A proteogenomic signature of age-related macular degeneration in blood

Age-related macular degeneration (AMD) is one of the most common causes of visual impairment in the elderly, with a complex and still poorly understood etiology. Whole-genome association studies have discovered 34 genomic regions associated with AMD. However, the genes and cognate proteins that mediate the risk, are largely unknown. In the current study, we integrate levels of 4782 human serum proteins with all genetic risk loci for AMD in a large population-based study of the elderly, revealing many proteins and pathways linked to the disease. Serum proteins are also found to reflect AMD severity independent of genetics and predict progression from early to advanced AMD after five years in this population. A two-sample Mendelian randomization study identifies several proteins that are causally related to the disease and are directionally consistent with the observational estimates. In this work, we present a robust and unique framework for elucidating the pathobiology of AMD.

Age related macular degeneration is a common cause of visual impairment in the elderly, but the etiology is not fully understood. Here, the authors use genetic data, serum proteomics, and AMD phenotypic data from a large Icelandic cohort to discover proteins altered in, causally related to AMD or signifying progression of advanced AMD.

Abstract 3376: Molecular drivers of endothelial hypoxic adaption during angiogenesis deciphered using the Berg Interrogative Biology® platform

Angiogenesis is a key feature of tumor progression providing oxygen and nutrients required for tumor cell growth, hypoxia being a major driver of this phenomenon. A systems biology approach using the Berg Interrogative Biology® platform was implemented to identify drivers of the endothelial cell (EC) angiogenic response to hypoxia. To determine the proteomic profile of proliferating ECs and non-proliferating confluent ECs exposed to normoxia or hypoxia, a functional proteomic approach employing activity-based probes and phosphorylation analysis was utilized. Kinases and ATPases were labeled with ATP-binding domain enrichment probes and titanium dioxide enrichment of phosphopeptides was employed for capture of protein phosphorylation events. Phenotypic assays including proliferation rates, apoptosis, mitochondrial superoxide and ROS/NO signaling were included as a measure of EC phenotype. Comparative proteomics, kinase activity, phosphoproteomics and assay data were integrated using an AI based Bayesian Network Inference approach to investigate causal signaling networks in order to elucidate the complexity and dynamics of angiogenesis and more specifically, the role of hypoxia in driving intracellular signaling in response to changes in oxygen tension. High confidence causal networks identified novel proteins that modulate the EC hypoxic response, validation of which are in process. Previously characterized proteins that are responsive to hypoxia were also identified in the hypoxic, but not normoxic signaling networks, namely Aldoc, Rac1, mTor, Cav-1 and Bax. Endothelial proliferation rate is closely related to both hydrogen peroxide and nitric oxide signaling, as has previously been reported. Novel regulatory networks that determine these interactions were identified. Using the Berg Interrogative Biology® platform, we are deciphering both the effects of the hypoxic microenvironment, and the unique characteristics of proliferating ECs by applying integrated functional proteomic assays and a systems approach to determine global changes in intracellular signaling in response to hypoxia.

Citation Format: Tony E. Walshe, Justin Bourdelais, Viatcheslav R. Akmaev, Leonardo O. Rodrigues, Socheata Lao, Stephane Gesta, Michael A. Kiebish, Vivek K. Vishnudas, Rangaprasad Sarangarajan, Niven R. Narain. Molecular drivers of endothelial hypoxic adaption during angiogenesis deciphered using the Berg Interrogative Biology® platform. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3376.

