Therapeutic activity of lipoxin A4 in TiO2-induced arthritis in mice: NF-κB and Nrf2 in synovial fluid leukocytes and neuronal TRPV1 mechanisms

Background

Lipoxin A4 (LXA4) has anti-inflammatory and pro-resolutive roles in inflammation. We evaluated the effects and mechanisms of action of LXA4 in titanium dioxide (TiO2) arthritis, a model of prosthesis-induced joint inflammation and pain.

Methods

Mice were stimulated with TiO2 (3mg) in the knee joint followed by LXA4 (0.1, 1, or 10ng/animal) or vehicle (ethanol 3.2% in saline) administration. Pain-like behavior, inflammation, and dosages were performed to assess the effects of LXA4 in vivo.

Results

LXA4 reduced mechanical and thermal hyperalgesia, histopathological damage, edema, and recruitment of leukocytes without liver, kidney, or stomach toxicity. LXA4 reduced leukocyte migration and modulated cytokine production. These effects were explained by reduced nuclear factor kappa B (NFκB) activation in recruited macrophages. LXA4 improved antioxidant parameters [reduced glutathione (GSH) and 2,2-azino-bis 3-ethylbenzothiazoline-6-sulfonate (ABTS) levels, nuclear factor erythroid 2-related factor 2 (Nrf2) mRNA and Nrf2 protein expression], reducing reactive oxygen species (ROS) fluorescent detection induced by TiO2 in synovial fluid leukocytes. We observed an increase of lipoxin receptor (ALX/FPR2) in transient receptor potential cation channel subfamily V member 1 (TRPV1)+ DRG nociceptive neurons upon TiO2 inflammation. LXA4 reduced TiO2-induced TRPV1 mRNA expression and protein detection, as well TRPV1 co-staining with p-NFκB, indicating reduction of neuronal activation. LXA4 down-modulated neuronal activation and response to capsaicin (a TRPV1 agonist) and AITC [a transient receptor potential ankyrin 1 (TRPA1) agonist] of DRG neurons.

Conclusion

LXA4 might target recruited leukocytes and primary afferent nociceptive neurons to exert analgesic and anti-inflammatory activities in a model resembling what is observed in patients with prosthesis inflammation.

Vaccines Alone Cannot Slow the Evolution of SARS-CoV-2

The rapid emergence of immune-evading viral variants of SARS-CoV-2 calls into question the practicality of a vaccine-only public-health strategy for managing the ongoing COVID-19 pandemic. It has been suggested that widespread vaccination is necessary to prevent the emergence of future immune-evading mutants. Here, we examined that proposition using stochastic computational models of viral transmission and mutation. Specifically, we looked at the likelihood of emergence of immune escape variants requiring multiple mutations and the impact of vaccination on this process. Our results suggest that the transmission rate of intermediate SARS-CoV-2 mutants will impact the rate at which novel immune-evading variants appear. While vaccination can lower the rate at which new variants appear, other interventions that reduce transmission can also have the same effect. Crucially, relying solely on widespread and repeated vaccination (vaccinating the entire population multiple times a year) is not sufficient to prevent the emergence of novel immune-evading strains, if transmission rates remain high within the population. Thus, vaccines alone are incapable of slowing the pace of evolution of immune evasion, and vaccinal protection against severe and fatal outcomes for COVID-19 patients is therefore not assured.

RvD1 disrupts nociceptor neuron and macrophage activation, and neuroimmune communication reducing pain and inflammation in gouty arthritis in mice

BACKGROUND AND PURPOSE

Gouty arthritis is characterised by an intense inflammatory response to monosodium urate crystals (MSU), which induces severe pain. Current therapies are often ineffective in reducing gout-related pain. Resolvin D1 (RvD1) is a specialised pro-resolving lipid mediator with anti-inflammatory and analgesic proprieties. In this study, we evaluated the effects and mechanisms of action of RvD1 in an experimental mouse model of gouty arthritis, an aim that was not pursued previously in the literature.

EXPERIMENTAL APPROACH

Male mice were treated with RvD1 (intrathecally or intraperitoneally) before or after intraarticular stimulation with MSU. Mechanical hyperalgesia was assessed using an electronic von Frey aesthesiometer. Leukocyte recruitment was determined by knee joint wash cell counting and immunofluorescence. IL-1β production was measured by ELISA. Phosphorylated NF-kB and apoptosis-associated speck-like protein containing CARD (ASC) were detected by immunofluorescence, and mRNA expression was determined by RT-qPCR. CGRP release was determined by EIA and immunofluorescence. MSU crystal phagocytosis was evaluated by confocal microscopy.

KEY RESULTS

RvD1 inhibited MSU-induced mechanical hyperalgesia in a dose- and time-dependent manner by reducing leukocyte recruitment and IL-1β production in the knee joint. Intrathecal RvD1 reduced the activation of peptidergic neurons and macrophages as well as silenced nociceptor to macrophage communication and macrophage function. CGRP stimulated MSU phagocytosis and IL-1β production by macrophages. RvD1 downmodulated this phenomenon directly by acting on macrophages, and indirectly by inhibiting CGRP release and CGRP-dependent activation of macrophages.

