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Oncostatin M (OSM) is a potent modulator of human lung-derived epithelial cell function. This cytokine binds two distinct receptor complexes: type I OSM receptor which is also a functional receptor for leukemia inhibitory factor (LIF), and type II OSM-specific receptor. The role of these two distinct receptors in mediating the response of individual cell types to OSM has not been delineated. In contrast to LIF, OSM induces synthesis of α1-antichymotrypsin and α1-antiproteinase inhibitor in lung-derived epithelial cells. The differential responsiveness to LIF and OSM suggested that the response of lung epithelial cells to OSM may be mediated by the OSM-specific receptor. Therefore, we characterized lung-derived epithelial cells for the expression of type II OSM receptor mRNAs, and the regulation of the mRNAs encoding the components of the OSM-specific receptor by cytokines and dexamethasone.

Activated T lymphocytes are present in human atherosclerotic lesions and autoantibodies to antigens within lesions have been detected in serum, but the roles of the cellular and humoral immune systems in atherogenesis have not been determined. The effect of total lymphocyte deficiency on atherogenesis was investigated by crossing apo E-deficient mice (which develop atherosclerosis resembling human disease) with mice deficient in RAG2 (which is required for normal B and T lymphocyte development). Mice were placed on a fat- and cholesterol-enriched diet for 12 wk. RAG2-deficient mice had no serum autoantibodies, in contrast to the high titers in RAG2+/- littermates. There were no T lymphocytes and a markedly reduced number of MHC class II-positive macrophages in atherosclerotic lesions of RAG2-deficient mice. Despite these differences, RAG2-deficient mice developed atherosclerosis similar in extent to that in immunocompetent littermates, based on quantification by two independent methods. In conclusion, the absence of autoantibodies and T lymphocytes did not influence the extent of aortic atherosclerotic lesions in apo E-deficient mice.

The tyrosine kinases Syk and Lyn are activated in B lymphocytes following antibody induced cross-linking of the B cell receptor for antigen (BCR). It has been suggested that activation of Syk is dependent on Lyn. We tested this hypothesis by comparing the phosphorylation and activation of several downstream effector molecules in parental DT40, DT40Syk- and DT40Lyn- B cells. The phosphorylation and activation of p90Rsk was ablated in Syk-deficient B cells but unaffected in Lyn-deficient B cells while the phosphorylation/activation of Ras GTPase activating protein (Ras GAP) and mitogen activated protein (MAP) kinase required both Syk and Lyn. Thus, these data indicate that Syk can be activated in the absence of Lyn after BCR cross-linking and results in the activation of p90Rsk via a MAP kinase-independent pathway in DT40Lyn- cells. We also demonstrated that BCR mediates the activation of p70S6k. However, activation of p70S6k in DT40Syk- and DT40Lyn- cells was comparable with that observed in parental cells. Thus, either Syk or Lyn may be sufficient for activation of p70S6k, or activation of p70S6k occurs independently of both Syk and Lyn. The kinase activity of Syk was required for the phosphorylation/activation of each of these downstream effector molecules but only the phosphorylation of Ras GAP was affected in cells expressing a mutant of Syk in which tyrosines 525 and 526 were substituted to phenlyalanines.

Fibroblast activation protein (FAP) has long been known to be expressed in the stroma of breast cancer. However, very little is known if the magnitude of FAP expression within the stroma may have a prognostic value and reflect the heterogeneous biology of the tumor cell. An earlier study had suggested that stromal FAP expression in breast cancer was inversely proportional to prognosis. We, therefore, hypothesized that stromal FAP expression may correlate with clinicopathologic variables and may serve as an adjunct prognostic factor in breast cancer. We evaluated the expression of FAP in a panel of breast cancer tissues (n = 52) using a combination of immunostain analyses at the tissue and single-cell level using freshly frozen or freshly digested human breast tumor samples, respectively. Our results showed that FAP expression was abundantly expressed in the stroma across all breast cancer subtypes without significant correlation with clinicopathologic factors. We further identified a subset of FAP-positive (or FAP(+)) stromal cells that also expressed CD45, a pan-leukocyte marker. Using freshly dissociated human breast tumor specimens (n = 5), we demonstrated that some of these FAP(+)CD45(+) cells were CD11b(+)CD14(+)MHC-II(+), indicating that they were likely tumor-associated macrophages (TAMs). Although FAP(+)CD45(+) cells have been demonstrated in the mouse tumor stroma, our results demonstrating that human breast TAMs expressed FAP were novel and suggested that existing and future FAP-directed therapy may have dual-therapeutic benefits targeting both stromal mesenchymal cells and immune cells such as TAMs. More work is needed to explore the role of FAP as a potential targetable molecule in breast cancer treatment.

Changes in tissue and organ stiffness occur during development and are frequently symptoms of disease. Many cell types respond to the stiffness of substrates and neighboring cells in vitro and most cell types increase adherent area on stiffer substrates that are coated with ligands for integrins or cadherins. In vivo cells engage their extracellular matrix (ECM) by multiple mechanosensitive adhesion complexes and other surface receptors that potentially modify the mechanical signals transduced at the cell/ECM interface. Here we show that hyaluronic acid (also called hyaluronan or HA), a soft polymeric glycosaminoglycan matrix component prominent in embryonic tissue and upregulated during multiple pathologic states, augments or overrides mechanical signaling by some classes of integrins to produce a cellular phenotype otherwise observed only on very rigid substrates. The spread morphology of cells on soft HA-fibronectin coated substrates, characterized by formation of large actin bundles resembling stress fibers and large focal adhesions resembles that of cells on rigid substrates, but is activated by different signals and does not require or cause activation of the transcriptional regulator YAP. The fact that HA production is tightly regulated during development and injury and frequently upregulated in cancers characterized by uncontrolled growth and cell movement suggests that the interaction of signaling between HA receptors and specific integrins might be an important element in mechanical control of development and homeostasis.

We report that receptor mediated transcytosis can be utilized to facilitate tumor penetration by drug loaded nanoparticles (NPs). We synthesized hyaluronan (HA) coated silica nanoparticles (SNPs) containing a highly fluorescent core to target CD44 expressed on the cancer cell surface. Although prior studies have primarily focused on CD44 mediated endocytosis to facilitate cellular uptake of HA-NPs by cancer cells, we discovered that, once internalized, the HA-SNPs could be transported out of the cells with their cargo. The exported NPs could be taken up by neighboring cells. This enabled the HA-SNPs to penetrate deeper inside tumors and reach a much greater number of tumor cells in 3D tumor models, presumably through tandem cycles of CD44 mediated endocytosis and exocytosis. When doxorubicin (DOX) was loaded onto the NPs, better penetration of multilayered tumor cells was observed with much improved cytotoxicities against both drug sensitive and drug resistant cancer spheroids compared to the free drug. Thus, targeting receptors such as CD44 that can readily undergo recycling between the cell surface and interior of the cells can become a useful strategy to enhance the tumor penetration potential of NPs and the efficiency of drug delivery through receptor mediated transcytosis.

