β4 integrin is involved in statin-induced endothelial cell death

Ping-Pong-Tumor and Host in Pancreatic Cancer Progression

Metastasis is the main cause of high pancreatic cancer (PaCa) mortality and trials dampening PaCa mortality rates are not satisfying. Tumor progression is driven by the crosstalk between tumor cells, predominantly cancer-initiating cells (CIC), and surrounding cells and tissues as well as distant organs, where tumor-derived extracellular vesicles (TEX) are of major importance. A strong stroma reaction, recruitment of immunosuppressive leukocytes, perineural invasion, and early spread toward the peritoneal cavity, liver, and lung are shared with several epithelial cell-derived cancer, but are most prominent in PaCa. Here, we report on the state of knowledge on the PaCIC markers Tspan8, alpha6beta4, CD44v6, CXCR4, LRP5/6, LRG5, claudin7, EpCAM, and CD133, which all, but at different steps, are engaged in the metastatic cascade, frequently via PaCIC-TEX. This includes the contribution of PaCIC markers to TEX biogenesis, targeting, and uptake. We then discuss PaCa-selective features, where feedback loops between stromal elements and tumor cells, including distorted transcription, signal transduction, and metabolic shifts, establish vicious circles. For the latter particularly pancreatic stellate cells (PSC) are responsible, furnishing PaCa to cope with poor angiogenesis-promoted hypoxia by metabolic shifts and direct nutrient transfer via vesicles. Furthermore, nerves including Schwann cells deliver a large range of tumor cell attracting factors and Schwann cells additionally support PaCa cell survival by signaling receptor binding. PSC, tumor-associated macrophages, and components of the dysplastic stroma contribute to perineural invasion with signaling pathway activation including the cholinergic system. Last, PaCa aggressiveness is strongly assisted by the immune system. Although rich in immune cells, only immunosuppressive cells and factors are recovered in proximity to tumor cells and hamper effector immune cells entering the tumor stroma. Besides a paucity of immunostimulatory factors and receptors, immunosuppressive cytokines, myeloid-derived suppressor cells, regulatory T-cells, and M2 macrophages as well as PSC actively inhibit effector cell activation. This accounts for NK cells of the non-adaptive and cytotoxic T-cells of the adaptive immune system. We anticipate further deciphering the molecular background of these recently unraveled intermingled phenomena may turn most lethal PaCa into a curatively treatable disease.

Statins use and cancer: an update

After initial concerns regarding the association of statins with increased incidences of cancer and elevated cancer-related mortality, there are now plenty of data on the antitumor, cytostatic and cytotoxic effectiveness of this class of drugs. Here, we present a short review of possible mechanisms of antineoplastic activity obtained from preclinical research and the influence of statins on cancer treatment. In the second part of the article, we focus on the most recent data from observational clinical trials, as well as meta-analyses regarding cancer incidence and mortality in patients treated with statins.

A small molecule induces integrin β4 nuclear translocation and apoptosis selectively in cancer cells with high expression of integrin β4

Increased integrin β4 (ITGB4) level is accompanied by malignant progression of multiple carcinomas. However, selective therapeutic strategies against cancer cells expressing a high level of ITGB4 have not been reported. Here, for the first time, we report that a chiral small molecule, SEC, selectively promotes apoptosis in cancer cells expressing a high level of ITGB4 by inducing ITGB4 nuclear translocation. Nuclear ITGB4 can bind to the ATF3 promoter region and activate the expression of ATF3, then upregulate the downstream pro-apoptosis genes. Furthermore, SEC promoted the binding of annexin A7 (ANXA7) to ITGB4 and increased ANXA7 GTPase activity. Activated ANXA7 promoted ITGB4 nuclear translocation by triggering ITGB4 phosphorylation at Y1494. SEC also inhibited the growth of xenograft tumors in the avian embryo model. We identified a small molecule, SEC, with selective pro-apoptosis effects on cancer cells with high expression of ITGB4, both in vitro and in vivo, by triggering the binding of ITGB4 and ANXA7, ITGB4 nuclear trafficking, and pro-apoptosis gene expression.

Endothelial α6β4 integrin protects during experimental autoimmune encephalomyelitis-induced neuroinflammation by maintaining vascular integrity and tight junction protein expression

Background

Extracellular matrix (ECM) proteins play critical functions regulating vascular formation and function. Laminin is a major component of the vascular basal lamina, and transgenic mice deficient in astrocyte or pericyte laminin show defective blood-brain barrier (BBB) integrity, indicating an important instructive role for laminin in cerebral blood vessels. As previous work shows that in the normal brain, vascular expression of the laminin receptor α6β4 integrin is predominantly restricted to arterioles, but induced on all vessels during neuroinflammation, it is important to define the role of this integrin in the maintenance of BBB integrity.