Abstract 212: BPM 31510 synergizes gemcitabine efficacy in pancreatic adenocarcinoma via mechanism independent of its anti-Warburg influence on metabolism

Pancreatic adenocarcinoma (PanCa) is associated with poor prognosis and overall survival. Current first-line therapeutics are cytotoxic agents targeting DNA based mechanistic end-points for efficacy, their use limited by dose associated toxicity. There is a critical need for therapeutics with novel mechanisms amenable to combination with current standard-of-care chemotherapy to improve outcomes. BPM 31510 is a drug that targets cellular metabolism networks, effectuating an anti-Warburg effect in cancer. The documented high metabolic phenotype observed in PanCa provided rationale for investigation of BPM 31510 alone and in combination with gemcitabine in in vitro and in vivo PanCa models. Based on BPM 31510 EC50/EC>90 values for MIA-PaCa-2 and Panc-1 PanCa cell lines in vitro, the PanCa cells were significantly more sensitive to BPM 31510 compared to fibroblasts. BPM 31510 treatment in a time- and dose-dependent manner decreased the PI- and Annexin V-negative (viable) population and a concomitant increase in the percentage of Annexin V-positive cells, with PI indicative of early and late apoptosis. The anti-cancer activity of BPM 31510 was assessed in vivo using MIA-PaCa-2 tumor-bearing immune-compromised mice. Treatment with increasing doses of BPM 31510 (0.5-50 mg/kg IP, 3X/week) significantly improved survival outcomes, with the highest dose extending median survival by more than 36 days compared to saline control. Moreover, combined treatment with BPM 31510 and gemcitabine (150 mg/kg IV, 1X/week, given on cycles, 3 weeks on 1 week) resulted in further extension of median survival over either treatment alone. The mechanistic underpinnings for the enhanced efficacy of combination treatment were explored in vitro. In MIA-PaCa-2 cells, co-treatment with BPM 31510 and gemcitabine increased indices of regulated cell death higher than observed for either treatment alone. In contrast, although treatment with either BPM 31510 or gemcitabine alone increased caspase-3 activity, co-treatment did not enhance caspase-3 activation, suggesting that BPM 31510 augments gemcitabine cytotoxicity through independent mechanisms. In fact, BPM31510, and not gemcitabine, increased the mitochondrial uncoupling efficient ratio and Stateapparent in MIA-PaCa-2 cells. Nonetheless, co-treatment with BPM 31510 and gemcitabine synergistically decreased the mitochondrial membrane potential (ΔΨm) in cells prior to cell death. Taken together, these data indicate that BPM 31510-driven bioenergetic alterations are separate from the effects of gemcitabine; however, their effects converge at the mitochondrion to dissipate ΔΨm and activate regulated cell death. The data suggests that combination of BPM 31510 with gemcitabine in pancreatic cancer will effectuate an efficacy response via independent mechanisms with improvement in therapeutic outcome.

Citation Format: Tulin Dadali, Anne R. Diers, Rakib Ouro-Djobo, Justin Bourdelais, Ezer Benaim, Bianca Jambhekar, Tony E. Walshe, Vivek K. Vishnudas, Joaquin J. Jimenez, Rangaprasad Sarangarajan, Niven R. Narain. BPM 31510 synergizes gemcitabine efficacy in pancreatic adenocarcinoma via mechanism independent of its anti-Warburg influence on metabolism. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 212.

Abstract C117: BPM 31510 enhances efficacy of gemcitabine through orthogonal mechanisms in a preclinical model of pancreatic adenocarcinoma