Interleukin-4 was one of the first cytokines to be intensively studied and remains one of the most interesting and biologically important ([1][1]). It has a distinctive spectrum of biological activities, many of which are unique to IL-4 or to both IL-4 and IL-13 but are not shared by other cytokine

Infusion of T cells expressing chimeric antigen receptors (CAR T cells) is still relatively ineffective in solid tumors due to the presence of immunosuppressive mediators (such as prostaglandin E2 (PGE2) and adenosine), and poor T cell trafficking. Since PGE2 and adenosine activate protein kinase A (PKA), which then inhibits T cell receptor (TCR) activation, we generated CAR T cells that expressed a small peptide called the “regulatory subunit I anchoring disruptor” (RIAD) that inhibits the association of protein kinase A (PKA) with ezrin; this interaction is required for the negative effects of PKA on TCR activation. After exposure to PGE2 or adenosine in vitro, CAR-RIAD T cells showed increased TCR signaling, more cytokine release, and enhanced killing of tumor cells compared to CAR T cells. When injected into tumor-bearing mice, murine and human CAR-RIAD T cells demonstrated enhanced anti-tumor efficacy compared to CAR T cells due to increased T cell infiltration of established tumors, and attenuated tumor-induced hypofunction. Subsequent in vitro assays showed that both mouse and human CAR-RIAD cells migrated more efficiently than CAR cells in response to the chemokine CXCL10 and also adhered better to various matrices. Our data therefore show that the addition of the RIAD peptide to adoptively transferred CAR T cells augments their efficacy by increasing their effector function and by improving trafficking into tumor sites. This treatment strategy should therefore be considered for clinical application in treating solid tumors. Citation Format: Kheng Newick, Shaun O'Brien, Jing Sun, Veena Kapoor, Steve Maceyko, Albert Lo, Ellen Pure, Ed K. Moon, Steven M. Albelda. Blockade of protein kinase A (PKA) localization augments the trafficking and anti-tumor efficacy of adoptively transferred chimeric antigen receptor-expressing T cells. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr B27.

CD44 is a cell surface adhesion molecule that plays a role in leukocyte extravasation, leukopoiesis, T lymphocyte activation, and tumor metastasis. The principal known ligand for CD44 is the glycosaminoglycan hyaluronate, (HA), a major constituent of extracellular matrices. CD44 expression is required but is not sufficient to confer cellular adhesion to HA, suggesting that the adhesion function of the receptor is regulated. We recently demonstrated that CD44 in primary leukocytes is phosphorylated in a cell type- and activation state-dependent fashion. In this study we demonstrate that serines 325 and 327 within the cytoplasmic domain of CD44 are required for the constitutive phosphorylation of CD44 in T cells. Furthermore, we demonstrate that cells expressing mutated CD44 containing a serine to glycine substitution at position 325 or a serine to alanine substitution at amino acid 327 are defective in HA binding, CD44-mediated adhesion of T cells to smooth muscle cells, as well as ligand-induced receptor modulation. The effect of these mutations can be partially reversed by a monoclonal anti-CD44 antibody that enhances CD44-mediated HA binding.

Many solid tumors in human exhibit highly desmoplastic stroma, the result of a fibroproliferative response and accumulation of provisional matrix. Stroma plays myriad functions in cancer. Cancer associated fibroblasts (CAFs) and the extracellular matrix (ECM) they deposit act as a scaffold that imposes architectural order and defines the spatial relationship of neoplastic cells and their precursors to a multitude of other non-transformed components in the microenvironment of both primary tumors and metastases. Reactive stroma is also enriched in growth and angiogenic factors, presents chemoattractants that promote the recruitment of bone marrow-derived cells, and can modulate inflammatory and immune cell function, all of which can contribute to its tumor permissive nature relative to normal stroma. CAFs however are heterogeneous and their phenotypic and functional diversity remain ill-defined. Furthermore, adaptation to the dynamic and regionally diverse nature of the microenvironment and cross-talk with tumor cells and infiltrating cells can drive co-evolution of the phenotype and function of stromal cells and matrix architecture adding to the spatial and temporal complexity of the stromal compartment. The expression of smooth muscle actin (SMA) is a well-recognized and defining marker of myofibroblasts but the proportion of CAFs that express this marker varies between tumor types and between individual tumors of any particular tumor type. A significant proportion of CAFs in virtually all human carcinomas however, express the cell surface protease fibroblast activation protein (FAP) that is also expressed on a subset of M2-like tumor-associated macrophages. SMA and FAP expressing populations overlap to varying degrees in different tumors and tumor types. We developed an adoptive cell transfer approach employing chimeric antigen receptor (CAR) expressing T cells to define the function of FAP expressing cells in various tumor types. Our studies indicate that FAP+ cells are required for the generation and maintenance of desmoplastic stroma and that depletion of FAP+ cells can inhibit tumor growth through both immune-dependent and immune-independent mechanisms. Moreover, we found that the anti-tumor activity of FAP- CAR T cells and the mechanisms by which FAP-targeted CAR T cells inhibited growth and progression in different tumor models was a function of the degree of desmoplasia and tumor immunogenicity. Taken together with data recently published by others, our data suggest that at least in models of pancreatic cancer, a subset of highly proliferating SMA+ cells and FAP+ cells play distinct and possibly opposing roles in tumor progression and this must be taken into account in the rational design of stroma targeted therapies. Citation Format: Ellen Puré. Tumor stroma: Immunomodulatory functions and a target of immunotherapy. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr IA18.

Prostacyclin (PGI(2)) is a vasodilator and platelet inhibitor, properties consistent with cardioprotection. More than a decade ago, inhibition of cyclooxygenase-2 (COX-2) by the nonsteroidal anti-inflammatory drugs (NSAIDs) rofecoxib and celecoxib was found to reduce the amount of the major metabolite of PGI(2) (PGI-M) in the urine of healthy volunteers. This suggested that NSAIDs might cause adverse cardiovascular events by reducing production of cardioprotective PGI(2). This prediction was based on the assumption that the concentration of PGI-M in urine likely reflected vascular production of PGI(2) and that other cardioprotective mediators, especially nitric oxide (NO), were not able to compensate for the loss of PGI(2). Subsequently, eight placebo-controlled clinical trials showed that NSAIDs that block COX-2 increase adverse cardiovascular events. We connect tissue-specific effects of NSAID action and functional correlates in mice with clinical outcomes in humans by showing that deletion of COX-2 in the mouse vasculature reduces excretion of PGI-M in urine and predisposes the animals to both hypertension and thrombosis. Furthermore, vascular disruption of COX-2 depressed expression of endothelial NO synthase and the consequent release and function of NO. Thus, suppression of PGI(2) formation resulting from deletion of vascular COX-2 is sufficient to explain the cardiovascular hazard from NSAIDs, which is likely to be augmented by secondary mechanisms such as suppression of NO production.

Suppression of cyclooxygenase 2 (COX-2)–derived prostacyclin (PGI 2 ) is sufficient to explain most elements of the cardiovascular hazard from nonsteroidal antinflammatory drugs (NSAIDs). However, randomized trials are consistent with the emergence of cardiovascular risk during chronic dosing with NSAIDs. Although deletion of the PGI 2 receptor fosters atherogenesis, the importance of COX-2 during development has constrained the use of conventional knockout (KO) mice to address this question. We developed mice in which COX-2 was deleted postnatally, bypassing cardiorenal defects exhibited by conventional KOs. When crossed into ApoE-deficient hyperlipidemic mice, COX-2 deletion accelerated atherogenesis in both genders, with lesions exhibiting leukocyte infiltration and phenotypic modulation of vascular smooth muscle cells, as reflected by loss of α-smooth muscle cell actin and up-regulation of vascular cell adhesion molecule-1. Stimulated peritoneal macrophages revealed suppression of COX-2–derived prostanoids and augmented 5-lipoxygenase product formation, consistent with COX-2 substrate rediversion. Although deletion of the 5-lipoxygenase activating protein (FLAP) did not influence atherogenesis, it attenuated the proatherogeneic impact of COX-2 deletion in hyperlipidemic mice. Chronic administration of NSAIDs may increasingly confer a cardiovascular hazard on patients at low initial risk. Promotion of atherogenesis by postnatal COX-2 deletion affords a mechanistic explanation for this observation. Coincident inhibition of FLAP may offer an approach to attenuating such a risk from NSAIDs.