Methods

α6β4 integrin expression was analyzed using dual immunofluorescence (dual-IF) of brain sections taken from the mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). To investigate the role of endothelial α6β4 integrin, transgenic mice lacking β4 integrin in endothelial cells (β4-EC-KO) and wild-type (WT) littermates were subject to EAE, and clinical score and various neuropathological parameters were examined by immunofluorescence. In addition, β4 integrin null brain endothelial cells (BECs) were examined in culture for expression of tight junction proteins using immunocytochemistry and flow cytometry.

Results

Cerebrovascular expression of β4 integrin was markedly upregulated during EAE progression, such that by the acute stage of EAE (day 21), the vast majority of blood vessels expressed β4 integrin. In the EAE model, while the β4-EC-KO mice showed the same time of disease onset as the WT littermates, they developed significantly worse clinical disease over time, resulting in increased clinical score at the peak of disease and maintained elevated thereafter. Consistent with this, the β4-EC-KO mice showed enhanced levels of leukocyte infiltration and BBB breakdown and also displayed increased loss of the endothelial tight junction proteins claudin-5 and ZO-1. Under pro-inflammatory conditions, primary cultures of β4KO BECs also showed increased loss of claudin-5 and ZO-1 expression.

Conclusions

Taken together, our data suggest that α6β4 integrin upregulation is an inducible protective mechanism that stabilizes the BBB during neuroinflammatory conditions.

Identification of New Small Molecules as Apoptosis Inhibitors in Vascular Endothelial Cells

Vascular endothelial cell (VEC) apoptosis is involved in the development of atherosclerosis and other cardiovascular diseases. We previously found that ethyl 1-(2-hydroxy-3-aroxypropyl)-3-aryl-1H-pyrazole -5-carboxylate derivatives (3a-o) play important roles in cell fate control. In this study, among the 15 compounds, we further screened 2 compounds, 3d and 3k, that suppressed VEC apoptosis induced by deprivation of serum and fibroblast growth factor 2. To clarify which chiral enantiomers of 3d and 3k functioned, we synthesized 3d-S and its enantiomer 3d-R, 3k-S, and its enantiomer 3k-R. Then, we investigated the apoptosis-inhibiting activity of the chiral compounds in VECs. Four small molecules, 3d-S, 3d-R, 3k-S, 3k-R, significantly elevated VEC viability and inhibited apoptosis. Furthermore, these small molecules could obviously decrease the level of integrin β4 that plays a key role in the regulation of VEC apoptosis. 3k-S and 3k-R increased Bcl-2/Bax ratio and reduced reactive oxygen species levels dramatically. Therefore, we provide new VEC apoptosis inhibitors. These compounds may be potential agents in the prevention of vascular diseases associated with VEC apoptosis.

Critical role for integrin-β4 in the attenuation of murine acute lung injury by simvastatin

The statins are a class of 3-hydroxy-3-methylglutaryl-coenzyme A-reductase inhibitors that are recognized to have pleiotropic properties. We previously reported the attenuation of LPS-induced murine acute lung injury (ALI) by simvastatin in vivo and identified relevant effects of simvastatin on endothelial cell (EC) signaling, activation, and barrier function in vitro. In particular, simvastatin induces the upregulation of integrin-β4, which in turn inhibits EC inflammatory responses via attenuation of MAPK signaling. The role of integrin-β4 in murine ALI protection by simvastatin, however, is unknown. We initially confirmed a time- and dose-dependent effect of simvastatin on increased integrin-β4 mRNA expression in human lung EC with peak protein expression evident at 16 h. Subsequently, reciprocal immunoprecipitation demonstrated an attenuation of LPS-induced integrin-β4 tyrosine phosphorylation by simvastatin (5 μM, 16 h). Increased expression of EC inflammatory cytokines [IL-6, IL-8, monocyte chemoattractant protein (MCP)-1, regulated on activation normal T cell expressed and secreted (RANTES)] by LPS (500 ng/ml, 4 h) was also significantly attenuated by simvastatin pretreatment (5 μM, 16 h), but this effect was reversed by cotreatment with an integrin-β4-blocking antibody. Finally, although simvastatin (20 mg/kg) conferred significant protection in murine ALI as evidenced by decreased bronchoalveolar lavage fluid cell counts, protein, inflammatory cytokines (IL-6, IL-1β, MCP-1, RANTES), decreased Evans blue dye albumin extravasation in lung tissue, and changes on lung histology, these effects were reversed by the integrin-β4-blocking antibody (IV, 1 mg/kg, 2 h before LPS). These findings support integrin-β4 as an important mediator of ALI protection by simvastatin and implicate signaling by integrin-β4 as a novel therapeutic target in patients with ALI.

