Tumor cells induce COX-2 and mPGES-1 expression in microvascular endothelial cells mainly by means of IL-1 receptor activation

A reverse translational approach reveals the protective roles of Mangifera indica in inflammatory bowel disease

Inflammatory bowel diseases (IBDs) are chronic intestinal disorders often characterized by a dysregulation of T cells, specifically T helper (Th) 1, 17 and T regulatory (Treg) repertoire. Increasing evidence demonstrates that dietary polyphenols from Mangifera indica L. extract (MIE, commonly known as mango) mitigate intestinal inflammation and splenic Th17/Treg ratio. In this study, we aimed to dissect the immunomodulatory and anti-inflammatory properties of MIE using a reverse translational approach, by initially using blood from an adult IBD inception cohort and then investigating the mechanism of action in a preclinical model of T cell-driven colitis. Of clinical relevance, MIE modulates TNF-α and IL-17 levels in LPS spiked sera from IBD patients as an ex vivo model of intestinal barrier breakdown. Preclinically, therapeutic administration of MIE significantly reduced colitis severity, pathogenic T-cell intestinal infiltrate and intestinal pro-inflammatory mediators (IL-6, IL-17A, TNF-α, IL-2, IL-22). Moreover, MIE reversed colitis-induced gut permeability and restored tight junction functionality and intestinal metabolites. Mechanistic insights revealed MIE had direct effects on blood vascular endothelial cells, blocking TNF-α/IFN-γ-induced up-regulation of COX-2 and the DP2 receptors. Collectively, we demonstrate the therapeutic potential of MIE to reverse the immunological perturbance during the onset of colitis and dampen the systemic inflammatory response, paving the way for its clinical use as nutraceutical and/or functional food.

The microsomal prostaglandin E synthase-1/prostaglandin E2 axis induces recovery from ischaemia via recruitment of regulatory T cells

AIMS

Microsomal prostaglandin E synthase-1 (mPGES-1)/prostaglandin E2 (PGE2) induces angiogenesis through the prostaglandin E2 receptor (EP1-4). Among immune cells, regulatory T cells (Tregs), which inhibit immune responses, have been implicated in angiogenesis, and PGE2 is known to modulate the function and differentiation of Tregs. We hypothesized that mPGES-1/PGE2-EP signalling could contribute to recovery from ischaemic conditions by promoting the accumulation of Tregs.

METHODS AND RESULTS

Wild-type (WT), mPGES-1-deficient (mPges-1-/-), and EP4 receptor-deficient (Ep4-/-) male mice, 6-8 weeks old, were used. Hindlimb ischaemia was induced by femoral artery ligation. Recovery from ischaemia was suppressed in mPges-1-/- mice and compared with WT mice. The number of accumulated forkhead box protein P3 (FoxP3)+ cells in ischaemic muscle tissue was decreased in mPges-1-/- mice compared with that in WT mice. Expression levels of transforming growth factor-β (TGF-β) and stromal cell derived factor-1 (SDF-1) in ischaemic tissue were also suppressed in mPges-1-/- mice. The number of accumulated FoxP3+ cells and blood flow recovery were suppressed when Tregs were depleted by injecting antibody against folate receptor 4 in WT mice but not in mPges-1-/- mice. Recovery from ischaemia was significantly suppressed in Ep4-/- mice compared with that in WT mice. Furthermore, mRNA levels of Foxp3 and Tgf-β were suppressed in Ep4-/- mice. Moreover, the number of accumulated FoxP3+ cells in ischaemic tissue was diminished in Ep4-/- mice compared with that in Ep4+/+ mice.

CONCLUSION

These findings suggested that mPGES-1/PGE2 induced neovascularization from ischaemia via EP4 by promoting the accumulation of Tregs. Highly selective EP4 agonists could be useful for the treatment of peripheral artery disease.