Background Breast cancer is a heterogeneous disease for which prognosis and treatment strategies are largely governed by the receptor status (estrogen, progesterone and Her2) of the tumor cells. Gene expression profiling of whole breast tumors further stratifies breast cancer into several molecular subtypes which also co-segregate with the receptor status of the tumor cells. We postulated that cancer associated fibroblasts (CAFs) within the tumor stroma may exhibit subtype specific gene expression profiles and thus contribute to the biology of the disease in a subtype specific manner. Several studies have reported gene expression profile differences between CAFs and normal breast fibroblasts but in none of these studies were the results stratified based on tumor subtypes. Methods To address whether gene expression in breast cancer associated fibroblasts varies between breast cancer subtypes, we compared the gene expression profiles of early passage primary CAFs isolated from twenty human breast cancer samples representing three main subtypes; seven ER+, seven triple negative (TNBC) and six Her2+. Results We observed significant expression differences between CAFs derived from Her2+ breast cancer and CAFs from TNBC and ER + cancers, particularly in pathways associated with cytoskeleton and integrin signaling. In the case of Her2+ breast cancer, the signaling pathways found to be selectively up regulated in CAFs likely contribute to the enhanced migration of breast cancer cells in transwell assays and may contribute to the unfavorable prognosis of Her2+ breast cancer. Conclusions These data demonstrate that in addition to the distinct molecular profiles that characterize the neoplastic cells, CAF gene expression is also differentially regulated in distinct subtypes of breast cancer.

Objective Several transcription factors determine the cell fate decision between granulocytes and monocytes, but the upstream signal transduction pathways that govern myelopoiesis are largely unknown. Based on our observation of aberrant myeloid cell representation in hematopoietic tissues of 12/15-lipoxygenase (12/15-LOX)-deficient (Alox15) mice, we tested the hypothesis that polyunsaturated fatty acid metabolism regulates myelopoiesis. Materials and Methods Multicolor flow cytometric analysis and methylcellulose assays were used to compare myelopoiesis and the differentiative capacity of progenitors from Alox15 and wild-type mice. Furthermore, we elucidated the mechanism by which 12/15-LOX is involved in regulation of myelopoiesis. Results Granulopoiesis in Alox15 mice is increased while monopoiesis is reduced. Moreover, there is an accumulation of granulocyte-macrophage progenitors that exhibit defective differentiation. Mechanistically, we demonstrate that transcriptional activity of interferon regulatory factor-8 (Irf8), which regulates myelopoiesis, is impaired in Alox15 progenitors and bone marrow-derived macrophages due to loss of 12/15-LOX-mediated redox regulation of Irf8 nuclear accumulation. Restoration of redox signaling in Alox15 bone marrow cells and granulocyte-macrophage progenitors reversed the defect in myeloid differentiation. Conclusions These data establish 12/15-LOX-mediated redox signaling as a novel regulator of myelopoiesis and Irf8.

Atherosclerotic cardiovascular disease (ASCVD) frequently clusters in families. Although environmental factors such as diet, exercise, and smoking play a role in ASCVD, genetic factors are a major determinant of ASCVD risk. For example, in a study of Swedish twins, males with a dizygotic twin who died of premature coronary heart disease had a 4.3-fold increased risk of also dying from coronary heart disease, and if the twin was monozygotic, this risk increased to 14.9-fold.1 The genetic risk of ASCVD is conferred in part through known metabolic risk factors such as hypertension, dyslipidemia, and diabetes mellitus. However, these risk factors alone do not account for the entire genetic contribution to risk of ASCVD, and there remains substantial interest in the identification of additional genetic cardiovascular risk factors. Like humans, mouse strains differ considerably in their genetic predisposition to atherosclerosis.2 Most mouse strains are resistant to atherosclerosis even when fed an atherogenic diet; the C3H strain is a prototypical-resistant mouse strain. In contrast, C57BL/6J mice have been extensively studied as the mouse strain that is most susceptible to atherosclerosis when fed an atherogenic high-fat, high-cholesterol, cholic acid–containing diet.3 Initially, the focus on C57BL/6J mice centered on differences in plasma lipid levels, especially reduced HDL cholesterol levels, in response to the atherogenic diet4 and attempts to map gene loci linked to the phenotype of low HDL cholesterol.5 However, previous studies did not distinguish whether these differences in lipid profiles were restricted to particular dietary challenges or reflect an underlying genetic factor that contributes to atherosclerosis susceptibility. Furthermore, recent studies have suggested that C57BL/6J mice differ from less-susceptible strains in their response to inflammatory stimuli.6 7 Given the interest in atherosclerosis as an inflammatory disease,8 this has led to the hypotheses that C57BL/6J mice may be genetically …

Interleukin-12 (IL-12) is critical for resistance toToxoplasma gondiiduring both the acute and chronic stages of infection. However, the cellular and molecular pathways that regulate IL-12 production during chronic toxoplasmosis are incompletely defined. We recently discovered that 12/15-lipoxygenase (12/15-LOX), which oxidizes unsaturated lipids in macrophages, is a novel and selective regulator of IL-12 production. We now demonstrate the essential role of this enzyme in the chronic phase of toxoplasmosis. Although 12/15-LOX-deficient mice were resistant to acuteT. gondiiinfection, 80% of 12/15-LOX-deficient mice died during chronic toxoplasmosis, compared to no deaths in wild-type controls. The morbidity of chronically infected 12/15-LOX mice was associated with an increase in brain inflammation and parasite burden. These data suggest that the evolution of the immune response toT. gondiiis accompanied by an increasing requirement for 12/15-LOX-mediated signaling. Consistent with this conclusion, 12/15-LOX activity was enhanced during chronic, but not acute, toxoplasmosis. Furthermore, the enhanced susceptibility of 12/15-LOX-deficient mice to chronic toxoplasmosis was associated with reduced production of IL-12 and gamma interferon (IFN-γ) that was not evident during acute infection. Importantly, ex vivo IFN-γ production by 12/15-LOX-deficient splenocytes could be rescued by the addition of recombinant IL-12. These data establish that 12/15-LOX is a critical mediator of the chronic type 1 inflammatory response and that immune mediators can be subject to distinct cellular and/or molecular mechanisms of regulation at different stages of inflammation.

There are two key processes underlying ligand-induced receptor endocytosis: receptor ubiquitylation and remodeling of the actin cytoskeleton. Tyrosine kinases play critical roles in both receptor endocytosis and actin reorganization. Interestingly, members of the Abl family are the only known tyrosine kinases that possess an actin-binding domain and thus have the potential to directly regulate the actin cytoskeleton. However, the role of non-transforming cAbl in receptor endocytosis remains undefined. We report that cAbl promotes ligand-induced antigen receptor endocytosis in B lymphocytes. We show that pharmacologic inhibition or genetic deletion of cAbl causes a defect in tyrosine phosphorylation of the cytoskeletal adapter CrkII. cAbl inhibition or ablation also impairs Rac activation downstream of CrkII, as well as antigen receptor capping and endocytosis. Although phosphorylation of CrkII has been suggested to maintain it in a closed inactive conformation, we demonstrate that it is in fact essential for the activation of Rac. On the other hand, association of CrkII with cCbl, a key mediator of receptor ubiquitylation, does not require CrkII phosphorylation and is cAbl-independent. Phosphorylation of cCbl itself is also cAbl-independent. Our results thus indicate that CrkII links receptor engagement to cytoskeletal remodeling by coupling cCbl- and cAbl-mediated signaling pathways that cooperatively regulate ligand-induced receptor endocytosis.

A killer T lymphocyte must both seek and destroy transformed cells within cancerous tissue in order to eliminate a tumor. Although lymphocytes are constitutively non-adherent cells, they undergo facultative polarity during migration and upon interaction with cells presenting cognate antigen, suggesting that lymphocyte polarity might be critical for tumor cell rejection. Using two-photon imaging of tumor-infiltrating T lymphocytes, we found that CD44, a receptor for extracellular matrix proteins and glycosaminoglycans, is crucial for interstitial navigation within tumors as well as efficiency of target cell screening. CD44 functions as a critical regulator of intra-tumoral movement by stabilizing cell polarity in migrating T cells. Stable anterior-posterior asymmetry is maintained by CD44 independently of its extracellular domain. Instead, migratory polarity depends on the recruitment of ERM-proteins by the intracellular domain of CD44 to the posterior cellular protrusion. These data provide evidence that facultative polarity mediated by CD44 is a key regulator of killer T cell migration and navigation, and that even moderate disturbances in the ability to seek out transformed cells have profound effects on the capacity to ultimately reject tumors.

