Human Angiopoietin-1 Research Articles

Angiopoietin-2 and the Vascular Endothelial Growth Factor Promote Migration and Invasion in Hepatocellular Carcinoma- and Intrahepatic Cholangiocarcinoma-Derived Spheroids.

Aggressive hepatocellular carcinoma (HCC) overexpressing Angiopoietin-2 (ANG-2) (a protein linked with angiogenesis, proliferation, and epithelial-mesenchymal transition (EMT)), shares 95% of up-regulated genes and a similar poor prognosis with the proliferative subgroup of intrahepatic cholangiocarcinoma (iCCA). We analyzed the pro-invasive effect of ANG-2 and its regulator vascular endothelial growth factor (VEGF) on HCC and CCA spheroids to uncover posUsible common ways of response. Four cell lines were used: Hep3B and HepG2 (HCC), HuCC-T1 (iCCA), and EGI-1 (extrahepatic CCA). We treated the spheroids with recombinant human (rh) ANG-2 and/or VEGF and then observed the changes at the baseline, after 24 h, and again after 48 h. Proangiogenic stimuli increased migration and invasion capability in HCC- and iCCA-derived spheroids and were associated with a modification in EMT phenotypic markers (a decrease in E-cadherin and an increase in N-cadherin and Vimentin), especially at the migration front. Inhibitors targeting ANG-2 (Trebananib) and the VEGF (Bevacizumab) effectively blocked the migration ability of spheroids that had been stimulated with rh-ANG-2 and rh-VEGF. Overall, our findings highlight the critical role played by ANG-2 and the VEGF in enhancing the ability of HCC- and iCCA-derived spheroids to migrate and invade, which are key processes in cancer progression.

Stem Cell Secretome Modulated by Arsenicum album 30C Ameliorates Lipopolysaccharide-induced Cytokine Storm in Blood Mononuclear Cells in vitro.

The therapeutic effectiveness of mesenchymal stem cells (MSCs) and their secretome can be enhanced by means of physical, chemical and biological preconditioning. Arsenicum album 30C (AA30) has been one of the leading homeopathic medicines used in prophylaxis against SARS-CoV-2 infection. This study aimed to investigate whether AA30 preconditioning could influence the growth factors and cytokine profile of the human dental pulp-derived MSC (DPD-MSC) secretome. Also, to test the efficacy of the AA30-preconditioned DPD-MSC secretome in ameliorating the lipopolysaccharide (LPS)-induced cytokine storm in human peripheral blood mononuclear cells (PBMCs) as an in-vitro cellular model. The cytotoxicity of AA30 was assessed in DPD-MSCs by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Growth factors and cytokine levels in the AA30-preconditioned DPD-MSC secretome were analysed by fluorescence-activated cell sorting (FACS) analysis. The angiogenic potential of the AA30-preconditioned DPD-MSC secretome was assessed by chick yolk-sac membrane (YSM) assay. Culture medium with 0.001% ethanol was used as vehicle control. The efficacy of the AA30-preconditioned DPD-MSC secretome in ameliorating the cytokine storm was assessed in LPS pre-treated PBMCs. The mRNA and protein expression of inflammatory markers such as IL-1β, IL-6 and IL-10 were analysed by using RT-PCR and FACS analysis respectively. AA30 did not exhibit cytotoxicity in the concentration range of 1% to 50%. Furthermore, the AA30-preconditioned DPD-MSC secretome exhibited a significant increase in the levels of angiogenic factors, such as human angiopoietin-2, EPO and PDGF-AA, and decreased levels of cytokines, such as TNF-α, CXCL-8 and IL-6. The AA30-preconditioned DPD-MSC secretome showed augmented angiogenesis compared to vehicle controls. The DPD-MSC secretome ameliorated LPS-induced mRNA and protein expression of IL-1β, IL-6 and IL-10 in PBMCs. The AA30-preconditioned DPD-MSC secretome augmented angiogenesis and ameliorated the LPS-induced cytokine storm in human PBMCs in vitro. Our data demonstrate that AA30 preconditioning enhances the therapeutic potency of MSCs and their secretome.

