2-mediated dysbiosis predisposes mice to transmissible colitis and colorectal cancer

Instability in the composition of gut bacterial communities (dysbiosis) has been linked to common human intestinal disorders, such as Crohn's disease and colorectal cancer. Here, we show that dysbiosis caused by Nod2 deficiency gives rise to a reversible, communicable risk of colitis and colitis-associated carcinogenesis in mice. Loss of either Nod2 or RIP2 resulted in a proinflammatory microenvironment that enhanced epithelial dysplasia following chemically induced injury. The condition could be improved by treatment with antibiotics or an anti-interleukin-6 receptor-neutralizing antibody. Genotype-dependent disease risk was communicable via maternally transmitted microbiota in both Nod2-deficient and WT hosts. Furthermore, reciprocal microbiota transplantation reduced disease risk in Nod2-deficient mice and led to long-term changes in intestinal microbial communities. Conversely, disease risk was enhanced in WT hosts that were recolonized with dysbiotic fecal microbiota from Nod2-deficient mice. Thus, we demonstrated that licensing of dysbiotic microbiota is a critical component of disease risk. Our results demonstrate that NOD2 has an unexpected role in shaping a protective assembly of gut bacterial communities and suggest that manipulation of dysbiosis is a potential therapeutic approach in the treatment of human intestinal disorders.

Itk and antigen specific CD8+ T cell memory differentiation (110.8)

Abstract It has been shown that Itk, a Tec kinase family member, is important for T cell development and differentiation. CD4+ and CD8+ T cells in Itk-/- mice display innate memory phenotype. Since Itk-/- CD8+ T cells preferentially develop into innate memory T cells in thymus, we aimed to determine whether naïve Itk-/- CD8+ T cells also preferentially differentiate into memory T cells after primary response to foreign antigens. To study the intrinsic and extrinsic effects of Itk in naïve CD8+ T cell differentiation into memory T cells, we used an OVA-Listeria monocytogenes infection model in which naïve OTI Rag1-/- T cells or OTI Itk-/- Rag1-/- T cells were adoptively transferred into Itk-/- or WT recipient mice. We found that naïve OTI ITK-/- Rag1-/- T cells have comparable ability to WT OTI Rag-/- T cells in memory T cell differentiation after a 5-week infection in WT hosts. In contrast, WT OTI Rag1-/- T cells are deficient in differentiating into memory T cells when placed in Itk-/- hosts. Although Itk affects the CD8+ T cell development in the thymus, its absence does not affect antigen specific CD8+ memory T cell differentiation. However, Itk-/- mice have an impaired environment for naïve CD8+ T cells differentiation into memory T cells during L. monocytogenes infection. These results suggest that Itk expression in cells other than CD8+ T cells is critical for supporting the antigen specific CD8+ T cell memory differentiation.

Krüppel-like factor 4 (KLF4) promotes the survival of natural killer cells and maintains the number of conventional dendritic cells in the spleen

The development and survival of NK cells rely on a complex, spatiotemporal gene expression pattern regulated by specific transcription factors in NK cells and tissue-specific microenvironments supported by hematopoietic cells. Here, we show that somatic deletion of the KLF4 gene, using inducible and lineage-specific cre-transgenic mice, leads to a significant reduction of NK cells (NK1.1(+) TCR-β(-)) in the blood and spleen but not in the BM, liver, or LNs. Functional and immunophenotypic analyses revealed increased apoptosis of CD27(+/-) CD11b(+) NK cells in the spleen of KLF4-deficient mice, although remaining NK cells were able to lyse tumor target cells and produce IFN-γ. A normal recovery of adoptively transferred KLF4-deficient NK cells in WT hosts suggested that the survival defect was not intrinsic of NK cells. However, BM chimeras using KLF4-deficient mice as donors indicated that reduced survival of NK cells depended on BM-derived hematopoietic cells in the spleen. The number of CD11c(hi) DCs, which are known to support NK cell survival, was reduced significantly in the spleen of KLF4-deficient mice, likely a result of a lower number of precDC progenitor cells in this tissue. Taken together, our data suggest that the pluripotency-associated gene KLF4 is required for the maintenance of DCs in the spleen and consequently, survival of differentiated NK cells in this tissue.

Abstract 3451: Lack of CD47 in the tumor microenvironment enhances anti-tumor adaptive immune responses when combined with ionizing radiation

Abstract Over half of the new cancer patients diagnosed this year in the United States will require ionizing radiation (IR) therapy as part of their course of treatment. Achieving a curative response, however, is limited by detrimental side effects and off-target toxicities of IR to normal cells. We previously demonstrated that CD47 null mice or blockade of CD47 confers radioprotection to normal tissues including radiosensitive hematopoietic progenitors. On the other hand, blockade of CD47 enhanced the radiation-induced tumor growth delay in two syngenic mouse models. One possible explanation for this observation is that, by protecting tumor-associated immune cells, CD47 suppression increases tumor immune surveillance. To examine the role of T cell immunity, we used the F15-12 RM mouse fibrosarcoma model in athymic mice. Blockade of CD47 in combination with IR did not alter tumor growth in these T-cell deficient mice versus IR alone. However, adoptive transfer of CD8+ T-cells in combination with CD47 blockade and IR significantly enhanced the reduction in tumor growth when compared to tumors of mice irradiated in combination with the T cell transfer alone (186 ± 50 vs. 370 ± 123 mm3 respectively, N=8). In vitro experiments showed that blockade of CD47 enhances antigen dependent CD8+ mediated cytotoxicity of tumor cells. Furthermore, in a syngeneic tumor model of B16 melanoma we observed over a 50% reduction in volume of irradiated tumors in a CD47-/- host versus a WT host. Immunohistochemical staining indicated an increase of intratumoral CD8+ cytotoxic T-cells. Further analysis indicated that lack or blockade of CD47 in combination with IR resulted in a significant increase in granzyme B expression, further indicating that the increased target cell death may be mediated by this pathway. CD47 suppression may also reduce tumor growth by altering the immunosuppressive factor VEGF. In both tumor models, either blockade of or lack of CD47 in combination with IR was associated with a reduction in VEGF. VEGF is a potent pro-angiogenic factor and a potent immunosuppressive factor that inhibits activation of cytotoxic T-cells. Our findings indicate that agents targeting CD47 enhance anti-tumor T cell immunity when combined with radiation. Combining CD47 suppression with IR and adoptive T cell transfer may increase the percentage of curative responses. 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 3451. doi:1538-7445.AM2012-3451