CD44 contributes to inflammation and fibrosis in response to injury. As fibroblast recruitment is critical to wound healing, we compared cytoskeletal architecture and migration of wild-type (CD44WT) and CD44-deficient (CD44KO) fibroblasts. CD44KO fibroblasts exhibited fewer stress fibers and focal adhesion complexes, and their migration was characterized by increased velocity but loss of directionality, compared with CD44WT fibroblasts. Mechanistically, we demonstrate that CD44WT cells generated more active TGFβ than CD44KO cells and that CD44 promotes the activation of TGFβ via an MMP-dependent mechanism. Reconstitution of CD44 expression completely rescued the phenotype of CD44KO cells whereas exposure of CD44KO cells to exogenous active TGFβ rescued the defect in stress fibers and migrational velocity, but was not sufficient to restore directionality of migration. These results resolve the TGFβ-mediated and TGFβ-independent effects of CD44 on fibroblast migration and suggest that CD44 may be critical for the recruitment of fibroblasts to sites of injury and the function of fibroblasts in tissue remodeling and fibrosis.

Microsomal (m) prostaglandin (PG) E 2 synthase(S)-1, an enzyme that catalyzes the isomerization of the cyclooxygenase (COX) product, PGH 2 , into PGE 2 , is a major source of PGE 2 in vivo . mPGES-1 deletion in mice was found to modulate experimentally evoked pain and inflammation and atherogenesis is retarded in mPGES-1 knockout (KO) mice. The impact of mPGES-1 deletion on formation of angiotensin II (Ang II)-induced abdominal aortic aneurysms (AAA) was studied in mice lacking the low density lipoprotein receptor (LDLR −/− ). AngII infusion increased aortic macrophage recruitment and nitrotyrosine staining while upregulating both mPGES-1 and COX-2 and urinary excretion of the major metabolite of PGE 2 (PGE-M). Deletion of mPGES-1 decreased both the incidence and severity of AAA and depressed excretion of both PGE-M and 8, 12-iso-iPF 2a -VI, which reflects lipid peroxidation in vivo . While Ang II infusion augmented prostaglandin biosynthesis, deletion of mPGES-1 resulted in rediversion to PGD 2 , reflected by its major urinary metabolite. However, deletion of the PGD 2 receptor, DP1, did not affect AAA in Ang II infused LDLR −/− mice. These observations indicate that deletion of mPGES-1 protects against AAA formation by AngII in hyperlipidemic mice, perhaps by decreasing oxidative stress. Inhibition of mPGES-1 may represent an effective treatment to limit aneurysm occurrence and expansion.

High molecular weight (HMW) hyaluronan (HA) is widely distributed in the extracellular matrix, but its biological activities remain incompletely understood. We previously reported that HMW-HA binding to CD44 antagonizes mitogen-induced S-phase entry in vascular smooth muscle cells (SMCs; Cuff, C.A., D. Kothapalli, I. Azonobi, S. Chun, Y. Zhang, R. Belkin, C. Yeh, A. Secreto, R.K. Assoian, D.J. Rader, and E. Puré. 2001. J. Clin. Invest. 108:1031–1040); we now characterize the underlying molecular mechanism and document its relevance in vivo. HMW-HA inhibits the mitogen-dependent induction of cyclin D1 and down-regulation of p27kip1 in vascular SMCs. p27kip1 messenger RNA levels were unaffected by HMW-HA, but the expression of Skp2, the rate-limiting component of the SCF complex that degrades p27kip1, was reduced. Rescue experiments identified cyclin D1 as the primary target of HMW-HA. Similar results were observed in fibroblasts, and these antimitogenic effects were not detected in CD44-null cells. Analysis of arteries from wild-type and CD44-null mice showed that the effects of HMW-HA/CD44 on cyclin D1 and Skp2 gene expression are detected in vivo and are associated with altered SMC proliferation after vascular injury.

Solid tumors recruit and activate a heterogeneous population of non-transformed stromal cells (CASCs) in the tumor microenvironment (TME). There has been growing interest in the field to develop strategies to treat cancer and circumvent resistance to therapy by targeting CASCs. Defining the phenotypic subsets and the function of distinct subpopulations including myofibroblasts (defined by the expression of SMA) and the overlapping but distinct population of CASCs expressing Fibroblast Activation Protein (FAP) will be critical to informing the rational design of stromal-targeted therapies. FAP is a membrane serine protease that is selectively up-regulated in CASCs including cancer-associated fibroblasts (CAFs), mesenchymal stem cells (MSCs), and a subset of M2 macrophages, of virtually all common human epithelial cancers. Based on its selective expression on CASCs across a wide range of tumor types, we engineered FAP-specific chimeric antigen receptor expressing T cells (FAP-CAR T cells) and adoptively transferred them into tumor bearing mice to: 1) define the requirement for FAP+ cells for the accumulation and maintenance of a desmoplastic matrix; 2) define the relationship between the degree of desmoplasia, the capacity of FAP-CAR T cells to disrupt the tumor stroma and to inhibit tumor growth; and 3) determine whether FAP-CAR T cells can inhibit tumor growth through immune independent mechanisms. We found that FAP+ CACSs are responsible for maintaining the desmoplastic response and that conditional depletion following treatment with FAP-CAR T cells inhibits growth of human lung cancer xenografts and mouse pancreatic tumors in an immune-independent fashion. Taken together with recently published studies (1-3), our data provide important distinctions between the function of FAP+ CASCs and SMA+ myofibroblasts and provide support for further development of FAP+ stromal cell-targeted therapies for a wide range of solid tumors. Reference: 1. Feig, C., Jones, J. O., Kraman, M., Wells, R. J., Deonarine, A., Chan, D. S., et al. (2013). Targeting CXCL12 from FAP-expressing carcinoma-associated fibroblasts synergizes with anti-PD-L1 immunotherapy in pancreatic cancer. Proc Natl Acad Sci USA 110, 20212-20217. 2. Ozdemir, B. C., Pentcheva-Hoang, T., Carstens, J. L., Zheng, X., Wu, C. C., Simpson, T. R., et al. (2014). Depletion of carcinoma-associated fibroblasts and fibrosis induces immunosuppression and accelerates pancreas cancer with reduced survival. Cancer Cell 25, 719-734. 3. Wang, L. C., Lo, A., Scholler, J., Sun, J., Majumdar, R. S., Kapoor, V., et al. (2014). Targeting fibroblast activation protein in tumor stroma with chimeric antigen receptor T cells can inhibit tumor growth and augment host immunity without severe toxicity. Cancer Immunol Res 2, 154-166. Citation Format: Albert Lo, Liang-Chuan S Wang, John Scholler, James Monslow, Diana Avery, Rebecca A. Evans, David J. Bajor, Amy C. Durham, Elizabeth L. Buza, Robert H. Vonderheide, Carl H. June, Steven M. Albelda, Ellen Puré. Depleting cells expressing fibroblast activation protein disrupts tumor-promoting desmoplasia. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3187. doi:10.1158/1538-7445.AM2015-3187

