Inhibition of Lysyl Oxidases Improves Drug Diffusion and Increases Efficacy of Cytotoxic Treatment in 3D Tumor Models

Tumors are characterized by a rigid, highly cross-linked extracellular matrix (ECM), which impedes homogeneous drug distribution and potentially protects malignant cells from exposure to therapeutics. Lysyl oxidases are major contributors to tissue stiffness and the elevated expression of these enzymes observed in most cancers might influence drug distribution and efficacy. We examined the effect of lysyl oxidases on drug distribution and efficacy in 3D in vitro assay systems. In our experiments elevated lysyl oxidase activity was responsible for reduced drug diffusion under hypoxic conditions and consequently impaired cytotoxicity of various chemotherapeutics. This effect was only observed in 3D settings but not in 2D-cell culture, confirming that lysyl oxidases affect drug efficacy by modification of the ECM and do not confer a direct desensitizing effect. Both drug diffusion and efficacy were strongly enhanced by inhibition of lysyl oxidases. The results from the in vitro experiments correlated with tumor drug distribution in vivo, and predicted response to therapeutics in murine tumor models. Our results demonstrate that lysyl oxidase activity modulates the physical barrier function of ECM for small molecule drugs influencing their therapeutic efficacy. Targeting this process has the potential to significantly enhance therapeutic efficacy in the treatment of malignant diseases.

Cardiac RKIP induces a beneficial β-adrenoceptor-dependent positive inotropy

In heart failure therapy, it is generally assumed that attempts to produce a long-term increase in cardiac contractile force are almost always accompanied by structural and functional damage. Here we show that modest overexpression of the Raf kinase inhibitor protein (RKIP), encoded by Pebp1 in mice, produces a well-tolerated, persistent increase in cardiac contractility that is mediated by the β1-adrenoceptor (β1AR). This result is unexpected, as β1AR activation, a major driver of cardiac contractility, usually has long-term adverse effects. RKIP overexpression achieves this tolerance via simultaneous activation of the β2AR subtype. Analogously, RKIP deficiency exaggerates pressure overload-induced cardiac failure. We find that RKIP expression is upregulated in mouse and human heart failure, indicative of an adaptive role for RKIP. Pebp1 gene transfer in a mouse model of heart failure has beneficial effects, suggesting a new therapeutic strategy for heart failure therapy.

Four different synthetic peptides of proteolipid protein induce a distinct antibody response in MP4-induced experimental autoimmune encephalomyelitis

Here we studied the autoantibody specificity elicited by proteolipid protein (PLP) in MP4-induced experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis (MS). In C57BL/6 (B6) mice, antibodies were induced by immunization with one of the two extracellular and by the intracellular PLP domain. Antibodies against extracellular PLP were myelin-reactive in oligodendrocyte cultures and induced mild spinal cord demyelination upon transfer into B cell-deficient J(H)T mice. Remarkably, also antibodies against intracellular PLP showed binding to intact oligodendrocytes and were capable of inducing myelin pathology upon transfer into J(H)T mice. In MP4-immunized mice peptide-specific T(H)1/T(H)17 responses were mainly directed against the extracellular PLP domains, but also involved the intracellular epitopes. These data suggest that both extracellular and intracellular epitopes of PLP contribute to the pathogenesis of MP4-induced EAE already in the setting of intact myelin. It remains to be elucidated if this concept also applies to MS itself.

Abstract 280: Neointimal Hyperplasia in Allogeneic and Autologous Venous Grafts Appears Homogenous

Introduction: Cryopreserved venous allografts are considered as possible alternative to autologous venous grafts in peripheral bypass surgery. Neointima formation is responsible for poorer patency. For a better understanding of this process we investigated allogeneic and autologous venous grafts in arterial position by histologic means.

Materials and Methods: Allogeneic and autologous venous graft stenosis were examined by Ki67, CD31, CD34, CD3, CD20, vWF, CD68, actin, vimentin and desmin.

Results: The morphological Examination of autologous and cryopreserved allogeneic grafts appears very uniform. Dedifferentiated vascular smooth muscle cells are the main cellular effector in both grafts. Neoangiogenesis is abundant in the vessel media whereas immunologic infiltrates are largely absent.

