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Protein kinase A (PKA) is a holoenzyme that consists of a dimer of regulatory subunits and two inactive catalytic subunits that bind to the regulatory subunit dimer. Four regulatory subunits (RIα, RIβ, RIIα, RIIβ) and four catalytic subunits (Cα, Cβ, Cγ, Prkx) have been described in the human and mouse genomes. Previous studies showed that complete inactivation of the Prkar1a subunit (coding for RIα) in the germline leads to embryonic lethality, while Prkar1a–deficient mice are viable and develop schwannomas, thyroid, and bone neoplasms, and rarely lymphomas and sarcomas. Mice with inactivation of the Prkar2a and Prkar2b genes (coding for RIIα and RIIβ, respectively) are also viable but have not been studied for their susceptibility to any tumors. Cohorts of Prkar1a +/− , Prkar2a +/− , Prkar2a −/− , Prkar2b +/− and wild type (WT) mice have been observed between 5 and 25 months of age for the development of hematologic malignancies. Tissues were studied by immunohistochemistry; tumor-specific markers were also used as indicated. Cell sorting and protein studies were also performed. Both Prkar2a −/− and Prkar2a +/− mice frequently developed hematopoietic neoplasms dominated by histiocytic sarcomas (HS) with rare diffuse large B cell lymphomas (DLBCL). Southern blot analysis confirmed that the tumors diagnosed histologically as DLBCL were clonal B cell neoplasms. Mice with other genotypes did not develop a significant number of similar neoplasms. Prkar2a deficiency predisposes to hematopoietic malignancies in vivo. RIIα’s likely association with HS and DLBCL was hitherto unrecognized and may lead to better understanding of these rare neoplasms.

The most deadly complication of Plasmodium falciparum infection is cerebral malaria (CM) with a case fatality rate of 15-25% in African children despite effective antimalarial chemotherapy. There are no adjunctive treatments for CM, so there is an urgent need to identify new targets for therapy. Here we show that the glutamine analog 6-diazo-5-oxo-L-norleucine (DON) rescues mice from CM when administered late in the infection a time at which mice already are suffering blood-brain barrier dysfunction, brain swelling, and hemorrhaging accompanied by accumulation of parasite-specific CD8(+) effector T cells and infected red blood cells in the brain. Remarkably, within hours of DON treatment mice showed blood-brain barrier integrity, reduced brain swelling, decreased function of activated effector CD8(+) T cells in the brain, and levels of brain metabolites that resembled those in uninfected mice. These results suggest DON as a strong candidate for an effective adjunctive therapy for CM in African children.

Malaria is an infectious disease caused by parasites of several Plasmodium spp. Cerebral malaria (CM) is a common form of severe malaria resulting in nearly 700,000 deaths each year in Africa alone. At present, there is no adjunctive therapy for CM. Although the mechanisms underlying the pathogenesis of CM are incompletely understood, it is likely that both intrinsic features of the parasite and the human host’s immune response contribute to disease. The kinase mammalian target of rapamycin (mTOR) is a central regulator of immune responses, and drugs that inhibit the mTOR pathway have been shown to be antiparasitic. In a mouse model of CM, experimental CM (ECM), we show that the mTOR inhibitor rapamycin protects against ECM when administered within the first 4 days of infection. Treatment with rapamycin increased survival, blocked breakdown of the blood-brain barrier and brain hemorrhaging, decreased the influx of both CD4+ and CD8+ T cells into the brain and the accumulation of parasitized red blood cells in the brain. Rapamycin induced marked transcriptional changes in the brains of infected mice, and analysis of transcription profiles predicted that rapamycin blocked leukocyte trafficking to and proliferation in the brain. Remarkably, animals were protected against ECM even though rapamycin treatment significantly increased the inflammatory response induced by infection in both the brain and spleen. These results open a new avenue for the development of highly selective adjunctive therapies for CM by targeting pathways that regulate host and parasite metabolism., IMPORTANCE Malaria is a highly prevalent infectious disease caused by parasites of several Plasmodium spp. Malaria is usually uncomplicated and resolves with time; however, in about 1% of cases, almost exclusively among young children, malaria becomes severe and life threatening, resulting in nearly 700,000 deaths each year in Africa alone. Among the most severe complications of Plasmodium falciparum infection is cerebral malaria with a fatality rate of 15 to 20%, despite treatment with antimalarial drugs. Cerebral malaria takes a second toll on African children, leaving survivors at high risk of debilitating neurological defects. At present, we have no effective adjunctive therapies for cerebral malaria, and developing such therapies would have a large impact on saving young lives in Africa. Here we report results that open a new avenue for the development of highly selective adjunctive therapies for cerebral malaria by targeting pathways that regulate host and parasite metabolism.

Several mouse models of systemic lupus erythematosus, including FcγRIIB-KO and TLR7tg mice, develop an expansion of an atypical NK cell subset with functional similarity to cells referred as IFN-producing killer DCs or pre-mature NKs in other systems. In this study, we show that atypical NKs purified from spleens of systemic lupus erythematosus–prone mice, and identified as NK1.1+CD11c+CD122+MHC-II+, induce persistent autoimmune disease in an IFN-I– and CD40L-dependent manner when transferred to wild-type mice. A single transfer of 4 × 106 NK1.1+ cells from TLR7tg into wild-type induces a 2-wk–long wave of inflammatory cytokines in the serum; a sustained increase in T cell activation and follicular helper cells for the following months; and a progressive expansion of dendritic cells, monocytes, and granulocytes. Furthermore, IL-15 deficiency, which impedes development of NK cells, ameliorates the autoimmune pathology of TLR7tg mice. These results suggest that cells of the NK lineage can develop into cytokine-producing/APCs that affect the priming and progression of systemic autoimmune disease.

Here we show that iNOS-deficient mice display enhanced classically activated M1 macrophage polarization without major effects on alternatively activated M2 macrophages. eNOS and nNOS mutant mice show comparable M1 macrophage polarization compared with wild-type control mice. Addition of N6-(1-iminoethyl)-L-lysine dihydrochloride, an iNOS inhibitor, significantly enhances M1 macrophage polarization while S-nitroso-N-acetylpenicillamine, a NO donor, suppresses M1 macrophage polarization. NO derived from iNOS mediates nitration of tyrosine residues in IRF5 protein, leading to the suppression of IRF5-targeted M1 macrophage signature gene activation. Computational analyses corroborate a circuit that fine-tunes the expression of IL-12 by iNOS in macrophages, potentially enabling versatile responses based on changing microenvironments. Finally, studies of an experimental model of endotoxin shock show that iNOS deficiency results in more severe inflammation with an enhanced M1 macrophage activation phenotype. These results suggest that NO derived from iNOS in activated macrophages suppresses M1 macrophage polarization., In response to microbial ligands, IRF5 promotes pro-inflammatory M1 macrophage activation and production of nitrous oxide. Here the authors show that nitrous oxide modifies IRF5 tyrosine residues as a negative feedback, limiting the inflammatory response and protecting from endotoxin shock.