CONCLUSIONS AND IMPLICATIONS

This study reveals a hitherto unknown neuro-immune axis in gouty arthritis that is targeted by RvD1.

Capillary morphogenesis gene 2 (CMG2) mediates growth factor-induced angiogenesis by regulating endothelial cell chemotaxis

Anthrax protective antigen (PA) is a potent inhibitor of pathological angiogenesis with an unknown mechanism. In anthrax intoxication, PA interacts with capillary morphogenesis gene 2 (CMG2) and tumor endothelial marker 8 (TEM8). Here, we show that CMG2 mediates the antiangiogenic effects of PA and is required for growth-factor-induced chemotaxis. Using specific inhibitors of CMG2 and TEM8 interaction with natural ligand, as well as mice with the CMG2 or TEM8 transmembrane and intracellular domains disrupted, we demonstrate that inhibiting CMG2, but not TEM8 reduces growth-factor-induced angiogenesis in the cornea. Furthermore, the antiangiogenic effect of PA was abolished when the CMG2, but not the TEM8, gene was disrupted. Binding experiments demonstrated a broad ligand specificity for CMG2 among extracellular matrix (ECM) proteins. Ex vivo experiments demonstrated that CMG2 (but not TEM8) is required for PA activity in human dermal microvascular endothelial cell (HMVEC-d) network formation assays. Remarkably, blocking CMG2-ligand binding with PA or CRISPR knockout abolishes endothelial cell chemotaxis but not chemokinesis in microfluidic migration assays. These effects are phenocopied by Rho inhibition. Because CMG2 mediates the chemotactic response of endothelial cells to peptide growth factors in an ECM-dependent fashion, CMG2 is well-placed to integrate growth factor and ECM signals. Thus, CMG2 targeting is a novel way to inhibit angiogenesis.

Rapid relaxation of pandemic restrictions after vaccine rollout favors growth of SARS-CoV-2 variants: A model-based analysis

The development and deployment of several SARS-CoV-2 vaccines in a little over a year is an unprecedented achievement of modern medicine. The high levels of efficacy against transmission for some of these vaccines makes it feasible to use them to suppress SARS-CoV-2 altogether in regions with high vaccine acceptance. However, viral variants with reduced susceptibility to vaccinal and natural immunity threaten the utility of vaccines, particularly in scenarios where a return to pre-pandemic conditions occurs before the suppression of SARS-CoV-2 transmission. In this work we model the situation in the United States in May-June 2021, to demonstrate how pre-existing variants of SARS-CoV-2 may cause a rebound wave of COVID-19 in a matter of months under a certain set of conditions. A high burden of morbidity (and likely mortality) remains possible, even if the vaccines are partially effective against new variants and widely accepted. Our modeling suggests that variants that are already present within the population may be capable of quickly defeating the vaccines as a public health intervention, a serious potential limitation for strategies that emphasize rapid reopening before achieving control of SARS-CoV-2.

Controlling long-term SARS-CoV-2 infections can slow viral evolution and reduce the risk of treatment failure

The rapid emergence and expansion of novel SARS-CoV-2 variants threatens our ability to achieve herd immunity for COVID-19. These novel SARS-CoV-2 variants often harbor multiple point mutations, conferring one or more evolutionarily advantageous traits, such as increased transmissibility, immune evasion and longer infection duration. In a number of cases, variant emergence has been linked to long-term infections in individuals who were either immunocompromised or treated with convalescent plasma. In this paper, we used a stochastic evolutionary modeling framework to explore the emergence of fitter variants of SARS-CoV-2 during long-term infections. We found that increased viral load and infection duration favor emergence of such variants. While the overall probability of emergence and subsequent transmission from any given infection is low, on a population level these events occur fairly frequently. Targeting these low-probability stochastic events that lead to the establishment of novel advantageous viral variants might allow us to slow the rate at which they emerge in the patient population, and prevent them from spreading deterministically due to natural selection. Our work thus suggests practical ways to achieve control of long-term SARS-CoV-2 infections, which will be critical for slowing the rate of viral evolution.

Abstract 1822: RNA eding of AZIN1 increases cellular aggressiveness in prostate cancer

We report here nuclear localization of AZIN1, a protein commonly modified by RNA editing in cancer cells, is associated with significantly increased risk of death in prostate cancer. We further find that this nuclear localization is caused by RNA editing of a single base in the AZIN1 mRNA, which in turn leads to a single Ser to Gly substitution in the AZIN1 protein. This change alone is also sufficient to increase the aggressiveness of prostate cancer cells. Our results reveal that, unexpectedly, this editing event changes the binding repertoire of AZIN1, rather than changing its affinity for known targets.

Using droplet display PCR, we evaluated the presence of edited AZIN1 (edAZIN1) in aggressive prostate cancer using tissues with Gleason > 7, and found that 94% of these samples expressed edAZIN1.