Despite global advances in cancer detection and treatment in some indications, the early diagnosis and overall survival rate for pancreatic cancer (PanCa) remains dismal. Thus, there is a critical need for novel therapeutics that may combine well with standard-of-care therapy or work through novel mechanisms. Given that most pancreatic tumors exhibit a highly metabolic phenotype, we examined the effects of BPM 31510 employing in vitro and in vivo PanCa models. BPM 31510 is a metabolic-modulating agent that reverses the Warburg effect and is currently in clinical development for solid tumors alone and in combination with chemotherapy. Determination of BPM 31510 IC50 values in vitro demonstrated the PanCa cell lines MIA PaCa-2 and Panc-1 cells were significantly more sensitive to BPM 31510 (IC50 = 137 and 455 μM, respectively) compared to primary fibroblasts (IC50 = 1537 μM). IC50 and IC90 doses of BPM 31510 also decreased the viable cell population while concomitantly increasing Annexin V- and PI-positive populations in both PanCa cell types, indicating BPM 31510 induces programmed cell death. Furthermore, in combination with gemcitabine (0.1-5 μM), BPM 31510 (100 μM) decreased cell viability by more than 75% compared to either treatment alone. In vivo, treatment of MIA PaCa-2 tumor-bearing mice with increasing doses of BPM 31510 (0.5-50 mg/kg IP, 3X/week) significantly improved median survival in a dose-dependent manner, with the highest dose extending median survival by more than 36 days compared to saline control. Moreover, while median survival of MIA PaCa-2 tumor-bearing mice treated with BPM 31510 (50 mg/kg IP, 1X/day) or gemcitabine (150 mg/kg IV, 1X/week, given on cycles, 3 weeks on 1 week) monotherapy was 77 and 63 days, respectively, combination treatment resulted in median survival improvement to 113.5 days. Examination of alternative dosing regimens revealed that more frequent dosing of BPM 31510 (2X or 3X/day) alone and in combination with gemcitabine further extended median survival in this model. The preliminary mechanistic insight into additive efficacy of combination treatment was explored in vitro. BPM 31510 treatment alone significantly altered multiple aspects of mitochondrial function in MIA PaCa-2 cells, indicating that BPM 31510-driven bioenergetic alterations are separate from the effects of gemcitabine. Hence, these data demonstrate that BPM 31510 has a potent anti-cancer activity alone and in combination with standard-of-care chemotherapy in preclinical PanCa models.

Citation Format: Tulin Dadali, Anne R. Diers, Arleide Lee, Rakibou Ouro-Djobo, Justin Bourdelais, Ezer Benaim, Bianca Jambhekar, Tony E. Walshe, Joaquin J. Jimenez, Vivek K. Vishnudas, Rangaprasad Sarangarajan, Niven R. Narain. BPM 31510 enhances efficacy of gemcitabine through orthogonal mechanisms in a preclinical model of pancreatic adenocarcinoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C117.

Abstract A22: Identification of novel tumor derived factors that inhibit angiogenesis

Background: Cell-cell communication in the tumor micro-environment drive tumor growth and facilitate neovessel recruitment from the adjacent vasculature. The present study was designed to identify novel cancer derived factors that modulate the vascular endothelial response in a paracrine manner.

Methods: An array of cancer cell lines from multiple tissue types (Panc1; HepG2; LnCap; Skmel; Hep3B; PL45; SCC25; CaCo2; PaCa2; SKBR3) were grown under normoxic or hypoxic (1% oxygen) conditions for a total of 20 different conditions. After 48 hours, conditioned media was collected and filtered prior to testing on endothelial cells. The effects of the conditioned media on endothelial apoptosis, proliferation and tube formation were investigated. In tandem with these endothelial cell fate assays, the proteomic profile of these 20 conditions was profiled and assessed using the Berg Interrogative Biology™ platform.

Results & Discussion: Our results reveal that conditioned media from all cancer cells tested can alter endothelial cell apoptosis, proliferation rate and tube formation in 3D matrigel assays i.e. critical cell fate decisions that enable formation of nascent vessel formation. As predicted, the predominant effect of tumor-derived conditioned media on endothelial apoptosis was a protective anti-apoptotic effect, with the discernable exception of normoxic Panc1 derived media. An unexpected finding was the general anti-proliferative effects of tumor-derived conditioned media on endothelial cell growth, with the exception of Hep2G, LnCap and PaCa2 cell derived media. Using a media fractionation strategy and Interrogative Biology™, we identified several endothelial anti-apoptotic candidates from Panc1 cells within a unique molecular weight range. Upon application of ASO gene knockdown in Panc1 cells, these targets were verified for apoptotic and proliferation effects on vascular endothelial cells.

Conclusion: Specific factors that determine paracrine cell-cell interaction in the tumor microenvironment have been identified and validated employing Berg Interrogative Biology™. The technology presented herein represents a viable platform for identifying clinically relevant biomarkers and factors that alter cancer angiogenesis.