Intracellular angiopoietin-1 promotes TKI-resistance via activation of JAK/STAT5 pathway in chronic myeloid leukemia.

Drug resistance from BCR-ABL tyrosine kinase inhibitors (TKIs) and other chemotherapeutics results in treatment failure and disease progression in chronic myeloid leukemia (CML). However, the mechanism is still uncertain. In this study, we investigated the role of angiopoietin-1 (ANG-1) as a potential prognostic factor for drug resistance in CML. Both intracellular and secretory ANG-1 (iANG-1 and sANG-1) were overexpressed in multidrug-resistant CML samples. The IC50 value was higher in primary CD34+ CD38- cells with more ANG-1. Silencing ANG-1significantly sensitized three TKI-resistant CML cell lines to imatinib (IM) while recombinant human ANG-1 failed to retain cell survival in vitro. This indicated the important role of iANG-1 as opposed to sANG-1 in CML drug resistance. Moreover, a similar effect was observed in xenograft mice models bearing ANG-1-silenced CML cells. Subsequently, pathway analysis and protein validation experiments showed activation of the JAK/STAT pathway and augmentation of STAT5a phosphorylation in ANG-1 restored CML cells. Upstream Src phosphorylation, which plays a crucial role in CML drug resistance, was also upregulated as a key event in iANG-1-related JAK/STAT pathway activation. In conclusion, our study elucidated a new BCR-ABL independent molecular mechanism induced by intracytoplasmic ANG-1 overexpression as a potential strategy for overcoming CML resistance.

Pharmacodynamic and Antitumor Activity of BI 836880, a Dual VEGF and Angiopoietin 2 Inhibitor, Alone and Combined with Programmed Cell Death Protein-1 Inhibition.

VEGF and angiopoietin-2 (ANG2) have complementary roles in angiogenesis and promote an immunosuppressive tumor microenvironment. It is anticipated that combination of VEGF and ANG2 blockade could provide superior activity to blockade of either pathway alone, and that addition of VEGF/ANG2 inhibition to an anti-programmed cell death protein-1 (PD-1) antibody could change the tumor microenvironment to support T-cell-mediated tumor cytotoxicity. Here, we describe the pharmacologic and antitumor activity of BI 836880, a humanized bispecific nanobodyTM comprising two single variable domains blocking VEGF and ANG2, and an additional module for half-life extension in vivo BI 836880 demonstrated high affinity and selectivity for human VEGF-A and ANG2, resulting in inhibition of downstream signaling of VEGF/ANG2 and a decrease in endothelial cell proliferation and survival. In vivo, BI 836880 exhibited significant antitumor activity in all patient-derived xenograft models tested, showing significantly greater tumor growth inhibition (TGI) than bevacizumab (VEGF inhibition) and AMG386 (ANG1/2 inhibition) in a range of models. In a Lewis lung carcinoma syngeneic tumor model, combination of PD-1 inhibition with VEGF inhibition showed superior efficacy versus blockade of either pathway alone. TGI was further increased with addition of ANG2 inhibition to VEGF/PD-1 blockade. VEGF/ANG2 inhibition had a strong anti-angiogenic effect. Our data suggest that blockade of VEGF and ANG2 with BI 836880 may offer improved antitumor activity versus blockade of either pathway alone and that combining VEGF/ANG2 inhibition with PD-1 blockade can further enhance antitumor effects. Significance Statement VEGF and ANG2 play key roles in angiogenesis and have an immunosuppressive effect in the tumor microenvironment. Here, we show that BI 836880, a bispecific nanobodyTM targeting VEGF and ANG2, demonstrates substantial antitumor activity in preclinical models. Combining VEGF/ANG2 inhibition with blockade of the PD-1 pathway can further improve antitumor activity.