We further measured the expression and localization of AZIN1 in 202 prostate cancer specimens, along with 26 adjacent benign samples and found a negative association between nuclear localization and progression-free survival. Analysis of data from primary prostate cancer patients available via the Cancer Genome Atlas (n = 291 with edAZIN1 calls), the median proportion of edAZIN1 was 6.1% (interquartile range, 4.4 to 8.9). In multivariable models, edAZIN1 was higher with increasing expression of ADAR, a cancer-assoicated RNA editing enzyme, (by 2.8% points per interquartile range increase in ADAR expression; 95% CI, 2.3 to 3.4) and in tumors with higher genomic instability (by 0.6% points per interquartile range increase in copy number alteration burden; 95% CI, 0.3 to 0.9). Downstream, edAZIN1 was associated with higher Gleason grade, with a 2.8%-point difference in edAZIN1 between Gleason 3+3 and Gleason 9-10 tumors (95% CI, 1.2 to 4.5). Together, these results suggest that edAZIN1 is commonly expressed in prostate cancer cells and is associated with increased cellular ADAR expression, nuclear localization, and with increased cancer aggressiveness.

To determine if editing causes increased cellular aggressiveness, we transfected prostate cancer cell lines (PC3, DU145) with constructs coding for wild-type, pseudoedited, and uneditable mRNAs for AZIN1. We found that only constructs capable of coding for edited AZIN1 increased cancer cell aggressiveness. Constructs that were unable to undergo editing, showed no such increase.

The mechanism underlying the increased aggressiveness of cells expressing AZIN1 has been proposed to be caused by higher affinity binding of edAZIN1 to its known substrate, antizyme, relative to wild-type AZIN1, but this has not been shown directly. We therefore measured the affinity of edited and wild-type protein for antizyme, using a novel FRET sensor. Contrary to expectation, we found that editing decreased edAZIN affinity for antizyme, notwithstanding increased complex formation in vivo. We then used tandem affinity purification proteomics to identify selective AZIN1 and edAZIN1 interacting proteins. We identified an edAZIN1-specific complex containing several proteins that may be the driving force behind the nuclear shuttling of edAZIN. Tools developed in this study are now being used to explore the feasibility of developing small molecule drugs that interfere with AZIN1 binding to its preferred substrates and subsequently inhibit with cell growth pathways.

Citation Format: Aram Ghalali, Konrad H. Stopsack, James M. Rice, Liangzhe Wang, Shulin Wu, Chin Lee Wu, Bruce Zetter, Michael S. Rogers. RNA eding of AZIN1 increases cellular aggressiveness in prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1822.

A Canstatin-Derived Peptide Provides Insight into the Role of Capillary Morphogenesis Gene 2 in Angiogenic Regulation and Matrix Uptake

Capillary Morphogenesis Gene 2 protein (CMG2) is a transmembrane, integrin-like receptor and the primary receptor for the anthrax toxin. CMG2 also plays a role in angiogenic processes. However, the molecular mechanism that mediates the observed CMG2-related angiogenic effects is not fully elucidated. Previous studies have reported that CMG2 binds type IV collagen (Col-IV), a vital component of the vascular basement membrane, as well as other ECM proteins. Here, we further characterize the interaction between CMG2 and individual peptides from Col-IV and explore the effects of this interaction on angiogenesis. Using a peptide array, we observed that CMG2 preferentially binds peptide fragments of the NC1 (noncollagenous domain 1) domains of Col-IV. These domains are also known as the fragments arresten (from the α1 chain) and canstatin (from the α2 chain) and have documented antiangiogenic properties. A second peptide array was probed to map a putative peptide-binding epitope onto the Col-IV structure. A top hit from the initial array, a canstatin-derived peptide, binds to the CMG2 ligand-binding von Willebrand factor A (vWA) domain with a submicromolar affinity (peptide S16, K_d = 400 ± 200 nM). This peptide competes with anthrax protective antigen (PA) for CMG2 binding and does not bind CMG2 in the presence of EDTA. Together these data suggest that, like PA, S16 interacts with CMG2 at the metal-ion dependent adhesion site (MIDAS) of its vWA domain. CMG2 specifically mediates endocytic uptake of S16; both CMG2-/- endothelial cells and WT cells treated with PA show markedly reduced S16 uptake. Furthermore, S16 dramatically reduces directional endothelial cell migration with no impact on cell proliferation. These data demonstrate that this canstatin-derived peptide acts via CMG2 to elicit a marked effect on a critical process required for angiogenesis.

Effectiveness of Police Crisis Intervention Training Programs

Approximately 1,000 people in the United States were fatally shot by police officers during 2018, and people with mental illness were involved in approximately 25 percent of those fatalities. Crisis Intervention Team (CIT) training is a specialized police curriculum that aims to reduce the risk of serious injury or death during an emergency interaction between persons with mental illness and police officers. CIT has been implemented widely both nationally and internationally. Given the increasing resources devoted to CIT, efforts to analyze its effectiveness and outcomes relative to other approaches are important. Studies of CIT and similar interventions are found within both the mental health and the criminal justice arenas, which use very different terminologies, approaches, and outcome studies, rendering unified analyses challenging. This article describes the CIT model and reviews several recent systematic analyses of studies concerning the effects of CIT. Studies generally support that CIT has beneficial officer-level outcomes, such as officer satisfaction and self-perception of a reduction in use of force. CIT also likely leads to prebooking diversion from jails to psychiatric facilities. There is little evidence in the peer-reviewed literature, however, that shows CIT's benefits on objective measures of arrests, officer injury, citizen injury, or use of force.

