Angiopoietin-like 4 protein elevates the prosurvival intracellular O2(-):H2O2 ratio and confers anoikis resistance to tumors

Cancer cell survival during detachment from the ECM: multiple barriers to tumour progression

Epithelial cells require attachment to the extracellular matrix (ECM) for survival. However, during tumour progression and metastasis, cancerous epithelial cells must adapt to and survive in the absence of ECM. During the past 20 years, several cellular changes, including anoikis, have been shown to regulate cell viability when cells become detached from the ECM. In this Opinion article, we review in detail how cancer cells can overcome or take advantage of these specific processes. Gaining a better understanding of how cancer cells survive during detachment from the ECM will be instrumental in designing chemotherapeutic strategies that aim to eliminate ECM-detached metastatic cells.

Clinical relevance and therapeutic potential of angiopoietin-like protein 4 in hepatocellular carcinoma

Background

Development of novel adjuvant therapy to eradicate tumor angiogenesis and metastasis is a pressing need for patients with advanced hepatocellular carcinoma (HCC). We aimed to investigate the clinical relevance and therapeutic potential of angiopoietin-like 4 (ANGPTL4) in HCC.

Methods

ANGPTL4 mRNA levels in tumor and non-tumor liver tissues of HCC patients were analyzed to investigate its clinical relevance. The mechanisms of deregulation of ANGPTL4 in HCC were studied by copy number variation (CNV) and CpG methylation analyses. The orthotopic liver tumor nude mice model was applied using a human metastatic cell line. ANGPTL4-overexpressing adenovirus (Ad-ANGPTL4) was injected via portal vein to investigate its anti-tumorigenic and anti-metastatic potentials.

Results

HCC tissues expressed significantly lower levels of ANGPTL4 mRNA than non-tumor tissues. The copy number of ANGPTL4 gene in tumor tissues was significantly lower than in non-tumor tissues of HCC patients. Higher frequency of methylation of CpG sites of ANGPTL4 promoter was detected in tumor tissues compared to non-tumor tissues. Downregulation of ANGPTL4 mRNA in HCC was significantly associated with advanced tumor stage, presence of venous infiltration, poor differentiation, higher AFP level, appearance of tumor recurrence, and poor postoperative overall and disease-free survivals of HCC patients. Treatment with Ad-ANGPTL4 significantly inhibited the in vivo tumor growth, invasiveness and metastasis by promoting tumoral apoptosis, inhibiting tumoral angiogenesis and motility, and suppressing tumor-favorable microenvironment. Moreover, administration of recombinant ANGPTL4 protein suppressed the motility of HCC cells and altered the secretion profile of cytokines from macrophages.

Conclusion

ANGPTL4 is a diagnostic and prognostic biomarker for HCC patients and a potential therapeutic agent to suppress HCC growth, angiogenesis and metastasis.

ANGPTL4 regulates the metastatic potential of oral squamous cell carcinoma

Lymph node metastasis is a major factor for poor prognosis in oral squamous cell carcinoma (OSCC). However, the molecular mechanisms of lymph node metastasis are unclear. We determined that angiopoietin-like protein 4 (ANGPTL4) mRNA and protein expression were increased in OSCC cells established from the primary site in metastatic cases. In addition, ANGPTL4 expression in biopsy specimens was correlated with the presence of lymph node metastasis. Therefore, our initial findings suggest that OSCC cells expressing ANGPTL4 may possess metastatic ability. Furthermore, cell culture supernatants from OSCC cells that metastasized to the lymph node contain ANGPTL4 and promote invasive ability. These findings suggest that secreted ANGPTL4 may affect the invasive ability of OSCC. Moreover, the rates of positive ANGPTL4 expression at the primary site were significantly higher in the lymph node metastasis group. These results demonstrate that ANGPTL4 contributes to OSCC metastasis by stimulating cell invasion. Therefore, ANGPTL4 is a potential therapeutic target for preventing cancer metastasis.

Decreased expression of cystathionine β-synthase promotes glioma tumorigenesis

Cystathionine β-synthase (CBS) catalyzes metabolic reactions that convert homocysteine to cystathionine. To assess the role of CBS in human glioma, cells were stably transfected with lentiviral vectors encoding shRNA targeting CBS or a nontargeting control shRNA, and subclones were injected into immunodeficient mice. Interestingly, decreased CBS expression did not affect proliferation in vitro but decreased the latency period before rapid tumor xenograft growth after subcutaneous injection and increased tumor incidence and volume following orthotopic implantation into the caudate-putamen. In soft-agar colony formation assays, CBS knockdown subclones displayed increased anchorage-independent growth. Molecular analysis revealed that CBS knockdown subclones expressed higher basal levels of the transcriptional activator hypoxia-inducible factor 2α (HIF2α/EPAS1). HIF2α knockdown counteracted the effect of CBS knockdown on anchorage-independent growth. Bioinformatic analysis of mRNA expression data from human glioma specimens revealed a significant association between low expression of CBS mRNA and high expression of angiopoietin-like 4 (ANGPTL4) and VEGF transcripts, which are HIF2 target gene products that were also increased in CBS knockdown subclones. These results suggest that decreased CBS expression in glioma increases HIF2α protein levels and HIF2 target gene expression, which promotes glioma tumor formation.

IMPLICATIONS

CBS loss-of-function promotes glioma growth.

Redox circuitries driving Src regulation

SIGNIFICANCE

Here, we review recent advances with regard to the role of Src kinase in the regulation of cytoskeleton organization, cell adhesion, and motility, focusing on redox circuitries engaging this kinase for anchorage and motility, control of cell survival to anoikis, as well as metabolic deregulation, all features belonging to the new hallmarks of cancer.

RECENT ADVANCES

Several recent insights have reported that, alongside the well-known phosphorylation/dephosphorylation control, cysteine oxidation is a further mechanism of enzyme activation for both c-Src kinase and its oncogenic counterparts. Indeed, mounting evidence portrays redox regulation of Src kinase as a compulsory outcome in growth factors/cytokines signaling, integrin engagement, motility and invasiveness of tissues, receptor cross-talking at plasmamembrane, as well as during carcinogenesis and progression toward tumor malignancy or fibrotic disease. In addition, the kinase is an upstream regulator of NADPH oxidase-driven oxidants, a critical step for invadopodia formation and metastatic spread.

CRITICAL ISSUES

Not satisfactorily unraveled yet, the exact role of Src kinase in redox cancer biology needs to be implemented with studies that are aimed at clarifying (i) the exact hierarchy between oxidants sources, Src redox-dependent activation and the regulation of cell motility, and (ii) the actual susceptibility of invading cells to redox-based treatments, owing to the well-recognized ability of cancer cells to find new strategies to adapt to new environments.

FUTURE DIRECTIONS

Once these critical issues are addressed, redox circuitries involving Src kinase should potentially be used as both biomarkers and targets for personalized therapies in the fight against cancer or fibrotic diseases.

The basic biology of redoxosomes in cytokine-mediated signal transduction and implications for disease-specific therapies

Redox reactions have been established as major biological players in many cellular signaling pathways. Here we review mechanisms of redox signaling with an emphasis on redox-active signaling endosomes. Signals are transduced by relatively few reactive oxygen species (ROS), through very specific redox modifications of numerous proteins and enzymes. Although ROS signals are typically associated with cellular injury, these signaling pathways are also critical for maintaining cellular health at homeostasis. An important component of ROS signaling pertains to localization and tightly regulated signal transduction events within discrete microenvironments of the cell. One major aspect of this specificity is ROS compartmentalization within membrane-enclosed organelles such as redoxosomes (redox-active endosomes) and the nuclear envelope. Among the cellular proteins that produce superoxide are the NADPH oxidases (NOXes), transmembrane proteins that are implicated in many types of redox signaling. NOXes produce superoxide on only one side of a lipid bilayer; as such, their orientation dictates the compartmentalization of ROS and the local control of signaling events limited by ROS diffusion and/or movement through channels associated with the signaling membrane. NOX-dependent ROS signaling pathways can also be self-regulating, with molecular redox sensors that limit the local production of ROS required for effective signaling. ROS regulation of the Rac-GTPase, a required co-activator of many NOXes, is an example of this type of sensor. A deeper understanding of redox signaling pathways and the mechanisms that control their specificity will provide unique therapeutic opportunities for aging, cancer, ischemia-reperfusion injury, and neurodegenerative diseases.