Six cases of megakaryocytic leukemia (MKL) were identified and analyzed for morphology and molecular features. MKL were composed of megakaryocyte lineage cells ranging from immature to quite mature cells. VWF, GATA1 and RUNX1 were strongly expressed in megakaryocytes in both normal spleen and MKL as analyzed by immunohistochemistry (IHC). Altered expression of Meis1, Pbx1 and Psen2 and Lef1 in MKL detected with oligonucleotide microarrays was confirmed by qPCR and IHC. This is the first report of spontaneous MKL in mice, defining VWF as a biomarker for diagnosis and suggesting possible involvement of a series of genes in disease pathogenesis.

CDKN1B (p27) regulates cell-cycle progression at the G1-S transition by suppressing the cyclin E/CDK2 kinase complex. In normal lymphocytes and most human B cell non-Hodgkin lymphomas (NHL), there is an inverse correlation between proliferative activity and expression of p27; however, a subset of NHL with high mitotic indices expresses p27, which is inactive due to sequestration in nuclear protein complexes or due to cytoplasmic retention. Our studies of mouse B cell NHL also identified cases with high proliferative activity and high levels of p27 at a surprisingly high frequency. Here, p27 was complexed with D-type cyclins 1 and 3 and with the COPS9 protein, JAB1. In addition, we found cytoplasmic sequestration following phosphorylation by activated AKT.

IL-21 is a type I cytokine whose receptor is expressed on T, B, and NK cells. Within the B cell lineage, IL-21 regulates IgG1 production and cooperates with IL-4 for the production of multiple Ab classes in vivo. Using IL-21-transgenic mice and hydrodynamics-based gene delivery of IL-21 plasmid DNA into wild-type mice as well as in vitro studies, we demonstrate that although IL-21 induces death of resting B cells, it promotes differentiation of B cells into postswitch and plasma cells. Thus, IL-21 differentially influences B cell fate depending on the signaling context, explaining how IL-21 can be proapoptotic for B cells in vitro yet critical for Ag-specific Ig production in vivo. Moreover, we demonstrate that IL-21 unexpectedly induces expression of both Blimp-1 and Bcl-6, indicating mechanisms as to how IL-21 can serve as a complex regulator of B cell maturation and terminal differentiation. Finally, BXSB-Yaa mice, which develop a systemic lupus erythematosus-like disease, have greatly elevated IL-21, suggesting a role for IL-21 in the development of autoimmune disease.

The WEHI 231 B cell lymphoma is used as a model of self-tolerance by clonal deletion because B cell receptor (BCR) ligation results in apoptosis. Two critical events precede cell death: an early rise and fall in expression of MYC and cell-cycle arrest associated with enhanced expression of p21, p27, and p53. CTCF is a transcription factor identified as a repressor of MYC recently shown to cause cell growth inhibition. The present studies demonstrate that BCR ligation of WEHI 231 as well as of normal immature B cells greatly increased expression of CTCF in association with down-regulation of MYC followed by growth arrest and cell death. Conditional expression of CTCF in WEHI 231 mimicked BCR ligation with activated cells showing repressed expression of MYC, enhanced expression of p27, p21, p53, and p19 ARF , and inhibition of cell growth and induction of apoptosis. In keeping with a central role for CTCF in control of B cell death, conditional expression of a CTCF antisense construct in WEHI 231 resulted in inhibition of p27, p21, p53, and p19 ARF in association with enhanced expression of MYC. Activation of the endogenous CTCF locus by BCR ligation was also mimicked by three other routes to apoptotic death in WEHI 231: inhibition of the phosphoinositide 3-kinase or mTOR/FRAP signaling cascades and treatment with transforming growth factor (TGF)-β. Rapid activation of CTCF by BCR ligation or treatment with TGF-β was suppressed by ligation of CD40. These results demonstrate that CTCF is a common determinant to different pathways of death signaling in immature B cells.

There is evidence that autoimmune disease might be induced by deficient regulation of innate immune pathways that normally induce type I interferon in response to pathogen-derived nucleic acids. To investigate a potential role for nucleic acid sensing pathways with cytosolic localization and more ubiquitous expression, we tested the requirement for MAVS (dsRNA-sensing) or STING (dsDNA-sensing) in the lupus autoimmune disease developed by FcγRIIB-KO (R2−/−) mice. These experiments revealed that STING was mildly protective, while MAVS was an essential factor for autoimmune disease in R2−/− mice. We found that MAVS deficiency, but not type I IFN receptor deficiency, completely eliminated autoantibodies and autoimmune pathology in R2−/− mice. MAVS deficiency also eliminated spontaneous activation of B and T cells, germinal center formation and follicular helper T cell development. Using mixed bone marrow reconstitution experiments, we determined that MAVS was required for autoreactivity in a B cell intrinsic manner, with a profound effect on B cell survival in the germinal center. MAVS deficiency did not alter BCR-proximal signaling, but resulted in diminished long term proliferative capacity of B cells, with lower cyclin D2 and Bcl-xL expression 24 hours after anti-IgM stimulation. MAVS deficiency also resulted in B cell developmental defects, fewer total B cells but a skewing toward marginal zone and against the follicular B cell program. Overall MAVS seems to provide its costimulatory effect independent of type I IFN, by enhancing the activation of NFκB in situations where T cell help or other modes of costimulation are not present and most importantly, by providing survival stimulus for autoreactive B cells.

B cells express the innate immune system receptor, Toll like receptor 9 (TLR9), a potent regulator of B cell function, that signals in response to unmethylated CpG sequences in microbial DNA. A dichotomy in the function of the two major classes of CpG-containing oligonucleotides, namely CpG-A and CpG-B, appears to exist with CpG-A restricted to inducing type 1 interferon (type 1 IFN) in innate immune cells and CpG-B to activating B cells to proliferate and produce antibody and inflammatory cytokines. Although CpGs are candidates for adjuvants to boost the innate and adaptive immunity, our understanding of the effect of CpG-A and CpG-B on B cell responses is incomplete. We provide evidence that CpG-A activated B cells in vitro in a TLR9 dependent fashion resulting in the production of IL-6, proliferation, and alterations in the expression of a variety of B cell surface markers, albeit in a less robust fashion as compared to CpG-B. Neither CpGB nor CpG-A alone induced B cells to express type 1 IFN. However, when incorporated into the cationic lipid, DOTAP, CpG-A, but not CpG-B induced a robust type 1 IFN response in B cells both in vitro and in vivo. Conversely, CpG-B-DOTAP but not CpGA-DOTAP promoted B cell germinal center responses in vivo and the production of high affinity antibodies. We also provide evidence that difference in the function of CpGs versus DOTAP-associated-CpGs may be related to their intracellular trafficking in B cells since DOTAP enhances the trafficking of CpG-B but not CpG-A to late endosomal compartments. These findings have important implications for the use of CpG-A and CpG-B to augment type 1 IFN production versus B cell responses in vivo.