Are 90% of deaths from cancer caused by metastases?

Numerous publications have stated that metastases are responsible for 90% of cancer deaths, but data underlying this assertion has been lacking. Our objective was to determine what proportions of cancer deaths are caused by metastases. Population‐based data from the Cancer Registry of Norway for the years 2005‐2015 was analyzed. We compared all deaths in the Norwegian population where a cancer diagnosis was registered as cause of death. Deaths caused by cancer, with and without metastases, were analyzed, by sex and tumor group. For solid tumors, 66.7% of cancer deaths were registered with metastases as a contributing cause. Proportions varied substantially between tumor groups. Our data support the idea that the majority of deaths from solid tumors are caused by metastases. Thus, a better understanding of the biology of metastases and identification of druggable targets involved in growth at the metastatic site is a promising strategy to reduce cancer mortality.

Abstract 4888: Nuclear localization of antizyme inhibitor may be a marker for aggressiveness of prostate cancer

Antizyme suppresses cell cycle by inhibiting the polyamine synthesis through binding to the rate limiting enzyme ornithine decarboxylases (ODC). High levels of ODC have been reported in several forms of cancer, among them prostate cancer. Antizyme Inhibitor (AZIN) binds to antizyme and thereby blocks its inhibitory effect on ODC. Here, we have measured the expression and localization of AZIN in 202 prostate cancer specimens, along with 26 adjacent benign samples and found that nuclear localization of AZIN is associated with significantly lower survival. Upregulation and nuclear localization of AZIN have been observed in several cancers, as has editing of the AZIN1 mRNA. Others have hypothesized that the RNA- edited AZIN (edAZIN) may have an increased affinity to antizyme and that could explain the association of edAZIN to the various cancers. We have studied the mechanism behind the nuclear localization of AZIN and found the single base pair substitution caused by RNA editing is sufficient to result in nuclear localization of the protein in all cell types tested. To determine if the nuclear localization might result from increased antizyme-edAZIN affinity, we developed fluorescent protein FRET sensor for protein-protein interaction using Clover-AZIN and antizyme-mRuby2 fusion proteins. Unexpectedly, we found that the editing event modestly decreases edAZIN affinity for antizyme, notwithstanding increased interaction in vivo. Thus, the data indicate that the change in protein localization to the nucleus may be more important to oncogenic function than the actual degree of binding to antizyme. Other functional differences between edAZIN and AZIN might be explained by altered kinetics of binding, by the contribution of an additional adapter protein which modulates the intracellular antizyme:AZIN complex, or by competition for AZIN binding by other partners whose interaction is affected by the editing event. Finally, we identified AZIN and edAZIN interacting proteins by using tandem affinity purification and LC-MS-MS analysis. Among interacting proteins, we identified a complex containing two isoforms of nuclear actins (ACTG1 and ACTA2) and Myosin-9 that may be the driving force behind the nuclear shuttling of edAZIN.

Citation Format: Aram Ghalali, James M. Rice, Liangzhe Wang, Chin Lee Wu, Michael S. Rogers, Bruce Zetter. Nuclear localization of antizyme inhibitor may be a marker for aggressiveness of prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4888.

Abstract 207: CMG2 regulates angiogenesis through interactions with extracellular matrix

Angiogenesis is a critical process in cancer progression, facilitating initial tumor growth and allowing for metastasis into other tissues. Though several therapeutic agents are now available that reduce angiogenesis in vivo, all exhibit undesirable side effects, and none target more than one signaling pathway. This minimizes the potential to block additional signaling pathways and hence therapeutic applications, especially in cancers, which often utilize multiple signaling pathways. Capillary morphogenesis gene protein 2 (CMG2) is an integrin-like cellular receptor whose gene is highly upregulated during angiogenesis. Previously, we have demonstrated that CMG2 function is critical to neovascularization in vivo, and that CMG2 regulates angiogenesis through multiple signaling pathways, marking CMG2 as an effective target in development of multi-pathway antiangiogenic therapeutic agents.

CMG2 is also known to function as an anthrax toxin receptor, the mutation target in the rare genetic disease hyaline fibromatosis syndrome (HFS), and an interactor with extracellular matrix. Regarding HFS, it was recently shown that CMG2 knockouts lead to accumulation of extracellular matrix, especially collagen VI (Col-VI). To investigate a link between HFS and angiogenesis, we probed CMG2 affinity for several intact matrix proteins by ELISA, including laminin-111, fibronectin, and collagens I, IV, and VI. We discovered that CMG2 bound all these matrix proteins with similar affinity (Kd = 500-1000 nM). We then constructed a peptide array, containing the entire sequences of the collagen IV α1/α2 chains; fibronectin; and laminin-111 to identify CMG2-binding regions, using a 10-amino acid sliding window. We thereby identified a small peptide, designated S16, which binds CMG2 with high affinity and which inhibts angiogenic processes ex vivo. Since the integrin family of proteins regulate cell signaling and angiogenesis and are homologs of CMG2, we suspected that CMG2 may also function to regulate angiogenesis through matrix interactions. Consequently, we ran a higher resolution peptide array (2-amino acid sliding window) to identify specific matrix epitopes. In this expanded peptide array, we covered the sequences of the collagen IV α1 and α2 chains, collagen IV α3- α6 non-collagenous domains, collagen VI α1 and α2 chains, and portions of the collagen VI α3 chain and fibronectin. We noted several hits in each matrix protein on the array, including several in Col-VI, whose sequences map to specific vWFA domains in that matrix protein. We have now confirmed that CMG2 binds these collagen VI-derived peptides and their respective domains with high affinity. This has significant implications for the role of these domains in angiogenic phenotypes such as cell migration and adhesion. We anticipate that the interactions between these peptides and CMG2 can be exploited to develop multi-pathway inhibitors of angiogenesis.