The desmoplastic reaction, characterized by the recruitment and differentiation of a heterogeneous population of carcinoma-associated stromal cells (CASCs) as well as extensive extracellular matrix (ECM) deposition and remodeling, regulates tumorigenesis via complex and incompletely understood mechanisms. In virtually all epithelial-derived tumors, CASCs selectively express FAP, a cell surface serine protease that promotes tumorigenesis. We investigated the mechanisms that govern FAP expression as well as the mechanisms by which FAP regulates the intratumoral desmoplastic reaction and, consequently, lung tumor progression. A screen of soluble factors revealed (1) that the inducible expression and activity of FAP in lung fibroblasts depended on ECM components and (2) differential requirements for induction of FAP and αSMA (a canonical marker of myofibroblasts). Unlike TGFβ-mediated induction of αSMA expression, TGFβ-mediated induction of FAP expression depended on a collagen-rich substratum. These experiments underscored the fundamental role of ECM in mediating fibroblast differentiation. We further delineated bidirectional regulatory mechanisms between activated fibroblasts and ECM by studying FAP-dependent changes to ECM. Using two-photon second harmonic generation imaging, we found that activated FAP−/− lung fibroblasts deposited ECMs with a significant twofold enhancement of fibrillar collagen accumulation compared to WT fibroblast-derived ECMs. Immunoblots illustrated differences in type I collagen fragmentation in WT versus FAP−/− fibroblast-derived ECMs, substantiating prior evidence that FAP plays a role in the ordered proteolytic processing of fibrillar collagen. In addition, collagen contraction assays demonstrated that FAP negatively regulates fibroblast-mediated contraction of type I collagen. Collectively, these experiments highlight the importance of FAP in orchestrating fibroblast-dependent remodeling of intratumoral ECM composition and architecture. Lastly, by analyzing tumor burden in the spontaneous KrasG12D latent allele model, we found that FAP−/- mice had significantly smaller lung tumors than WT mice. However, the multiplicity of lung tumors did not differ between WT and FAP−/− mice. These results indicate that FAP promotes progression, rather than initiation, of lung tumorigenesis. Current analyses are studying differences in intratumoral ECM in this model and how these changes to lung CASC-derived ECM influence tumor cell proliferation. In summary, we have delineated bidirectional regulatory mechanisms between FAP and ECM as well as FAP-dependent regulation of the desmoplastic reaction and lung tumor progression. These studies further clarify the mechanisms by which the microenvironment promotes tumorigenesis and validate FAP as a potential therapeutic target in the treatment of cancer. Citation Format: Diana Avery, Michelle Jacob, Lisa Chang, Leslie Todd, Ellen Pure. The role of fibroblast activation protein (FAP) in lung tumorigenesis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-206. doi:10.1158/1538-7445.AM2015-LB-206

Intratumoral hypoxia and expression of Hypoxia Inducible Factor 1α (HIF1α) correlate with metastasis and poor survival in sarcoma patients. We demonstrate here that hypoxia controls sarcoma metastasis through a novel mechanism wherein HIF1α enhances expression of the intracellular enzyme procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2 (PLOD2). We show that loss of HIF1α or PLOD2 expression disrupts collagen modification, cell migration and pulmonary metastasis (but not primary tumor growth) in allograft and autochthonous LSL-KrasG12D/+; Trp53fl/fl murine sarcoma models. Biochemical analyses revealed that overexpression of HIF1α and PLOD2 in sarcoma cells alters collagen structure and organization. The increase in lysyl hydroxylation and concomitant loss of prolyl hydroxylation, promotes adherence of tumor cells, collagen-associated migration and tumor cell dissemination. Furthermore, ectopic PLOD2 expression restores migration and metastatic potential in HIF1α-deficient tumors, and analysis of human sarcomas reveal elevated HIF1α and PLOD2 expression in metastatic primary lesions. Pharmacological inhibition of PLOD enzymatic activity suppresses metastases. Collectively, these data indicate that HIF1α controls sarcoma metastasis through PLOD2-dependent collagen modification and organization in primary tumors. We conclude that PLOD2 is a novel therapeutic target in sarcomas and successful inhibition of this enzyme may reduce tumor cell dissemination. Citation Format: T.S. Karin Eisinger-Mathason, Minsi Zhang, Qiu Qiong, Nicolas Skuli, Michael S. Nakazawa, Tatiana Karakasheva, Vera Mucaj, Jessica E.S. Shay, Lars Stangenberg, Ellen Pure, Sam S. Yoon, David G. Kirsch, M. Celeste Simon. Hypoxia-dependent modification of collagen networks promotes sarcoma metastasis. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr A41. doi:10.1158/1538-7445.CHTME14-A41

Prostaglandin (PG) E 2 is formed from PGH 2 by a series of PGE synthase (PGES) enzymes. Microsomal PGES-1 −/− (mPGES-1 −/− ) mice were crossed into low-density lipoprotein receptor knockout (LDLR −/− ) mice to generate mPGES-1 −/− LDLR −/− s. Urinary 11α-hydroxy-9, 15-dioxo-2,3,4,5-tetranor-prostane-1,20-dioic acid (PGE-M) was depressed by mPGES-1 deletion. Vascular mPGES-1 was augmented during atherogenesis in LDLR −/− s. Deletion of mPGES-1 reduced plaque burden in fat-fed LDLR −/− s but did not alter blood pressure. mPGES-1 −/− LDLR −/− plaques were enriched with fibrillar collagens relative to LDLR −/− , which also contained small and intermediate-sized collagens. Macrophage foam cells were depleted in mPGES-1 −/− LDLR −/− lesions, whereas the total areas rich in vascular smooth muscle cell (VSMC) and matrix were unaltered. mPGES-1 deletion augmented expression of both prostacyclin (PGI 2 ) and thromboxane (Tx) synthases in endothelial cells, and VSMCs expressing PGI synthase were enriched in mPGES-1 −/− LDLR −/− lesions. Stimulation of mPGES-1 −/− VSMC and macrophages with bacterial LPS increased PGI 2 and thromboxane A 2 to varied extents. Urinary PGE-M was depressed, whereas urinary 2,3-dinor 6-keto PGF 1α , but not 2,3-dinor-TxB 2 , was increased in mPGES-1 −/− LDLR −/− s. mPGES-1-derived PGE 2 accelerates atherogenesis in LDLR −/− mice. Disruption of this enzyme retards atherogenesis, without an attendant impact on blood pressure. This may reflect, in part, rediversion of accumulated PGH 2 to augment formation of PGI 2 . Inhibitors of mPGES-1 may be less likely than those selective for cyclooxygenase 2 to result in cardiovascular complications because of a divergent impact on the biosynthesis of PGI 2 .

Fibroblast activation protein (FAPalpha) is a member of the cell surface dipeptidyl peptidase (DPP) family of serine proteases. In its dimer form, FAPalpha exhibits gelatinase, collagenase, and DPP activity in vitro. Reactive fibroblasts in healing wounds and stromal fibroblasts associated with epithelial tumors express FAPalpha. Idiopathic pulmonary fibrosis (IPF) is a disease of the lung characterized by progressive fibrosis with no clear etiology or molecular marker for disease activity. Recently, it has been shown that fibroblast FAPalpha expression is induced in liver cirrhosis, with an expression pattern distinct from alpha-smooth muscle actin (alpha-SMA). In this study, we determine whether FAPalpha expression is selectively induced in areas of ongoing tissue remodeling characterized by fibroblast foci in IPF. Human lung tissue was obtained from patients with IPF, centrilobular emphysema, and normal lung. Immunohistochemical studies were performed using anti-FAPalpha antibody and antibodies against alpha-SMA and CD26 (DPPIV), another member of the DPP family. We found that FAPalpha was not expressed in normal human lung tissue or tissue with evidence of centriacinar emphysema, but was induced in all patients with IPF and With a pattern distinct from that of CD26 found primarily on hyperplastic alveolar epithelium. Specifically, FAPalpha was detected in fibroblast foci and in fibrotic interstitium and not in the interstitium of adjacent architecturally normal lung. Alveolar/airway epithelium and vascular smooth muscle did not express FAPalpha. This is the first report of FAPalpha expression in IPF and our results suggest that FAPalpha is selectively induced in fibrotic foci, but not in normal or emphysematous lung. Future studies will address whether FAPalpha may be used as a marker for disease activity in IPF.