Conclusion: The uniform morphological appearance of allogeneic and autologous neointimal hyperplasia suggests an overreaction in venous grafts in response to non-immunological factors as reason for poorer clinical outcome of cryopreserved allografts.

Pathophysiology of isoprostanes in the cardiovascular system: implications of isoprostane-mediated thromboxane A2 receptor activation

Isoprostanes are free radical-catalysed PG-like products of unsaturated fatty acids, such as arachidonic acid, which are widely recognized as reliable markers of systemic lipid peroxidation and oxidative stress in vivo. Moreover, activation of enzymes, such as COX-2, may contribute to isoprostane formation. Indeed, formation of isoprostanes is considerably increased in various diseases which have been linked to oxidative stress, such as cardiovascular disease (CVD), and may predict the atherosclerotic burden and the risk of cardiovascular complications in the latter patients. In addition, several isoprostanes may directly contribute to the functional consequences of oxidant stress via activation of the TxA2 prostanoid receptor (TP), for example, by affecting endothelial cell function and regeneration, vascular tone, haemostasis and ischaemia/reperfusion injury. In this context, experimental and clinical data suggest that selected isoprostanes may represent important alternative activators of the TP receptor when endogenous TxA2 levels are low, for example, in aspirin-treated individuals with CVD. In this review, we will summarize the current understanding of isoprostane formation, biochemistry and (patho) physiology in the cardiovascular context.

Nestin(+) tissue-resident multipotent stem cells contribute to tumor progression by differentiating into pericytes and smooth muscle cells resulting in blood vessel remodeling

Tumor vessels with resistance to anti-angiogenic therapy are characterized by the normalization of the vascular structures through integration of mature pericytes and smooth muscle cells (SMC) into the vessel wall, a process termed vessel stabilization. Unfortunately, stabilization-associated vascular remodeling can result in reduced sensitivity to subsequent anti-angiogenic therapy. We show here that blockade of VEGF by bevacizumab induces stabilization of angiogenic tumor blood vessels in human tumor specimen by recruiting Nestin-positive cells, whereas mature vessels down-regulated Nestin-expression. Using xenograft tumors growing on bone-marrow (BM) chimera of C57Bl/6 wildtype and Nestin-GFP transgenic mice, we show for first time that Nestin(+) cells inducing the maturation of tumor vessels do not originate from the BM but presumably reside within the adventitia of adult blood vessels. Complementary ex vivo experiments using explants of murine aortas revealed that Nestin(+) multipotent stem cells (MPSCs) are mobilized from their niche and differentiated into pericytes and SMC through the influence of tumor-cell-secreted factors. We conclude that tissue-resident Nestin(+) cells are more relevant than BM-derived cells for vessel stabilization and therefore have to be considered in future strategies for anti-angiogenic therapy. The identification of proteins mediating recruitment or differentiation of local Nestin(+) cells with potential stem cell character to angiogenic blood vessels may allow the definition of new therapeutic targets to reduce tumor resistance against anti-angiogenic drugs.

Effect of cardiac rehabilitation on left atrial functions in patients with acute myocardial infarction

BACKGROUND

The objective of this study was to analyze the effects of cardiac rehabilitation (CR) on the atrial function of patients with acute myocardial infarction (AMI) who had been successfully revascularized through percutaneous coronary intervention (PCI).

METHODS

Forty-two AMI patients having undergone CR were enrolled in this observational study. Assessments were performed before and after 6 weeks of CR. Left atrial strain analysis was carried out by two-dimensional speckle tracking echocardiography. Left ventricular ejection fraction (LVEF) was measured by the biplane Simpson's method. Pulsed-wave Doppler at the tip of mitral valve leaflets enabled us to measure early (E) and late (A) diastolic filling velocities, deceleration time (DT) of early filling velocity and isovolumic relaxation time (IVRT). Left ventricle tissue velocity was measured by tissue Doppler imaging of the lateral mitral annulus (e') and E/e' was subsequently calculated. Ratio of E/e' to left atrium (LA) peak strain was used to estimate LA stiffness.

RESULTS

Following CR, LVEF (P=0.010), LA strain (P<0.001) and LA stiffness (P=0.013) all showed improvement, while other parameters remained unchanged.