Citation Format: Tony E. Walshe, Justin Bourdelais, Arleide Lee, Rakibou Ouro-Djobo, Vivek Vishnudas, Rangaprasad Sarangarajan, Niven Narain. Identification of novel tumor derived factors that inhibit angiogenesis. [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 A22.

Abstract 3358: Significant increase in survival of triple negative breast cancer animal model in response to BPM31510 alone or in combination with standard of care: BPM31510 mediated dynamic metabolic (Warburg) shift in breast cancer as potential mechanism

This study demonstrates that BPM 31510, a Coenzyme Q10 containing proprietary formulation to influences cellular metabolism that is deregulated in cancers and is now considered to be a “hallmark of cancer”. These studies demonstrate that BPM 31510 alone or in combination with standard of care significantly improved survival of triple negative breast cancer (TNBC) animal model. To further tease out beneficial effects of BPM31510, human breast cancer cells of varying receptor status (SKBR3, MDA-MB231) were subjected to either (a) pretreatment with BPM 31510 (6 h) followed co-incubation with chemotherapeutic agents for 48-72 h or (b) co-treatment with BPM 31510 and chemotherapeutic agents, and cancer cell responses were compared to non-tumorigenic mammary cells (MCF12A). Cellular bioenergetics profiling revealed that BPM 31510 shifted cellular metabolism from glycolysis to mitochondrial metabolism, and this metabolic shift was associated with significant increases in reactive oxygen species (ROS). Both BPM 31510 alone or pretreatment and cotreatment strategies with BPM 31510 plus standard of care resulted in significant decreases in viable breast cancer cells when compared to chemotherapeutic agents; however, minimal effects were observed in MCF12A cells. In contrast, BPM 31510 in combination with chemotherapeutic agents amplified caspase 3 activation and apoptotic cell death, indicating BPM 31510 enhances apoptotic signaling. Taken together, these data demonstrate that BPM 31510 is a novel agent that reengages the cellular metabolic and apoptotic machinery of cancer cells independent of genetic make-up underlying malignancy. In addition, BPM 31510 enhances the cytotoxicity of standard-of-care chemotherapeutic agents in breast cancer cells through regulation of mitochondrial metabolism and oxidative stress. These findings confirm that BPM 31510 is a novel, paradigm shifting agent with multiple utility (as a single agent or in combination) in breast cancer including TNBCs that otherwise have poor prognosis and limited therapeutic options.

Citation Format: Niven R. Narain, Anne R. Diers, Tony E. Walshe, Arleide Lee, Rakib Ouro-Djobo, Vivek K. Vishnudas, Ely Benaim, Rangaprasad Sarangarajan. Significant increase in survival of triple negative breast cancer animal model in response to BPM31510 alone or in combination with standard of care: BPM31510 mediated dynamic metabolic (Warburg) shift in breast cancer as potential mechanism. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3358. doi:10.1158/1538-7445.AM2014-3358

The role of shear-induced transforming growth factor-β signaling in the endothelium

OBJECTIVE

Vascular endothelial cells (ECs) are continuously exposed to blood flow that contributes to the maintenance of vessel structure and function; however, the effect of hemodynamic forces on transforming growth factor-β (TGF-β) signaling in the endothelium is poorly described. We examined the potential role of TGF-β signaling in mediating the protective effects of shear stress on ECs.

APPROACH AND RESULTS

Human umbilical vein ECs (HUVECs) exposed to shear stress were compared with cells grown under static conditions. Signaling through the TGF-β receptor ALK5 was inhibited with SB525334. Cells were examined for morphological changes and harvested for analysis by real-time polymerase chain reaction, Western blot analysis, apoptosis, proliferation, and immunocytochemistry. Shear stress resulted in ALK5-dependent alignment of HUVECs as well as attenuation of apoptosis and proliferation compared with static controls. Shear stress led to an ALK5-dependent increase in TGF-β3 and Krüppel-like factor 2, phosphorylation of endothelial NO synthase, and NO release. Addition of the NO donor S-nitroso-N-acetylpenicillamine rescued the cells from apoptosis attributable to ALK5 inhibition under shear stress. Knockdown of TGF-β3, but not TGF-β1, disrupted the HUVEC monolayer and prevented the induction of Krüppel-like factor 2 by shear.