Immunobiology of high-grade serous ovarian cancer: lessons for clinical translation

Treatment of high-grade serous ovarian cancer (HGSOC) remains challenging. Although HGSOC can potentially be responsive to immunotherapy owing to endogenous immunity at the molecular or T cell level, immunotherapy for this disease has fallen short of expectations to date. This Review proposes a working classification for HGSOC based on the presence or absence of intraepithelial T cells, and elaborates the putative mechanisms that give rise to such immunophenotypes. These differences might explain the failures of existing immunotherapies, and suggest that rational therapeutic approaches tailored to each immunophenotype might meet with improved success. In T cell-inflamed tumours, treatment could focus on mobilizing pre-existing immunity and strengthening the activation of T cells embedded in intraepithelial tumour myeloid niches. Conversely, in immune-excluded and immune-desert tumours, treatment could focus on restoring inflammation by reprogramming myeloid cells, stromal cells and vascular epithelial cells. Poly(ADP-ribose) polymerase (PARP) inhibitors, low-dose radiotherapy, epigenetic drugs and anti-angiogenesis therapy are among the tools available to restore T cell infiltration in HGSOC tumours and could be implemented in combination with vaccines and redirected T cells.

Impact of tumor microenvironment on adoptive T cell transfer activity

Recent advances in immunotherapy have revolutionized the treatment of cancer. The use of adoptive cell therapies (ACT) such as those based on tumor infiltrating lymphocytes (TILs) or genetically modified cells (transgenic TCR lymphocytes or CAR-T cells), has shown impressive results in the treatment of several types of cancers. However, cancer cells can exploit mechanisms to escape from immunosurveillance resulting in many patients not responding to these therapies or respond only transiently. The failure of immunotherapy to achieve long-term tumor control is multifactorial. On the one hand, only a limited percentage of the transferred lymphocytes is capable of circulating through the bloodstream, interacting and crossing the tumor endothelium to infiltrate the tumor. Metabolic competition, excessive glucose consumption, the high level of lactic acid secretion and the extracellular pH acidification, the shortage of essential amino acids, the hypoxic conditions or the accumulation of fatty acids in the tumor microenvironment (TME), greatly hinder the anti-tumor activity of the immune cells in ACT therapy strategies. Therefore, there is a new trend in immunotherapy research that seeks to unravel the fundamental biology that underpins the response to therapy and identifies new approaches to better amplify the efficacy of immunotherapies. In this review we address important aspects that may significantly affect the efficacy of ACT, indicating also the therapeutic alternatives that are currently being implemented to overcome these drawbacks.

Aspects of the Tumor Microenvironment Involved in Immune Resistance and Drug Resistance

The tumor microenvironment (TME) is a complex and ever-changing "rogue organ" composed of its own blood supply, lymphatic and nervous systems, stroma, immune cells and extracellular matrix (ECM). These complex components, utilizing both benign and malignant cells, nurture the harsh, immunosuppressive and nutrient-deficient environment necessary for tumor cell growth, proliferation and phenotypic flexibility and variation. An important aspect of the TME is cellular crosstalk and cell-to-ECM communication. This interaction induces the release of soluble factors responsible for immune evasion and ECM remodeling, which further contribute to therapy resistance. Other aspects are the presence of exosomes contributed by both malignant and benign cells, circulating deregulated microRNAs and TME-specific metabolic patterns which further potentiate the progression and/or resistance to therapy. In addition to biochemical signaling, specific TME characteristics such as the hypoxic environment, metabolic derangements, and abnormal mechanical forces have been implicated in the development of treatment resistance. In this review, we will provide an overview of tumor microenvironmental composition, structure, and features that influence immune suppression and contribute to treatment resistance.

Cytochrome P450: Implications for human breast cancer

The treatment options for breast cancer include endocrine therapy, targeted therapy and chemotherapy. However, some patients with triple-negative breast cancer cannot benefit from these methods. Therefore, novel therapeutic targets should be developed. The cytochrome P450 enzyme (CYP) is a crucial metabolic oxidase, which is involved in the metabolism of endogenous and exogenous substances in the human body. Some products undergoing the metabolic pathway of the CYP enzyme, such as hydroxylated polychlorinated biphenyls and 4-chlorobiphenyl, are toxic to humans and are considered to be potential carcinogens. As a class of multi-gene superfamily enzymes, the subtypes of CYPs are selectively expressed in breast cancer tissues, especially in the basal-like type. In addition, CYPs are essential for the activation or inactivation of anticancer drugs. The association between CYP expression and cancer risk, tumorigenesis, progression, metastasis and prognosis has been widely reported in basic and clinical studies. The present review describes the current findings regarding the importance of exploring metabolic pathways of CYPs and gene polymorphisms for the development of vital therapeutic targets for breast cancer.