Angiopoietin-2 inhibition attenuates kidney fibrosis by hindering chemokine C-C motif ligand 2 expression and apoptosis of endothelial cells

Plasma levels of angiopoietin-2 are increased in patients with chronic kidney disease (CKD). Moreover, mouse models of progressive kidney disease also demonstrate increased angiopoietin-2 in both plasmas and kidneys. The role of dysregulated angiopoietins in the progression of kidney disease has not been thoroughly investigated. Here, we found in a cohort of 319 patients with CKD that plasma angiopoietin-2 and angiopoietin-2/angiopoietin-1 ratios were positively associated with the development of kidney failure. In mice with progressive kidney disease induced by either ureteral obstruction or ischemia-reperfusion injury, overexpression of human angiopoietin-1 in the kidney tubules not only reduced macrophage infiltration in the initial stage post-injury but also attenuated endothelial cell apoptosis, microvascular rarefaction, and fibrosis in the advanced disease stage. Notably, angiopoietin-1 attenuated chemokine C-C motif ligand 2 (CCL2) expression in the endothelial cells of the fibrosing kidneys, and these protective effects led to attenuation of functional impairment. Mechanistically, angiopoietin-1 reduced CCL2-activated macrophage migration and protected endothelial cells against cell apoptosis induced by angiopoietin-2 and Wnt ligands. Based on this, we applied L1-10, an angiopoietin-2 inhibitor, to the mouse models of progressive kidney disease and found inhibitory effects on macrophage infiltration, microvascular rarefaction, and fibrosis. Thus, we defined the detrimental impact of increased angiopoietin-2 on kidney survival of patients with CKD which appears highlighted by angiopoietin-2 induced endothelial CCL2-activated macrophage infiltration and endothelial cell apoptosis in their kidneys undergoing fibrosis.

Combining CTLA-4 and angiopoietin-2 blockade in patients with advanced melanoma: a phase I trial

BackgroundAngiogenic factors promote the growth of tumor vasculature, modulate lymphocyte trafficking into tumors, and inhibit maturation of dendritic cells. We hypothesized that MEDI3617, a human IgG1 kappa monoclonal antibody directed...

Validation of a human angiopoietin-2 ELISA for measurement of angiopoietin-2 concentrations in canine plasma samples and supernatant of primary canine aortic endothelial cell cultures.

OBJECTIVE To assess 2 human ELISA kits for measurement of angiopoietin-1 and -2 concentrations in canine plasma samples, determine whether plasma angiopoeitin-2 concentration differed between septic and healthy dogs, and determine the effect of tumor necrosis factor-α (TNF-α) stimulation on angiopoeitin-2 release from primary canine aortic endothelial cells (pCAECs) in vitro. ANIMALS 10 healthy dogs and 10 septic dogs. PROCEDURES Human angiopoietin-1 and -2 ELISAs were used to detect recombinant canine angiopoietins-1 and -2 in canine plasma samples. The angiopoietin-2 ELISA was further validated by use of plasma samples from healthy and septic dogs and supernatants of pCAEC cultures. Associations between plasma angiopoeitin-2 and C-reactive protein (CRP) concentrations were examined. RESULTS Angiopoeitin-2 but not angiopoeitin-1 was detected in canine plasma samples by the respective ELISAs. The angiopoeitin-2 ELISA had excellent dilutional linearity, parallelism, accuracy, precision, and reproducibility for measurements in canine plasma samples and pCAEC supernatants. Plasma angiopoeitin-2 concentration was significantly higher in septic dogs (median, 25.5 ng/mL) than in healthy dogs (median, 6.7 ng/mL) and was positively correlated with plasma CRP concentration (R2 = 0.60). Stimulation of pCAECs with TNF-α resulted in a significant increase in supernatant angiopoietin-2 concentration. CONCLUSIONS AND CLINICAL RELEVANCE The tested human angiopoietin-2 ELISA kit was useful for measuring angiopoietin-2 concentrations in canine plasma samples and pCAEC supernatants. Sepsis appeared to increase angiopoietin-2 concentration in dogs in vivo, whereas TNF-α stimulation caused release of angiopoietin-2 from pCAECs in vitro. These findings support the use of angiopoietin-2 as a marker of endothelial cell activation and inflammation in dogs.

Angiopoietin-1 and angiopoietin-2 protect porcine iliac endothelial cells from human antibody-mediated complement-dependent cytotoxicity through phosphatidylinositide 3-kinase/AKT pathway activation.