Lupus is a systemic autoimmune disorder affecting multiple organ systems including the skin, kidneys, spleen, lungs, and brain. Severe SLE often manifests with multiple psychiatric and neurological sequelae, and may be accompanied by CNS vasculitis. However, the cellular contributors to CNS disease in lupus patients remain poorly defined. We have uncovered a unique bias for CD8+ T cell infiltration in the CNS of mice expressing multiple copies of Toll-like receptor 7 (TLR7[Tg]), which present with a lupus-like disease. These animals exhibit blood brain barrier damage and neuropathology in the presence of infiltrating T cells. However, genetic ablation of CD8+ T cells in lupus-prone mice by removal of the major histocompatibility complex (MHC) adaptor protein b2m results in aggravation of disease, suggesting the removal of a protective population. Relative to the peripheral CD8+ T cells in lupus-prone mice, those in the CNS represent the most activated lymphocytes in the animal, display a tissue resident-memory phenotype, and can home to the brain. We have also identified a population of CD8+ T cells in the cerebrospinal fluid (CSF) of several lupus patients. Similar to our animal model findings the human CD8+ T cells in the CSF have a large increase in antigen experience by surface phenotyping relative to lymphocytes from peripheral blood. Our ongoing studies aim to elucidate specifically how these CD8+ T cells enter the CNS and further clarify their role in neuropathology. Our findings suggest a possible mechanism of CNS pathology regulation that could have applicability to human neuropsychiatric manifestations of SLE.

Apoptotic cell (AC) clearance is essential for immune homeostasis. Here we show that mouse CD300f (CLM-1) recognizes outer membrane-exposed phosphatidylserine, and regulates the phagocytosis of ACs. CD300f accumulates in phagocytic cups at AC contact sites. Phosphorylation within CD300f cytoplasmic tail tyrosine-based motifs initiates signals that positively or negatively regulate AC phagocytosis. Y276 phosphorylation is necessary for enhanced CD300f-mediated phagocytosis through the recruitment of the p85α regulatory subunit of phosphatidylinositol-3-kinase (PI3K). CD300f-PI3K association leads to activation of downstream Rac/Cdc42 GTPase and mediates changes of F-actin that drive AC engulfment. Importantly, primary macrophages from CD300f-deficient mice have impaired phagocytosis of ACs. The biological consequence of CD300f deficiency is predisposition to autoimmune disease development, as FcγRIIB-deficient mice develop a systemic lupus erythematosus-like disease at a markedly accelerated rate if CD300f is absent. In this report we identify the mechanism and role of CD300f in AC phagocytosis and maintenance of immune homeostasis.

Malaria infection triggers vigorous host immune responses; however, the parasite ligands, host receptors, and the signaling pathways responsible for these reactions remain unknown or controversial. Malaria parasites primarily reside within RBCs, thereby hiding themselves from direct contact and recognition by host immune cells. Host responses to malaria infection are very different from those elicited by bacterial and viral infections and the host receptors recognizing parasite ligands have been elusive. Here we investigated mouse genome-wide transcriptional responses to infections with two strains of Plasmodium yoelii (N67 and N67C) and discovered differences in innate response pathways corresponding to strain-specific disease phenotypes. Using in vitro RNAi-based gene knockdown and KO mice, we demonstrated that a strong type I IFN (IFN-I) response triggered by RNA polymerase III and melanoma differentiation-associated protein 5, not Toll-like receptors (TLRs), binding of parasite DNA/RNA contributed to a decline of parasitemia in N67-infected mice. We showed that conventional dendritic cells were the major sources of early IFN-I, and that surface expression of phosphatidylserine on infected RBCs might promote their phagocytic uptake, leading to the release of parasite ligands and the IFN-I response in N67 infection. In contrast, an elevated inflammatory response mediated by CD14/TLR and p38 signaling played a role in disease severity and early host death in N67C-infected mice. In addition to identifying cytosolic DNA/RNA sensors and signaling pathways previously unrecognized in malaria infection, our study demonstrates the importance of parasite genetic backgrounds in malaria pathology and provides important information for studying human malaria pathogenesis.

Studies of lymphoid neoplasms occurring in normal or genetically engineered mice have revealed parallels and differences to non-Hodgkin lymphomas (NHL) of humans. Some mouse lymphomas have strong histologic similarities to the human NHL subsets including precursor B- and T-cell lymphoblastic, small lymphocytic, splenic marginal zone, and diffuse large-cell B-cell lymphomas (DLCL); whether molecular parallels also exist is under study. Others mouse types such as sIg+ lymphoblastic B-cell lymphoma have no histologic equivalent in human NHL even though they share molecular deregulation of BCL6 with human DLCL. Finally, Burkitt lymphoma does not appear to occur naturally in mice, but it can be induced with appropriately engineered transgenes.

BCL6 encodes a transcription factor deregulated by chromosomal translocations in human diffuse large cell B lymphomas (DLCL). This study was designed to determine whether Bcl6 might also be involved in lymphomas of mice. BCL6 protein was expressed at high levels in 90% or more of DLCL but not in low grade B lymphomas. Southern hybridisation studies demonstrated altered organisation of Bcl6 in three primary DLCL and the WEHI 231 B-cell lymphoma cell line but not in low grade tumours. Chromosomal painting and fluorescence in situ hybridisation (FISH) analyses of the WEHI 231 metaphase spreads revealed a T(5;16) translocation with Bcl6 on Chromosome 16 at the translocation breakpoint. Deregulated expression of BCL6 is thus likely to contribute to the genesis of DLCL of mice as well as of humans.

Alleles at the Fv1 gene of inbred mice confer resistance to infection and spread of vertically or horizontally transmitted murine leukemia viruses (MuLV). The nucleotide sequence of Fv1 bears similarity to the gag of a human endogenous retrovirus, HERV-L, but is more closely related to the gag-coding sequence of a newly described class of HERV-L-related mouse endogenous retroviruses designated MuERV-L. Both observations suggest an origin of Fv1 from endogenous gag sequences. The molecular definition of Fv1 provided an opportunity to determine the phylogeny of the gene among wild mice and its relation to MuERV-L. PCR primers, chosen to include most of the coding region of Fv1 for both the n and b alleles, were used to amplify sequences from animals of the genus Mus, which were then sequenced. Closely related products were obtained from almost all animals examined that evolved after the separation from Rattus, in which the homologous gene was shown to be absent. A phylogenetic tree generated with Fv1 sequence data differs noticeably from that developed with sequence data from other genes. In addition, non-synonymous changes were found to be present twice as frequently as synonymous changes, a fact that departs from the standard behavior of a structural gene. These observations suggest that the Fv1 gene may have been subjected to possible horizontal transfers as well as to positive Darwinian selection.

The G1 cyclin, cyclin D1, has been implicated in the development of human and mouse tumors. Here we describe immunohistochemical analyses of cyclin D1 for a large panel of mouse B cell tumors. In addition, we characterize cyclin D1 expression in a series of cultured cell lines that represent transformed B cells at different stages of development. Immunohistochemical analysis showed that for low-grade lymphomas, cyclin D1 was expressed by 83% of centroblastic–centrocytic (CBCC) and 14% of small lymphocytic lymphomas (SLL). For high-grade tumors, 28% of B lymphoblastic and 23% of centroblastic tumors expressed cyclin D1, while all immunoblastic lymphomas were negative. Studies of RNA and protein prepared from cultured B lineage tumors showed that cyclin D1 was expressed by all pre-B and most B cell tumors but not by cell lines representative of late B cell differentiation or by plasma cells. Expression of cyclin D1 in the lymphomas was not associated with alterations in the genomic structure of the Fis -1 ( Bcl -1) common proviral integration site or cyclin D1 itself or with cell growth activity as assessed by expression of proliferating cell nuclear antigen (PCNA).