Integrin beta4 attenuates SHP-2 and MAPK signaling and reduces human lung endothelial inflammatory responses

We previously identified the marked upregulation of integrin beta4 in human lung endothelial cells (EC) treated with simvastatin, an HMG coA-reductase inhibitor with vascular-protective and anti-inflammatory properties in murine models of acute lung injury (ALI). We now investigate the role of integrin beta4 as a novel mediator of vascular inflammatory responses with a focus on mitogen-activated protein kinases (MAPK) signaling and the downstream expression of the inflammatory cytokines (IL-6 and IL-8) essential for the full elaboration of inflammatory lung injury. Silencing of integrin beta4 (siITGB4) in human lung EC resulted in significant increases in both basal and LPS-induced phosphorylation of ERK 1/2, JNK, and p38 MAPK, consistent with robust integrin beta4 regulation of MAPK activation. In addition, siITB4 increased both basal and LPS-induced expression of IL-6 and IL-8 mRNA and protein secretion into the media. We next observed that integrin beta4 silencing increased basal and LPS-induced phosphorylation of SHP-2, a protein tyrosine phosphatase known to modulate MAPK signaling. In contrast, inhibition of SHP-2 enzymatic activity (sodium stibogluconate) abrogated the increased ERK phosphorylation associated with integrin beta4 silencing in LPS-treated EC and attenuated the increases in levels of IL-6 and IL-8 in integrin-beta4-silenced EC. These findings highlight a novel negative regulatory role for integrin beta4 in EC inflammatory responses involving SHP-2-mediated MAPK signaling. Upregulation of integrin beta4 may represent an important element of the anti-inflammatory and vascular-protective properties of statins and provides a novel strategy to limit inflammatory vascular syndromes.

Effects of statins on nitric oxide/cGMP signaling in human umbilical vein endothelial cells

Human umbilical vein endothelial cells (HUVECs) were established as in vitro models for the modulation of endothelial function and cell viability by statins. Emphasis was placed on the biphasic effects of the drugs on nitric oxide (NO) bioavailability and cytotoxicity, as well as drug interference with the interaction of endothelial NO synthase (eNOS) with caveolin-1 (Cav-1). Incubation of HUVECs with fluvastatin, lovastatin or cerivastatin for 24 h caused an approximately 3-fold upregulation of eNOS expression that was associated with increased eNOS activity and accumulation of cGMP. Cerivastatin exhibited the highest potency with an EC50 of 13.8 +/- 2 nM after 24 h, while having no effect after only 30 min. The effects of statins on eNOS expression were similar in control and Cav-1 knockdown cells, but the increase in eNOS activity was less pronounced in Cav-1-deficient cells. Statin-triggered cytotoxicity occurred at approximately 10-fold higher drug concentrations (maximal toxicity at 1-10 microM), was sensitive to mevalonate, and was significantly enhanced in the presence of NG-nitro-L-arginine. The overexpression of eNOS induced by clinically relevant concentrations of statins may contribute to the beneficial vascular effects of the drugs in patients. Stimulation of NO synthesis and cytotoxicity appear to share a common initial mechanism but involve distinct downstream signaling cascades that exhibit differential sensitivity to HMG-CoA reductase inhibition.

Diverse effects of statins on angiogenesis: new therapeutic avenues

Angiogenesis is an important process for a variety of physiologic and pathologic conditions. Different angiogenic modulating targets are under extensive investigation both experimentally and clinically. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are the first-line agents used in hypercholesterolemia. They are also characterized by having other benefits apart from their lipid-lowering effects. Among these pleiotropic effects are the pro- and antiangiogenic properties of statins. The pleiotropic effects of statins and how they modulate new blood vessel formation are discussed in this review. The currently available data from both animal and human studies regarding the effects of statins on angiogenesis in ischemic heart disease, stroke, ocular diseases, and cancer are also reviewed. Statins are safe, orally available agents that may acquire novel therapeutic indications through their angiogenic modulating effects.