Involvement of angiopoietin-like 4 in matrix remodeling during chondrogenic differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are considered for cartilage engineering given their ability to differentiate into chondrocytes. Chondrogenic differentiation of MSCs is currently triggered by micromass culture in the presence of a member of the TGF-β superfamily. However, the main constituents of the cartilaginous matrix, aggrecan and type II collagen, are degraded at the end of the differentiation process through induction of matrix metallopeptidase (MMP)13. We hypothesized that MSCs undergoing chondrogenic differentiation produce an intermediate cytokine that triggers this matrix remodeling. Analysis of transcriptomic data identified angiopoietin-like 4 (ANGPTL4) as one of the most strongly up-regulated gene encoding a secreted factor during TGF-β-induced chondrogenesis. To gain insight into the role of ANGPTL4 during chondrogenesis, we used recombinant ANGPTL4 as well as a RNA interference approach. Addition of exogenous ANGPTL4 during the course of TGF-β-induced differentiation reduced the mRNA levels of aggrecan and type II collagen, although it increased those of MMP1 and MMP13. Accordingly, deposition of aggrecan and total collagens was diminished, whereas release of MMP1 and MMP13 was increased. Conversely, transfection of MSCs with an siRNA targeting ANGPTL4 prior to induction of chondrogenesis increased expression of type II collagen and aggrecan, whereas it repressed that of MMP1, MMP3, and MMP13. A neutralizing antibody against integrin αVβ5, a known receptor for ANGPTL4, mimicked some of the effects observed after siRNA-mediated ANGPTL4 silencing. Our data provide evidence that ANGPTL4 promotes cartilage matrix remodeling by inhibiting expression of its two key components and by up-regulating the level of certain MMPs.

V-ATPase inhibition regulates anoikis resistance and metastasis of cancer cells

Fighting metastasis is a major challenge in cancer therapy and novel therapeutic targets and drugs are highly appreciated. Resistance of invasive cells to anoikis, a particular type of apoptosis induced by loss of cell-matrix contact, is a major prerequisite for their metastatic spread. Inducing anoikis in metastatic cancer cells is therefore a promising therapeutic approach. The vacuolar-ATPase (V-ATPase), a proton pump located at the membrane of acidic organelles, has recently come to focus as an antimetastatic cancer target. As V-ATPase inhibitors have shown to prevent invasion of tumor cells and are able to induce apoptosis, we proposed that V-ATPase inhibition induces anoikis-related pathways in invasive cancer cells. We used the V-ATPase inhibitor archazolid to investigate the mechanism of anoikis induction in various metastatic cancer cells (T24, MDA-MB-231, 4T1, 5637) in vitro. Anoikis induction by archazolid was characterized by decreased c-FLIP expression and caspase-8 activation as well as reduction of active integrin-β1 and an early increase of the proapoptotic protein BIM. However, we observed that archazolid also induces mechanisms opposing anoikis such as degradation of BIM mediated by extracellular signal-regulated kinase (ERK), Akt and Src kinases at later time points and induction of reactive oxygen species. Still, intravenous injection of archazolid-treated 4T1-Luc2 mouse breast cancer cells resulted in reduced metastasis in mouse lungs. Thus, V-ATPase inhibition is not only an interesting option to reduce cancer metastasis, but also to better understand anoikis resistance and to find choices to fight against it.

Angiopoietin-like 4 confers resistance to hypoxia/serum deprivation-induced apoptosis through PI3K/Akt and ERK1/2 signaling pathways in mesenchymal stem cells

Angiopoietin-like 4 (ANGPTL4) is a potential anti-apoptotic agent for various cells. We examined the protective effect of ANGPTL4 on hypoxia/serum deprivation (SD)-induced apoptosis of MSCs, as well as the possible mechanisms. MSCs were obtained from rat bone marrow and cultured in vitro. Apoptosis was induced by hypoxia/SD for up to 24 hr, and assessed by flow cytometry and TUNEL assay. Expression levels of Akt, ERK1/2, focal adhesion kinase (FAK), Src, Bcl-2, Bax, cytochrome C and cleaved caspase-3 were detected by Western blotting. Integrin β1 mRNA was detected by qRT-PCR. Mitochondrial membrane potential was assayed using a membrane-permeable dye. Hypoxia/SD-induced apoptosis was significantly attenuated by recombinant rat ANGPTL4 in a concentration dependent manner. Moreover, ANGPTL4 decreased the hypoxia/SD-induced caspase-3 cleavage and the cytochrome C release, but increased the Bcl-2/Bax ratio and the mitochondrial membrane potential. Decreased expression of integrin β1, the ANGPTL4 receptor was observed during hypoxia/SD conditions, however, such decrease was reversed by ANGPTL4. In addition, ANGPTL4 induced integrin β1-associated FAK and Src phosphorylation, which was blocked by anti-integrin β1 antibody. ANGPTL4 also reversed the hypoxia/SD-induced decrease of Akt and ERK 1/2 phosphorylation, and the effect of ANGPTL4 was abolished by inhibitors of either integrins, ERK1/2, or phosphatidylinositol 3-kinase (PI3K). Blocking integrinβ1, Akt or ERK largely attenuated anti-apoptotic effect of ANGPTL4. ANGPTL4 protects MSCs from hypoxia/SD-induced apoptosis by interacting with integrins to stimulate FAK complex, leading to downstream ERK1/2 and PI3K/Akt signaling pathways and mimicking the pathway in which MSCs contact with the extracellular matrix.

Chronic low dose-rate radiation down-regulates transcription related to mitosis and chromosomal movement similar to acute high dose in prostate cells

PURPOSE

Despite concerns over risks from exposure to low-dose ionizing radiations encountered in the environment and workplace, the molecular consequences of these exposures, particularly at representative doses and dose-rates, remains poorly understood.

MATERIALS AND METHODS

Using a novel flood source construct, we performed a direct comparison of genome-wide gene expression regulations resulting from exposure of primary human prostate fibroblast cultures to acute (10 cGy and 200 cGy) and longer-term chronic (1.0-2.45 cGy cumulative over 24 h) exposures.

RESULTS

Expression profiling showed significant differential regulation of 396 genes with no measureable changes in the acute 10 cGy dose. However, there were 106 genes in common between samples given an acute 200 cGy dose compared to those given chronic doses, most of which were decreased and related to cell cycle or chromosomal movement in M-phase. Biological pathway analysis showed decreases in cell cycle, chromosomal movement, cell survival and DNA replication, recombination and repair as well as a predicted activation of transcriptional regulators TP53, RB1 and CDKN2A. In agreement with these results, prostate epithelial cells given 200 cGy or chronic doses displayed functional decreases in proliferation and mitotic cells.

CONCLUSIONS

In summary, we showed a contrast to the common observation of constant or reduced effect per unit dose as the dose (acute) was diminished, that even very low total doses delivered chronically could rival the perturbing effect of acute doses 100 times as intense. Underscored is the importance of the means of dose delivery, shown to be as important as dose size when considering biologic effect.

A distinct reactive oxygen species profile confers chemoresistance in glioma-propagating cells and associates with patient survival outcome

AIMS

We explore the role of an elevated O2(-):H2O2 ratio as a prosurvival signal in glioma-propagating cells (GPCs). We hypothesize that depleting this ratio sensitizes GPCs to apoptotic triggers.

RESULTS

We observed that an elevated O2(-):H2O2 ratio conferred enhanced resistance in GPCs, and depletion of this ratio by pharmacological and genetic methods sensitized cells to apoptotic triggers. We established the reactive oxygen species (ROS) Index as a quantitative measure of a normalized O2(-):H2O2 ratio and determined its utility in predicting chemosensitivity. Importantly, mice implanted with GPCs of a reduced ROS Index demonstrated extended survival. Analysis of tumor sections revealed effective targeting of complementarity determinant 133 (CD133)- and nestin-expressing neural precursors. Further, we established the Connectivity Map to interrogate a gene signature derived from a varied ROS Index for the patterns of association with individual patient gene expression in four clinical databases. We showed that patients with a reduced ROS Index demonstrate better survival. These data provide clinical evidence for the viability of our O2(-):H2O2-mediated chemosensitivity profiles.