Endothelial Microsomal Prostaglandin E Synthetase-1 Upregulates Vascularity and Endothelial Interleukin-1β in Deteriorative Progression of Experimental Autoimmune Encephalomyelitis

Microsomal prostaglandin E synthetase-1 (mPGES-1) is an inducible terminal enzyme for the production of prostaglandin E₂ (PGE₂). In experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, mPGES-1 is induced in vascular endothelial cells (VECs) around inflammatory foci and facilitates inflammation, demyelination, and paralysis. Therefore, we investigated the role of CD31-positive VECs in mPGES-1-mediated EAE aggravation using immunohistochemical analysis and imaging of wild-type (wt) and mPGES-1-deficient (mPGES-1^-/-) mice. We demonstrated that EAE induction facilitated vascularity in inflammatory lesions in the spinal cord, and this was significantly higher in wt mice than in mPGES-1^-/- mice. In addition, endothelial interleukin-1β (IL-1β) production was significantly higher in wt mice than in mPGES-1^-/- mice. Moreover, endothelial PGE₂ receptors (E-prostanoid (EP) receptors EP1⁻4) were expressed after EAE induction, and IL-1β was induced in EP receptor-positive VECs. Furthermore, IL-1 receptor 1 expression on VECs was increased upon EAE induction. Thus, increased vascularity is one mechanism involved in EAE aggravation induced by mPGES-1. Furthermore, mPGES-1 facilitated the autocrine function of VECs upon EP receptor induction and IL-1β production, modulating mPGES-1 induction in EAE.

Mechanisms regulating T-cell infiltration and activity in solid tumors

T-lymphocytes play a critical role in cancer immunity as evidenced by their presence in resected tumor samples derived from long-surviving patients, and impressive clinical responses to various immunotherapies that reinvigorate them. Indeed, tumors can upregulate a wide array of defense mechanisms, both direct and indirect, to suppress the ability of Tcells to reach the tumor bed and mount curative responses upon infiltration. In addition, patient and tumor genetics, previous antigenic experience, and the microbiome, are all important factors in shaping the T-cell repertoire and sensitivity to immunotherapy. Here, we review the mechanisms that regulate T-cell homing, infiltration, and activity within the solid tumor bed. Finally, we summarize different immunotherapies and combinatorial treatment strategies that enable the immune system to overcome barriers for enhanced tumor control and improved patient outcome.

GP. Nanoliposomal delivery of cytosolic phospholipase A2 inhibitor arachidonyl trimethyl ketone for melanoma treatment

Drug resistance and toxicity are major limitations of cancer treatment and frequently occurs during melanoma therapy. Nanotechnology can decrease drug resistance by improving drug delivery, with limited toxicity. This study details the development of nanoparticles containing arachidonyl trifluoromethyl ketone (ATK), a cytosolic phospholipase A₂ inhibitor, which can inhibit multiple key pathways responsible for the development of recurrent resistant disease. Free ATK is toxic, limiting its efficacy as a therapeutic agent. Hence, a novel nanoliposomal delivery system called NanoATK was developed, which loads 61.7% of the compound and was stable at 4^oC for 12 weeks. The formulation decreased toxicity-enabling administration of higher doses, which was more effective at inhibiting melanoma cell growth compared to free-ATK. Mechanistically, NanoATK decreased cellular proliferation and triggered apoptosis to inhibit melanoma xenograft tumor growth without affecting animal weight. Functionally, it inhibited the cPLA₂, AKT, and STAT3 pathways. Our results suggest the successful preclinical development of a unique nanoliposomal formulation containing ATK for the treatment of melanoma.