The HMG-CoA Reductase Pathway, Statins and Angioprevention

Angiogenesis is one of the earliest and essential phenotypes acquired by tumors during carcinogenesis and thus might be a potential target for chemoprevention. Key to developing antiangiogenic chemoprevention is to identify new molecular targets and effective angiogenesis inhibitors. HMG-CoA reductase inhibitors, or statins, were originally designed to reduce cholesterol biosynthesis and have been extensively used as prevention drugs against hyperlipidemia and cardiovascular conditions. Recent research has found that statins promote endothelial death and inhibit experimental angiogenesis induced by growth factors or tumor, laying a foundation for developing statin-based angiopreventive strategies. This article reviews the biological effects of statins on endothelial cells and angiogenesis, possible underlying mechanisms and perspectives on future application of statins in preventing pathological angiogenesis.

Knockdown of integrin beta4 in primary cultured mouse neurons blocks survival and induces apoptosis by elevating NADPH oxidase activity and reactive oxygen species level

Recently, the specific roles of integrin beta4 in the signaling networks that drive pathological angiogenesis and tumor progression have been revealed. Our previous study showed that integrin beta4 might be involved in neuron survival signal transduction. To further our study on the role of integrin beta4 in the survival and apoptosis of primary cultured mouse neurons, we inhibited the expression of integrin beta4 by its specific small interfering RNA. Viability of the cells remarkably declined, and neurons underwent apoptosis with down-regulation of integrin beta4. Next, we investigated the effect of siRNA-mediated down-regulation of integrin beta4 on the level of intracellular reactive oxygen species and the activities of NADPH oxidase and superoxide dismutase. The level of reactive oxygen species in the neurons was elevated significantly, the activities of manganese-dependent superoxide dismutase and copper/zinc-dependent superoxide dismutase were not altered, but the activity of NADPH oxidase was increased. Furthermore, inhibition of NADPH oxidase by its specific inhibitor dibenziodolium chloride attenuated the neuronal death induced by integrin beta4 knockdown. The data suggest that integrin beta4 is a key factor in neuron survival and apoptosis and indicate that this integrin subunit might perform its action through regulating NADPH oxidase and the level of reactive oxygen species in neuronal survival and apoptosis.

Statins and the endothelium

Statins have been shown to have pleiotropic effects apart from serum lipid-lowering effect in human. One of the major target organs for the effects of statins is the vascular endothelium, which plays an important role in the development of atherosclerosis and angiogenesis. Recent numerous studies have shown that the statins' cholesterol-independent vascular effects appear to involve directly restoring or improving endothelial function by increasing NO production, promoting re-endothelialization after arterial injury, and inhibiting inflammatory responses within the vessel wall that are thought to contribute to atherosclerosis. This review provides an update of the unique effects of statins on endothelial cells including endothelial progenitor cells as well as highlighting the therapeutic potential of statins beyond their established lipid-lowering effects.

Anti-angiogenic and anti-inflammatory effects of statins: relevance to anti-cancer therapy

Angiogenesis is indispensable for the growth of solid tumors and angiogenic factors are also involved in the progression of hematological malignancies. Targeting the formation of blood vessels is therefore regarded as a promising strategy in cancer therapy. Interestingly, besides demonstration of some beneficial effects of novel anti-angiogenic compounds, recent data on the activity of already available drugs point to their potential application in anti-angiogenic therapy. Among these are the statins, the inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase. Statins are very efficient in the treatment of hypercholesterolemia in cardiovascular disorders; however, their effects are pleiotropic and some are not directly related to the inhibition of cholesterol synthesis. Some reports particularly highlight the pro-angiogenic effects of statins, which are caused by low, nanomolar concentrations and are regarded as beneficial for the treatment of cardiovascular diseases. On the other hand, the anti-angiogenic activities, observed at micromolar concentrations of statins, may be of special significance for cancer therapy. Those effects are caused by the inhibition of both proliferation and migration and induction of apoptosis in endothelial cells. Moreover, the statin-mediated inhibition of vascular endothelial growth factor synthesis, the major angiogenic mediator, may contribute to the attenuation of angiogenesis. It has been suggested that the anti-cancer effect of statins can be potentially exploited for the cancer therapy. However, several clinical trials aimed at the inhibition of tumor growth by treatment with very high doses of statins did not provide conclusive data. Herein, the reasons for those outcomes are discussed and the rationale for further studies is presented.