INNOVATION AND CONCLUSION

Gliomas are notoriously recurrent and highly infiltrative, and have been shown to arise from stem-like cells. We implicate an elevated O2(-):H2O2 ratio as a prosurvival signal in GPC self-renewal and proliferation. The ROS Index provides quantification of O2(-):H2O2-mediated chemosensitivity, an advancement in a previously qualitative field. Intriguingly, glioma patients with a reduced ROS Index correlate with longer survival and the Proneural molecular classification, a feature frequently associated with tumors of better prognosis. These data emphasize the feasibility of manipulating the O2(-):H2O2 ratio as a therapeutic strategy.

Ras and Rac1, frequently mutated in melanomas, are activated by superoxide anion, modulate Dnmt1 level and are causally related to melanocyte malignant transformation

A melanocyte malignant transformation model was developed in our laboratory, in which different melanoma cell lines were obtained after submitting the non-tumorigenic melanocyte lineage melan-a to sequential cycles of anchorage impediment. Our group has already showed that increased superoxide level leads to global DNA hypermemethylation as well increased Dnmt1 expression few hours after melanocyte anchorage blockade. Here, we showed that Ras/Rac1/ERK signaling pathway is activated in melanocytes submitted to anchorage impediment, regulating superoxide levels, global DNA methylation, and Dnmt1 expression. Interestingly, Ras and Rac1 activation is not related to codon mutations, but instead regulated by superoxide. Moreover, the malignant transformation was drastically compromised when melan-a melanocytes were submitted to sequential cycles of anchorage blockage in the presence of a superoxide scavenger. This aberrant signaling pathway associated with a sustained stressful condition, which might be similar to conditions such as UV radiation and inflammation, seems to be an early step in malignant transformation and to contribute to an epigenetic reprogramming and the melanoma development.

The cancer gene WWOX behaves as an inhibitor of SMAD3 transcriptional activity via direct binding

BACKGROUND

The WW domain containing protein WWOX has been postulated to behave as a tumor suppressor in breast and other cancers. Expression of this protein is lost in over 70% of ER negative tumors. This prompted us to investigate the phenotypic and gene expression effects of loss of WWOX expression in breast cells.

METHODS

Gene expression microarrays and standard in vitro assays were performed on stably silenced WWOX (shRNA) normal breast cells. Bioinformatic analyses were used to identify gene networks and transcriptional regulators affected by WWOX silencing. Co-immunoprecipitations and GST-pulldowns were used to demonstrate a direct interaction between WWOX and SMAD3. Reporter assays, ChIP, confocal microscopy and in silico analyses were employed to determine the effect of WWOX silencing on TGFβ-signaling.

RESULTS

WWOX silencing affected cell proliferation, motility, attachment and deregulated expression of genes involved in cell cycle, motility and DNA damage. Interestingly, we detected an enrichment of targets activated by the SMAD3 transcription factor, including significant upregulation of ANGPTL4, FST, PTHLH and SERPINE1 transcripts. Importantly, we demonstrate that the WWOX protein physically interacts with SMAD3 via WW domain 1. Furthermore, WWOX expression dramatically decreases SMAD3 occupancy at the ANGPTL4 and SERPINE1 promoters and significantly quenches activation of a TGFβ responsive reporter. Additionally, WWOX expression leads to redistribution of SMAD3 from the nuclear to the cytoplasmic compartment. Since the TGFβ target ANGPTL4 plays a key role in lung metastasis development, we performed a meta-analysis of ANGPTL4 expression relative to WWOX in microarray datasets from breast carcinomas. We observed a significant inverse correlation between WWOX and ANGPTL4. Furthermore, the WWOX(lo)/ANGPTL4(hi) cluster of breast tumors is enriched in triple-negative and basal-like sub-types. Tumors with this gene expression signature could represent candidates for anti-TGFβ targeted therapies.

CONCLUSIONS

We show for the first time that WWOX modulates SMAD3 signaling in breast cells via direct WW-domain mediated binding and potential cytoplasmic sequestration of SMAD3 protein. Since loss of WWOX expression increases with breast cancer progression and it behaves as an inhibitor of SMAD3 transcriptional activity these observations may help explain, at least in part, the paradoxical pro-tumorigenic effects of TGFβ signaling in advanced breast cancer.

Circulating angiopoietin-like 4 links proteinuria with hypertriglyceridemia in nephrotic syndrome

The molecular link between proteinuria and hyperlipidemia in nephrotic syndrome is not known. We show in the present study that plasma angiopoietin-like 4 (Angptl4) links proteinuria with hypertriglyceridemia through two negative feedback loops. In previous studies in a rat model that mimics human minimal change disease, we observed localized secretion by podocytes of hyposialylated Angptl4, a pro-proteinuric form of the protein. But in this study we noted high serum levels of Angptl4 (presumably normosialylated based on a neutral isoelectric point) in other glomerular diseases as well. Circulating Angptl4 was secreted by extrarenal organs in response to an elevated plasma ratio of free fatty acids (FFAs) to albumin when proteinuria reached nephrotic range. In a systemic feedback loop, these circulating pools of Angptl4 reduced proteinuria by interacting with glomerular endothelial αvβ5 integrin. Blocking the Angptl4-β5 integrin interaction or global knockout of Angptl4 or β5 integrin delayed recovery from peak proteinuria in animal models. But at the same time, in a local feedback loop, the elevated extrarenal pools of Angptl4 reduced tissue FFA uptake in skeletal muscle, heart and adipose tissue, subsequently resulting in hypertriglyceridemia, by inhibiting lipoprotein lipase (LPL)-mediated hydrolysis of plasma triglycerides to FFAs. Injecting recombinant human ANGPTL4 modified at a key LPL interacting site into nephrotic Buffalo Mna and Zucker Diabetic Fatty rats reduced proteinuria through the systemic loop but, by bypassing the local loop, without increasing plasma triglyceride levels. These data show that increases in circulating Angptl4 in response to nephrotic-range proteinuria reduces the degree of this pathology, but at the cost of inducing hypertriglyceridemia, while also suggesting a possible therapy to treat these linked pathologies.

C1q tumor necrosis factor-related protein-3 protects mesenchymal stem cells against hypoxia- and serum deprivation-induced apoptosis through the phosphoinositide 3-kinase/Akt pathway

Bone marrow (BM)-derived mesenchymal stem cells (MSCs) represent the leading candidate cell for tissue regeneration in the ischemic myocardium. However, the poor survival of stem cells transplanted into the ischemic myocardium presents a major obstacle in stem cell-based therapy. C1q tumor necrosis factor-related protein 3 (CTRP3) is a newly identified adipokine, similar to adiponectin, with beneficial effects on metabolic regulation. It has been shown to enhance the survival of cardiomyocytes during ischemia, while its expression is reduced following ischemia. In the present study, we examined the hypothesis that CTRP3 may enhance the survival of MSCs during exposure to hypoxia/serum deprivation (SD), and attempted to elucidate the underlying mechanisms. MSCs were obtained from rat bone marrow and cultured. Apoptosis was induced by hypoxia/SD for up to 24 h and the apoptotic rates were assessed by flow cytometry. MSC proliferation was measured using a Cell Counting kit-8 assay. The expression levels of Akt, Bcl-2, Bax, cytochrome c and cleaved caspase-3 were detected by western blot analysis. Mitochondrial membrane potential was examined using a membrane-permeable dye. CTRP3 significantly reduced hypoxia/SD-induced apoptosis in a concentration-dependent manner. The hypoxia/SD-induced decrease in the Bcl-2/Bax ratio and the mitochondrial membrane potential, and the increase in cytochrome c and caspase-3 levels were largely reversed by CTRP3. The anti-apoptotic effects of CTRP3 were blocked by inhibiting the activation of phosphoinositide 3-kinase (PI3K)/Akt signaling pathway with the PI3K inhibitor, LY294002. In conclusion, CTRP3 is a novel anti-apoptotic adipokine that protects MSCs from hypoxia/SD-induced apoptosis through the PI3K/Akt signaling pathway.