Microsomal Prostaglandin E Synthase-1 Facilitates an Intercellular Interaction between CD4⁺ T Cells through IL-1β Autocrine Function in Experimental Autoimmune Encephalomyelitis

Microsomal prostaglandin synthetase-1 (mPGES-1) is an inducible terminal enzyme that produces prostaglandin E₂ (PGE₂). In our previous study, we investigated the role of mPGES-1 in the inflammation and demyelination observed in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, using mPGES-1-deficient (mPGES-1^−/−) and wild-type (wt) mice. We found that mPGES-1 facilitated inflammation, demyelination, and paralysis and was induced in vascular endothelial cells and macrophages and microglia around inflammatory foci. Here, we investigated the role of interleukin-1β (IL-1β) in the intercellular mechanism stimulated by mPGES-1 in EAE spinal cords in the presence of inflammation. We found that the area invaded by CD4-positive (CD4⁺) T cells was extensive, and that PGE₂ receptors EP1–4 were more induced in activated CD4⁺ T cells of wt mice than in those of mPGES-1^−/− mice. Moreover, IL-1β and IL-1 receptor 1 (IL-1r1) were produced by 65% and 48% of CD4⁺ T cells in wt mice and by 44% and 27% of CD4⁺ T cells in mPGES-1^−/− mice. Furthermore, interleukin-17 (IL-17) was released from the activated CD4⁺ T cells. Therefore, mPGES-1 stimulates an intercellular interaction between CD4⁺ T cells by upregulating the autocrine function of IL-1β in activated CD4⁺ T cells, which release IL-17 to facilitate axonal and myelin damage in EAE mice.

Detection and Clinical Significance of COX-2 Gene SNPs in Gastric Cancer

Gastric cancer has high morbidity and mortality. Identification of patients with high gastric cancer risk at early stage will improve patient prognosis. In this study, we examined two single nucleotide polymorphism (SNP) sites of COX-2 gene in gastric cancer patients and explored the effect of the SNPs on the morbidity of gastric cancer. We found that the SNPs COX-2-1195G/A and COX-2-8473T/C are correlated with the occurrence of gastric cancer, and the patients with variants A and C of the SNPs are liable to have gastric cancer. Our study provides a potential method for screening of susceptible population of gastric cancer for early-stage intervention in patients.

Modulation of IL-1β reprogrammes the tumor microenvironment to interrupt oral carcinogenesis

Head and neck squamous cell carcinoma (HNSCC) development is a multistage process includes the normal, dysplasia and squamous cell carcinoma (SCC) stages. Recently, increasing evidence has suggested that the tumor microenvironment (TME) is an integral part of malignant transformation. Exploring certain key node genes in TME for future intervention in dysplasia to interrupt oral carcinogenesis was the primary goal of this research. To achieve this goal, systems biology approaches were first applied to the epithelia and fibroblasts collected at sequential stages in a 4-nitroquinoline-1-oxide (4NQO) - induced rat oral carcinogenesis model. Through bioinformatics network construction, IL-1β was identified as one of the key node genes in TME during carcinogenesis. Immunohistochemical staining of human and rat samples demonstrated that IL-1β expression patterns were parallel to the stages of malignant transformation. Silencing IL-1β with lentivirus-delivered shRNA significantly inhibited oral squamous cell carcinoma cell growth both in vivo and in vitro. Based on these findings, we hypothesized that IL-1β may be a chemoprevention target in TME during oral carcinogenesis. Therefore, we targeted IL-1 in the TME by oral mucosal injection of an IL-1 receptor antagonist in 4NQO rats. The results demonstrated that targeting IL-1 could interrupt oral carcinogenesis by reprogramming the TME.