Cytokines play crucial roles in inflammation, but their role in xenotransplantation remains elusive. We assessed the role of several cytokines using an in vitro model of human antibody-mediated complement-dependent cytotoxicity (CDC). Recombinant human angiopoietin-1 (Ang-1) protected porcine iliac endothelial cells (PIECs) from human antibody-mediated CDC. Interestingly, human angiopoietin-2 (Ang-2) had a similar protective effect on PIECs. By flow cytometry analysis, the extent of human IgM and IgG binding to PIECs did not decrease when PIECs were exposed to Ang-1/Ang-2. The mRNA level of complement regulators (CD46, CD55, CD59) was not upregulated in PIECs treated with Ang-1/Ang-2, both of which activated the PI3K/AKT pathway in PIECs. Wortmannin, which inhibits phosphatidylinositide 3-kinase (PI3K), suppressed Ang-1/Ang-2-induced AKT phosphorylation and consequent Ang-1/Ang-2-mediated protection of PIECs in human antibody-mediated CDC model. Moreover, dominant negative AKT also suppressed Ang-1/Ang-2-mediated protection of PIECs in this model. In conclusion, our data suggest that human Ang-1/Ang-2 induces the protection of PIECs from human antibody-mediated CDC by activating the PI3K/AKT pathway. Ang-1/Ang-2 is likely to protect porcine endothelial cells and may be beneficial in xenotransplantation research.

Abstract B18: Estrogen deficiency causes reawakening of dormant disseminated breast cancer cells via angiopoietin-1/Tie2 signaling

Abstract Introduction: Compared to premenopausal women, postmenopausal women with breast cancer are at increased risks of bone metastasis. When cancer cells migrate into bone marrow (BM), they stay dormant in stable microvasculature but proliferate in unstable microvasculature. Angiopoietin-1(ANGPT1)/Tie2 signaling regulates microvascular stability. ANGPT-1 stabilizes microvasculature, while ANGPT-2 destabilizes it and promotes neovascularization. We hypothesized that postmenopausal estrogen deficiency induces reawakening of the dormant tumor cells in BM through modulation of angiogenesis. We examined the effects of estrogen depletion on the proliferative status of breast cancer cells (BCCs) in a BM microvasculature model, and quantified the changes of ANGPT1 and ANGPT2 expressions in the model before and after estrogen depletion. Materials and Methods: Bone marrow microvasculature model was generated by using bone marrow mesenchymal stem cells (MSCs) and endothelial cells (ECs). To deplete estrogen in the model, charcoal-stripped serum-containing culture medium with or without 17β-estradiol (E2) were used. ANGPT1 and ANGPT2 protein levels in the model were determined by western blot. Estrogen receptor(ER)-positive MCF-7 and ER-negative MDA-MB-231 breast cancer cell lines were used. Fluorescence-tagged tumor cells were seeded in the BM microvasculature models with or without estrogen and their proliferation were monitored by microscope and microscope fluorescence reader. Recombinant human ANGPT1 (RhANGPT1) and Tie2-specific blocking antibody were used for ANGPT1/Tie2 signaling modulation. Results: ANGPT2 expression was significantly increased in BM microvasculature model exposed to prolonged estrogen depletion. ANGPT1 expression was not changed. BCCs in the estrogen-depleted BM microvasculature model grew significantly faster than those in the model supplemented with E2. Blocking ANGPT1/Tie2 signaling in the model by Tie2-specific blocking antibody enhanced BCC proliferation in presence of estrogen, whereas RhANGPT1-treatment inhibited BCC proliferation in estrogen-depleted BM microvasculature model. In further, RhANGPT1 protected BCCs from doxorubicin-induced apoptosis. RhANGPT1 inhibited proliferation of Tie2-expressing MDA-MB-231 cells in absence of BM MSCs or ECs, suggesting direct interaction of ANGPT1 and Tie2-expressing tumor cells. Conclusions: With in vitro disseminated breast cancer cell model, we confirmed that estrogen deficiency modified bone marrow microvasculature to more metastasis-prone environment. We identified the ANGPT1/Tie2 signaling as a key regulator of angiogenic tumor cell dormancy. The results suggest that postmenopausal estrogen deficiency may lead to reawakening of dormant BCCs by altering ANGPT1 and ANGPT2 levels in BM microvasculature. Angiogenic dormancy in association with estrogen implies a new strategy against metastatic recurrence in postmenopausal women with remote breast cancer history. Citation Format: Hyun Ho Han, Nam Hoon Cho, Suki Kang, Joo Hyun Lee, Ji Eun Kim. Estrogen deficiency causes reawakening of dormant disseminated breast cancer cells via angiopoietin-1/Tie2 signaling. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Angiogenesis and Vascular Normalization: Bench to Bedside to Biomarkers; Mar 5-8, 2015; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl):Abstract nr B18.