Role of Angptl4 in vascular permeability and inflammation

BACKGROUND

Angptl4 is a secreted protein involved in the regulation of vascular permeability, angiogenesis, and inflammatory responses in different kinds of tissues. Increases of vascular permeability and abnormality changes in angiogenesis contribute to the pathogenesis of tumor metastasis, ischemic-reperfusion injury. Inflammatory response associated with Angptl4 also leads to minimal change glomerulonephritis, wound healing. However, the role of Angptl4 in vascular permeability, angiogenesis, and inflammation is controversy. Hence, an underlying mechanism of Angptl4 in different kind of tissues needs to be further clarified.

METHODS

Keywords such as angptl4, vascular permeability, angiogenesis, inflammation, and endothelial cells were used in search tool of PUBMED, and then the literatures associated with Angptl4 were founded and read.

RESULTS

Data have established Angptl4 as the key modulator of both vascular permeability and angiogenesis; furthermore, it may also be related to the progression of metastatic tumors, cardiovascular events, and inflammatory diseases. This view focuses on the recent advances in our understanding of the role of Angptl4 in vascular permeability, angiogenesis, inflammatory signaling and the link between Angptl4 and multiple diseases such as cancer, cardiovascular diseases, diabetic retinopathy, and kidney diseases.

CONCLUSIONS

Taken together, Angptl4 modulates vascular permeability, angiogenesis, inflammatory signaling, and associated diseases. The use of Angptl4-modulating agents such as certain drugs, food constituents (such as fatty acids), nuclear factor (such as PPARα), and bacteria may treat associated diseases such as tumor metastasis, ischemic-reperfusion injury, inflammation, and chronic low-grade inflammation. However, the diverse physiological functions of Angptl4 in different tissues can lead to potentially deleterious side effects when used as a therapeutic target. In this regard, a better understanding of the underlying mechanisms for Angptl4 in different tissues is necessary.

Loss of TAK1 increases cell traction force in a ROS-dependent manner to drive epithelial-mesenchymal transition of cancer cells

Epithelial–mesenchymal transition (EMT) is a crucial step in tumor progression, and the TGFβ–SMAD signaling pathway as an inductor of EMT in many tumor types is well recognized. However, the role of non-canonical TGFβ–TAK1 signaling in EMT remains unclear. Herein, we show that TAK1 deficiency drives metastatic skin squamous cell carcinoma earlier into EMT that is conditional on the elevated cellular ROS level. The expression of TAK1 is consistently reduced in invasive squamous cell carcinoma biopsies. Tumors derived from TAK1-deficient cells also exhibited pronounced invasive morphology. TAK1-deficient cancer cells adopt a more mesenchymal morphology characterized by higher number of focal adhesions, increase surface expression of integrin α5β1 and active Rac1. Notably, these mutant cells exert an increased cell traction force, an early cellular response during TGFβ1-induced EMT. The mRNA level of ZEB1 and SNAIL, transcription factors associated with mesenchymal phenotype is also upregulated in TAK1-deficient cancer cells compared with control cancer cells. We further show that TAK1 modulates Rac1 and RhoA GTPases activities via a redox-dependent downregulation of RhoA by Rac1, which involves the oxidative modification of low-molecular weight protein tyrosine phosphatase. Importantly, the treatment of TAK1-deficient cancer cells with Y27632, a selective inhibitor of Rho-associated protein kinase and antioxidant N-acetylcysteine augment and hinders EMT, respectively. Our findings suggest that a dysregulated balance in the activation of TGFβ–TAK1 and TGFβ–SMAD pathways is pivotal for TGFβ1-induced EMT. Thus, TAK1 deficiency in metastatic cancer cells increases integrin:Rac-induced ROS, which negatively regulated Rho by LMW-PTP to accelerate EMT.

Activation of the leukotriene B4 receptor 2-reactive oxygen species (BLT2-ROS) cascade following detachment confers anoikis resistance in prostate cancer cells

The majority of prostate cancer-related deaths are associated with advanced and metastatic malignancies. Although anoikis resistance has been recognized as one of the hallmarks of metastatic prostate malignancies, the molecular events that cause anoikis resistance are poorly understood. In this study, we found that the detachment of PC-3 prostate cancer cells caused a time-dependent increase in the expression level of the leukotriene B4 receptor-2 (BLT2) and that BLT2 played a critical role in establishing anoikis resistance in these cells. Blocking BLT2 with the pharmacological inhibitor LY255283 or with RNAi knockdown clearly abolished anoikis resistance and resulted in severe apoptotic death. Additionally, we demonstrated that the activation of NADPH oxidase (NOX) and subsequent generation of reactive oxygen species (ROS) were downstream of BLT2 signaling and led to the activation of NF-κB, thus establishing anoikis resistance during cell detachment. Furthermore, we observed that the ectopic expression of BLT2 in normal prostate PWR-1E cells rendered the cells resistant to anoikis and apparently diminished apoptotic cell death following detachment. Taken together, our results suggest that BLT2-NOX-ROS-NF-κB cascade induction during detachment confers a novel mechanism of anoikis resistance in prostate cancer cells and potentially contributes to prostate cancer progression.

Clinical significance of angiopoietin-like protein 4 expression in tissue and serum of esophageal squamous cell carcinoma patients

Angiopoietin-like protein 4 (ANGPTL4) has been reported to promote tumor growth, metastasis, and angiogenesis under certain conditions. The aim of this study was to examine ANGPTL4 expression in tumor and serum tissues from esophageal squamous cell carcinoma (ESCC) patients. A total of 78 ESCC patients treated with radical resection were enrolled in this study. Immunohistochemistry was used to detect ANGPTL4 expression in ESCC tissues. Serum ANGPTL4 levels were determined via enzyme-linked immunosorbent assay (ELISA). The receiver operating characteristics curve was constructed to describe diagnostic specificity and sensitivity. There were 52 cases (69.2 %) showing a higher level of ANGPTL4 expression in tumor tissues than that in normal tissues, and the rate of ANGPTL4 protein high/moderate expression in ESCC and normal tissues was 55.1 % (43/78) and 6.4 % (5/78), respectively, with a significant difference (P < 0.001). Moreover, the high/moderate of ANGPTL4 protein was significantly associated with lymph metastasis, clinical stage, and adverse 2-year progression-free survival. In addition, serum ANGPTL4 level in ESCC patients was much higher than that in patients with benign esophageal disease (P < 0.001), and area under the curve was 0.94 (95 % CI 0.886390-0.978173, P < 0.001). But serum ANGPTL4 level was significantly decreased at post-operative 7-10 days (P = 0.004). ANGPTL4 upregulation may play an important role in ESCC development, and serum ANGPTL4 level may be a potential tumor marker for ESCC diagnosis and prognosis.

Uncovering a key to the process of metastasis in human cancers: a review of critical regulators of anoikis

PURPOSE

Anoikis ('homelessness' in Greek) is a form of apoptosis following the detachment of cells from the appropriate extracellular matrix (Chiarugi and Giannoni in Biochem Pharmacol 76:1352-1364, 2008). Resistance to anoikis is a critical mediator of metastasis in cancer by enabling cancer cells to survive during invasion and transport in the blood and lymph. Numerous regulators and mechanisms of anoikis in human cancer have been proposed to date. Consequently, the identification of key regulators of anoikis that can be targeted to at least partially restore anoikis sensitivity in cancer cells is important in the development of therapies to treat metastatic cancer.

METHODS

A literature search focusing on the regulators of anoikis in human cancer was performed on the Medline, Embase and Scopus databases.

RESULTS

Mcl-1, Cav-1, Bcl-(xL), cFLIP, 14-3-3ζ and Bit1 appear to regulate anoikis in human cancer by participating in the intrinsic apoptotic pathway, extrinsic apoptotic pathway or caspase-independent pathways. Mcl-1, Cav-1, Bcl-(xL), cFLIP and 14-3-3ζ are suppressors of anoikis, and their upregulation confers anoikis resistance to cancer cells. Bit1 is a promoter of anoikis and is downregulated to confer anoikis resistance in metastatic cancer.

CONCLUSION

Anoikis is a complex process involving the crosstalk between different signalling pathways. The dysregulated expression of key regulators of anoikis that participate in these signalling pathways promotes anoikis resistance in human cancer. These regulators of anoikis might therefore be the targets for developing therapies to overcome anoikis resistance in metastatic cancer.