Expression of IL-1α correlates with distant metastasis in patients with head and neck squamous cell carcinoma

The presence of IL-1 in human cancers is associated with aggressive tumor biology but its prognostic value is unknown. We studied whether IL-1α expression is a prognostic marker of distant metastasis in patients with head and neck squamous cell carcinoma (HNSCC). IL-1α mRNA and protein levels were determined in tumor samples and cancer cell lines using RT-PCR and ELISA. The effects of constitutive IL-1α expression by tumor lines were characterized. IL-1α mRNA and protein secretion were higher in tumor samples from patients who later developed distant metastasis than in patients who did not. By using distant metastasis as a dependent variable, patients were classified into two categories of IL-1α transcript-levels. The high-IL-1α group had a significantly lower five-year distant metastasis-free survival than the low-IL-1α group [70.0% (CI 95%: 55.9-84.1%) vs 94.7% (CI 95%:90.2-99.2%)]. When IL-1α transcript-levels were combined with clinical factors related to tumor metastasis, the predictive power of the model increased significantly. Additionally, transcript levels of IL-1α correlated significantly with those of the IL-1 family genes and genes related to the metastatic process. IL-1 treatment of microvascular endothelial cells increased adhesion of HNSCC cells but no differences were found based on constitutive IL-1α expression by tumor cells. Nevertheless, IL-1α produced by tumor cells effectively increased their transmigration across the endothelium. We found a significant relationship between IL-1α expression and development of distant metastasis in HNSCC patients. IL-1α expression could help to define a subset of patients at high risk of distant metastasis who could benefit from adjuvant treatment.

Immunological hallmarks of stromal cells in the tumour microenvironment

A dynamic and mutualistic interaction between tumour cells and the surrounding stroma promotes the initiation, progression, metastasis and chemoresistance of solid tumours. Far less understood is the relationship between the stroma and tumour-infiltrating leukocytes; however, emerging evidence suggests that the stromal compartment can shape antitumour immunity and responsiveness to immunotherapy. Thus, there is growing interest in elucidating the immunomodulatory roles of the stroma that evolve within the tumour microenvironment. In this Review, we discuss the evidence that stromal determinants interact with leukocytes and influence antitumour immunity, with emphasis on the immunological attributes of stromal cells that may foster their protumorigenic function.

Upregulation of C-C chemokine receptor type 7 expression by membrane-associated prostaglandin E synthase-1/prostaglandin E2 requires glycogen synthase kinase 3β-mediated signal transduction in colon cancer cells

C-C chemokine receptor type 7 (CCR7) is involved in the development and progressions of chronic inflammatory diseases and cancer; therefore, signaling pathways that regulate CCR7 expression may represent novel molecular therapeutic targets. Previous studies by our group revealed that CCR7 is important in colon cancer progression and a is linked with cyclooxygenase (COX)‑2‑derived prostaglandin (PG)E2. Induction of COX‑2 and membrane‑associated PGE synthase 1 (mPGES‑1), which are overexpressed in numerous cancer types, cooperatively enhance PGE2 expression, which contributes to carcinogenesis and cancer progression. The present study investigated whether CCR7 expression is associated with the levels of mPGES‑1-derived PGE2. The results showed that mPGES‑1‑dependent release of PGE2 was markedly induced in colon cancer cells after transient transfection with mPGES‑1 overexpression vector, accompanied by elevated CCR7 expression. PGE2 levels and CCR7 expression were markedly attenuated in colon cancer cells in which mPGES‑1 was blocked, which identified mPGES‑1 as a potential therapeutic target for the regulation of CCR7 expression. Finally, overexpression of CCR7 was partly mediated through the AKT/glycogen synthase kinase 3β signaling pathway dependent on the binding of mPGES‑1-derived PGE2 to the prostaglandin EP4 receptor. Thus, in addition to inhibitors of mPGES‑1 expression, EP4 antagonists and AKT/GSK-3β inhibitors may emerge as potential therapeutics to reduce CCR7 expression in colon cancer.