Array-based discovery of aptamer pairs.

Affinity reagent pairs that recognize distinct epitopes on a target protein can greatly improve the sensitivity and specificity of molecular detection. Importantly, such pairs can be conjugated to generate reagents that achieve two-site “bidentate” target recognition, with affinities greatly exceeding either monovalent component. DNA aptamers are especially well-suited for such constructs, because they can be linked via standard synthesis techniques without requiring chemical conjugation. Unfortunately, aptamer pairs are difficult to generate, primarily because conventional selection methods preferentially yield aptamers that recognize a dominant “hot spot” epitope. Our array-based discovery platform for multivalent aptamers (AD-MAP) overcomes this problem to achieve efficient discovery of aptamer pairs. We use microfluidic selection and high-throughput sequencing to obtain an enriched pool of aptamer sequences. Next, we synthesize a custom array based on these sequences, and perform parallel affinity measurements to identify the highest-affinity aptamer for the target protein. We use this aptamer to form complexes that block the primary binding site on the target, and then screen the same array with these complexes to identify aptamers that bind secondary epitopes. We used AD-MAP to discover DNA aptamer pairs that bind distinct sites on human angiopoietin-2 with high affinities, even in undiluted serum. To the best of our knowledge, this is the first work to discover new aptamer pairs using arrays. We subsequently conjugated these aptamers with a flexible linker to construct ultra-high-affinity bidentate reagents, with equilibrium dissociation constants as low as 97 pM: >200-fold better than either component aptamer. Functional studies confirm that both aptamers critically contribute to this ultrahigh affinity, highlighting the promise of such reagents for research and clinical use.

Cellular Reporter Systems for High-Throughput Screening of Interactions Between Bioactive Matrices and Human Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSC) and factors secreted by them are essential components of the hematopoietic stem cell (HSC) niche within the bone marrow microenvironment. It has been shown that the extracellular matrix (ECM) can influence HSC-supportive potential of MSC and is a prerequisite for the proper signaling of morphogens. Therefore, we aimed at the identification of ECM components and candidate morphogens capable of enhancing the expression of HSC-supportive proteins in human MSC, namely, angiopoietin-1 (Ang-1) and stromal cell-derived factor 1 (SDF-1). For this purpose, highly sensitive secreted dual reporter constructs for Ang-1 and SDF-1 were established. These newly designed dual reporter systems enable continuous monitoring of the Ang-1 and SDF-1 promoter activity in an immortalized human MSC line cultured on ECM/morphogen microarrays. Reporter arrays showed that Ang-1 and SDF-1 expression can be induced by different ECM/morphogen combinations. In addition, continuous monitoring of promoter activity allows delineating time-dependent effects of the ECM and morphogens. Thus, we identified that collagen I and vitronectin in combination with Wnt3a favored SDF-1 expression over time, while only transiently inducing the expression of Ang-1. Taken together, the newly developed reporter systems allow for the monitoring of Ang-1 and SDF-1 promoter activity induced by morphogens and the ECM in a combinatorial and high-throughput manner. This technology might therefore be helpful to optimize culture conditions, which favor the activity of MSC as feeder cells for various types of stem and progenitor cells.