Effect of angiopoietin-like protein 4 on rat pulmonary microvascular endothelial cells exposed to LPS

Pulmonary microvascular endothelial cells (PMVECs) possess highly proliferative and angiogenic capacities and are localized at the critical interface between the blood and microvessel wall; they are the primary targets of inflammatory cytokines during lung inflammation. Angiopoietin-like protein 4 (Angptl4) is a circulating protein that has recently been im-plicated in the regulation of angiogenesis and metastasis. This study aimed to investigate the effect of Angptl4 on rat PMVECs (RPMVECs) exposed to lipopolysaccharide (LPS). The cell culture was stimulated with LPS. Total Angptl4 cDNA was obtained from Source BioScience. The PCR product was cloned into the pcDNA3.1-eGFP or the pcDNA3.1‑eGFP‑Angptl4 vector, which were then transfected into the RPMVECs using SuperFect transfection reagent. The Angptl4 mRNA levels, protein levels and cell morphology of the RPMVECs in the experimental groups were detected using real time-PCR, western blot analysis, MTT assay, ELISA and confocal microscopy methods, respective-ly. The Angptl4 expression vector, pcDNA3.1‑eGFP-Angptl4, was successfully constructed. The Angptl4 mRNA level in the LPS-pcDNA3.1-eGFP-transfected group (blank control) was slightly increased and was significantly higher in the experimental group compared with the empty vector and blank control group with significant differences. Pro-apoptotic caspase-8, -9 and Bax protein were inhibited, while p-AKT/AKT and p-Mek1/2 protein expression was also decreased. The rosiglitazone group had significantly decreased levels of the inflammatory cytokine, tumor necrosis factor (TNF)-α (P<0.01). The overexpression of Angptl4 inhibited the LPS-induced increase in the permeability of the RPMVECs, which was associated with the depolymerization of central F-actin in the RPMVECs. In conclusion, our study demonstrates that the overexpression of Angptl4 exerts protective, anti-inflammatory and anti-angiogenic effects. It re-presents a novel therapeutic target gene for the treatment of acute lung injury induced by LPS.

ANGPTL4 is a secreted tumor suppressor that inhibits angiogenesis

Tumor suppressors with extracellular function are likely to have advantages as targets for cancer therapy, but few are known. Here, we focused on angiopoietin-like 4 (ANGPTL4), which is a secreted glycoprotein involved in lipoprotein metabolism and angiogenesis, is methylation-silenced in human cancers, but has unclear roles in cancer development and progression. We found a deletion mutation in its coiled-coil domain at its N-terminal in human gastric cancers, in addition to hypermethylation of the ANGPTL4 promoter CpG islands. Forced expression of wild-type ANGPTL4, but not ANGPTL4 with the deletion, at physiological levels markedly suppressed in vivo tumorigenicity and tumor angiogenesis, indicating that the latter caused the former. Tumor-derived ANGPTL4 suppressed in vitro vascular tube formation and proliferation of human umbilical vascular endothelial cells, partly due to suppression of ERK signaling. These showed that ANGPTL4 is a genetically and epigenetically inactivated secreted tumor suppressor that inhibits tumor angiogenesis.

The oncogene HER2/neu (ERBB2) requires the hypoxia-inducible factor HIF-1 for mammary tumor growth and anoikis resistance

ERBB2, a receptor tyrosine kinase amplified in breast cancer, is a well established regulator of tumor growth in vivo and anoikis resistance leading to disruption of architecture in three-dimensional mammary epithelial acinar structures in vitro. ERBB2 promotes anoikis resistance by maintaining signaling pathways and by rescuing metabolic defects and thus inhibiting accumulation of deleterious reactive oxygen species. Recent evidence suggests that hypoxia, via hypoxia-inducible factors (HIFs), can inhibit anoikis; thus, we hypothesized that HIF-1 may play a role in ERBB2-mediated anoikis resistance and oncogenesis. Indeed, tumors isolated from MMTV-Neu mice contain elevated HIF-1α levels and tumor cells created from MMTV-Neu mice harboring deletion of Hif1α alleles reduced primary tumor growth in vivo. ERBB2 overexpressing cancer cells stabilize HIF under normoxic conditions and require HIF-1 for ERBB2-mediated anchorage-independence, three-dimensional culture growth and anoikis resistance. HIF-1 reduction in ERBB2 cells was associated with induction of the pro-anoikis protein BIM and decreased ERK and AKT signaling during cell detachment. ERBB2-mediated inhibition of metabolic defects, including decreased reactive oxygen species generation in suspension, required HIF-1 expression that was critical for ERBB2-mediated oncogenesis. Gene expression profiling of hypoxic three-dimensional acinar structures identified a number of genes elevated in response to hypoxia that are known ERBB2 targets, suggesting that hypoxic conditions and ERBB2 overexpression share both phenotypic and genetic components via HIF-1 regulation. Thus, our data demonstrate that ERBB2 requires HIF-1 for tumor growth and suggest that HIF is a major downstream regulator of ERBB2 that protects cells from anoikis and metabolic stress caused by decreased matrix adhesion.

Redox regulation of protein kinases

Reactive oxygen species (ROS) have been long regarded as by-products of a cascade of reactions stemming from cellular oxygen metabolism, which, if they accumulate to toxic levels, can have detrimental effects on cellular biomolecules. However, more recently, the recognition of ROS as mediators of cellular communications has led to their classification as signalling mediators in their own right. The prototypic redox-regulated targets downstream of ROS are the protein tyrosine phosphatases, and the wealth of research that has focused on this area has come to shape our understanding of how redox-signalling contributes to and facilitates protein tyrosine phosphorylation signalling cascades. However, it is becoming increasingly apparent that there is more to this system than simply the negative regulation of protein tyrosine phosphatases. Identification of redox-sensitive kinases such as Src led to the slow emergence of a role for redox regulation of tyrosine kinases. A flow of evidence, which has increased exponentially in recent times as a result of the development of new methods for the detection of oxidative modifications, demonstrates that, by concurrent oxidative activation of tyrosine kinases, ROS fine tune the duration and amplification of the phosphorylation signal. A more thorough understanding of the complex regulatory mechanism of redox-modification will allow targeting of both the production of ROS and their downstream effectors for therapeutic purposes. The present review assesses the most relevant recent literature that demonstrates a role for kinase regulation by oxidation, highlights the most significant findings and proposes future directions for this crucial area of redox biology.

Nox4-dependent ROS modulation by amino endoperoxides to induce apoptosis in cancer cells

Tumor metastasis is the main cause of death in cancer patients. Anoikis resistance is one critical malefactor of metastatic cancer cells to resist current clinical chemotherapeutic treatments. Although endoperoxide-containing compounds have long been suggested as anticancer drugs, few have been clinically employed due to their instability, complex synthesis procedure or low tumor cell selectivity. Herein, we describe a one-pot strategy to synthesize novel amino endoperoxides and their derivatives with good yields and stabilities. In vitro cell-based assays revealed that 4 out of the 14 amino endoperoxides selectively induce metastatic breast carcinoma cells but not normal breast cells to undergo apoptosis, in a dose-dependent manner. Mechanistic studies showed that the most potent amino endoperoxide, 4-Me, is selective for cancer cells expressing a high level of Nox4. The anticancer effects are further shown to be associated with reduced O₂⁻:H₂O₂ ratio and increased ·OH level in the cancerous cells. Animal study showed that 4-Me impairs orthotopic breast tumor growth as well as tumor cell metastasis to lymph nodes. Altogether, our study suggests that anticancer strategies that focus on redox-based apoptosis induction in tumors are clinically viable.

Angiopoietin-like protein 1 suppresses SLUG to inhibit cancer cell motility

Angiopoietin-like protein 1 (ANGPTL1) is a potent regulator of angiogenesis. Growing evidence suggests that ANGPTL family proteins not only target endothelial cells but also affect tumor cell behavior. In a screen of 102 patients with lung cancer, we found that ANGPTL1 expression was inversely correlated with invasion, lymph node metastasis, and poor clinical outcomes. ANGPTL1 suppressed the migratory, invasive, and metastatic capabilities of lung and breast cancer cell lines in vitro and reduced metastasis in mice injected with cancer cell lines overexpressing ANGPTL1. Ectopic expression of ANGPTL1 suppressed the epithelial-to-mesenchymal transition (EMT) by reducing the expression of the zinc-finger protein SLUG. A microRNA screen revealed that ANGPTL1 suppressed SLUG by inducing expression of miR-630 in an integrin α(1)β(1)/FAK/ERK/SP1 pathway-dependent manner. These results demonstrate that ANGPTL1 represses lung cancer cell motility by abrogating the expression of the EMT mediator SLUG.