The E3 ligase ARF-BP1 governs the balance of life and death decisions by directing the degradation of p53 and enhancing the transcriptional activity of MYC. We find B cells selectively deficient in ARF-BP1 have many defects in developing and mature B cells associated with increased expression of p53 and reduced expression of Myc. Overexpression of Myc results in suppression of p53 and complete reversal of defects induced by ARF-BP1 deficiency. These findings indicate that the dynamic balance between MYC and p53 required for normal B cell maturation and function is finely tuned and critically dependent on the activities of ARF-BP1.

Systemic lupus erythematosus (SLE) is an autoimmune disorder affecting multiple organ systems including the skin, kidneys, spleen, lungs, and brain. Severe SLE often manifests with multiple psychiatric and neurological sequelae, and may be accompanied by CNS vasculitis. However, the cellular contributors to CNS disease in lupus patients remain poorly defined. Our data demonstrate a unique lymphocyte bias in the CNS of mice expressing multiple copies of Toll-like receptor 7 (TLR7[Tg], FcgRIIB-Yaa), which present with a lupus-like disease. Lupus-prone mice have a substantial population of infiltrating CD8+ T cells in the CNS, a bias that is not present in other peripheral lymphoid or non-lymphoid tissues. These animals exhibit blood-brain barrier damage and neuropathology in the presence of the infiltrating lymphocytes. However, genetic ablation of CD8+ T cells in lupus-prone mice by removal of the major histocompatibility complex (MHC) adaptor protein b2m results in aggravation of disease, suggesting the removal of a protective population. Circulating CD8+ T cells in lupus-prone mice display an activated phenotype, express a number of surface trafficking and adhesion molecules, and can home to the CNS. The endothelium of the brain, but not of other peripheral organs in these mice is activated, expressing adhesion markers complementary to those found on infiltrating CD8+ T cells. Our ongoing studies aim to elucidate specifically how these CD8+ T cells enter the CNS and further clarify their role in neuropathology. Our findings suggest a possible mechanism regulating CNS pathology that could have applicability to human neuropsychiatric manifestations of SLE.

Transcriptional activation of MYC is a hallmark of many B cell lineage neoplasms. MYC provides a constitutive proliferative signal but can also initiate ARF-dependent activation of p53 and apoptosis. The E3 ubiquitin ligase, ARF-BP1, encoded by HUWE1, modulates the activity of both the MYC and the ARF-p53 signaling pathways, prompting us to determine if it is involved in the pathogenesis of MYC-driven B cell lymphomas. ARF-BP1 was expressed at high levels in cell lines from lymphomas with either wild type or mutated p53 but not in ARF-deficient cells. Downregulation of ARF-BP1 resulted in elevated steady state levels of p53, growth arrest and apoptosis. Co-immunoprecipitation studies identified a multiprotein complex comprised of ARF-BP1, ARF, p53, MYC and the multifunctional DNA-binding factor, CTCF, which is involved in the transcriptional regulation of MYC, p53 and ARF. ARF-BP1 bound and ubiquitylated CTCF leading to its proteasomal degradation. ARF-BP1 and CTCF thus appear to be key cofactors linking the MYC proliferative and p53-ARF apoptotic pathways. In addition, ARF-BP1 could be a therapeutic target for MYC-driven B lineage neoplasms, even if p53 is inactive, with inhibition reducing the transcriptional activity of MYC for its target genes and stabilizing the apoptosis-promoting activities of p53.

Amphiregulin (AR), a member of the epidermal growth factor (EGF) family, was found to be as potent as EGF in stimulating the anchorage-dependent growth (ADG) of immortalized, nontransformed human mammary epithelial MCF-10A cells. MCF-10A cells transformed by either an activated human c-Ha-ras protooncogene (MCF-10A ras) or by overexpression of a nonactivated rat c-neu gene (MCF-10A neu) exhibited a 35% reduction in the response to AR in ADG when compared to MCF-10A cells, but AR was still as potent as EGF in these transformants. Exogenous AR exhibited only 15-20% of the activity of EGF in stimulating the anchorage-independent growth, a response that is normally dependent upon exogenous EGF, of the oncogene-transformed MCF-10A cells. MCF-10A cells express low levels of a 1.4-kb AR mRNA transcript, while MCF-10A ras and MCF-10A neu cells display a 15- to 30-fold increase in the levels of AR mRNA and endogenous AR protein as determined by Western blot analysis. Exogenous EGF was found to induced both the AR mRNA and protein in the MCF-10A parental and transformed cells. A 20-mer phosphorothioate antisense deoxyoligonucleotide complementary to the 5' sequence of AR mRNA was able to significantly reduce the levels of endogenous AR protein and to inhibit the EGF-stimulated ADG and anchorage-independent growth of MCF-10A ras and MCF-10A neu cells. These data suggest that AR may function as an EGF-dependent autocrine growth factor in mammary epithelial cells that have been transformed by either a point-mutated c-Ha-ras or c-neu.

TH17 cells are recognized as a unique subset of T helper cells that have critical roles in the pathogenesis of autoimmunity and tissue inflammation. Although RORγt is necessary for the generation of TH17 cells, the molecular mechanisms underlying the functional diversity of TH17 cells are not fully understood. Here we show that a member of interferon regulatory factor (IRF) family of transcription factors, IRF8, has a critical role in silencing TH17-cell differentiation. Mice with a conventional knockout, as well as a T cell-specific deletion, of the Irf8 gene exhibited more efficient TH17 cells. Indeed, studies of an experimental model of colitis showed that IRF8 deficiency resulted in more severe inflammation with an enhanced TH17 phenotype. IRF8 was induced steadily and inhibited TH17-cell differentiation during TH17 lineage commitment at least in part through its physical interaction with RORγt. These findings define IRF8 as a novel intrinsic transcriptional inhibitor of TH17-cell differentiation., The molecular mechanisms that regulate TH17 cell diversity are poorly understood. Ouyang et al. show that the transcription factor interferon regulatory factor-8 is required for TH17-cell differentiation and that its absence increases the severity of an experimental model of colitis.

Transcriptional control of marginal zone (MZ) and follicular (FO) B cell development remains incompletely understood. The transcription factor, IFN regulatory factor (IRF)8, is known to play important roles in the differentiation of early B cells. In this article, we demonstrate that IRF8 is also required for normal development of MZ and FO B cells. Mice with a conventional knockout of Irf8 (IRF8−/−) or a point mutation in the IRF association domain of IRF8 had increased numbers of MZ B cells. To determine the B cell-intrinsic effects of IRF8 deficiency, we generated mice with a conditional allele of Irf8 crossed with CD19-Cre mice (designated IRF8-conditional knockout [CKO]). These mice had enlarged MZ and increased numbers of MZ and FO B cells compared with controls. The FO B cells of CKO mice exhibited reduced expression of CD23 and moderately increased expression of CD21. Gene-expression profiling showed that increased B cell production in IRF8-CKO mice was associated with changes in expression of genes involved in regulation of transcription, signaling, and inflammation. Functional studies showed that IRF8-CKO mice generated normal Ab responses to T-independent and T-dependent Ags. Thus, IRF8 controls the expansion and maturation of MZ and FO B cells but has little effect on B cell function.