Ectopic expression of human angiopoietin-1 promotes functional recovery and neurogenesis after focal cerebral ischemia

Neuropathologic processes such as cerebral ischemia can enhance neurogenesis. Angiopoietin-1 (Ang1) emerges as a critical regulator of physiological and pathological angiogenesis during embryonic and postnatal life. Although Ang1 could protect peripheral vasculature from vascular leakage following ischemic injury, the role of Ang1 in long-term neurological recovery after ischemic stroke remains elusive. This study aims to examine whether Ang1 overexpression via lentivirus-mediated gene transfer enhances neurovascular remodeling and improves functional outcome in a rat model of focal cerebral ischemia. Our results demonstrated that lentivirus-mediated Ang1 gene transfer led to improved neurological behavior and reduced infarction volume, and protected against blood–brain barrier (BBB) leakage in the ischemic rats. In addition, we revealed that these effects of Ang1 are related to the ability of Ang1 to increase vascular density and accelerate endogenous neuronal differentiation. These findings suggest that Ang1 is a promising agent for the treatment of cerebral ischemia.

Angiopoietin-2–Induced Arterial Stiffness in CKD

The mechanism of vascular calcification in CKD is not understood fully, but may involve collagen deposition in the arterial wall upon osteo/chondrocytic transformation of vascular smooth muscle cells (VSMCs). Increased levels of circulating angiopoietin-2 correlate with markers of CKD progression and angiopoietin-2 regulate inflammatory responses, including intercellular and vascular adhesion and recruitment of VSMCs. Here, we investigate the potential role of angiopoietin-2 in the pathogenesis of arterial stiffness associated with CKD. In a cohort of 416 patients with CKD, the plasma level of angiopoietin-2 correlated independently with the severity of arterial stiffness assessed by pulse wave velocity. In mice subjected to 5/6 subtotal nephrectomy or unilateral ureteral obstruction, plasma levels of angiopoietin-2 also increased. Angiopoietin-2 expression markedly increased in tubular epithelial cells of fibrotic kidneys but decreased in other tissues, including aorta and lung, after 5/6 subtotal nephrectomy. Expression of collagen and profibrotic genes in aortic VSMCs increased in mice after 5/6 subtotal nephrectomy and in mice producing human angiopoietin-2. Angiopoietin-2 stimulated endothelial expression of chemokines and adhesion molecules for monocytes, increased Ly6C(low) macrophages in aorta, and increased the expression of the profibrotic cytokine TGF-β1 in aortic endothelial cells and Ly6C(low) macrophages. Angiopoietin-2 blockade attenuated expression of monocyte chemokines, profibrotic cytokines, and collagen in aorta of mice after 5/6 subtotal nephrectomy. This study identifies angiopoietin-2 as a link between kidney fibrosis and arterial stiffness. Targeting angiopoietin-2 to attenuate inflammation and collagen expression may provide a novel therapy for cardiovascular disease in CKD.

A phase Ib study of combined angiogenesis blockade with REGN910 (SAR307746), a selective monoclonal antibody (MAb) against angiopoietin-2 (Ang2) and ziv-aflibercept in patients with advanced solid tumor malignancies.

TPS2618 Background: REGN910 is a selective, fully human Angiopoietin-2 (ANG-2) MAb, which potently blocks signaling through the Tie2 receptor. Ziv-aflibercept (ZAFL) is a recombinant human fusion protein that acts as a decoy receptor for vascular endothelial growth factor (VEGF)-A, VEGF-B, and placental growth factor (PlGF), thereby preventing the interaction of these ligands with their receptors. In several mouse xenograft models, combination of the 2 anti-angiogenic compounds, REGN910 and ZAFL, demonstrated significantly enhanced tumor growth inhibition relative to either agent alone, suggesting that dual angiogenic blockade is worth exploring in cancer patients. Methods: This phase 1b study employs a standard 3+3 dose escalation design exploring 5 different combination treatment dose levels of REGN910 and ZAFL. Once the recommended phase 2 dose (RD) of the combination treatment is determined, additional patients will be enrolled in a safety expansion cohort, for a planned total enrollment of up to 40 patients. The primary study objectives are to evaluate the safety and determine the RD of the 2 drugs in combination when both are administered IV every 2 weeks in patients with advanced solid tumors. Secondary endpoints include characterization of the PK and potential immunogenicity of REGN910 and ZAFL when given in combination, evaluation of correlative PD biomarkers related to REGN910 and ZAFL, and identification of antitumor activity. Enrollment to cohorts 1 and 2 has been completed without DLT. Enrollment to cohort 3 opened in December 2012. Updated enrollment status will be presented. Reference: ClinicalTrials.gov Identifier: NCT01688960. Clinical trial information: NCT01688960.