Expression and Cellular Localization of 15-Hydroxy-Prostaglandin-Dehydrogenase in Abdominal Aortic Aneurysm

PGE₂ has been implicated in abdominal aortic aneurysm (AAA) associated hypervascularization. PGE₂-metabolism involves 15-hydroxyprostaglandin-dehydrogenase (15-PGDH) the expression of which in AAA is unknown. The aim of this study was to examine the expression and cell distribution of 15-PGDH in AAA. Here, we show that 15-PGDH mRNA levels were significantly higher in aorta samples from patients undergoing AAA repair than in those from healthy multiorgan donors. Consequently, the ratio of metabolized PGE₂ secreted by aortic samples was significantly higher in AAA. AAA production of total PGE₂ and PGE₂ metabolites correlated positively with PGI₂ production, while the percentage of metabolized PGE₂ correlated negatively with the total amount of PGE₂ and with PGI₂. Transcript levels of 15-PGDH were statistically associated with leukocyte markers but did not correlate with microvascular endothelial cell markers. Immunohistochemistry revealed 15-PGDH in the areas of leukocyte infiltration in AAA samples, mainly associated with CD45-positive cells, but not in normal aorta samples. We provide new data concerning 15-PGDH expression in human AAA, showing that 15-PGDH is upregulated in AAA and mainly expressed in infiltrating leukocytes. Our data suggest that microvasculature was not involved in PGE₂ catabolism, reinforcing the potential role of microvasculature derived PGE₂ in AAA-associated hypervascularization.

Targeting the tumor vasculature to enhance T cell activity

T cells play a critical role in tumor immune surveillance as evidenced by extensive mouse-tumor model studies as well as encouraging patient responses to adoptive T cell therapies and dendritic cell vaccines. It is well established that the interplay of tumor cells with their local cellular environment can trigger events that are immunoinhibitory to T cells. More recently it is emerging that the tumor vasculature itself constitutes an important barrier to T cells. Endothelial cells lining the vessels can suppress T cell activity, target them for destruction, and block them from gaining entry into the tumor in the first place through the deregulation of adhesion molecules. Here we review approaches to break this tumor endothelial barrier and enhance T cell activity.

Active smoking increases microsomal PGE2-synthase-1/PGE-receptor-4 axis in human abdominal aortic aneurysms

Background. The cyclooxygenase- (COX-) 2/microsomal PGE-synthase- (mPGES-) 1/PGE-receptor- (EP-) 4 axis could play a key role in the physiopathology of abdominal aortic aneurysm (AAA) in humans. In this study, we investigated the influence of cardiovascular risk factors on the expression of the PGE₂ pathway in human AAA. Methods. Aortic (n = 89) and plasma (n = 79) samples from patients who underwent AAA repair were collected. Patients were grouped according to risk factors. COX-isoenzymes, mPGES-1, EPs, α-actin, and CD45 and CD68 transcripts levels were quantified by QRT-PCR and plasma PGE₂ metabolites by EIA. Results. Current smoking (CS) patients compared to no-CS had significantly higher local levels of mPGES-1 (P = 0.009), EP-4 (P = 0.007), and PGE₂ metabolites plasma levels (P = 0.008). In the multiple linear regression analysis, these parameters remained significantly enhanced in CS after adding confounding factors. Results from association studies with cell type markers suggested that the increased mPGES-1/EP-4 levels were mainly associated with microvascular endothelial cells. Conclusions. This study shows that elements of the PGE₂ pathway, which play an important role in AAA development, are increased in CS. These results provide insight into the relevance of tobacco smoking in AAA development and reinforce the potential of mPGES-1 and EP-4 as targets for therapy in AAA patients.

Skewing of immune cell cytokine production by mediators from adipocytes and endothelial cells

Since adipose tissue is composed of adipocytes as well as other cell types including endothelial cells, this study sought to determine how mediators from adipocytes and from endothelial cells impact on immune cell production of cytokines. A minimalistic design was used in which media conditioned by adipocytes or by endothelial cells were added individually or as a mixture to normal spleen cells. Media from adipocytes or endothelial cells each stimulated spleen cell production of Th1 cytokines, Th2 cytokines, most of the measured inflammatory cytokines, and some chemokines. However, a mixture of media conditioned by adipocytes and by endothelial cells inhibited production of Th1 cytokines and skewed reactivity toward a Th2 and inflammatory phenotype. Adiponectin, but not leptin, was shown to contribute to the skewing of immune responsiveness to endothelial cell-derived mediators.