Citation Format: Samuel R. Garrard, Mark Gold, Tsz Ming Tsang, Sai Lun Lee, David Fogg, Rachael Dannenberg, Michael S. Rogers, Kenneth A. Christensen. CMG2 regulates angiogenesis through interactions with extracellular matrix [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 207.

Developing a novel FRET assay, targeting the binding between Antizyme-AZIN

Antizyme inhibitor (AZIN) stimulates cell proliferation by binding to and sequestering the cell cycle suppressor antizyme. Despite the important role of the antizyme-AZIN protein-protein interaction (PPI) in cell cycle regulation, there are no assays for directly measuring the binding of AZIN to antizyme that are amenable to high throughput screening. To address this problem, we developed and validated a novel antizyme-AZIN intramolecular FRET sensor using clover and mRuby2 fluorescent proteins. By introducing alanine mutations in the AZIN protein, we used this sensor to probe the PPI for key residues governing the binding interaction. We found that like many PPIs, the energy of the antizyme-AZIN binding interaction is distributed across many amino acid residues; mutation of individual residues did not have a significant effect on disrupting the PPI. We also examined the interaction between Clover-AZIN and antizyme-mRuby2 in cells. Evidence of a direct interaction between Clover-AZIN and antizyme-mRuby2 was observed within cells, validating the use of this FRET sensor for probing intracellular antizyme-AZIN PPI. In conclusion, we have developed and optimized a FRET sensor which can be adapted for high throughput screening of either in vitro or intracellular activity.

A paradoxical method to enhance compensatory lung growth: Utilizing a VEGF inhibitor

Exogenous vascular endothelial growth factor (VEGF) accelerates compensatory lung growth (CLG) in mice after unilateral pneumonectomy. In this study, we unexpectedly discovered a method to enhance CLG with a VEGF inhibitor, soluble VEGFR1. Eight-week-old C57BL/6 male mice underwent left pneumonectomy, followed by daily intraperitoneal (ip) injection of either saline (control) or 20 μg/kg of VEGFR1-Fc. On post-operative day (POD) 4, mice underwent pulmonary function tests (PFT) and lungs were harvested for volume measurement and analyses of the VEGF signaling pathway. To investigate the role of hypoxia in mediating the effects of VEGFR1, experiments were repeated with concurrent administration of PT-2385, an inhibitor of hypoxia-induced factor (HIF)2α, via orogastric gavage at 10 mg/kg every 12 hours for 4 days. We found that VEGFR1-treated mice had increased total lung capacity (P = 0.006), pulmonary compliance (P = 0.03), and post-euthanasia lung volume (P = 0.049) compared to control mice. VEGFR1 treatment increased pulmonary levels of VEGF (P = 0.008) and VEGFR2 (P = 0.01). It also stimulated endothelial proliferation (P < 0.0001) and enhanced pulmonary surfactant production (P = 0.03). The addition of PT-2385 abolished the increase in lung volume and endothelial proliferation in response to VEGFR1. By paradoxically stimulating angiogenesis and enhancing lung growth, VEGFR1 could represent a new treatment strategy for neonatal lung diseases characterized by dysfunction of the HIF-VEGF pathway.

Heparin impairs angiogenic signaling and compensatory lung growth after left pneumonectomy

Children with hypoplastic lung diseases, such as congenital diaphragmatic hernia, can require life support via extracorporeal membrane oxygenation and systemic anticoagulation, usually in the form of heparin. The role of heparin in angiogenesis and organ growth is inconclusive, with conflicting data reported in the literature. This study aimed to investigate the effects of heparin on lung growth in a model of compensatory lung growth (CLG). Compared to the absence of heparin, treatment with heparin decreased the vascular endothelial growth factor (VEGF)-mediated activation of VEGFR2 and mitogenic effect on human lung microvascular endothelial cells in vitro. Compared to non-heparinized controls, heparinized mice demonstrated impaired pulmonary mechanics, decreased respiratory volumes and flows, and reduced activity levels after left pneumonectomy. They also had lower lung volume, pulmonary septal surface area and alveolar density on morphometric analyses. Lungs of heparinized mice displayed decreased phosphorylation of VEGFR2 compared to the control group, with consequential downstream reduction in markers of cellular proliferation and survival. The use of bivalirudin, an alternative anticoagulant that does not interact with VEGF, preserved lung growth and pulmonary mechanics. These results demonstrated that heparin impairs CLG by reducing VEGFR2 activation. These findings raise concern for the clinical use of heparin in the setting of organ growth or regeneration.