CONCLUSIONS

Shear stress of HUVECs induces TGF-β3 signaling and subsequent activation of Krüppel-like factor 2 and NO, and represents a novel role for TGF-β3 in the maintenance of HUVEC homeostasis in a hemodynamic environment.

Vascular endothelial growth factor is important for brown adipose tissue development and maintenance

Vascular endothelial growth factor (VEGF) is critical for angiogenesis, but also has pleiotropic effects on several nonvascular cells. Our aim was to investigate the role of VEGF in brown adipose tissue (BAT). We show that VEGF expression increases 2.5-fold during differentiation of cultured murine brown adipocytes and that VEGF receptor-2 is phosphorylated, indicating VEGF signaling. VEGF increased proliferation in brown preadipocytes in vitro by 70%, and blockade of VEGF signaling using anti-VEGFR2 antibody DC101 increased brown adipocyte apoptosis, as determined by cell number and activation of caspase 3. Systemic VEGF neutralization in mice, accomplished by adenoviral expression of soluble Flt1, resulted in 7-fold increase in brown adipocyte apoptosis, mitochondrial degeneration, and increased mitophagy compared to control mice expressing a null adenovirus. Absence of the heparan sulfate-binding VEGF isoforms, VEGF164 and VEGF188, resulted in abnormal BAT development in mice at E15.5, with fewer brown adipocytes and lower mitochondrial protein compared to wild-type littermates. These results suggest a role for VEGF in brown adipocytes and preadipocytes to promote survival, proliferation, and normal mitochondria and development.

Abstract 1736: Mitochondrial priming of apoptotic machinery in pancreatic cancer by BPM 31510 to enhance efficacy of chemotherapy

Recent evidence suggests that the cytotoxic effects of chemotherapy, specifically in cancer cells is a consequence of “pre-treatment priming” event wherein exposure to the chemotherapeutic agents pushes the cancer cells beyond an apoptotic threshold to effectuate cell death. (Letai, A et. al, Science. 2011 Nov 25;334 (6059) BPM 31510 is a ubidecarenone containing proprietary formulation that effectuates a metabolic switch from glycolysis towards enhanced mitochondrial oxidative phosphorylation resulting in the recapitulation of apoptosis in cancer. The current study was aimed at investigating whether pretreatment with BPM 31510 results in mitochondrial priming, thereby augmenting the cytotoxic effect of standard of care chemotherapeutic agents. The human derived pancreatic cancer cell line Mia-Paca-2 was subjected to either (a) pretreatment with BPM 31510 followed by co-treatment with gemcitabine or (b) co-treatment with BPM 31510 and gemcitabine. BPM 31510 exposure resulted in decreased cell proliferation rates that were significantly higher than gemcitabine alone in Mia-Paca-2 cell line. Pre-treatment with BPM 31510 augmented the cytotoxic potential of gemcitabine, a phenomenon that was also observed in the co-treatment regimen. In vivo pancreatic cancer model using Mia-Paca-2 cell lines were developed to further investigate the priming effect of BPM 31510. Results demonstrate that 1-week and 2-week pretreatment with intravenous BPM 31510 followed by gemcitabine results in improved survival in the pancreatic cancer model compared to the co-treatment regimen. The data demonstrates that addition of BPM

31510 synergizes the cytotoxic effect of gemcitabine in pancreatic cancer. In addition, pretreatment with BPM 31510 followed by gemcitabine treatment is associated with improved survival. Taken together, the data suggest that BPM 31510 may be a viable mitochondrial priming agent to sensitize cancer cells to the cytotoxic effects of gemcitabine in pancreatic cancer.