Emitting species during chemiluminescence of coelenterate luciferin analogue depended on the fluorescence quantum yield of coelenteramide analogue, on the fluorescence lifetime of its anion, and on the proton concentration of the media.

Background: The canonical function of EEF1A2, normally expressed only in muscle, brain, and heart, is in translational elongation, but recent studies suggest a non-canonical function as a proto-oncogene that is overexpressed in a variety of solid tumors including breast and ovary. Transcriptional profiling of a spectrum of primary mouse B cell lineage neoplasms showed that transcripts encoding EEF1A2 were uniquely overexpressed in plasmacytomas (PCT), tumors of mature plasma cells. Cases of human multiple myeloma expressed significantly higher levels of EEF1A2 transcripts than normal bone marrow plasma cells. High-level expression was also a feature of a subset of cell lines developed from mouse PCT and from the human MM.Methodology/Principal Findings: Heightened expression of EEF1A2 was not associated with increased copy number or coding sequence mutations. shRNA-mediated knockdown of Eef1a2 transcripts and protein was associated with growth inhibition due to delayed G1-S progression, and effects on apoptosis that were seen only under serum-starved conditions. Transcriptional profiles and western blot analyses of knockdown cells revealed impaired JAK/STAT and PI3K/AKT signaling suggesting their contributions to EEF1A2-mediated effects on PCT induction or progression.Conclusions/Significance: EEF1A2 may play contribute to the induction or progression of some PCT and a small percentage of MM. Eef1a2 could also prove to be a useful new marker for a subset of MM and, ultimately, a possible target for therapy.

IRF8, a transcription factor restricted primarily to hematopoietic cells, is known to influence the differentiation and function of dendritic cells (DC), macrophages, granulocytes and B cells. In human tonsil, IRF8 is expressed at high levels by intrafollicular macrophages and DC, but at much lower levels by tingible body macrophages in germinal centers (GCs) and little, if at all, by follicular DC. Spleens of IRF8-defficient mice had reduced numbers of white pulp follicles and GCs that were irregular in shape. The frequency of follicular B cells was significantly reduced while the population of marginal zone (MZ) B cells was increased. In addition, MZ macrophages were reduced in number and abnormally distributed, while metallophilic macrophages were normal. These findings demonstrate differential requirements for IRF8 among distinct subsets of B cells, DC, and macrophages.

This abstract is being presented as a short talk in the scientific program. A full abstract is printed in the Proffered Abstracts section (PR05) of the Conference Proceedings. Citation Format: Amy Paschall, Ruihua Zhang, Kankana Bardhan, Chen-Feng Qi, Liang Peng, Geming Lu, Jianjun Yang, Miriam Merad, Mary Zimmerman, Tracy McGaha, Gang Zhou, Andrew Mellor, Scott I. Abrams, Herbert Morse, Keiko Ozato, Huabao Xiong, Kebin Liu. IRF8 regulates GM-CSF expression in T cells and tumor cells to mediate myeloid-derived suppressor cell differentiation. [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 A84.

Myeloid cells are a heterogenous and abundant population of haematopoietic cells that are virtually present in all mammalian tissues, where they monitor local microenvironment to maintain homeostasis. All myeloid cells originate from the pluripotent hematopoietic stem cells that undergo progressive restriction in their lineage potential to give rise to mature granulocytes and macrophages. Lineage restriction and differentiation are regulated by timely activation of specific set of lineage-specific transcription factors in concert with down-regulation of other set(s) of transcription factors that are important for alternative cell lineage potential. Altered expression of these lineage-specific transcription factors often leads to deregulation of myelopoiesis and resultant hematopoietic disorders. Therefore, lineage-specific transcription factors are essential for myeloid cell lineage differentiation and maturation. Mice with a null mutation of irf8, the gene that encodes IFN regulatory factor 8 (IRF8), exhibit massive accumulation of CD11b+Gr1+ immature myeloid cells (IMCs). Therefore, IRF8 is a myeloid cell lineage-specific transcription factor that plays an essential function in the regulation of myelopoiesis. Particularly, IRF8 may determine differentiation, lineage commitment, and immune function of monocytes versus granulocytes under physiological conditions. A hallmark of cancer-bearing mice is the accumulation of CD11b+Gr1+ myeloid-derived suppressor cells (MDSCs). Interestingly, IRF8 is silenced in MDSCs from tumor-bearing mice. Therefore, IRF8 is apparently a key transcription factor that mediates MDSC differentiation. However, the molecular mechanism underlying IRF8 regulation of MDSCs is largely unknown. Because MDSCs is induced by inflammation, we therefore hypothesized that IRF8 may repress the expression of proinflammatory factors to mediate differentiation of MDSCs/IMCs under physiological and pathological conditions. To test this hypothesis, we made use of conventional IRF8 KO mice, mice with IRF8 deficiency only in myeloid cells, mice with IRF8 deficiency only in T cells, and tumor-bearing mouse models. Here we report an intriguing finding that although IRF8 conventional mice exhibit deregulated myeloid cell differentiation and resultant accumulation of CD11b+Gr1+ IMCs, surprisingly, mice with IRF8 deficiency only in myeloid cells exhibit normal myeloid cell lineage differentiation. Instead, mice with IRF8 deficiency only in T cells exhibited deregulated myeloid cell differentiation and IMC accumulation. We further demonstrated that IRF8-deficient T cells exhibit elevated GM-CSF expression and secretion. Treatment of mice with GM-CSF increased IMC accumulation, and adoptive transfer of IRF8-deficient T cells, but not GM-CSF-deficient T cells, increased IMC accumulation in the recipient chimera mice. Moreover, overexpression of IRF8 decreased GM-CSF expression in T cells. These data thus determine that IRF8 functions in T cells to repress GM-CSF expression to suppress IMCs. However, in tumor-bearing mice, IRF8 is silenced in MDSCs but not in T cells, suggesting a different mechanism of MDSC regulation by IRF8. We observed that silencing IRF8 using IRF8-specific siRNA dramatically increase GM-CSF expression in tumor cells. Therefore, IRF8 represses GM-CSF expression in tumor cells to mediate MDSC differentiation. In summary, we determine that IRF8 regulates GM-CSF expression in T cells and tumor cells, respectively, to mediate myelopoiesis under physiological and pathological conditions. This abstract is also presented as Poster A84. Citation Format: Amy Paschall, Ruihua Zhang, Kankana Bardhan, Chen-Feng Qi, Liang Peng, Geming Lu, Jianjun Yang, Miriam Merad, Mary Zimmerman, Tracy McGaha, Gang Zhou, Andrew Mellor, Scott I. Abrams, Herbert Morse, Keiko Ozato, Huabao Xiong, Kebin Liu. IRF8 regulates GM-CSF expression in T cells and tumor cells to mediate myeloid-derived suppressor cell differentiation. [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 PR05.