Abstract LB-311: Characterization of the antizyme/antizyme inhibitor protein-protein interaction using a novel FRET sensor

The protein-protein interaction (PPI) between the tumor suppressor antizyme (AZ) and its endogenous regulator antizyme inhibitor (AZIN) has recently been demonstrated to be important in several human cancers. AZIN siRNA treatment reduces AZIN expression and slows prostate cancer cell growth in vitro and in vivo but is not currently a viable therapeutic strategy. To further probe the AZ/AZIN PPI and to screen for potential small molecule inhibitors, we have developed a FRET assay (Z score &gt;0.7) utilizing the Clover (donor) and mRuby2 (acceptor) fluorescent proteins linked to AZIN and AZ, respectively. An alanine mutant screen of 43 amino acid positions in the AZIN protein revealed 2 hotspots that dramatically affect the affinity for the AZ protein, thereby identifying key regions for disruption by potential therapeutics. Furthermore, mutating the N327 and Y331 positions in ornithine decarboxylase (ODC) to equivalent residues in the homologous AZIN protein, increased the affinity of ODC for AZ, providing evidence for key residues that contribute to AZ/AZIN PPI. In addition, the S367G AZIN mutation, which is associated with an mRNA editing event in hepatocellular carcinoma, further increases the affinity of AZIN for AZ and supports a mechanism of AZ sequestration as an important driver in cancer cell growth. Taken together, this data expands our current understanding of the contribution of different amino acid residues to the AZ/AZIN binding interaction. The development of small molecule inhibitors to target these regions of the AZIN protein would rescue the tumor suppressive activity of AZ and present a novel therapeutic opportunity for the treatment of prostate cancer and hepatocellular carcinoma.

Note: This abstract was not presented at the meeting.

Citation Format: James M. Rice, Michael S. Rogers, Bruce R. Zetter. Characterization of the antizyme/antizyme inhibitor protein-protein interaction using a novel FRET sensor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-311. doi:10.1158/1538-7445.AM2017-LB-311

Identification of Padi2 as a novel angiogenesis-regulating gene by genome association studies in mice

Recent findings indicate that growth factor-driven angiogenesis is markedly influenced by genetic variation. This variation in angiogenic responsiveness may alter the susceptibility to a number of angiogenesis-dependent diseases. Here, we utilized the genetic diversity available in common inbred mouse strains to identify the loci and candidate genes responsible for differences in angiogenic response. The corneal micropocket neovascularization assay was performed on 42 different inbred mouse strains using basic fibroblast growth factor (bFGF) pellets. We performed a genome-wide association study utilizing efficient mixed-model association (EMMA) mapping using the induced vessel area from all strains. Our analysis yielded five loci with genome-wide significance on chromosomes 4, 8, 11, 15 and 16. We further refined the mapping on chromosome 4 within a haplotype block containing multiple candidate genes. These genes were evaluated by expression analysis in corneas of various inbred strains and in vitro functional assays in human microvascular endothelial cells (HMVECs). Of these, we found the expression of peptidyl arginine deiminase type II (Padi2), known to be involved in metabolic pathways, to have a strong correlation with a haplotype shared by multiple high angiogenic strains. In addition, inhibition of Padi2 demonstrated a dosage-dependent effect in HMVECs. To investigate its role in vivo, we knocked down Padi2 in transgenic kdrl:zsGreen zebrafish embryos using morpholinos. These embryos had disrupted vessel formation compared to control siblings. The impaired vascular pattern was partially rescued by human PADI2 mRNA, providing evidence for the specificity of the morphant phenotype. Taken together, our study is the first to indicate the potential role of Padi2 as an angiogenesis-regulating gene. The characterization of Padi2 and other genes in associated pathways may provide new understanding of angiogenesis regulation and novel targets for diagnosis and treatment of a wide variety of angiogenesis-dependent diseases.

Electronic Medical Record Validation: Exploring the Reliability of Intracranial Pressure Data Abstracted From the Electronic Medical Record–Pilot

Background and Purpose: Intracranial pressure (ICP) monitoring is crucial to decision making for neurologically injured patients, yet measurement of ICP varies greatly among practitioners. Methods: Unblinded, nonrandomized, observational pilot study comparing ICP values collected using pen and paper (P&P), electronic medical record (EMR), and video data with continuous data acquisition (CDA) technology. Results: ICP values did not significantly differ between EMR and P&P records, despite an average of 16 minutes difference in reporting times. ICP values varied significantly when comparing CDA data to EMR or paper. Conclusion: The results of this pilot study put in to question the validity of ICP values that are recorded in the medical record, which has implications for patient care and research.