Loss of the α2β1 integrin alters human papilloma virus-induced squamous carcinoma progression in vivo and in vitro.

Expression of the α2β1 integrin, a receptor for collagens and laminin, is altered during tumor progression. Recent studies have linked polymorphisms in the α2 integrin gene with oral, squamous cell carcinoma (SCC). To determine the α2β1 integrin's role in SCC progression, we crossed α2-null mice with K14-HPV16 transgenic animals. Pathological progression to invasive carcinoma was evaluated in HPV-positive, α2-null (HPV/KO) and HPV-positive, wild-type (HPV/WT) animals. α2β1 integrin expression stimulated progression from hyperplasia and papillomatosis to dysplasia with concomitant dermal mast cell infiltration. Moreover, lymph node metastasis was decreased by 31.3% in HPV/KO, compared to HPV/WT, animals. To evaluate the integrin-specific impact on the malignant epithelium versus the microenvironment, we developed primary tumor cell lines. Although transition from dysplasia to carcinoma was unaltered during spontaneous tumor development, isolated primary HPV/KO SCC cell lines demonstrated decreased migration and invasion, compared to HPV/WT cells. When HPV/WT and HPV/KO SCC cells were orthotopically injected into WT or KO hosts, tumor α2β1 integrin expression resulted in decreased tumor latency, regardless of host integrin status. HPV/WT SCC lines failed to demonstrate a proliferative advantage in vitro, however, the HPV/WT tumors demonstrated increased growth compared to HPV/KO SCC lines in vivo. Although contributions of the integrin to the microenvironment cannot be excluded, our studies indicate that α2β1 integrin expression by HPV-transformed keratinocytes modulates SCC growth and progression.

Abstract 415: Dynamic interplay of tumor and microenvironmental contributions of the α2β1 integrin in squamous cell carcinoma

Abstract The complex interplay between tumor cells and their surrounding microenvironment define cancer progression. The α2β1 integrin, expressed by subsets of epithelial, endothelial, fibroblast, and inflammatory cells, is a receptor for matrix and non-matrix ligands, including collagens, laminins, and immunomodulatory molecules C1q and collectins. Altered α2β1 integrin expression in cancer has been linked to tumor progression; recent studies have linked polymorphisms in the α2β1 integrin with oral, squamous cell carcinoma (SCC). We hypothesized that the α2β1 integrin functions in SCC initiation or progression by modulating interactions between the squamous epithelium and/or tumor microenvironment. To determine the role of α2β1 integrin expression on SCC progression, we crossed α2β1 integrin-null mice with K14-HPV transgenic animals, a well-established model of epithelial carcinogenesis. Progression from hyperplasia to dysplasia and invasive carcinoma was evaluated in HPV-positive, α2β1 integrin-null (HPV/KO) and HPV-positive, wild-type (HPV/WT) animals. Our data demonstrate that during SCC progression, expression of the α2β1 integrin stimulates progression from hyperplasia and papillomatosis to dysplasia. Decreased dysplasia in HPV/KO animals at early time points of tumor progression directly correlated with reduced dermal mast cell infiltration. Moreover, lymph node metastasis was decreased by 31.3% and associated with alterations in lymphatic vasculature within the tumor microenvironment of HPV/KO, compared to HPV/WT, animals. Since these studies utilized global α2β1 integrin knockout mice, we developed primary tumor cell lines to evaluate the integrin-specific impacts on the malignant epithelium versus the host microenvironment. Although transition from dysplasia to carcinoma was unaltered in our original tumor studies, isolated primary HPV/KO SCC cell lines had decreased invasion in a 3D transwell migration assay, compared to HPV/WT cells. When HPV/WT and HPV/KO SCC cell lines were orthotopically injected into either WT or KO hosts, α2β1 integrin-specific expression on tumor cells decreased tumor latency, regardless of host integrin status. HPV/WT SCC lines failed to demonstrate a proliferative advantage in vitro, however, the HPV/WT tumors demonstrated increased growth rates compared to HPV/KO SCC lines in vivo. Therefore, these latter data suggest that contributions of the tumor microenvironment cannot be excluded and are likely modulating SCC growth characteristics. Our studies indicate the α2β1 integrin plays diverse roles during tumor progression, acting on the tumor and tumor microenvironment. Although the α2β1 integrin plays no obvious role during normal development, exposure to physiological stresses, such as cancer, unmasks functions of the α2β1 integrin to reveal its importance in tissue biology. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 415. doi:10.1158/1538-7445.AM2011-415