During hematopoiesis, hematopoietic stem cells differentiate into granulocytes and macrophages via a distinct differentiation program that is controlled by myeloid lineage-specific transcription factors. Mice with a null mutation of IFN Regulatory Factor 8 (IRF8) accumulate CD11b+Gr1+ myeloid cells that phenotypically and functionally resemble tumor-induced myeloid-derived suppressor cells (MDSCs), indicating an essential role of IRF8 in myeloid cell lineage differentiation. However, whether IRF8 functions intrinsically or extrinsically in regulation of myeloid cell differentiation is not fully understood. Here we report an intriguing finding that mice with IRF8 deficiency only in myeloid cells exhibit no abnormal myeloid cell lineage differentiation. Instead, mice with IRF8 deficiency only in T cells exhibited MDSC accumulation. We further demonstrated that IRF8-deficient T cells exhibit elevated GM-CSF expression and secretion. Treatment of mice with GM-CSF increased MDSC accumulation, and adoptive transfer of IRF8- deficient T cells, but not GM-CSF-deficient T cells, increased MDSC accumulation in the recipient mice. Overexpression of IRF8 decreased GM-CSF in T cells. Our data determine that in addition to its intrinsic role as an apoptosis regulator in myeloid cells, IRF8 also acts extrinsically to repress GM-CSF expression in T cells to control myeloid cell lineage differentiation, revealing a novel mechanism of adaptive immune cell regulation of myelopoiesis in vivo.

Several mouse models of SLE, including FcgRIIB-KO and TLR7tg mice, develop an expansion of an atypical NK cell subset with functional similarity to cells referred as IKDCs or pre-mNKs in other systems and identified as NK1.1+CD11c+CD122+MHC-II+. These cells belong to the NK cell lineage because they depend on IL15 and express E4BP4. Functionally they are cytotoxic, produce type I and type II interferons upon activation and they are efficient antigen presenting cells both through MHC-II expression and in cross-presentation to CD8s. These atypical NK cells are responsive to TLR stimulation and thus are most abundant in mice with high copy number of the Tlr7 gene. They are highly proliferative as assessed by in vivo BrdU incorporation. Transferring 4 million atypical NKs purified from spleens of SLE-prone mice into WT induces a 2-week-long wave of inflammatory cytokines in the serum, a sustained increase in T cell activation and follicular helper cells for the following months, and a progressive expansion of dendritic cells, monocytes and granulocytes. Furthermore IL15 deficiency, which impedes development of NK cells, ameliorates the autoimmune pathology of TLR7tg mice. These results suggest that cells of the NK lineage can develop into cytokine producing/antigen-presenting cells that affect the priming and progression of systemic autoimmune disease.

Chromosomal translocations juxtaposing immunoglobulin (Ig) and MYC genes are the hallmarks of human Burkitt lymphoma (BL), with deregulated MYC expression being a critical factor in pathogenesis. By inserting an intact mouse Myc gene into the mouse genome, proximal to the Ig enhancer Eμ, the effect of a precise mimic of the major t(8;14) translocation of human endemic BL (eBL) could be investigated. Knock-in mice developed IgM-positive B-cell tumors, with most being typical of eBL by histology and immunophenotype, including expression of the germinal center (GC)–associated protein, BCL6. Unlike eBL, however, analysis of Ig VH sequences revealed no significant level of somatic mutation. Thus, constitutive expression of Myc in the knock-in mice is apparently able to induce “Burkitt-like” lymphomas before antigen stimulation and formation of a GC. In contrast, human eBL development occurs in a GC or post-GC site with a likely contribution to pathogenesis from Epstein-Barr virus (EBV) and other epigenetic factors.

Publisher Summary Investigators have sought to understand the pathogenesis of hematopoietic neoplasms in mice as models for human disease. The spontaneous diseases of mice form an essential foundation of knowledge about efforts to molecularly model specific diseases, because it will be critically important to distinguish induced from background cases. Gene expression profiling of histologically defined spontaneous neoplasm provides additional richness to these analyses. One of the most striking findings to come from the latter studies is the intimate relationship between morphologic and genetic diagnoses. This clearly indicates that the pathologist—in screening hundreds of gene readouts that determine cell size, cytoplasmic volume, nuclear shape, chromatin pattern, and nucleolar number, size, and position—provides a valuable foil to play against the molecular fingerprints portrayed by the data from microarrays. The synergy provided by these approaches in understanding the disease holds tremendous promise for developing better treatments for human hematologic neoplasm.

The cytokine interleukin-21 (IL-21) is closely related to IL-2 and IL-15, and their receptors all share the common cytokine receptor γ chain, γc, which is mutated in humans with X-linked severe combined immunodeficiency disease (XSCID). We demonstrate that, although mice deficient in the receptor for IL-21 (IL-21R) have normal lymphoid development, after immunization, these animals have higher production of the immunoglobulin IgE, but lower IgG1, than wild-type animals. Mice lacking both IL-4 and IL-21R exhibited a significantly more pronounced phenotype, with dysgammaglobulinemia, characterized primarily by a severely impaired IgG response. Thus, IL-21 has a significant influence on the regulation of B cell function in vivo and cooperates with IL-4. This suggests that these γc-dependent cytokines may be those whose inactivation is primarily responsible for the B cell defect in humans with XSCID.

TheTCL1protooncogene is overexpressed in many mature B cell lymphomas, especially from AIDS patients. To determine whether aberrant expression promotes B cell transformation, we generated a murine model in which aTCL1transgene was overexpressed at similar levels in both B and T cells. Strikingly, transgenic mice developed Burkitt-like lymphoma (BLL) and diffuse large B cell lymphoma (DLBCL) with attendant Bcl-6 expression and mutated JHgene segments at a very high penetrance beginning at 4 months of age. In contrast, only one mouse developed a T cell malignancy at 15 months, consistent with a longer latency for transformation of T cells byTCL1. Activation of premalignant splenic B cells by means of B cell antigen receptor (BCR) engagement resulted in significantly increased proliferation and augmented AKT-dependent signaling, including increased S6 ribosomal protein phosphorylation. Transgenic spleen cells also survived longer than wild-type spleen cells in long-term culture. Together these data demonstrate thatTCL1is a powerful oncogene that, when overexpressed in both B and T cells, predominantly yields mature B cell lymphomas.

In normal human germinal centre (GC) B-cells and post-GC B-cell lymphomas, a region in the first intron of the BCL6 gene, termed the major mutations cluster (MMC) exhibits somatic point mutations and deletions with patterns very similar to those seen in the variable regions of immunoglobulin (Ig) genes. In studies of mouse post-GC diffuse large cell lymphoma, Burkitt lymphomas, and plasmacytomas, direct sequencing or cold SSCP analyses revealed no mutations within a 686-bp region in Bcl6 intron 1 with 72% identity to the human MMC. The mouse Bcl6 locus must be inaccessible to the mutational machinery responsible for somatic mutations of Ig and BCL6 in humans.