Computational modelling of LY303511 and TRAIL-induced apoptosis suggests dynamic regulation of cFLIP

MOTIVATION

TRAIL has been widely studied for the ability to kill cancer cells selectively, but its clinical usefulness has been hindered by the development of resistance. Multiple compounds have been identified that sensitize cancer cells to TRAIL-induced apoptosis. The drug LY303511 (LY30), combined with TRAIL, caused synergistic (greater than additive) killing of multiple cancer cell lines. We used mathematical modelling and ordinary differential equations to represent how LY30 and TRAIL individually affect HeLa cells, and to predict how the combined treatment achieves synergy.

RESULTS

Model-based predictions were compared with in vitro experiments. The combination treatment model was successful at mimicking the synergistic levels of cell death caused by LY30 and TRAIL combined. However, there were significant failures of the model to mimic upstream activation at early time points, particularly the slope of caspase-8 activation. This flaw in the model led us to perform additional measurements of early caspase-8 activation. Surprisingly, caspase-8 exhibited a transient decrease in activity after LY30 treatment, prior to strong activation. cFLIP, an inhibitor of caspase-8 activation, was up-regulated briefly after 30 min of LY30 treatment, followed by a significant down-regulation over prolonged exposure. A further model suggested that LY30-induced fluctuation of cFLIP might result from tilting the ratio of two key species of reactive oxygen species (ROS), superoxide and hydrogen peroxide. Computational modelling extracted novel biological implications from measured dynamics, identified time intervals with unexplained effects, and clarified the non-monotonic effects of the drug LY30 on cFLIP during cancer cell apoptosis.

Cancer-stromal cell interactions mediated by hypoxia-inducible factors promote angiogenesis, lymphangiogenesis, and metastasis

Interactions between cancer cells and stromal cells, including blood vessel endothelial cells (BECs), lymphatic vessel endothelial cells (LECs), bone marrow-derived angiogenic cells (BMDACs) and other bone marrow-derived cells (BMDCs) play important roles in cancer progression. Intratumoral hypoxia, which affects both cancer and stromal cells, is associated with a significantly increased risk of metastasis and mortality in many human cancers. Recent studies have begun to delineate the molecular mechanisms underlying the effect of intratumoral hypoxia on cancer progression. Reduced O2 availability induces the activity of hypoxia-inducible factors (HIFs), which activate the transcription of target genes encoding proteins that play important roles in many critical aspects of cancer biology. Included among these are secreted factors, including angiopoietin 2, angiopoietin-like 4, placental growth factor, platelet-derived growth factor B, stem cell factor (kit ligand), stromal-derived factor 1, and vascular endothelial growth factor. These factors are produced by hypoxic cancer cells and directly mediate functional interactions with BECs, LECs, BMDACs and other BMDCs that promote angiogenesis, lymphangiogenesis, and metastasis. In addition, lysyl oxidase (LOX) and LOX-like proteins, which are secreted by hypoxic breast cancer cells, remodel extracellular matrix in the lungs, which leads to BMDC recruitment and metastatic niche formation.

Inverse PPARβ/δ agonists suppress oncogenic signaling to the ANGPTL4 gene and inhibit cancer cell invasion

Besides its established functions in intermediary metabolism and developmental processes, the nuclear receptor peroxisome proliferator-activated receptor β/δ (PPARβ/δ) has a less defined role in tumorigenesis. In the present study, we have identified a function for PPARβ/δ in cancer cell invasion. We show that two structurally divergent inhibitory ligands for PPARβ/δ, the inverse agonists ST247 and DG172, strongly inhibit the serum- and transforming growth factor β (TGFβ)-induced invasion of MDA-MB-231 human breast cancer cells into a three-dimensional matrigel matrix. To elucidate the molecular basis of this finding, we performed chromatin immunoprecipitation sequencing (ChIP-Seq) and microarray analyses, which identified the gene encoding angiopoietin-like 4 (ANGPTL4) as the major transcriptional PPARβ/δ target in MDA-MB-231 cells, previously implicated in TGFβ-mediated tumor progression and metastatic dissemination. We show that the induction of ANGPTL4 by TGFβ and other oncogenic signals is strongly repressed by ST247 and DG172 in a PPARβ/δ-dependent fashion, resulting in the inhibition of ANGPTL4 secretion. This effect is attributable to these ligands' ability to induce a dominant transcriptional repressor complex at the site of transcription initiation that blocks preinitiation complex formation through an histone deacetylase-independent, non-canonical mechanism. Repression of ANGPTL4 transcription by inverse PPARβ/δ agonists is functionally linked to the inhibition of cancer cell invasion into a three-dimensional matrix, as (i) invasion of MDA-MB-231 cells is critically dependent on ANGPTL4 expression, (ii) recombinant ANGPTL4 stimulates invasion, and (iii) reverses the inhibitory effect of ST247 and DG172. These findings indicate that a PPARβ/δ-ANGPTL4 pathway is involved in the regulation of tumor cell invasion and that its pharmacological manipulation by inverse PPARβ/δ agonists is feasible.

FLT3-driven redox-modulation of Ezrin regulates leukaemic cell migration

The concept of reactive oxygen species (ROS) being produced via the activation of specific oncogenes provides a basis for generating genomic instability and pro-survival signalling in tumour cells. The purpose of this study was to identify downstream targets of NADPH oxidase (Nox)-derived ROS signalling in acute myeloid leukaemia cells, by performing a proteomic analysis utilizing two-dimensional phosphotyrosine immunoblotting. The majority of the targets identified were cytoskeletal-associated proteins including Ezrin, a known regulator of the cytoskeleton, which was examined further. The study demonstrated that inhibition of Nox enzymes, using diphenyleneiodonium chloride in the acute myeloid leukaemia cell line MOLM-13, resulted in a decrease in Ezrin tyrosine phosphorylation and also triggered a shift in Ezrin sub-cellular localization as detected by immunofluorescence. The change in Ezrin localization coincided with altered cell morphology, observed using scanning electron microscopy and a decreased ability to migrate through a polycarbonate transwell membrane. Similar effects were observed upon inhibition of the oncogenic receptor tyrosine kinase FLT3 using the staurosporine derivate PKC412, implicating a role for FLT3 as an upstream regulator of Ezrin. Our results indicate that FLT3 drives production of ROS by Nox, which stimulates changes in Ezrin tyrosine phosphorylation and localization via redox regulation of Src. Furthermore, inhibition of FLT3 signalling leads to alterations in MOLM-13 cell morphology and has a significant influence on cell motility.

Angiopoietin-like protein 4: health effects, modulating agents and structure-function relationships

Angiopoietin-like protein 4 (ANGPTL4) has been identified as a multifunctional signal protein. It is produced by a variety of tissues, and is secreted into the bloodstream in glycosylated, oligomerized, native and cleaved isoforms to modulate physiological events such as angiogenesis, cell differentiation and the crosstalk between liver, brain, adipose and muscle tissue in lipid and glucose metabolism. In addition, the expression and isoform appearance of ANGPTL4 are modified by the intestinal microbiota. With an eye on an effective strategy to improve health using ANGPTL4, we will focus on: health issues associated with ANGPTL4 expression, including obesity, Type 2 diabetes, cardiovascular diseases and cancer; several modulators of ANGPTL4 of chemical, microbiological, food and host origin; and the correlation of the specific ANGPTL4 isoforms with these modulators and their health effects.