Spontaneous reversion of the angiogenic phenotype to a nonangiogenic and dormant state in human tumors

The angiogenic switch, a rate-limiting step in tumor progression, has already occurred by the time most human tumors are detectable. However, despite significant study of the mechanisms controlling this switch, the kinetics and reversibility of the process have not been explored. The stability of the angiogenic phenotype was examined using an established human liposarcoma xenograft model. Nonangiogenic cells inoculated into immunocompromised mice formed microscopic tumors that remained dormant for approximately 125 days (vs. <40 days for angiogenic cells) whereupon the vast majority (>95%) initiated angiogenic growth with second-order kinetics. These original, clonally derived angiogenic tumor cells were passaged through four in vivo cycles. At each cycle, a new set of single-cell clones was established from the most angiogenic clone and characterized for in vivo for tumorigenic activity. A total of 132 single-cell clones were tested in the second, third, and fourth in vivo passage. Strikingly, at each passage, a portion of the single-cell clones formed microscopic, dormant tumors. Following dormancy, like the original cell line, these revertant tumors spontaneously switched to the angiogenic phenotype. Finally, revertant clones were transcriptionally profiled and their angiogenic output determined. Collectively, these data demonstrate that the angiogenic phenotype in tumors is malleable and can spontaneously revert to the nonangiogenic phenotype in a population of human tumor cells.

IMPLICATIONS

Leveraging the rate of reversion to the nonangiogenic phenotype and tumor dormancy may be a novel anticancer strategy.

Melanocyte-secreted fibromodulin promotes an angiogenic microenvironment

Studies have established that pigmentation can provide strong, protective effects against certain human diseases. For example, angiogenesis-dependent diseases such as wet age-related macular degeneration and infantile hemangioma are more common in light-skinned individuals of mixed European descent than in African-Americans. Here we found that melanocytes from light-skinned humans and albino mice secrete high levels of fibromodulin (FMOD), which we determined to be a potent angiogenic factor. FMOD treatment stimulated angiogenesis in numerous in vivo systems, including laser-induced choroidal neovascularization, growth factor-induced corneal neovascularization, wound healing, and Matrigel plug assays. Additionally, FMOD enhanced vascular sprouting during normal retinal development. Deletion of Fmod in albino mice resulted in a marked reduction in the amount of neovascularization induced by retinal vein occlusion, corneal growth factor pellets, and Matrigel plugs. Our data implicate the melanocyte-secreted factor FMOD as a key regulator of angiogenesis and suggest an underlying mechanism for epidemiological differences between light-skinned individuals of mixed European descent and African-Americans. Furthermore, inhibition of FMOD in humans has potential as a therapeutic strategy for treating angiogenesis-dependent diseases.

Abstract 5076: Identification and anti-angiogenic effects of small molecule inhibitors of TEM8

Tumor endothelial marker 8 (TEM8) is a gene upregulated on colonic tumor endothelium compared to quiescent normal endothelium. Inhibition of TEM8 using antibodies potently inhibits the growth of a variety of tumor types in mice. This inhibition of tumor growth is accompanied by a reduction in microvessel density within the tumors. Thus, TEM8 appears to represent a tumor specific endothelial marker that has a functional role in tumor angiogenesis. TEM8 is also a receptor for anthrax toxin. In the current study, we used chemical libraries to identify small molecule inhibitors of TEM8 that may have efficacy as inhibitors of tumor angiogenesis and anthrax toxin.

We conducted a fluorescence resonance energy transfer (FRET) based screen of over 270,000 small molecules in order to identify molecules that inhibit the interaction of TEM8 with its well-known ligand anthrax protective antigen (PA). We describe here the identification and anti-angiogenic effects of small molecules that bind to TEM8.

From the initial screen 280 molecules inhibited TEM8/PA interaction by greater than 50%. A secondary screen involved the elucidation of IC50 values for these 280 compounds as inhibitors of the TEM8/PA interaction. Twelve compounds had measurable IC50s in the micromolar range. The anti-angiogenic effects of these compounds were studied in vitro. Of the 12 compounds tested in a human microvascular endothelial cell (HMVEC) proliferation assay, 3 compounds significantly inhibited endothelial cell proliferation after 24 hours (P &lt;0.05), and 5 compounds significantly inhibited proliferation at 72 hours (P &lt;0.05). None of the compounds exhibited measurable cytotoxicity. One of the five compounds tested for effects on HMVEC migration, significantly inhibited migration on a fibronectin coated-surface by 78% (P&lt;0.01).

We have identified a number of small molecule inhibitors of TEM8, some of which display anti-angiogenic effects in vitro. Should these inhibitors also display potent anti-angiogenic effects in vivo, they may serve as lead compounds for the future development of TEM8 therapeutic small molecules. Future studies will focus on determining the effects of these molecules on tumor growth and angiogenesis in mouse models.