Citation Format: Niven R. Narain, Tony E. Walshe, Arleide Lee, Rakib Ouro-Djoba, Lucia Mauro, Adel Yunis, Vivek K. Vishnudas, Rangaprasad Sarangarjan, Joaquin J. Jimenez. Mitochondrial priming of apoptotic machinery in pancreatic cancer by BPM 31510 to enhance efficacy of chemotherapy. [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 1736. doi:10.1158/1538-7445.AM2013-1736

Expression and role of VEGF--a in the ciliary body

PURPOSE

The role of VEGF-A in the normal ciliary body is largely unexplored. The ciliary body is similar in many respects to the choroid plexus of the brain, and we demonstrated previously the importance of VEGF-A in maintenance of choroid plexus vasculature and ependymal cells. Therefore, the role of VEGF-A in ciliary body homeostasis was explored.

METHODS

Swiss-Webster mice (VEGF-LacZ) were used to determine VEGF-A expression during ciliary body development and in the adult. VEGFR2 expression was determined in adult wild type C56BL/6J mice. Systemic VEGF-A neutralization in vivo was achieved with adenovirus-mediated overexpression of soluble VEGFR1 (sFlt1). Following VEGF-A neutralization, the ciliary epithelium was analyzed by light microscopy and transmission electron microscopy (TEM). The effect of VEGF-A blockade on ciliary body function also was assessed by measuring intraocular pressure.

RESULTS

VEGF-A expression was detected at embryonic day 18.5 (E18.5), the onset of ciliary process formation. In the adult ciliary body, VEGF-A was expressed by the pigmented epithelium, whereas VEGFR2 was localized primarily to the capillary endothelium and nonpigmented epithelium. Systemic VEGF-A neutralization led to a thinning of the nonpigmented epithelium, vacuolization of the pigmented epithelium, loss of capillary fenestrations, and thrombosis. These changes were associated with impaired ciliary body function, as evidenced by decreased intraocular pressure in sFlt1-overexpressing animals (15.31 ± 2.06 mm Hg) relative to controls (18.69 ± 1.49 mm Hg).

CONCLUSIONS

VEGF-A has an important role in ciliary body homeostasis. Potential for undesired off-target effects should be considered with the chronic use of anti-VEGF-A therapies.

Abstract 2335: API 31510 - a novel anti-angiogenic modulator of endothelial cells and the tumor microenvironment

Progression of tumor size greater than 2-5mm in size requires induction of angiogenesis to supply the tumor with oxygen and nutrients. Angiogenesis occurs due to intra-tumoral cell release of endothelial mitogenic factors in response to hypoxia or genetic mutation. There are currently numerous endogenous proteins in clinical development as therapeutic anti-angiogenesis targets e.g. VEGF and PlGF. Herein, we have investigated a novel anti-angiogenic agent API 31510 currently subject of late stage clinical trials in skin cancers and a Phase I for solid tumors. Human umbilical vein endothelial cell (HUVEC) fate decisions that modulate the angiogenic phenotype were examined in the presence of 100 µM or 1500 µM 31510 or excipient and compared to untreated control cells. Endothelial cell fate assays for apoptosis, proliferation, migration and 3-D tube formation within matrigel were performed. Morphological & flow cytometric analysis of annexin V/propidium iodide positive cells revealed an increase in HUVEC apoptosis in the presence of 1500 µM 31510, compared to excipient or control cells. Concomitant with increased cell death due to 31510, HUVEC cell counts were significantly decreased in the presence of 1500 µM 31510. To assess the potential effects of 31510 on endothelial migration, we examined HUVEC migration 5 hours post-wound generation, in an endothelial scratch assay. Both 31510 and excipient significantly impaired HUVEC migration at both 100 and 1500 µM concentration, demonstrating anti-migratory activity of both the excipient and 31510. In order to determine if the 31510 anti-tumor activity is due to effects on endothelial sprouting angiogenesis, we examined endothelial tube formation in 3-D matrigel cultures over time. Addition of 1500 µM excipient in both the gel and overlying media impaired tube formation compared to control. Moreover, addition of 1500 µM 31510 further impaired HUVEC tube formation compared to both excipient and control untreated cells. These effects were noted as early as 24 hours after seeding and up to 96 hours in culture. Moreover, histological analyses from excised tumors from pre-clinical animal models in melanoma, SCC, liver cancer, and pancreatic cancer confirm a hallmark downregulation in angiogenic signaling and infrastructure. Anti-tumor activity of 31510 is likely due, at least is part, to inhibition of tumor recruitment of local blood supply for neo-vessel formation. Taken together, these studies reveal that 31510 alters endothelial migration, proliferation, apoptosis and tube formation. These studies strongly support a role for API 31510 as a novel anti-angiogenic agent that limits the angiogenic capacity of endothelial cells while modulating tumor angiogenesis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2335. doi:1538-7445.AM2012-2335