Protein kinase casein kinase 2-mediated upregulation of N-cadherin confers anoikis resistance on esophageal carcinoma cells

Previously, we reported that high PKCK2 activity could protect cancer cells from death receptor-mediated apoptosis through phosphorylation of procaspase-2. Because anoikis is another form of apoptosis, we asked whether PKCK2 could similarly confer resistance to anoikis on cancer cells. Human esophageal squamous cancer cell lines with high PKCK2 activity (HCE4 and HCE7) were anoikis-resistant, whereas cell lines with low PKCK2 activity (TE2 and TE3) were anoikis-sensitive. Because the cells showed different sensitivity to anoikis, we compared the expression of cell adhesion molecules between anoikis-sensitive TE2 and anoikis-resistant HCE4 cells using cDNA microarray. We found that E-cadherin is expressed only in TE2 cells; whereas N-cadherin is expressed instead of E-cadherin in HCE4 cells. To examine whether PKCK2 activity could determine the type of cadherin expressed, we first increased intracellular PKCK2 activity in TE2 cells by overexpressing the PKCK2α catalytic subunit using lentivirus and found that high PKCK2 activity could switch cadherin expression from type E to N and confer anoikis resistance. Conversely, a decrease in PKCK2 activity in HCE4 cells by knockdown of PKCK2α catalytic subunit using shRNA induced N- to E-cadherin switching and the anoikis-resistant cells became sensitive. In addition, N-cadherin expression correlated with PKB/Akt activation and increased invasiveness. We conclude that high intracellular PKCK2 activity confers anoikis resistance on esophageal cancer cells by inducing E- to N-cadherin switching.

Anti-cAngptl4 Ab-conjugated N-TiO(2) /NaYF(4) :Yb,Tm nanocomposite for near infrared-triggered drug release and enhanced targeted cancer cell ablation

Nanomedicine: NIR-active N-TiO(2) /NaYF(4) :Yb,Tm nanocomposites (NCs) were synthesized for the first time and its potential applications in drug release and targeted cancer cell ablation are explored. Upon 980 nm laser irradiation, the anti-cAngptl4 Ab-conjugated N-TiO(2) /NaYF(4) :Yb,Tm NCs shows a significant increase in apoptotic A-5RT3 cells when compared with that of the unconjugated NCs. The mechanisms for NIR-induced photocatalysis, drug release and targeted cancer cell killing are proposed.

Angptl4 maintains in vivo repopulation capacity of CD34+ human cord blood cells

OBJECTIVES

Methods to expand hematopoietic stem cells (HSCs) ex vivo encompass an attractive approach that would substantially broaden the clinical applicability of HSCs derived from cord blood (CB). Recently, members of the angiopoietin-like (Angptl) family of growth factors were shown to expand both murine and human HSCs. Specifically, Angptl5 has been implicated in the expansion of human NOD/SCID-repopulating cells (SRCs) ex vivo. Here, we sought to evaluate the potential of additional Angptls to expand human SRCs from CB. Additionally, the purpose of this study was to evaluate the reproducibility of Angptl-mediated expansion of SRCs across independent experiments.

METHODS

Human CD34(+) cells from CB were cultured in vitro for eleven or 8 d in the presence or absence of Angptls. The reconstitution capacity of expanded cells was subsequently measured in vivo by transplantation into NOD/SCID or NSG mice and compared with that of uncultured cells.

RESULTS

We report here that Angptl4 functions to maintain SRC activity of CD34(+) CB-derived cells ex vivo as assayed in NOD/SCID and NSG mice. However, all Angptls tested, including Angptl1, Angptl4, and Angptl5, were associated with variation between experiments.

CONCLUSION

Our findings indicate that Angptl4 and Angptl5 can lead to increased engraftment capacity of SRCs, but more frequently, these factors are associated with maintenance of SRC activity during ex vivo culture. Thus, Angptl-mediated expansion of SRCs ex vivo is associated with more interexperimental variation than previously thought. We conclude that Angptls would be useful in instances where there is a need to maintain HSCs ex vivo, such as during transduction for gene therapy applications.

NADPH oxidases as regulators of tumor angiogenesis: current and emerging concepts

SIGNIFICANCE

Reactive oxygen species (ROS) such as superoxide, hydrogen peroxide, and peroxynitrite are generated ubiquitously by all mammalian cells and have been understood for many decades as inflicting cell damage and as causing cancer by oxidation and nitration of macromolecules, including DNA, RNA, proteins, and lipids.

RECENT ADVANCES

A current concept suggests that ROS can also promote cell signaling pathways triggered by growth factors and transcription factors that ultimately regulate cell proliferation, differentiation, and apoptosis, all of which are important hallmarks of tumor cell proliferation and angiogenesis. Moreover, an emerging concept indicates that ROS regulate the functions of immune cells that infiltrate the tumor environment and stimulate angiogenesis, such as macrophages and specific regulatory T cells.

CRITICAL ISSUES

In this article, we highlight that the NADPH oxidase family of ROS-generating enzymes are the key sources of ROS and, thus, play an important role in redox signaling within tumor, endothelial, and immune cells thereby promoting tumor angiogenesis.

FUTURE DIRECTIONS

Knowledge of these intricate ROS signaling pathways and identification of the culprit NADPH oxidases is likely to reveal novel therapeutic opportunities to prevent angiogenesis that occurs during cancer and which is responsible for the revascularization after current antiangiogenic treatment.

EMT and oxidative stress: a bidirectional interplay affecting tumor malignancy

SIGNIFICANCE

Epithelial-mesenchymal transition (EMT) is emerging as a driving force in tumor progression, enabling cancer cells to evade their "homeland" and to colonize remote locations. In this review, we focus on the emerging views dealing with a redox control of EMT and with the importance of a pro-oxidant environment, both in cancer and stromal cells, to attain an improvement in tumor malignancy.

RECENT ADVANCES

The variety of signals able to promote EMT is large and continuously growing, ranging from soluble factors to components of the extracellular matrix. Compelling evidence highlights reactive oxygen species (ROS) as crucial conspirators in EMT engagement.

CRITICAL ISSUES

Tumor microenvironment exploits a fascinating role in ensuring EMT outcome within the primary tumor, granting for the achievement of an essential selective advantage for cancer cells. Cancer-associated fibroblasts, macrophages, and hypoxia are major players in this scenario, exerting a propelling role for EMT, as well as for invasiveness, stemness, and dissemination of metastatic cells.

FUTURE DIRECTIONS

Future research focused on EMT should address some key points that are still unclear. They include: i) the role of the reverse phenomenon (i.e., mesenchymal-epithelial transition) that is likely regulated in the final stages of tumor progression, or that of mesenchymal-amoeboid transition, a plasticity program of cancer cells, which often follows EMT and offers a further metastatic advantage, and ii) the molecular basis of the correlation between stemness, EMT and ROS content.

Emerging roles of angiopoietin-like 4 in human cancer

Angiopoietin-like 4 (ANGPTL4) is best known for its role as an adipokine involved in the regulation of lipid and glucose metabolism. The characterization of ANGPTL4 as an adipokine is largely due to our limited understanding of the interaction partners of ANGPTL4 and how ANGPTL4 initiates intracellular signaling. Recent findings have revealed a critical role for ANGPTL4 in cancer growth and progression, anoikis resistance, altered redox regulation, angiogenesis, and metastasis. Emerging evidence suggests that ANGPTL4 function may be drastically altered depending on the proteolytic processing and posttranslational modifications of ANGPTL4, which may clarify several conflicting roles of ANGPTL4 in different cancers. Although the N-terminal coiled-coil region of ANGPTL4 has been largely responsible for the endocrine regulatory role in lipid metabolism, insulin sensitivity, and glucose homeostasis, it has now emerged that the COOH-terminal fibrinogen-like domain of ANGPTL4 may be a key regulator in the multifaceted signaling during cancer development. New insights into the mechanistic action of this functional domain have opened a new chapter into the possible clinical application of ANGPTL4 as a promising candidate for clinical intervention in the fight against cancer. This review summarizes our current understanding of ANGPTL4 in cancer and highlights areas that warrant further investigation. A better understanding of the underlying cellular and molecular mechanisms of ANGPTL4 will reveal novel insights into other aspects of tumorigenesis and the potential therapeutic value of ANGPTL4.

