Tina Friis

Influence of angiogenesis inhibitors on endothelial cell morphology in vitro

Human umbilical vein endothelial cells (HUVEC) propagated in co‐culture with fibroblasts form capillary‐like networks of tubes. Here we characterize the morphology and ultrastructure of HUVEC in such co‐cultures and investigate the influence of different angiogenesis inhibitors on endothelial cell morphology. Addition of angiogenesis inhibitors to the co‐culture disrupted endothelial network formation and influenced endothelial cell morphology in two distinct ways. Instead of characteristic capillary‐like networks, the endothelial cell morphology appeared as either short cords or compact cell clusters of variable size. Electron microscopy (EM) showed that in co‐culture untreated HUVEC formed capillary‐like tubes with lumina and retained important ultrastructural and physiological properties of endothelial cells in functional vessels as they contained both Weibel‐Palade bodies and transport vesicles. Immuno‐EM showed that the endothelial cell marker CD 31 stained endothelial membranes at cell‐cell contacts, and at the luminal and abluminal side of the capillary‐like tubes, although most abundantly at the luminal membranes. No ultrastructural signs of apoptosis were seen in HUVEC in inhibitor‐treated co‐cultures. Our results demonstrate that treatment with levamisole or anti‐VEGF inhibits endothelial cell differentiation into tubes or instead induces formation of compact endothelial cell clusters. Treatment with platelet factor 4, suramin and TNP‐470 results in formation of short endothelial cell cords. We discuss the implications of these findings.

A quantitative ELISA-based co-culture angiogenesis and cell proliferation assay

Since solid tumours and metastases depend on adequate blood supply, much research is focused on inhibition of angiogenesis. Unfortunately, most known angiogenesis inhibitors have serious side effects when used as therapeutic agents in man. It is therefore important to develop methods to identify well‐tolerated and efficient angiogenesis inhibitors. As a method for identification of new angiogenesis inhibitors we have further developed the procedure described by Bishop et al. (Angiogenesis 1999;3:335–44) to a quantitative ELISA‐based fibroblast and endothelial cell co‐culture angiogenesis assay. In each well of a 96‐microwell plate, human umbilical vein endothelial cells (HUVEC) are seeded onto normal human dermal fibroblasts (NHDF) and propagated in co‐culture for 72 h with or without a potential angiogenesis inhibitor. The effect on total cell proliferation is evaluated by quantitative immunochemical measurement of DNA, and on endothelial tube formation by quantification of CD 31, von Willebrand factor, and collagen IV. After ELISA reading, the morphology of the tubular structures formed by HUVEC is visualised with BCIP/NBT, permitting a quantitative result and a qualitative evaluation of cell morphology from the same well. We have used the assay to demonstrate the effect of well‐known angiogenesis inhibitors on HUVEC tube formation.

Levamisole inhibits angiogenesis in vitro and tumor growth in vivo.

The synthetic anthelmintic compound Levamisole has previously been used in cancer treatment as an adjuvant in combination with 5-fluorouracil. Its mode of action remains unclear, but an immune-stimulatory effect has been suggested. Here, we show that Levamisole inhibits angiogenesis in vitro and tumor growth in vivo. In vitro, Levamisole specifically inhibits proliferation and differentiation of endothelial cells propagated in co-culture with fibroblasts. In vivo, Levamisole inhibits the growth in nude mice of a transplanted human tumor. The use of nude mice as tumor hosts permits the discrimination between the angiogenesis inhibitory effect of Levamisole and its assumed immune-stimulatory effect. Our findings support a possible therapeutic effect of angiogenesis inhibitors in the treatment of cancer and call for further investigations of the mechanism(s) underlying the anti-angiogenic effect of Levamisole.

Methyl effect in azumamides provides insight into histone deacetylase inhibition by macrocycles.

Natural, nonribosomal cyclotetrapeptides have traditionally been a rich source of inspiration for design of potent histone deacetylase (HDAC) inhibitors. We recently disclosed the total synthesis and full HDAC profiling of the naturally occurring azumamides ( J. Med. Chem. 2013 , 56 , 6512 ). In this work, we investigate the structural requirements for potent HDAC inhibition by macrocyclic peptides using the azumamides along with a series of unnatural analogues obtained through chemical synthesis. By solving solution NMR structures of selected macrocycles and combining these findings with molecular modeling, we pinpoint crucial enzyme-ligand interactions required for potent inhibition of HDAC3. Docking of additional natural products confirmed these features to be generally important. Combined with the structural conservation across HDACs 1-3, this suggests that while cyclotetrapeptides have provided potent and class-selective HDAC inhibitors, it will be challenging to distinguish between the three major class I deacetylases using these chemotypes.