CD44, a major receptor for glycosaminoglycan hyaluronan (HA), is a broadly distributed cell surface glycoprotein implicated in multiple functions, including tumor growth and dissemination. The affinity of surface CD44 for HA is subject to regulation at several levels. CD44 is found in multiple phases, including as an integral transmembrane protein and as soluble fragment of the extracellular domain found in the circulation and other body fluids. Transmembrane CD44 and its ability to interact with HA have been a focus of numerous studies in the past, but the function of soluble CD44 remains obscure. Interestingly, malignant diseases are often associated with an increase in the plasma level of CD44. The delineation of the HA binding capacity of tumor-derived soluble CD44 is an important step toward understanding the biological function of this molecule. In this study, we demonstrate that tumor cells activated to bind HA by cytokines rapidly release CD44 upon treatment with phorbol ester (PMA). The affinity for HA of the soluble CD44 released in response to PMA varied depending on the cytokine pretreatment. These results suggest that the function of tumor-derived soluble CD44, like the transmembrane form of the receptor, can be regulated.

Epstein-Barr Virus (EBV) is a potentially oncogenic herpesvirus that infects >90% of the world's population. EBV exists predominantly as a latent infection in B lymphocytes, with periodic lytic-cycle reactivation essential for cellular and host transmission. Viral reactivation can be stimulated by ligand-induced activation of B-cell-receptor (BCR)-coupled signaling pathways. The critical first step in the transition from latency to the lytic cycle is the expression of the viral immediate-early gene BZLF1 through the transcription activation of its promoter, Zp. However, the BCR-coupled signal transduction cascade(s) leading to the induction of Zp and the expression of the BZLF1 gene product, Zta, is currently unclear. A major obstacle to delineating the relevant signal transduction events has been the lack of a model of EBV infection that is amenable to genetic manipulation. The use of the avian B-cell line DT40 has proven to be a powerful tool for delineating BCR-mediated signal transduction pathways that appear to be highly conserved between avian and mammalian systems. We demonstrate that the DT40 cell line is a robust and genetically tractable system for the study of BCR-mediated signaling pathways leading to transcriptional activation of BZLF1. Using this system, we demonstrate that activation of Zp requires the BCR-coupled protein tyrosine kinases Syk and Btk and that it is positively regulated by Lyn. Thus, the use of DT40 cells has allowed us to delineate the early signaling components required for BCR-dependent reactivation of latent EBV, and this system is likely to prove useful for further dissection of the downstream signaling cascades involved.

The prostanoid prostacyclin (PGI2) inhibits aortic smooth muscle cell proliferation by blocking cell cycle progression from G1-to S-phase. However, the mechanism of this inhibition is poorly understood. We report here that the PGI2 mimetic, cicaprost, inhibits the induction of cyclin A and activation of the cyclin A promoter in primary and established rodent aortic smooth muscle cells. The inhibition of cyclin A gene expression is associated with a block in cyclin E-cdk2 activity and phosphorylation of both the retinoblastoma protein and p107. Inactivation of pocket proteins with human papilloma virus protein E7 partially, but not completely, restored cyclin A promoter activity in cicaprost-treated cells. Complementary studies showed that occupancy of the cAMP response element (CRE) is required for efficient activation of the cyclin A promoter in aortic smooth muscle cells, that the CRE is primarily occupied by the CRE-binding protein (CREB) and phospho-CREB, and that cicaprost blocks the binding of CREB and phospho-CREB to the cyclin A promoter CRE. Treatment with pertussis toxin reversed the inhibitory effects of cicaprost on CRE occupancy, cyclin E-cdk2 activity, and S phase entry, suggesting the involvement of Gi signaling in cicaprost action. We conclude that PGI2 inhibits proliferation of aortic smooth muscle cells by coordinately blocking CRE- and pocket protein-dependent cyclin A gene expression.

HDL and its associated apo, APOE, inhibit S-phase entry of murine aortic smooth muscle cells. We report here that the antimitogenic effect of APOE maps to the N-terminal receptor‐binding domain, that APOE and its N-terminal domain inhibit activation of the cyclin A promoter, and that these effects involve both pocket protein‐dependent and independent pathways. These antimitogenic effects closely resemble those seen in response to activation of the prostacyclin receptor IP. Indeed, we found that HDL and APOE suppress aortic smooth muscle cell cycle progression by stimulating Cox-2 expression, leading to prostacyclin synthesis and an IP-dependent inhibition of the cyclin A gene. Similar results were detected in human aortic smooth muscle cells and in vivo using mice overexpressing APOE. Our results identify the Cox-2 gene as a target of APOE signaling, link HDL and APOE to IP action, and describe a potential new basis for the cardioprotective effect of HDL and APOE.

Based on the comments and data from Taylor et al,[1][1] we conclude that the various 12/15-lipoxygenase–deficient (Alox15) mice exhibit more similarities than differences. The majority of Alox15 mice in our colony and those we purchased from The Jackson Laboratory appeared healthy although they

CD44 is a transmembrane glycoprotein known to be involved in endothelial cell recognition, lymphocyte trafficking, and regulation of cytokine gene expression in inflammatory diseases. In the present study, we demonstrated that the expression of CD44 mRNA was induced in a mouse model of cerebral ischemia. A potential role of CD44 in ischemic brain injury was investigated using CD44-deficient (CD44-/-) mice. Over 50% (p0.05, n = 14) and 78% (p0.05, n = 10) reduction in ischemic infarct was observed in CD44-/- mice compared with that of wild-type mice following transient (30 min ischemia) and permanent (24 h) occlusion of the middle cerebral artery (MCAO), respectively. Similarly, significant improvement was observed in neurological function in CD44-/- mice as evidenced by spontaneous and forced motor task scores. The marked protection from ischemic brain injury in CD44-/- mice was associated with normal physiological parameters, cytokine gene expression, astrocyte and microglia activation as compared with wild-type mice. However, in CD44-/- mice, significantly lower expression of soluble interleukin-1beta protein was noted after brain ischemia. Our data provide new evidence on the potential role of CD44 in brain tissue in response to ischemia and may suggest that this effect might be associated with selective reduction in inflammatory cytokines such as interleukin-1beta.

CD44 is a receptor for the matrix glycosaminoglycan hyaluronan. Proteoglycan forms of CD44 also exhibit affinity for fibronectin and collagen as well as chemokines and growth factors. CD44 plays a role in autoimmunity, inflammation, and tumor progression. Soluble CD44 (sCD44) is found in plasma, and the levels of sCD44 correlate with immune function and some malignancies. The mechanisms by which sCD44 is generated and its function are unknown. We demonstrate here that normal bronchial epithelial cells spontaneously release sCD44. Exposure to phagocyte- and bacterium-derived proteinases markedly increased the release of sCD44 from epithelial cells. The spontaneously released sCD44 was incorporated into high molecular mass complexes derived from the matrix that also contained chondroitin sulfate, fibronectin, hyaluronan, and collagens I and IV. Enzymatic digestion with proteinases liberated sCD44 from the high molecular mass complex. Consistent with the homology of CD44 to proteoglycan core and link proteins, these data suggest that CD44 spontaneously released from normal bronchial epithelial cells can accumulate as an integral component of the matrix, where it may play a role in the organization of matrices and in anchoring growth factors and chemokines to the matrix. Increases in plasma CD44 during immune activation and tumor progression therefore may be a manifestation of the matrix remodeling that occurs in the face of the enhanced proteolytic activity associated with infection, inflammation, and tumor metastasis, leading to alterations in cell-matrix interactions.