Control of the adaptive immune response by tumor vasculature

The endothelium is nowadays described as an entire organ that regulates various processes: vascular tone, coagulation, inflammation, and immune cell trafficking, depending on the vascular site and its specific microenvironment as well as on endothelial cell-intrinsic mechanisms like epigenetic changes. In this review, we will focus on the control of the adaptive immune response by the tumor vasculature. In physiological conditions, the endothelium acts as a barrier regulating cell trafficking by specific expression of adhesion molecules enabling adhesion of immune cells on the vessel, and subsequent extravasation. This process is also dependent on chemokine and integrin expression, and on the type of junctions defining the permeability of the endothelium. Endothelial cells can also regulate immune cell activation. In fact, the endothelial layer can constitute immunological synapses due to its close interactions with immune cells, and the delivery of co-stimulatory or co-inhibitory signals. In tumor conditions, the vasculature is characterized by an abnormal vessel structure and permeability, and by a specific phenotype of endothelial cells. All these abnormalities lead to a modulation of intra-tumoral immune responses and contribute to the development of intra-tumoral immunosuppression, which is a major mechanism for promoting the development, progression, and treatment resistance of tumors. The in-depth analysis of these various abnormalities will help defining novel targets for the development of anti-tumoral treatments. Furthermore, eventual changes of the endothelial cell phenotype identified by plasma biomarkers could secondarily be selected to monitor treatment efficacy.

Microvascular COX-2/mPGES-1/EP-4 axis in human abdominal aortic aneurysm

We investigated the prostaglandin (PG)E2 pathway in human abdominal aortic aneurysm (AAA) and its relationship with hypervascularization. We analyzed samples from patients undergoing AAA repair in comparison with those from healthy multiorgan donors. Patients were stratified according to maximum aortic diameter: low diameter (LD) (<55 mm), moderate diameter (MD) (55-69.9 mm), and high diameter (HD) (≥70 mm). AAA was characterized by abundant microvessels in the media and adventitia with perivascular infiltration of CD45-positive cells. Like endothelial cell markers, cyclooxygenase (COX)-2 and the microsomal isoform of prostaglandin E synthase (mPGES-1) transcripts were increased in AAA (4.4- and 1.4-fold, respectively). Both enzymes were localized in vascular cells and leukocytes, with maximal expression in the LD group, whereas leukocyte markers display a maximum in the MD group, suggesting that the upregulation of COX-2/mPGES-1 precedes maximal leukocyte infiltration. Plasma and in vitro tissue secreted levels of PGE2 metabolites were higher in AAA than in controls (plasma-controls, 19.9 ± 2.2; plasma-AAA, 38.8 ± 5.5 pg/ml; secretion-normal aorta, 16.5 ± 6.4; secretion-AAA, 72.9 ± 6.4 pg/mg; mean ± SEM). E-prostanoid receptor (EP)-2 and EP-4 were overexpressed in AAA, EP-4 being the only EP substantially expressed and colocalized with mPGES-1 in the microvasculature. Additionally, EP-4 mediated PGE2-induced angiogenesis in vitro. We provide new data concerning mPGES-1 expression in human AAA. Our findings suggest the potential relevance of the COX-2/mPGES-1/EP-4 axis in the AAA-associated hypervascularization.