An azumamide C analogue without the zinc-binding functionality

Histone deacetylase (HDAC) inhibitors have attracted considerable attention due to their promise as therapeutic agents. Most HDAC inhibitors adhere to a general “cap-linker-Zn2+-binding group” architecture but recent studies have indicated that potent inhibition may be achieved without a Zn2+-coordinating moiety. Herein, we describe the synthesis of an azumamide analogue lacking its native Zn2+-binding group and evaluation of its inhibitory activity against recombinant human HDAC1–11. Furthermore, kinetic investigation of the inhibitory mechanism of both parent natural product and synthetic analogue against HDAC3-NCoR2 is reported as well as their activity against Burkitts lymphoma cell proliferation.

Ultrastructural characterization of mesenchymal stromal cells labeled with ultrasmall superparamagnetic iron-oxide nanoparticles for clinical tracking studies.

Abstract Introduction. To evaluate survival and engraftment of mesenchymal stromal cells (MSCs) in vivo, it is necessary to track implanted cells non-invasively with a method, which does not influence cellular ultrastructure and functional characteristics. Iron-oxide particles have been applied for cell tracking for years, but knowledge regarding possible cytotoxic ultrastructural changes subsequent to iron-oxide particle labeling is limited. Hence, the purpose of this study was to label MSCs with dextran-coated ultrasmall super-paramagnetic iron-oxide (USPIO) particles conjugated with the transduction sequence of trans-activator of transcription (TAT) (IODEX-TAT) and evaluate the effect of labeling on ultrastructure, viability, phenotype and proliferative capacity of the cells. Materials and methods. MSCs were labeled with 5 and 10 μg IODEX-TAT/105 cells for 2, 6 and 21 hours. IODEX-TAT uptake and cellular ultrastructure were determined by electron microscopy. Cell viability was determined by propidium iodide staining and cell proliferation capacity by 5-bromo-2-deoxyuridine (BrdU) incorporation. Maintenance of stem cell surface markers was determined by flow cytometry. Results. IODEX-TAT labeling for 2, 6 and 21 h did not influence cellular ultrastructure or viability. Moreover, neither stem cell surface markers nor cell proliferation capacity was affected by labeling with IODEX-TAT. Conclusion. Our results demonstrate that labeling of MSCs for 21 h with a clinically relevant dose of 10 μg IODEX-TAT/105 cells is feasible and does not affect MSC ultrastructure, viability, phenotype or proliferation capacity.

Influence of Levamisole and Other Angiogenesis Inhibitors on Angiogenesis and Endothelial Cell Morphology in Vitro

Angiogenesis, the formation of new blood vessels from existing vessels is required for many physiological processes and for growth of solid tumors. Initiated by hypoxia, angiogenesis involves binding of angiogenic factors to endothelial cell (EC) receptors and activation of cellular signaling, differentiation, migration, proliferation, interconnection and canalization of ECs, remodeling of the extracellular matrix and stabilization of newly formed vessels. Experimentally, these processes can be studied by several in vitro and in vivo assays focusing on different steps in the process. In vitro, ECs form networks of capillary-like tubes when propagated for three days in coculture with fibroblasts. The tube formation is dependent on vascular endothelial growth factor (VEGF) and omission of VEGF from the culture medium results in the formation of clusters of undifferentiated ECs. Addition of angiogenesis inhibitors to the coculture system disrupts endothelial network formation and influences EC morphology in two distinct ways. Treatment with antibodies to VEGF, soluble VEGF receptor, the VEGF receptor tyrosine kinase inhibitor SU5614, protein tyrosine phosphatase inhibitor (PTPI) IV or levamisole results in the formation of EC clusters of variable size. This cluster morphology is a result of inhibited EC differentiation and levamisole can be inferred to influence and block VEGF signaling. Treatment with platelet factor 4, thrombospondin, rapamycin, suramin, TNP-470, salubrinal, PTPI I, PTPI II, clodronate, NSC87877 or non-steriodal anti-inflammatory drugs (NSAIDs) results in the formation of short cords of ECs, which suggests that these inhibitors have an influence on later steps in the angiogenic process, such as EC proliferation and migration. A humanized antibody to VEGF is one of a few angiogenesis inhibitors used clinically for treatment of cancer. Levamisole is approved for clinical treatment of cancer and is interesting with respect to anti-angiogenic activity in vivo since it inhibits ECs in vitro with a morphology resembling that obtained with antibodies to VEGF.