Abstract 2227: Aptamer selection for cancer markers: High-throughput, quantitative selection and characterization of nucleic acid aptamers for human angiopoietin-2.

Abstract Abstract Nucleic acid-based aptamers represent a promising class of affinity reagents, as they can be chemically synthesized and modified, undergo reversible folding and exhibit excellent stability. Thus, the identification of aptamers that bind to specific cancer markers may serve as a powerful tool for early diagnosis and treatments of cancers. Unfortunately, conventional methods of aptamer generation remain inherently low-throughput in nature, and there is a pressing need for alternative technologies that can generate high quality aptamers in a high-throughput and economical manner. Towards the goal of accelerating aptamer discovery, we have developed the Quantitative Parallel Aptamer Selection System (QPASS) - an integrated platform that combines microfluidic selection, next-generation sequencing and in situ-synthesized aptamer arrays for parallel binding measurements. As a model, we used QPASS to select aptamers that specifically bind to human angiopoietin-2, an important mediator of angiogenesis and a biomarker of colon, prostate and breast cancers; after microfluidic selection and sequencing, we fabricated a custom aptamer array containing 120,000 sequences representing the most enriched aptamer candidates. Using this array, we simultaneously obtained equilibrium dissociation constants (Kd) and binding specificity data for these candidate aptamers in a massively parallel manner. Furthermore, we show that our array can operate directly in undiluted serum, enabling rapid identification of aptamers that perform optimally in complex mixtures. By exploiting the scalability and commercial availability of high-throughput sequencing and nucleic acid arrays, the QPASS platform offers the capability to simultaneously analyze and characterize unprecedented numbers of aptamer candidates—either against a common cancer marker, or for screening in parallel against multiple different biomarkers. Citation Format: Minseon Cho, Seung Soo Oh, Jeff Nie, Ron Stewart, Michael Eisenstein, James Chambers, Jamey D. Marth, James A. Thomson, Tom H. Soh. Aptamer selection for cancer markers: High-throughput, quantitative selection and characterization of nucleic acid aptamers for human angiopoietin-2. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2227. doi:10.1158/1538-7445.AM2013-2227

Construction and identification of human Angiopoietin2 prokaryotic expression vector

Objective To construct the human Angiopoietin2 prokaryotic expression vector.Methods Complete Angiopoietin2 gene was cloned by reverse transcription-polymerase chain reaction (RTPCR) fromin vitro cultured human umbilical vein endothelial cells (HUVECs),then the gene was cloned into pET32a plasmid expression system,and ultimately Angiopoietin2 was stablely expressed in E.coli BL21.Angiopoietin2 protein was then purified and identified by condensate gel electrophoresis,SDS-PAGE and gene sequencing.Results The cloned Angiopoietin2 gene fragment from HUVECs was about 1.5 Kb,the Angiopoietin2 protein was expressed by pET32a plasmid expression system,and it was predicated about 70 kDa protein by SDS-PAGE.Conclusion The prokaryotic expression vector of Angiopoietin2 is successfully constructed by recombinant DNA techniques. Key words: Angiopoietin; Prokaryotic expression vector

Erratum to: Recombinant Human Angiopoietin-1 Ameliorates the Expressions of ZO-1, Occludin, VE-cadherin, and PKCα Signaling after Focal Cerebral Ischemia/Reperfusion in Rats

Erratum to: Recombinant Human Angiopoietin-1 Ameliorates the Expressions of ZO-1, Occludin, VE-cadherin, and PKCα Signaling after Focal Cerebral Ischemia/Reperfusion in Rats

Recombinant canstatin inhibits angiopoietin‐1‐induced angiogenesis and lymphangiogenesis