CONCLUSION

Post-AMI cardiac rehabilitation and revascularization by PCI might have favourable effects on LA function.

Impact of genetic variability in the ABCG2 gene on ABCG2 expression, function, and interaction with AT1 receptor antagonist telmisartan

The ATP-binding cassette transporter ABCG2 plays a prominent role in cardiovascular and cancer pathophysiology, is involved in the pathogenesis of gout, and affects pharmacokinetics of numerous drugs. Telmisartan, a widely used AT1 receptor antagonist, inhibits the transport capacity of ABCG2 and may cause drug-drug interactions, especially in individuals carrying polymorphism that facilitate the telmisartan-ABCG2 interaction. Thus, the aim of this study was to identify ABCG2 polymorphisms and somatic mutations with relevance for the telmisartan-ABCG2 interaction. For this purpose, a cellular system for the conditional expression of ABCG2 was established. ABCG2 variants were generated via site-directed mutagenesis. Interaction of telmisartan with these ABCG2 variants was investigated in HEK293-Tet-On cells using the pheophorbide A efflux assay. Moreover, expression of ABCG2 variants was studied in these cells. Importantly, protein levels of the Q141K and F489L variant were significantly reduced, a phenomenon that was partly reversed by pharmacological proteasome inhibition. Moreover, basal pheophorbide A efflux capacity of S248P, F431L, and F489L variants was significantly impaired. Interestingly, inhibition of ABCG2-mediated pheophorbide A transport by telmisartan was almost abolished in cells expressing the R482G variant, whereas it was largely increased in cells expressing the F489L variant. We conclude that the arginine residue at position 482 of the ABCG2 molecule is of major importance for the interaction of telmisartan with this ABC transporter. Furthermore, individuals carrying the F489L polymorphism may be at increased risk of developing adverse drug reactions in multi-drug regimens involving ABCG2 substrates and telmisartan.

Ceacam1 deletion causes vascular alterations in large vessels

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) promotes hepatic insulin clearance and endothelial survival. However, its role in the morphology of macrovessels remains unknown. Mice lacking Ceacam1 (Cc1-/-) exhibit hyperinsulinemia, which causes insulin resistance and fatty liver. With increasing evidence of an association among hyperinsulinemia, fatty liver disease, and atherosclerosis, we investigated whether Cc1-/- exhibited vascular lesions in atherogenic-prone aortae. Histological analysis revealed impaired endothelial integrity with restricted fat deposition and aortic plaque-like lesions in Cc1-/- aortae, likely owing to their limited lipidemia. Immunohistochemical analysis indicated macrophage deposition, and in vitro studies showed increased leukocyte adhesion to aortic wall, mediated in part by elevation in vascular cell adhesion molecule 1 levels. Basal aortic eNOS protein and NO content were reduced, in parallel with reduced Akt/eNOS and Akt/Foxo1 phosphorylation. Ligand-induced vasorelaxation was compromised in aortic rings. Increased NADPH oxidase activity and plasma 8-isoprostane levels revealed oxidative stress and lipid peroxidation in Cc1-/- aortae. siRNA-mediated CEACAM1 knockdown in bovine aortic endothelial cells adversely affected insulin's stimulation of IRS-1/PI 3-kinase/Akt/eNOS activation by increasing IRS-1 binding to SHP2 phosphatase. This demonstrates that CEACAM1 regulates both endothelial cell autonomous and nonautonomous mechanisms involved in vascular morphology and NO production in aortae. Systemic factors such as hyperinsulinemia could contribute to the pathogenesis of these vascular abnormalities. Cc1-/- mice provide a first in vivo demonstration of distinct CEACAM1-dependent hepatic insulin clearance linking hepatic to macrovascular abnormalities.