Hematopoietic neoplasms developing in AKXD recombinant inbred, NFS.V + and ICSBP knockout mice were assessed using morphologic, cytologic and molecular criteria that relate these disorders to human lymphoma and leukemia. Lymphoma types included precursor T-cell and B-cell lymphoblastic, small lymphocytic, splenic marginal zone, follicular, and diffuse large cell (DLCL). In addition to previously defined subtypes of DLCL composed of centroblasts or immunoblasts, two additional subtypes are defined here: lymphoblastic lymphoma like (LL) and lymphoma characterized by a histiocytic reaction (HS). DLCL(HS) were distinguished from true histiocytic lymphomas by the presence of clonal Ig gene rearrangements.

Chromosomal translocations juxtaposing the MYC protooncogene with regulatory sequences of immunoglobulin (Ig) H chain or kappa (Ig kappa) or lambda (Ig lambda) L chain genes and effecting deregulated expression of MYC are the hallmarks of human Burkitt lymphoma (BL). Here we report that lymphomas with striking similarities to BL develop in mice bearing a mutated human MYC gene controlled by a reconstructed Ig lambda locus encompassing all the elements required for establishment of locus control in vitro. Diffusely infiltrating lymphomas with a typical starry sky appearance occurred in multiple founders and an established line, indicating independence from positional effects. Monoclonal IgM(+)CD5(-)CD23(-) tumors developed from an initially polyclonal population of B cells. These results demonstrate that the phenotype of B lineage lymphomas induced by MYC dysregulation is highly dependent on cooperativity among the regulatory elements that govern expression of the protooncogene and provide a new system for studying the pathogenesis of BL.

In mammals, a subset of genes inherit gametic marks that establish parent of origin-dependent expression patterns in the soma ([1] and references therein). The currently most extensively studied examples of this phenomenon, termed genomic imprinting, are the physically linked Igf2 (insulin-like growth factor II) and H19 genes, which are expressed mono-allelically from opposite parental alleles [1,2]. The repressed status of the maternal Igf2 allele is due to cis elements that prevent the H19 enhancers [3] from accessing the Igf2 promoters on the maternal chromosome [4,5]. A differentially methylated domain (DMD) in the 5′ flank of H19 is maintained paternally methylated and maternally unmethylated [6,7]. We show here by gel-shift and chromatin immunopurification analyses that binding of the highly conserved multivalent factor CTCF ([8,9] and references therein) to the H19 DMD is methylation-sensitive and parent of origin-dependent. Selectively mutating CTCF-contacting nucleotides, which were identified by methylation interference within the extended binding sites initially revealed by nuclease footprinting, abrogated the H19 DMD enhancer-blocking property. These observations suggest that molecular mechanisms of genomic imprinting may use an unusual ability of CTCF to interact with a diverse spectrum of variant target sites, some of which include CpGs that are responsible for methylation-sensitive CTCF binding in vitro and in vivo.

Germinal centers (GC) are the sites of antigen-driven B cell switch recombination, V(D)J gene hypermutation, and selection to generate high-affinity CD38+ memory B cells. A marked expansion of GC associated with hypergammaglobulinemia followed by complete disruption of normal splenic architecture and a striking drop in immunoglobulin levels are prominent features of the murine retrovirus-induced immunodeficiency syndrome, MAIDS. B cell lymphomas are frequent in long-term infected mice. Normal GC formation is critically dependent on a number of genes including the transcription factor, Bcl6. Deregulated expression of BCL6 protein has been implicated in the development of human and mouse B cell lymphomas. Another nuclear protein, SWAP-70, has been identified as a subunit of the protein complex, SWAP, that recombines switch regions in vitro. To develop a fuller understanding of B cell biology in MAIDS, we examined the characteristics of BCL6, SWAP-70, CD38, and peanut agglutinin (PNA)-staining cells during the course of the disease. The levels of both nuclear proteins increased rapidly until 6–8 weeks after infection. During this time frame, BCL6 was expressed at highest levels in the usually rare CD4+ Thy1− T cell subset as well as in B cells. At later times, BCL6 levels dropped to undetectable levels while SWAP-70 levels continued to increase. Changes in the levels of either protein could not be ascribed to transcriptional regulation. PNA-reactive cells decreased in concert with BCL6 while CD38 staining increased with SWAP-70. These results demonstrate that progression of MAIDS results in the massive accumulation of B cells with the morphology of secretory cells that behave like post-GC cells for expression of BCL6 and CD38, and for PNA-staining but with abnormally high-level expression of SWAP-70.

Introduction of ecotropic murine leukemia virus (MuLV) induction loci onto the low-lymphoma, ecotropic MuLV-negative strain, NFS, yielded strains of mice (NFS.V+) that develop a high incidence of hematopoietic neoplasms (1, 2) comprising primarily lymphomas of B cell origin. Histopathologic studies of 645 lymphomas yielded morphologic diagnoses compatible with synonyms provided by the Kiel (3) and REAL (4) classifications of human B lymphomas but applied to the mouse (Table 1). The “Bethesda/Kiel” terminology will be used here. The speculative “LIP/REAL” classification is based on studies suggesting uniting parallels with human neoplasms of these types (e.g., Siminovitch, this volume, for mouse MCL equivalent). MZL, diagnosed only once previously, in NZB (5), were unexpectedly most common in our series, at 36% (Hartley et al., manuscript in preparation)

DUSP3 (also called VHR) is a member of the dual-specificity protein phosphatase family which can dephosphorylate target proteins at phosphoserine/threonine and phosphotyrosine residuals. There are evidences that DUSP3 is highly expressed in cervical and prostate cancers, and may exert its function in inhibiting apoptosis. By analyzing publicly available data on diffuse large B-cell lymphoma (DLBCL), we found that the expression levels of DUSP3 mRNA were inversely associated with overall survival (OS) in DLBCL. Patients with low levels of DUSP3 mRNA had significant longer OS than did those with high levels of DUSP3 (P=0.0002) (Figure 1). The association between the levels of DUSP3 mRNA and clinical outcome was confirmed using an independent DLBCL cohort. To decipher the role of DUSP3 in DLBCL, we used lentiviral system to stably express shRNA against DUSP3 in the DLBCL cell line, OCI-Ly01. Reduced expression of DUSP3 was associated with significantly decreased proliferation of cells as compared to the control group (P Disclosures: No relevant conflicts of interest to declare.