We describe the effect of recombinant canstatin, the NC1 domain of the α2 chain of Type IV collagen, on suppression of angiogenesis and lymphangiogenesis both in vitro and in vivo. Recombinant canstatin produced from stably transformed Drosophila S2 cells reduced the expression of angiopoietin-1 in hypoxia mimetic agent, CoCl(2) -treated CT-26 cells. Recombinant canstatin inhibited proliferation, tube formation and migration of human angiopoietin-1 (rhAngpt-1)-treated human umbilical vein endothelial cells (HUVEC) and lymphatic endothelial cells (LEC). Recombinant canstatin suppressed the expression of Tie-2 and vascular endothelial growth factor-3 (VEGFR-3) transcripts in rhAngpt-1-treated HUVEC and LEC, respectively. The inhibitory effect of recombinant canstatin on tumor growth was also investigated using a heterotopic CT-26 colon carcinoma animal (BALB/c mice) model. Recombinant canstatin reduced the final volume and weight of tumors, and blood and lymphatic vessel densities of tumors, which were evaluated by CD-31 and LYVE-1 immunostaining. Immunohistochemical analysis showed that recombinant canstatin dramatically reduced the expression of angiopoietin-1 in CT-26 colon carcinoma-induced tumor, but not the expression of VEGF-C. Tie-2 and VEGFR-3 expressions were also reduced in recombinant canstatin-treated tumors. These results indicate that recombinant canstatin has anti-tumoral activities against CT-26 colon carcinoma cells. Recombinant canstatin reduces the expression of angiopoietin-1 in hypoxia-induced CT-26 cells and inhibits the angiogenic and lymphangiogenic signaling induced by angiopoietin-1. Recombinant canstatin probably inhibits angiogenesis and lymphangiogenesis via suppression of the integrin-dependent FAK signaling induced by angiopoietin-1/Tie-2 and/or VEGFR-3.

Recombinant Human Angiopoietin-1 Ameliorates the Expressions of ZO-1, Occludin, VE-cadherin, and PKCα Signaling after Focal Cerebral Ischemia/Reperfusion in Rats

This study was performed to determine whether recombinant human angiopoietin-1 (Ang-1) decreases the permeability of the blood-brain barrier (BBB) in focal cerebral ischemia and reperfusion rats, whether Ang-1 opens the BBB by affecting tight junction associated proteins zonula occluden-1 (ZO-1), occludin and adherens junction protein vascular endothelial (VE)-cadherin, and whether the protein kinase C (PKC)α/myosin light chain (MLC) signaling pathway involves in it. The rats were divided into eight groups randomly: (1) sham-operated group, (2) ischemia group, (3-5) ischemia-reperfusion (middle cerebral artery occlusion and reperfusion (MCAO/R) 12 h, 48 h, and 7 days) and 0.9% saline groups, (6-8) ischemia-reperfusion (MCAO/R 12 h, 48 h, and 7 days) and Ang-1 groups. The BBB permeability was assessed by Evans blue extravasation. The messenger RNA and protein expressions of ZO-1, occludin, and VE-cadherin were determined by reverse transcription-polymerase chain reaction, western blot, and immunohistochemistry assays. The BBB permeability was significantly decreased after Ang-1 injection. The expressions of ZO-1, occludin, and VE-cadherin were increased after Ang-1 injection. These were in accordance with the results of immunohistochemistry assays. PKCα and phosphorylated MLC (p-MLC) expressions were decreased after Ang-1 injection. This study demonstrated that Ang-1 may decrease the permeability of BBB in MCAO/R rat by upregulation of ZO-1, occludin, and VE-cadherin. The decreased expressions of PKCα and p-MLC induced by Ang-1 also involved in this process.

Osteogenic and angiogenic effects of mesenchymal stromal cells with co-transfected human Ang-1 gene and BMP2 gene

To increase the osteogenic and angiogenic effects of marrow-derived mesenchymal stromal cells (MSCs), we co-transfected (by means of lentivirus) the human angiopoietin-1 gene (hAng-1) and human bone morphogenetic protein 2 gene (hBMP2) into MSCs. Real-time PCR and ELISA showed that both genes were successfully co-expressed in the MSCs with expression sustained until the eighth week. The alkaline phosphatase activity of the MSCs was more significantly augmented by the co-transfection with both genes than by any single gene transfection. These results demonstrate that the combined gene therapy with hAng-1 and hBMP2 using lentivirally co-transfected MSCs is feasible.