CEACAM1 expression in oligodendrocytes of the developing rat brain shows a spatiotemporal relation to myelination and is altered in a model of encephalopathy of prematurity

CEACAM1 is the founder molecule of the family of 'carcinoembryonic antigen-related cell adhesion molecules' and part of the immunoglobulin superfamily. Due to its role as a coreceptor to many other receptors (e.g. Toll-like receptor 2, Toll-like receptor 4, T-cell receptor, B-cell receptor, epidermal growth factor receptor and vascular endothelial growth factor receptor) and its different isoforms, CEACAM1 is a multifunctional protein with an impact on proliferation and differentiation of multiple cell types. Although different modes of action in other tissues are described, the role of CEACAM1 in the developing brain remains elusive. Here we report for the first time that CEACAM1 is expressed ontogenetically in oligodendrocytes of the developing rat brain, and that CEACAM1 expression has a spatiotemporal relation to myelination. In addition, CEACAM1 expression is altered in a model of hyperoxia- and inflammation-induced encephalopathy of prematurity, a myelination disorder of children born preterm. Furthermore, primary oligodendrocytes stimulated with CEACAM1 show increased myelination. Therefore, we postulate that CEACAM1 is, at least in part, involved in hyperoxia- and inflammation-induced disruption of myelination, but may also play a role in intact myelination as it is ontogenetically expressed in myelinating oligodendrocytes.

Impact of AT2 receptor deficiency on postnatal cardiovascular development

BACKGROUND

The angiotensin II receptor subtype 2 (AT2 receptor) is ubiquitously and highly expressed in early postnatal life. However, its role in postnatal cardiac development remained unclear.

METHODOLOGY/PRINCIPAL FINDINGS

Hearts from 1, 7, 14 and 56 days old wild-type (WT) and AT2 receptor-deficient (KO) mice were extracted for histomorphometrical analysis as well as analysis of cardiac signaling and gene expression. Furthermore, heart and body weights of examined animals were recorded and echocardiographic analysis of cardiac function as well as telemetric blood pressure measurements were performed. Moreover, gene expression, sarcomere shortening and calcium transients were examined in ventricular cardiomyocytes isolated from both genotypes. KO mice exhibited an accelerated body weight gain and a reduced heart to body weight ratio as compared to WT mice in the postnatal period. However, in adult KO mice the heart to body weight ratio was significantly increased most likely due to elevated systemic blood pressure. At postnatal day 7 ventricular capillarization index and the density of α-smooth muscle cell actin-positive blood vessels were higher in KO mice as compared to WT mice but normalized during adolescence. Echocardiographic assessment of cardiac systolic function at postnatal day 7 revealed decreased contractility of KO hearts in response to beta-adrenergic stimulation. Moreover, cardiomyocytes from KO mice showed a decreased sarcomere shortening and an increased peak Ca(2+) transient in response to isoprenaline when stimulated concomitantly with angiotensin II.

CONCLUSION

The AT2 receptor affects postnatal cardiac growth possibly via reducing body weight gain and systemic blood pressure. Moreover, it moderately attenuates postnatal vascularization of the heart and modulates the beta adrenergic response of the neonatal heart. These AT2 receptor-mediated effects may be implicated in the physiological maturation process of the heart.

LINE-1 retrotransposition events regulate gene expression after X-ray irradiation

Long interspersed nuclear element-1 (LINE-1) retrotransposons are mobile elements that insert into new genomic locations via reverse transcription of an RNA intermediate. The mechanism of retrotransposition is not entirely understood. The integration of these elements occurs by target-primed reverse transcription (TPRT), which initiates double-strand breaks (DSBs) during the LINE-1 integration. Also, X-ray is known to induce DNA damage. The aim of this study was to evaluate the potential effects of LINE-1 de novo retrotransposition on the expression of different genes after X-ray irradiation in human endothelial cells. After stable transfection of the human hybrid endothelial cell line EA.hy926 with the human LINE-1 element, we analyzed the expression of different genes after irradiation with 5 Gy X-rays by reverse transcription-polymerase chain reaction (RT-PCR). We determine the expression level of phosphorylated p53 and γ-histone H2AX protein levels upon X-ray irradiation with 5 Gy for 24 h. Our results showed that EA.hy926 LINE-1 cell clones react with a strong upregulation of phosphorylated p53 protein, already 15 min after irradiation compared to the wild type (WT) cells. Also, the expression of γ-histone H2AX protein was elevated in the cell clones with retrotransposition events 15 min after irradiation, whereas the WT cells have a delayed expression of phosphorylated histone H2AX protein. Taken together, our findings provide that LINE-1 retrotransposition events regulate different gene expression after irradiation in the EA.hy926 cell line.