Endothelial cells in the eyes of an immunologist

Endothelial cell activation in the process of tumor angiogenesis and in various aspects of vascular biology has been extensively studied. However, endothelial cells also function in other capacities, including in immune regulation. Compared to the more traditional immune regulatory populations (Th1, Th2, Treg, etc.), endothelial cells have received far less credit as being immune regulators. Their regulatory capacity is multifaceted. They are critical in both limiting and facilitating the trafficking of various immune cell populations, including T cells and dendritic cells, out of the vasculature and into tissue. They also can be induced to stimulate immune reactivity or to be immune inhibitory. In each of these parameters (trafficking, immune stimulation and immune inhibition), their role can be physiological, whereby they have an active role in maintaining health. Alternatively, their role can be pathological, whereby they contribute to disease. In theory, endothelial cells are in an ideal location to recruit cells that can mediate immune reactivity to tumor tissue. Furthermore, they can activate the immune cells as they transmigrate across the endothelium into the tumor. However, what is seen is the absence of these protective effects of endothelial cells and, instead, the endothelial cells succumb to the defense mechanisms of the tumor, resulting in their acquisition of a tumor-protective role. To understand the immune regulatory potential of endothelial cells in protecting the host versus the tumor, it is useful to better understand the other circumstances in which endothelial cells modulate immune reactivities. Which of the multitude of immune regulatory roles that endothelial cells can take on seems to rely on the type of stimulus that they are encountering. It also depends on the extent to which they can be manipulated by potential dangers to succumb and contribute toward attack on the host. This review will explore the physiological and pathological roles of endothelial cells as they regulate immune trafficking, immune stimulation and immune inhibition in a variety of conditions and will then apply this information to their role in the tumor environment. Strategies to harness the immune regulatory potential of endothelial cells are starting to emerge in the non-tumor setting. Results from such efforts are expected to be applicable to being able to skew endothelial cells from having a tumor-protective role to a host-protective role.

Prostanoids in tumor angiogenesis: therapeutic intervention beyond COX-2

Prostanoids regulate angiogenesis in carcinoma and chronic inflammatory disease progression. Although prostanoid biosynthetic enzymes and signaling have been extensively analyzed in inflammation, little is known about how prostanoids mediate tumor-induced angiogenesis. Targeted cyclooxygenase (COX)-2 inhibition in tumor, stromal and endothelial cells is an attractive antiangiogenic strategy; however, the associated cardiovascular side effects have led to the development of a new generation of nonsteroidal anti-inflammatory drugs (NSAIDs) acting downstream of COX. These agents target terminal prostanoid synthases and prostanoid receptors, which may also include several peroxisome proliferator-activated receptors (PPARs). Here, we discuss the role of prostanoids as modulators of tumor angiogenesis and how prostanoid metabolism reflects complex cell-cell crosstalk that determines tumor growth. Finally, we discuss the potential of new NSAIDs for the treatment of angiogenesis-dependent tumor development.

Microsomal prostaglandin E synthase-1 is involved in multiple steps of colon carcinogenesis

Accumulating evidence indicates that cyclooxygenase (COX)-2-derived prostaglandin (PG) E(2) is involved in the development of various tumors, including colorectal cancer. However, the precise contribution of microsomal PGE synthase (mPGES)-1, a terminal enzyme that acts downstream of COX-2 in the PGE(2)-biosynthetic pathway, to multiple processes of tumor development is not yet fully understood. Here, we show the pro-tumorigenic role of mPGES-1 in chemical carcinogen-induced colon carcinogenesis and intrasplenic tumor transplantation models. Genetic deletion of mPGES-1 significantly reduced both the total number and size of colorectal polyps at 18 weeks after azoxymethane administration with reduced nuclear translocation of β-catenin, altered expression profiles of chemokines/cytokines and increased production of antitumorigenic PGs, prostaglandin D(2) and prostacyclin in tumor tissues. At an early stage (6 weeks), mPGES-1 deficiency significantly reduced the number of aberrant crypt foci, while its transgenic overexpression increased the number. Furthermore, the growth of intrasplenically transplanted tumor cells was suppressed in mPGES-1 knockout (KO) mice. Co-culture of tumor cells with bone marrow-derived macrophages (BM-MΦs) isolated from wild-type (WT) mice resulted in the induction of mPGES-1 in BM-MΦs and increased the growth of tumor cells in vitro, whereas mPGES-1-null BM-MΦs failed to facilitate tumor growth. The adoptive transfer of WT BM-MΦs into mPGES-1 KO mice restored the growth of transplanted tumor cells, indicating that mPGES-1 in MΦs is important for the growth of adjacent tumor cells. Taken together, our findings suggest that the inhibition of mPGES-1 is an alternative therapeutic target for colorectal and possibly other cancers.