Reduction of total and LDL cholesterol reduces atherosclerosis and clinical cardiovascular events. High density lipoprotein (HDL) cholesterol levels have a strong inverse association with atherosclerosis, and overexpression of apolipoprotein A-I (apoA-I), the major protein component of HDL, reduces atherosclerosis in hypercholesterolemic animals. However, little is known about the potential for additive or synergistic effects between cholesterol reduction and apoA-I overexpression on atherosclerosis. In the current study, we tested the hypothesis that significant reduction of plasma cholesterol combined with overexpression of apoA-I would reduce atherosclerosis to a greater extent than either one alone. We used somatic gene transfer of the LDL receptor (to induce cholesterol reduction) and apoA-I in LDL receptor deficient mice fed a Western type diet and compared the combination to expression of each gene alone and to controls. Atherosclerosis was quantitated using two independent methods, by en face analysis of the entire aorta and by cross-sectional analysis of the aortic root. Although the reduction of cholesterol was transient, expression of the LDL receptor alone significantly reduced atherosclerosis by 45% in the aorta and 44% in the aortic root compared with controls. Overexpression of human apoA-I alone reduced atherosclerosis by 42% in the aorta and 44% in the aortic root compared with controls. Co-expression of the LDL receptor with apoA-I resulted in significantly higher levels of apoA-I than expression of apoA-I alone. Although co-expression of the LDL receptor and apoA-I reduced atherosclerosis by 37% in the aorta and 32% in the aortic root compared with controls, the reduction in atherosclerosis was no different than that seen with expression of the LDL receptor alone or apoA-I alone. In summary, in this relatively short-term murine model, simultaneous reduction of cholesterol and expression of apoA-I was associated with higher levels of apoA-I than expression of apoA-I alone but did not result in greater reduction in atherosclerosis compared with either one alone.

The interaction of activated CD44 with its ligand, low m.w. hyaluronan, is involved in inflammation, but no role has been identified for this interaction in the regulation of an immune response to infection. In these studies, infection of C57BL/6 mice with Toxoplasma gondii resulted in increased expression of CD44 on T cells, B cells, NK cells, and macrophages, and a small percentage of CD4+ T cells express an activated form of CD44. Administration of anti-CD44 to infected mice prevented the development of a CD4+ T cell-dependent, infection-induced inflammatory response in the small intestine characterized by the overproduction of IFN-γ. The protective effect of anti-CD44 treatment was associated with reduced production of IFN-γ, but not IL-12, in vivo and in vitro. Furthermore, the addition of low m.w. hyaluronan to cultures of splenocytes or purified CD4+ T cells from infected mice resulted in the production of high levels of IFN-γ, which was dependent on IL-12 and TCR stimulation. Together, these results identify a novel role for CD44 in the regulation of IFN-γ production by CD4+ T cells during infection and demonstrate a role for CD44 in the regulation of infection-induced immune pathology.

Apolipoprotein E is a multifunctional protein synthesized by hepatocytes and macrophages. Plasma apoE is largely liver-derived and known to regulate lipoprotein metabolism. Macrophage-derived apoE has been shown to reduce the progression of atherosclerosis in mice. We tested the hypothesis that liver-derived apoE could directly induce regression of pre-existing advanced atherosclerotic lesions without reducing plasma cholesterol levels. Aged low density lipoprotein (LDL) receptor-deficient (LDLR(-/-)) mice were fed a western-type diet for 14 weeks to induce advanced atherosclerotic lesions. One group of mice was sacrificed for evaluation of atherosclerosis at base line, and two other groups were injected with a second generation adenoviruses encoding human apoE3 or a control empty virus. Hepatic apoE gene transfer increased plasma apoE levels by 4-fold at 1 week, and apoE levels remained at least 2-fold higher than controls at 6 weeks. There were no significant changes in plasma total cholesterol levels or lipoprotein composition induced by expression of apoE. The liver-derived human apoE gained access to and was retained in arterial wall. Compared with base-line mice, the control group demonstrated progression of atherosclerosis; in contrast, hepatic apoE expression induced highly significant regression of advanced atherosclerotic lesions. Regression of lesions was accompanied by the loss of macrophage-derived foam cells and a trend toward increase in extracellular matrix of lesions. As an index of in vivo oxidant stress, we quantitated the isoprostane iPF(2 alpha)-VI and found that expression of apoE markedly reduced urinary, LDL-associated, and arterial wall iPF(2 alpha)-VI levels. In summary, these results demonstrate that liver-derived apoE directly induced regression of advanced atherosclerosis and has anti-oxidant properties in vivo that may contribute to its anti-atherogenic effects.

CD44, a receptor for hyaluronan (HA), has been implicated in tumor growth and metastasis. Most CD44-positive cells fail to exhibit constitutive HA receptor function but CD44-mediated HA binding on hematopoetic cells can be induced by antibody cross-linking of the receptor and by physiologic stimuli, including cytokines. We now demonstrate that oncostatin M (OSM) and transforming growth factor-beta1, cytokines known to regulate the growth of tumor cells, stimulate HA binding in lung epithelial-derived tumor cells. In lung epithelial-derived tumor cells, cytokine-induced binding resulted from post-translational modification of the receptor. OSM-induced HA binding was associated with a reduction in N-linked carbohydrate content of CD44. In addition, OSM induced HA binding via a novel mechanism requiring sulfation of chondroitin sulfate chains linked to CD44. The mechanism underlying transforming growth factor-beta1 induced HA binding was distinct from the effects of OSM. The data presented indicate that modulation of the glycosylation and sulfation of CD44 by cytokines provides mechanisms for regulating cell adhesion during tumor growth and metastasis.

Background —The ability of apolipoprotein (apo)A-I to induce regression of preexisting atherosclerotic lesions has not been determined, and a mouse model of atherosclerosis regression has not yet been reported. Methods and Results —LDL receptor–deficient mice were fed a western-type diet for 5 weeks to induce atherosclerotic lesions. A second-generation recombinant adenovirus encoding human apoA-I or a control adenovirus were injected intravenously in order to express apoA-I in the liver. Three days after injection, total apoA-I levels in mice injected with the apoA-I–expressing adenovirus were 216±16.0 mg/dL, compared with 68.0±3.0 mg/dL in control virus–injected mice ( P P Conclusions —Liver-directed gene transfer of human apoA-I resulted in significant regression of preexisting atherosclerotic lesions in LDL receptor–deficient mice as assessed by 2 independent methods.

Hallmarks of chronic inflammation and tissue fibrosis are increased influx of activated inflammatory cells, mediator release, and increased turnover and production of the extracellular matrix (ECM). Recent evidence has suggested that fragments of the ECM component hyaluronan play a role in chronic inflammation by inducing macrophage expression of chemokines. Interferon-gamma (IFN-gamma), an important regulator of macrophage functions, has been shown to induce the C-X-C chemokines Mig and IP-10. These chemokines affect T-cell recruitment and inhibit angiogenesis. The purpose of this investigation was to determine the effect of hyaluronan (HA) on IFN-gamma-induced Mig and IP-10 expression in mouse macrophages. We found a marked synergy between HA and IFN-gamma on Mig and IP-10 mRNA and protein expression in mouse macrophages. This was most significant with Mig, which was not induced by HA alone. The synergy was specific for HA, was not dependent on new protein synthesis, was not mediated by tumor necrosis factor-alpha, was selective for Mig and IP-10, and occurred at the level of gene transcription. These data suggest that the ECM component HA may influence chronic inflammatory states by working in concert with IFN-gamma to alter macrophage chemokine expression.

Inflammation is associated with production of cytokines and chemokines that recruit and activate inflammatory cells. Interleukin (IL) 12 produced by macrophages in response to various stimuli is a potent inducer of interferon (IFN) γ production. IFN-γ, in turn, markedly enhances IL-12 production. Although the immune response is typically self-limiting, the mechanisms involved are unclear. We demonstrate that IFN-γ inhibits production of chemokines (macrophage inflammatory proteins MIP-1α and MIP-1β). Furthermore, pre-exposure to tumor necrosis factor (TNF) inhibited IFN-γ priming for production of high levels of IL-12 by macrophagesin vitro. Inhibition of IL-12 by TNF can be mediated by both IL-10-dependent and IL-10-independent mechanisms. To determine whether TNF inhibition of IFN-γ-induced IL-12 production contributed to the resolution of an inflammatory responsein vivo, the response of TNF+/+and TNF−/−mice injected withCorynebacterium parvumwere compared. TNF−/−mice developed a delayed, but vigorous, inflammatory response leading to death, whereas TNF+/+mice exhibited a prompt response that resolved. Serum IL-12 levels were elevated 3-fold inC. parvum-treated TNF−/−mice compared with TNF+/+mice. Treatment with a neutralizing anti-IL-12 antibody led to resolution of the response toC. parvumin TNF−/−mice. We conclude that the role of TNF in limiting the extent and duration of inflammatory responsesin vivoinvolves its capacity to regulate macrophage IL-12 production. IFN-γ inhibition of chemokine production and inhibition of IFN-γ-induced IL-12 production by TNF provide potential mechanisms by which these cytokines can exert anti-inflammatory/repair function(s).