Circulating angiostatin, bFGF, and Tie2/TEK levels and their prognostic impact in bladder cancer

OBJECTIVE

To assess the role and prognostic significance of angiostatin, basic fibroblast growth factor (bFGF), and tyrosine endothelial kinase (TEK/Tie2) in transitional cell bladder carcinoma.

MATERIALS AND METHODS

Angiostatin, bFGF, and TEK serum concentrations were measured in 82 bladder cancer patients and 20 age-matched healthy controls using enzyme-linked immunosorbent assay. Results were compared with clinicopathologic and follow-up data with the Mann-Whitney U test and Kaplan-Meier, univariate and multivariate Cox regression analyses.

RESULTS

We found significantly decreased angiostatin and TEK serum levels and mildly elevated bFGF concentrations in samples of bladder cancer patients compared with controls (P < .001, P < .001, and P = .083, respectively). Furthermore, high TEK serum levels were correlated with poor disease-specific and metastasis-free survival in muscle-invasive bladder cancer (P = .013, P = .018), whereas angiostatin and bFGF concentrations did not show any correlation with patients' prognosis. Multivariate analysis revealed high TEK levels (<1.60 ng/mL) as borderline significant independent risk-factor of disease-specific survival (HR 1.83, 95% CI 0.97-3.44, P = .061) and metastasis-free survival (HR 2.65, 95% CI 0.93-7.55, P = .069).

CONCLUSION

The characteristic differences in the circulating levels of angiostatin, TEK, and bFGF between patients and controls, suggest the presence of a tumor-induced proangiogenic milieu in bladder cancer. Serum TEK levels may contribute to a more reliable preoperative risk stratification in muscle-invasive bladder cancer and therefore may help to optimize therapeutic decisions.

Tumor vessel stabilization and remodeling by anti-angiogenic therapy with bevacizumab

Bevacizumab-resistant tumor vessels were characterized by an increased vessel diameter and normalization of vascular structures by the recruitment of mature pericytes and smooth muscle cells. Here, we analyzed human liver metastases which were taken at clinical relapse in patients with colorectal adenocarcinoma treated with anti-angiogenic therapy using the humanized monoclonal anti-VEGF bevacizumab. Tumor vessels which are resistant to anti-VEGF therapy are increased in size and characterized by a normalization of the vascular bed. These results were confirmed using NOD SCID mice as animal model and xenograft transplantation of human PC-3 prostate carcinoma cells in combination with bevacizumab treatment. Our results confirmed that anti-angiogenic therapy results in enhanced vascular remodeling by vascular stabilization. This process is apparently accompanied by enhanced necrosis of tumor tissue. These processes interfere with the efficacy of anti-angiogenic therapy because of reduced susceptibility of stabilized vessels by this therapy. These results demonstrate the importance for the development of second generation anti-angiogenic combination therapy concepts to rule out the balance between vascular stabilization followed by a possible de-stabilization making the remained vessels susceptible to a second wave of anti-angiogenic therapy.

Serum endostatin levels correlate with enhanced extracellular matrix degradation and poor patients' prognosis in bladder cancer

Endostatin, the proteolytic fragment of collagen XVIII, is an inhibitor of angiogenesis and tumor growth. Interestingly, elevated circulating endostatin levels have been found to correlate with poor patients' prognosis in several cancers. The aim of this study was to assess the prognostic value of endostatin in bladder cancer (BC) and to gain insight into the mechanisms involved in its production. This retrospective study included a total of 337 patients with BC and 103 controls. Collagen XVIII gene expression was analyzed using real-time PCR (n = 82). Endostatin tissue localization was assessed by immunohistochemistry (n = 27). Endostatin serum (n = 87) and urine (n = 153) levels were determined by ELISA. In 12 cases, both serum and paraffinized tissue samples from the same patients were available. We found decreased collagen XVIII tissue expression and increased endostatin urine and serum concentration in samples of patients with BC compared to controls. High serum endostatin levels correlated with the presence of lymph node metastases and MMP-7 concentrations and were independently associated with poor metastasis-free and disease-specific survival. Immunohistochemical analysis revealed a strong endostatin staining in the wall of tumor associated blood vessels in superficial but not in muscle-invasive BCs. Based on these, we concluded that elevated endostatin levels in patients with BC are the consequence of enhanced extracellular matrix degradation and are independent from collagen XVIII expression. Furthermore, serum endostatin levels may provide prognostic information independent from histopathological parameters and may therefore help to optimize therapy decisions. Loss of endostatin expression in tumor associated blood vessels might represent an important step supporting tumor-induced angiogenesis.