Background: Histiocytic sarcoma (HS) is an aggressive hematological neoplasm that responds poorly to therapy. The molecular etiology and pathology of this disease remain unclear, hampering the development of an effective therapy. Therefore, a need for more, and more realistic, animal models remains. Lymphoproliferative disorders have been reported in mice deficient for the prkar1a gene coding for the regulatory subunit type 1A of protein kinase A (PKA), but nothing is known about the role of type II PKA regulatory subunits in hematologic malignancies. Methods: Mice deficient for the Prkar1a and Prkar2a alleles were previously reported (Kirschner et al, 2005 και Burton et al, 1997) and were kept on a mixed genetic background (C57BL/129Sv). Mice were crossed to create prkar2a+/- and prkar2a-/-. Mice were phenotyped at the ages of 3-6-9-12-18 months or when they exhibited signs of advanced disease. Tissues were collected for histological and molecular analysis. Results: Unexpectedly, mice deficient for the prkar2a allele(s) developed lymphomas, with significant higher incidence compared to the prkar1a+/- mice [8/13 (61.5%) of the prkar2a+/- and 5/8 (62.5%) of the prkar2a-/- vs. 3/21(14.2%) of the prkar1a+/-, Fisher's exact test p=0.02]. Histology studies of sections stained with H&E revealed a variety of pathologic changes in lymphoid and non-lymphoid tissues. Lesions characteristic of histiocytic sarcoma (HS) were found in spleen and abdominal lymph nodes, sometimes associated with leukemic infiltrates in lung and bone marrow (BM). Abnormal megakaryopoiesis in spleen and BM was associated with cells actively phagocytosing red cells, others with a pseudo Gaucher-like appearance and increased immature forms. Erythropoiesis was reduced in BM and spleen. Vascular thrombi were associated with schistocytosis. Accumulations of mostly mature plasma cells and some plasmablasts were present in the splenic red pulp together with large, active germinal centers. Cells with characteristics of diffuse large B cell lymphoma often occupied expanded splenic follicles and lymph nodes. Kidneys exhibited degenerative changes in glomeruli and tubules. Median age at presentation was 18 months (range 16-25 months). FACS analysis of BM cells revealed a decrease in late pro-B cells in the prkar2a deficient mice compared to the wild-type, indicating a developmental block at this stage of early B cell differentiation. Interestingly, Southern blot analysis of these B cell lymphomas showed that in most cases they were monoclonal with either one or both IgH alleles rearranged. Conclusions: Our data indicate that PRKAR2a may be involved in the development of malignant lesions of the hematologic lineage. The presented mouse model can be used to gain insights into the molecular and cellular origins of this rare neoplasm and provide a preclinical model in which to test novel therapeutic strategies. Citation Format: Emmanouil Saloustros, Paraskevi Salpea, Lina Gugglioti, Kittman Tsang, Anelia Horvath, Maria Nesterova, Chen-Feng Qi, Herbert C. Morse III, Constantine A. Stratakis. Novel hematopoietic neoplasms in prkar2a- deficient mice. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3854. doi:10.1158/1538-7445.AM2013-3854

Antibody-dependent cellular cytotoxicity (ADCC) has been suggested to be an important defense mechanism against tumors. The effects of recombinant human macrophage colony-stimulating factor (rhM-CSF) on ADCC activity of human monocytes were investigated. Human peripheral monocytes were pre-incubated for 72 h with rhM-CSF at various concentrations (50, 100, 200, 400 U/ml) and then used as effector cells in a 24-h 111-Indium release assay. Human carcinoma cell lines LS-174T, CBS, and KLE were used as targets to react with anti-carcinoma monoclonal antibodies (mAbs: murine D612, murine CC49, and chimeric CC49). A significant increase in ADCC activity was observed after monocytes were incubated in 100-400 U/ml of human rhM-CSF. Variation in ADCC activity of monocytes among donors was observed. The enhancement of ADCC activity was blocked by the addition of a neutralizing antibody to rhM-CSF. Less D612 mAb was required for the rhM-CSF-treated monocytes to mediate an equivalent level of ADCC activity as compared to the untreated monocytes. Because of the low levels of rhM-CSF required in these studies to enhance ADCC, treatment of monocytes alone with comparable levels of rhM-CSF did not enhance antibody-independent cytotoxicity. Moreover, it is demonstrated here that recombinant human interleukin-4 (rhIL-4) and rhM-CSF can have a synergistic effect of monocyte-mediated ADCC on human tumor cells. These results thus indicate that rhM-CSF augments ADCC of human peripheral blood monocytes using mAbs to human carcinomas, suggesting a potential role for rhM-CSF in cancer immunotherapy.

The expression of three epidermal growth factor (EGF)-related peptides, transforming growth factor alpha (TGF-alpha), amphiregulin (AR) and cripto-1 (CR-1), was examined by immunocytochemistry (ICC) in 68 primary infiltrating ductal (IDCs) and infiltrating lobular breast carcinomas (ILCs), and in 23 adjacent non-involved human mammary tissue samples. Within the 68 IDC and ILC specimens, 54 (79%) expressed immunoreactive TGF-alpha, 52 (77%) expressed AR and 56 (82%) expressed CR-1. Cytoplasmic staining was observed with all of the antibodies, and this staining could be eliminated by preabsorption of the antibodies with the appropriate peptide immunogen. Cytoplasmic staining with all of the antibodies was confined to the carcinoma cells, since no specific immunoreactivity could be detected in the surrounding stromal or endothelial cells. In addition to cytoplasmic reactivity, the AR antibody also exhibited nuclear staining in a number of the carcinoma specimens. No significant correlations were found between the percentage of carcinoma cells that were positive for TGF-alpha, AR or CR-1 and oestrogen receptor status, axillary lymph node involvement, histological grade, tumour size, proliferative index, loss of heterozygosity on chromosome 17p or overall patient survival. However, a highly significant inverse correlation was observed between the average percentage of carcinoma cells that expressed AR in individual tumours and the presence of a point-mutated p53 gene. Likewise, a significantly higher percentage of tumour cells in the ILC group expressed AR as compared with the average percentage of tumour cells that expressed AR in the IDC group. Of the 23 adjacent, non-involved breast tissue samples, CR-1 could be detected by ICC in only three (13%), while TGF-alpha was found in six (26%) and AR in ten (43%) of the non-involved breast tissues. These data demonstrate that breast carcinomas express multiple EGF-related peptides and show that the differential expression of CR-1 in malignant breast epithelial cells may serve as a potential tumour marker for breast cancer. Images Figure 1

Both monoclonal antibodies (MAbs) and human T cells have been used in human tumor immunotherapy protocols. Tumor-infiltrating lymphocytes (TILs) and MAbs that can mediate antibody-dependent cell-mediated cytotoxicity (ADCC) via human effector cells have shown antitumor effects in both animal models and clinical trials. One potential novel approach would be to combine these two modalities in the creation of a T cell capable of secreting antitumor immunoglobulins (Ig), in essence, creating an antitumor Ig "factory" at the tumor site. In the studies reported here, we have cloned the D612 MAb Ig genes and generated a chimeric D612 IgG1 containing the murine variable region and human constant region. D612 MAb has been shown to mediate lysis of human colon carcinomas via effector cell-mediated ADCC. We have demonstrated that following transfection, chimeric D612 can be expressed and secreted by the human T-cell line MOLT-4 at a rate of 0.25 micrograms/ml per 10(6) cells in 72 hours. The secreted Ig retained its antigen-binding properties as assayed by competition radioimmunoassay and also its ability to mediate ADCC against human tumor cells. To our knowledge, this is the first demonstration of the production of a chimeric IgG by human T cells and opens the possibility of a therapeutic approach in which TILs secrete humanized antitumor MAb capable of mediating ADCC at the tumor site.