The current model of lymphocyte extravasation into areas of inflammation involves the sequential engagement of multiple cell adhesion molecules (CAMs) expressed on lymphocytes and endothelial cells. In addition, the expression of CAMs and the elaboration of matrix by subendothelial/submucosal cells may contribute to the retention and stimulation of infiltrating cells in an inflammatory lesion. We previously demonstrated that mitogen-activated T cells adhered to airway smooth muscle (ASM) in an integrin-dependent fashion. ASM are MHC class II-negative and expressed low basal levels of intercellular adhesion molecule-1 (ICAM-1). In this study, we demonstrate that anti-CD3-stimulated peripheral blood T cells also adhere to ASM and markedly upregulate ICAM-1 expression and induce the expression of MHC class II on ASM. The induction of HLA-DR was completely inhibited, and the induction of ICAM-1 partially inhibited, by neutralizing antibody against interferon-gamma. Furthermore, in studies with bronchoalveolar lavage-derived T cells isolated from atopic donors following local antigen challenge, we observed adhesion to ASM and upregulation of ASM expression of ICAM-1 and HLA-DR similar to that seen with in vitro-activated T cells. Finally, we found that despite expression of ICAM-1 and HLA-DR, ASM could not present alloantigen to CD4+ T cells. These findings suggest that the interaction of activated T cells with parenchymal cells of the lung such as airway smooth muscle affects the phenotype of myocytes and thus may have significant implications for inflammatory diseases such as asthma or transplant rejection.

Rationale: The recent success of chimeric antigen receptor (CAR) T cell therapy in treating leukemia has brought new enthusiasm to this strategy. While the majority of CAR research has been primarily focused on targeting tumor cells, our group is developing a new CAR construct to target Fibroblast Activation Protein (FAP), a molecule that is highly and selectively expressed on cancer-associated fibroblasts (CAFs). It is well known that these CAFs play an important role in tumor development and tumor progression. Thus, we hypothesized that the immune-mediated destruction of CAFs by adoptively transferred FAP-CAR T cells would inhibit tumor growth in pre-clinical tumor models. Experimental procedures: The 73.3 anti-mouse FAP hybridoma was sequenced to obtain the single chain Fv to insert into our existing CAR construct with the 4-1BB and CD3ζ intracellular signaling domains. Different combinations of FAP-CAR constructs were synthesized and transduced into human T cells first to screen for optimal structure-activity response. The best two FAP-CAR constructs were then selected to transduce into mouse T cells for in vitro cytotoxicity and cytokine assays, as well as in vivo studies. To evaluate the in vivo efficacy, 2 tumor cell lines, AE17 (mouse mesothelioma) and TC1 (mouse lung cancer), were inoculated subcutaneously into flanks of syngeneic C57Bl6 mice. When the flank tumors reached 150 mm3, 10 million CAR T cells were injected through tail vein and tumors were then monitored. Tumor tissues were collected at the end of the study to evaluate the effect of CAR T cells on tumor microenvironment by flow cytometry and/or by immunohistochemistry. Results: All 8 different combinations of anti-mouse FAP CAR constructs expressed on human T cells showed target-specific activities against 3T3parental (FAP-null) versus 3T3FAP cells, in terms of cytotoxicity and cytokine production. The two best FAP-CAR constructs were then transduced into mouse T cells and re-tested for cytotoxicity and cytokine production against 3T3parental and 3T3-FAP fibroblasts, and again showed target-specific killing and cytokine production. When FAP-CAR T cells were adoptively transferred into tumor bearing mice, tumor growth inhibition (~50%) was observed in both flank tumor models while control T cells did not show any efficacy. No toxicity was detected in the animal studies. We found that FAP-CAR T cell-treated tumors had significantly more apoptotic and less proliferating tumor cells, less matrix (collagen, fibronectin), less M2 macrophages and fewer blood vessels, in comparison with the untreated and control T cell-treated tumors. To assure specificity, similar in vivo studies were also carried out in FAP knockout mice. In the KO mice, all the anti-tumor activity of FAP-CAR T cells was lost. Conclusion: Here, we demonstrate the feasibility of inhibiting tumor growth by targeting tumor stroma, instead of tumor cells, with adoptively transferred CAR T cells. We detected no safety issues with these stroma-targeted CAR T cells. We also showed that the anti-tumor effects induced by our T cells were specific to FAP. We are currently evaluating different CAR constructs against human FAP with a goal of conducting a clinical trial. This abstract is also presented as Poster A5. Citation Format: Liang-Chuan S. Wang, Albert Lo, John Scholler, Carl H. June, Ellen Pure, Steven M. Albelda. Fibroblast activation protein as a universal target for chimeric antigen receptor T cell therapy in solid tumors. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr PR14.

Nanoparticles (NPs) are being extensively studied as carriers for drug delivery, but they often have limited penetration inside tumors. We envision that by targeting an endocytic receptor on the cell surface, the uptake of NPs can be significantly enhanced through receptor mediated endocytosis. In addition, if the receptor is recycled to the cell surface, the NP cargo can be transported out of the cells, which is then taken up by neighboring cells thus enhancing solid tumor penetration. To validate our hypothesis, in the first of two articles, we report the synthesis of doxorubicin (DOX)-loaded, hyaluronan (HA) coated silica nanoparticles (SNPs) containing a highly fluorescent core to target CD44, a receptor expressed on the cancer cell surface. HA was conjugated onto amine-functionalized SNPs prepared through an oil-water microemulsion method. The immobilization of the cytotoxic drug DOX was achieved through an acid sensitive hydrazone linkage. The NPs were fully characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential measurements, thermogravimetric analysis (TGA), UV-vis absorbance, and nuclear magnetic resonance (NMR). Initial biological evaluation experiments demonstrated that compared to ligand-free SNPs, the uptake of HA-SNPs by the CD44-expressing SKOV-3 ovarian cancer cells was significantly enhanced when evaluated in the 2D monolayer cell culture. Mechanistic studies suggested that cellular uptake of HA-SNPs was mainly through CD44 mediated endocytosis. HA-SNPs with immobilized DOX were endocytosed efficiently by the SKOV-3 cells as well. The enhanced tumor penetration and drug delivery properties of HA-SNPs will be evaluated in 3D tumor models in the subsequent paper.

Though Abl inhibitors are often successful therapies for the initial stages of chronic myelogenous leukemia (CML), refractory cases highlight the need for novel molecular insights. We demonstrate that mice deficient in the enzyme 12/15-lipoxygenase (12/15-LO) develop a myeloproliferative disorder (MPD) that progresses to transplantable leukemia. Although not associated with dysregulation of Abl, cells isolated from chronic stage 12/15-LO–deficient (Alox15) mice exhibit increased activation of the phosphatidylinositol 3–kinase (PI3-K) pathway, as indicated by enhanced phosphorylation of Akt. Furthermore, the transcription factor interferon consensus sequence binding protein (ICSBP) is hyperphosphorylated and displays decreased nuclear accumulation, translating into increased levels of expression of the oncoprotein Bcl-2. The ICSBP defect, exaggerated levels of Bcl-2, and prolonged leukemic cell survival associated with chronic stage Alox15 MPD are all reversible upon treatment with a PI3-K inhibitor. Remarkably, the evolution of Alox15 MPD to leukemia is associated with additional regulation of ICSBP on an RNA level, highlighting the potential usefulness of the Alox15 model for understanding the transition of CML to crisis. Finally, 12/15-LO expression suppresses the growth of a human CML–derived cell line. These data identify 12/15-LO as an important suppressor of MPD via its role as a critical upstream effector in the regulation of PI3-K–dependent ICSBP phosphorylation.