Vascular wall as a reservoir for different types of stem and progenitor cells

Tissue regeneration and several diseases such as tumor and atherosclerosis depend on new vessel formation by both angiogenesis and vasculogenesis. Endothelial cells (ECs) are widely considered to be the active cellular component in these processes, followed by contractile cells such as pericytes and smooth muscle cells. The best known sources providing these cell types or their progenitors are ECs lining the vessel lumen and bone marrow. As easily evident, the vessel wall was recognized as being a passive player to a great extent except ECs of the vascular intima. Particularly, the vascular adventitia has been considered as a passive layer rather than an active part of the vessel wall. But results provided during the last few years have led to a revision of this classical view because of an apparent stem cell niche function of the vascular adventitia. This review aims to sum up findings identifying the vessel wall as an important stem cell reservoir and discusses its impact on health and disease.

Matrix metalloproteinases and their clinical relevance in urinary bladder cancer

Matrix metalloproteinases (MMPs) have important roles in several cancer-supporting cellular processes, such as extracellular matrix (ECM) remodeling, angiogenesis, apoptosis, epithelial-to-mesenchymal transition and cell proliferation. This broad range of activity has led to considerable interest in the use of MMPs in the clinical setting as diagnostic or prognostic biomarkers and as therapeutic targets. Levels of the different MMPs can be measured in several sample types, including paraffin-embedded or fresh frozen tissue, serum, plasma and urine, and by various analytical methodologies, such as immunohistochemistry, real-time PCR, western and northern blot analyses, enzyme-linked immunosorbent assay and zymography. Several MMPs have been identified as having potential diagnostic or prognostic utility, whether alone or in combination with currently available diagnostic tests or imaging modalities. Although the early broad-spectrum anti-MMP agents showed a lack of efficacy, our continually improving understanding of the complex physiologic and pathologic roles of MMPs might enable the development of new MMP-specific and tumor-specific therapies. Accordingly, MMPs will continue to be the subjects of intensive research in bladder cancer.

Elevated serum matrix metalloproteinase 7 levels predict poor prognosis after radical prostatectomy

Elevated matrix metalloproteinase-7 (MMP-7) tissue expression and serum concentration have been shown to be associated with cancer progression and metastasis. The aim of our study was to assess the prognostic value of preoperative circulating MMP-7 levels in serum samples of patients with clinically localized prostate cancer. Furthermore, we compared the serum MMP-7 levels between patients with organ confined and metastatic prostate cancer. MMP-7 levels were measured in 93 patients with localized prostate cancer, 13 patients with distant bone metastasis and in sera of 19 controls using enzyme-linked immunosorbent assay. The results were compared to the clinical follow-up data. We did not find any significant difference in MMP-7 serum levels between patients and controls (p = 0.268). Circulating MMP-7 serum concentration was significantly elevated in patients with distant metastasis (p < 0.001). For the detection of distant prostate cancer metastasis, using a cut-off value of 3.7 ng/ml, a specificity of 69% and a sensitivity of 92% were observed. Multivariate analysis identified high MMP-7 serum concentration as an independent risk factor for prostate cancer-related death both in a preoperative and a postoperative model (p = 0.003 and 0.018, respectively). Furthermore, the evaluation of predictive models revealed that addition of serum MMP-7 levels to the preoperatively available predictors improves prognostic accuracy (the concordance index increased from 0.631 to 0.734 when MMP-7 was included). Based on these, we concluded that MMP-7 is a potential marker to identify patients with metastatic prostate cancer. In clinically localized prostate cancer, MMP-7 may provide independent prognostic information, thereby helping to optimize therapy decisions.