Oxidative stress, tumor microenvironment, and metabolic reprogramming: a diabolic liaison

Conversely to normal cells, where deregulated oxidative stress drives the activation of death pathways, malignant cells exploit oxidative milieu for its advantage. Cancer cells are located in a very complex microenvironment together with stromal components that participate to enhance oxidative stress to promote tumor progression. Indeed, convincing experimental and clinical evidence underline the key role of oxidative stress in several tumor aspects thus affecting several characteristics of cancer cells. Oxidants influence the DNA mutational potential, intracellular signaling pathways controlling cell proliferation and survival and cell motility and invasiveness as well as control the reactivity of stromal components that is fundamental for cancer development and dissemination, inflammation, tissue repair, and de novo angiogenesis. This paper is focused on the role of oxidant species in the acquisition of two mandatory features for aggressive neoplastic cells, recently defined by Hanahan and Weinberg as new “hallmarks of cancer”: tumor microenvironment and metabolic reprogramming of cancer cells.

Binding of carbon nanotube to BMP receptor 2 enhances cell differentiation and inhibits apoptosis via regulating bHLH transcription factors

Biomaterials that can drive stem cells to an appropriate differentiation level and decrease apoptosis of transplanted cells are needed in regenerative medicine. Nanomaterials are promising novel materials for such applications. Here we reported that carboxylated multiwalled carbon nanotube (MWCNT 1) promotes myogenic differentiation of mouse myoblast cells and inhibits cell apoptosis under the differentiation conditions by regulating basic helix-loop-helix transcription factors. MWCNT 1 attenuates bone morphogenetic protein receptor (BMPR) signaling activity by binding to BMPR2 and attenuating the phosphorylation of BMPR1. This molecular understanding allowed us to tune stem cell differentiation to various levels by chemical modifications, demonstrating human control of biological activities of nanoparticles and opening an avenue for potential applications of nanomaterials in regenerative medicine.

Intronic cis-regulatory modules mediate tissue-specific and microbial control of angptl4/fiaf transcription

The intestinal microbiota enhances dietary energy harvest leading to increased fat storage in adipose tissues. This effect is caused in part by the microbial suppression of intestinal epithelial expression of a circulating inhibitor of lipoprotein lipase called Angiopoietin-like 4 (Angptl4/Fiaf). To define the cis-regulatory mechanisms underlying intestine-specific and microbial control of Angptl4 transcription, we utilized the zebrafish system in which host regulatory DNA can be rapidly analyzed in a live, transparent, and gnotobiotic vertebrate. We found that zebrafish angptl4 is transcribed in multiple tissues including the liver, pancreatic islet, and intestinal epithelium, which is similar to its mammalian homologs. Zebrafish angptl4 is also specifically suppressed in the intestinal epithelium upon colonization with a microbiota. In vivo transgenic reporter assays identified discrete tissue-specific regulatory modules within angptl4 intron 3 sufficient to drive expression in the liver, pancreatic islet β-cells, or intestinal enterocytes. Comparative sequence analyses and heterologous functional assays of angptl4 intron 3 sequences from 12 teleost fish species revealed differential evolution of the islet and intestinal regulatory modules. High-resolution functional mapping and site-directed mutagenesis defined the minimal set of regulatory sequences required for intestinal activity. Strikingly, the microbiota suppressed the transcriptional activity of the intestine-specific regulatory module similar to the endogenous angptl4 gene. These results suggest that the microbiota might regulate host intestinal Angptl4 protein expression and peripheral fat storage by suppressing the activity of an intestine-specific transcriptional enhancer. This study provides a useful paradigm for understanding how microbial signals interact with tissue-specific regulatory networks to control the activity and evolution of host gene transcription.

Histone H3 lysine 56 methylation regulates DNA replication through its interaction with PCNA

Histone modifications play important roles in regulating DNA-based biological processes. Of the modified sites, histone H3 lysine 56 (H3K56) is unique in that it lies within the globular core domain near the entry-exit sites of the nucleosomal DNA superhelix and its acetylation state in yeast is a marker for newly synthesized histones in transcription, DNA repair, and DNA replication. We now report the presence of H3K56 monomethylation (H3K56me1) in mammalian cells and find that the histone lysine methytransferase G9a/KMT1C is required for H3K56me1 both in vivo and in vitro. We also find that disruption of G9a or H3K56 impairs DNA replication. Furthermore, H3K56me1 associates with the replication processivity factor PCNA primarily in G1 phase of the cell cycle and, directly, in vitro. These results find H3K56me1 in mammals and indicate a role for H3K56me1 as a chromatin docking site for PCNA prior to its function in DNA replication.

Anoikis resistance: an essential prerequisite for tumor metastasis

Metastasis is a multistep process including dissociation of cancer cells from primary sites, survival in the vascular system, and proliferation in distant target organs. As a barrier to metastasis, cells normally undergo an apoptotic process known as “anoikis,” a form of cell death due to loss of contact with the extracellular matrix or neighboring cells. Cancer cells acquire anoikis resistance to survive after detachment from the primary sites and travel through the circulatory and lymphatic systems to disseminate throughout the body. Because recent technological advances enable us to detect rare circulating tumor cells, which are anoikis resistant, currently, anoikis resistance becomes a hot topic in cancer research. Detailed molecular and functional analyses of anoikis resistant cells may provide insight into the biology of cancer metastasis and identify novel therapeutic targets for prevention of cancer dissemination. This paper comprehensively describes recent investigations of the molecular and cellular mechanisms underlying anoikis and anoikis resistance in relation to intrinsic and extrinsic death signaling, epithelial-mesenchymal transition, growth factor receptors, energy metabolism, reactive oxygen species, membrane microdomains, and lipid rafts.

Angiopoietin-like gene expression in the mouse uterus during implantation and in response to steroids

The purpose of this work was to determine if and where Angiopoietin-like genes are expressed in the mouse uterus during the implantation period of pregnancy and to determine if uterine expression of such genes is controlled by estrogen or progesterone. We found that all six known murine angiopoietin-like genes were expressed in the mouse uterus during implantation. The expression of four genes was controlled by either estrogen or progesterone. Only the levels of angiopoietin-like 4 (Angptl4) mRNA dramatically increased in implantation segments of the uterus during decidualization and was conceptus-independent. Due to this increased expression and the fact that angiopoietin-like 4 protein plays a role in lipid metabolism and angiogenesis in other tissues, only the expression of Angptl4 was further examined in the uterus and developing placenta. Angptl4 mRNA was localized to subpopulations of the endometrial stromal fibroblast and endothelial cell populations during decidualization. It was also localized to the ectoplacental cone, trophoblast giant cells and parietal endoderm of the conceptus at this time. By mid-pregnancy, Angptl4 mRNA was localized mainly to the mesometrial lymphoid aggregate region plus mesometrial endothelial cells of the uterus, as well as in various cell types of the conceptus. Additional work showed that Angptl4 expression increases in mouse endometrial stromal cells as they undergo decidualization in vitro. As in other cell types, the expression of Angptl4 in endometrial stromal cells was increased in response to an agonist of the peroxisome proliferator activated receptors. Taken together, the results of this work support the hypothesis that locally expressed Angptl4 might play a role in local uterine/placental lipid metabolism and vascular changes during implantation and thus provide a basis for future research.

Matricellular proteins: a sticky affair with cancers

The multistep process of metastasis is a major hallmark of cancer progression involving the cointeraction and coevolution of the tumor and its microenvironment. In the tumor microenvironment, tumor cells and the surrounding stromal cells aberrantly secrete matricellular proteins, which are a family of nonstructural proteins in the extracellular matrix (ECM) that exert regulatory roles via a variety of molecular mechanisms. Matricellular proteins provide signals that support tumorigenic activities characteristic of the metastastic cascade such as epithelial-to-mesenchymal (EMT) transition, angiogenesis, tumor cell motility, proliferation, invasion, evasion from immune surveillance, and survival of anoikis. Herein, we review the current understanding of the following matricellular proteins and highlight their pivotal and multifacted roles in metastatic progression: angiopoietin-like protein 4 (ANGPTL4), CCN family members cysteine-rich angiogenic inducer 61 (Cyr61/CCN1) and CCN6, osteopontin (OPN), secreted protein acidic and rich in cysteine (SPARC), tenascin C (TNC), and thrombospondin-1 and -2 (TSP1, TSP2). Insights into the signaling mechanisms resulting from the interaction of these matricellular proteins and their respective molecular partner(s), as well as their subsequent contribution to tumor metastasis, are discussed. In addition, emerging evidences of their promising potential as therapeutic options and/or targets in the treatment of cancer are also highlighted.