Citation Format: Lorna Cryan, Marinya Roznik, Aaron McBride, Robert D'Amato, Kenneth Christensen, Michael S. Rogers. Identification and anti-angiogenic effects of small molecule inhibitors of TEM8. [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 5076. doi:10.1158/1538-7445.AM2013-5076

Abstract 3890: Antiangiogenic small molecule antagonists of the anthrax toxin receptor CMG2

We have previously shown that the anthrax protective antigen mutant PASSSR can inhibit endothelial cell migration, VEGF and bFGF driven angiogenesis in the corneal micropocket assay, and tumor growth. However anthrax toxin has three reported receptors (CMG2, TEM8, and β1 integrin) that might mediate antiangiogenic effects. Knockdown of β1 integrin in endothelial cells had no effect on PASSSR inhibition of migration and circulating levels of PASSSR in mice are too low for significant integrin occupancy. Using soluble extracellular domain constructs fused to the antibody Fc region to improve pharmacokinetics, we observed that CMG2-Fc inhibits angiogenesis, while TEM8-Fc does not. Similarly, treatment of mice undergoing the corneal micropocket assay with the SR8F7C7 anti-CMG2 antibody resulted in dose-dependent inhibition of bFGF-induced corneal neovascularization, while the L2 anti-TEM8 antibody had no effect at a dose that has potent antitumor activity. Thus, CMG2 blockade, but not TEM8 blockade, can inhibit corneal angiogenesis. To assess the role of CMG2 in angiogenesis in vivo without pharmacologic intervention, we performed the corneal micropocket assay on knockout mice, and observed that knockout mice exhibit a dramatic decrease in angiogenesis vs. wild-type controls. Also, PASSSR does not further inhibit corneal angiogenesis in CMG2−/− mice. This is consistant with the ex vivo observation that CMG2 knockdown reduces the ability of HMVEC to migrate to serum and knockdown cells are no longer inhibited by PASSSR.

To allow identification of CMG2 antagonists, we developed a high-throughput FRET-based screening assay. Validation of the assay suggested that tannic acid may inhibit this protein. However, further analysis demonstrated that this activity is attributable not to tannic acid, but instead to a hydrolysis product (PGG) that contaminated our tannic acid sample. We found that PGG inhibits CMG2 with an IC50 of 300 nM, a value consistent with serum levels achieved by antiangiogenic and antitumor dosing. PGG also inhibited endothelial cell migration and angiogenesis in the corneal micropocket assay, demonstrating that this compound can inhibit not only CMG2-PA binding, but also angiogenesis. Further screening of small molecule libraries identified several additional compounds that inhibit endothelial cell migration and angiogenesis in the corneal micropocket assay. In addition, we identified one compound that stimulates both activities. This important result reveals that CMG2 modulators can both stimulate and inhibit angiogenesis, ruling out indirect effects (such as compound toxicity) as a general explanation for the observed effects on angiogenesis. These results demonstrate small molecule modulation of CMG2 and identify potential pharmacoactive leads. Together, these data strongly suggest that small molecule CMG2 antagonists can be used as antiangiogenic therapies.

Citation Format: Lorna M. Cryan, P. Christine Ackroyd, Shugeng Cao, Jon Clardy, Kenneth A. Christensen, Michael S. Rogers. Antiangiogenic small molecule antagonists of the anthrax toxin receptor CMG2. [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 3890. doi:10.1158/1538-7445.AM2013-3890

1,2,3,4,6-Penta-O-galloyl-β-D-glucopyranose inhibits angiogenesis via inhibition of capillary morphogenesis gene 2

Capillary morphogenesis gene 2 (CMG2) is a transmembrane extracellular matrix binding protein that is also an anthrax toxin receptor. We have shown that high-affinity CMG2 binders can inhibit angiogenesis and tumor growth. We recently described a high-throughput FRET assay to identify CMG2 inhibitors. We now report the serendipitous discovery that PGG (1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose) is a CMG2 inhibitor with antiangiogenic activity. PGG is a gallotannin produced by a variety of medicinal plants that exhibits a wide variety of antitumor and other activities. We find that PGG inhibits CMG2 with a submicromolar IC50 and it also inhibits the migration of human dermal microvascular endothelial cells at similar concentrations in vitro. Finally, oral or intraperitoneal administration of PGG inhibits angiogenesis in the mouse corneal micropocket assay in vivo. Together, these results suggest that a portion of the in vivo antitumor activity of PGG may be the result of antiangiogenic activity mediated by inhibition of CMG2.

Identification of small molecules that inhibit the interaction of TEM8 with anthrax protective antigen using a FRET assay

Tumor marker endothelial 8 (TEM8) is a receptor for the protective antigen (PA) component of anthrax toxin. TEM8 is upregulated on endothelial cells lining the blood vessels within tumors, compared with normal blood vessels. A number of studies have demonstrated a pivotal role for TEM8 in developmental and tumor angiogenesis. We have also shown that targeting the anthrax receptors with a mutated form of PA inhibits angiogenesis and tumor formation in vivo. Here we describe the development and testing of a high-throughput fluorescence resonance energy transfer assay to identify molecules that strongly inhibit the interaction of PA and TEM8. The assay we describe is sensitive and robust, with a Z' value of 0.8. A preliminary screen of 2310 known bioactive library compounds identified ebselen and thimerosal as inhibitors of the TEM8-PA interaction. These molecules each contain a cysteine-reactive transition metal, and complementary studies indicate that their inhibition of interaction is due to modification of a cysteine residue in the TEM8 extracellular domain. This is the first demonstration of a high-throughput screening assay that identifies inhibitors of TEM8, with potential application for antianthrax and antiangiogenic diseases.