Synthesis and Antiangiogenic Activity of N-Alkylated Levamisole Derivatives

Inhibition of angiogenesis is a promising addition to current cancer treatment strategies. Neutralization of vascular endothelial growth factor by monoclonal antibodies is clinically effective but may cause side effects due to thrombosis. Low molecular weight angiogenesis inhibitors are currently less effective than antibody treatment and are also associated with serious side effects. The discovery of new chemotypes with efficient antiangiogenic activity is therefore of pertinent interest. (S)-Levamisole hydrochloride, an anthelminthic drug approved for human use and with a known clinical profile, was recently shown to be an inhibitor of angiogenesis in vitro and exhibited tumor growth inhibition in mice. Here we describe the synthesis and in vitro evaluation of a series of N-alkylated analogues of levamisole with the aim of characterizing structure–activity relationships with regard to inhibition of angiogenesis. N-Methyllevamisole and p-bromolevamisole proved more effective than the parent compound, (S)-levamisole hydrochloride, with respect to inhibition of angiogenesis and induction of undifferentiated cluster morphology in human umbilical vein endothelial cells grown in co-culture with normal human dermal fibroblasts. Interestingly, the cluster morphology caused by N-methyllevamisole was different than the clusters observed for levamisole, and a third “cord-like” morphology resembling that of the known drug suramin was observed for an aniline-containing derivative. New chemotypes exhibiting antiangiogenic effects in vitro are thus described, and further investigation of their underlying mechanism of action is warranted.

Comparison of antibody assays for detection of autoantibodies to Ro 52, Ro 60 and La associated with primary Sjögren's syndrome.

Anti-Ro(52/60) and anti-La constitute the hallmark autoantibodies in primary Sjögrens syndrome, being present in 40-70% of sera. Several anti-Ro/La assays exist, but antibody detection appears to be assay-specific, thus the aim of this study was to compare several anti-Ro/La assays. In total, 96 sera from individuals with primary Sjögrens syndrome and 114 healthy controls were tested for anti-Ro 52/60 and anti-La in 17 immunoassays. Especially the immunoassays used for detection of anti-Ro 52 differed in their sensitivity (48-79%), while only small differences in sensitivities were observed for the anti-Ro 60 (69-77%) anti-La (39-44%) assays. Concordances of 65%, 79% and 73% for the anti-Ro 52, anti-Ro 60 and anti-La assays were found, respectively. The majority of the assays yielded high specificities, primarily ranging from 97 to 100%, except from a single anti-Ro 60 assay, which yielded a specificity of 79%. Occasionally, reactivity levels were increased in a few assays, indicating that false-positive results can be obtained when applying assays of reduced specificity. In general, the commercial assays appeared to perform better than the in-house analyses. When correcting the in-house assays for background reactivity, sensitivities were reduced by approximately 7%, 17%, and 19% for anti-Ro 52, anti-Ro 60 and anti-La assays, respectively, illustrating the pitfalls when applying immunoassays for detection of autoantibodies, which in theory may apply to commercial assays as well. Finally, increased total sensitivities were obtained when combining assays. These studies contribute to clarify the clinical utility of immunoassays for detection of autoantibodies of Ro 52, Ro 60 and La and illustrate that the most efficient strategy to maximize antibody sensitivity is to combine several assays.

Synthesis and Anti-Angiogenic Effect of Conjugates Between Serum Albumin and Non-Steroidal Anti-Inflammatory Drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit tumor growth and angiogenesis. Covalent linkage of naproxen to human serum albumin (HSA) has been shown to target it efficiently to the liver and this may potentially be exploited for liver-selective inhibition of angiogenesis. With the aim of investigating the anti-angiogenic efficiency of NSAID-HSA conjugates in vitro, three NSAIDs, aspirin, ibuprofen, and naproxen were conjugated to HSA using different concentrations of their N-hydroxysuccinimide esters. Conjugation ratios from 10 to 50 were achieved and the conjugates retained a growth inhibitory effect on endothelial cells at or above the level of the non-conjugated NSAIDs in an in vitro angiogenesis assay.