Role of shear-stress-induced VEGF expression in endothelial cell survival

Vascular endothelial growth factor (VEGF) plays a crucial role in developmental and pathological angiogenesis. Expression of VEGF in quiescent adult tissue suggests a potential role in the maintenance of mature blood vessels. We demonstrate, using a Vegf-lacZ reporter mouse model, that VEGF is expressed by arterial but not by venous or capillary endothelial cells (ECs) in vivo. Using an in vitro model, we show that arterial shear stress of human umbilical vein ECs (HUVECs) decreases apoptosis and increases VEGF expression, which is mediated by the induction of Krüppel-like factor 2 (KLF2). Additionally, shear stress stimulates the expression of VEGF receptor 2 (VEGFR2) and is associated with its activation. Knockdown of VEGF in shear stressed HUVECs blocks the protective effect of shear stress, resulting in EC apoptosis equivalent to that in control ECs cultured under static conditions. Similarly, treatment of ECs subjected to arterial shear stress with the VEGF receptor tyrosine kinase inhibitor SU1498, or VEGFR2 neutralizing antiserum, led to increased apoptosis, demonstrating that the mechanoprotection from increased shear is mediated by VEGFR2. Taken together, these studies suggest that arterial flow induces VEGF-VEGFR2 autocrine-juxtacrine signaling, which is a previously unidentified mechanism for vascular EC survival in adult arterial blood vessels.

Heat treatment of retinal pigment epithelium induces production of elastic lamina components and antiangiogenic activity

Age-related macular degeneration (AMD) is the leading cause of blindness in the Western world. In advanced AMD, new vessels from choriocapillaris (CC) invade through the Bruch's membrane (BrM) into the retina, forming choroidal neovascularization (CNV). BrM, an elastic lamina that is located between the retinal pigment epithelium (RPE) and CC, is thought to act as a physical and functional barrier against CNV. The BrM of patients with early AMD are characterized by decreased levels of antiangiogenic factors, including endostatin, thrombospondin-1 (TSP-1), and pigment epithelium-derived factor (PEDF), as well as by degeneration of the elastic layer. Motivated by a previous report that heat increases elastin expression in human skin, we examined the effect of heat on human ARPE-19 cell production of BrM components. Heat treatment stimulated the production of BrM components, including TSP-1, PEDF, and tropoelastin in vitro and increased the antiangiogenic activity of RPE measured in a mouse corneal pocket assay. The effect of heat on experimental CNV was investigated by pretreating the retina with heat via infrared diode laser prior to the induction of CNV. Heat treatment blocked the development of experimental CNV in vivo. These findings suggest that heat treatment may restore BrM integrity and barrier function against new vessel growth.

Microvascular retinal endothelial and pericyte cell apoptosis in vitro: role of hedgehog and Notch signaling

PURPOSE

Aberrant retinal blood flow is a hallmark of retinopathies and may be a causative factor in their pathophysiology. In this study, the effects of pulsatile flow on hedgehog and Notch control of retinal endothelial cell and pericyte apoptosis were examined.

METHODS

The levels of hedgehog and Notch signaling components in bovine retinal endothelial cells (BRECs) and pericytes (BRPs) were examined in vitro under static conditions and after exposure to pulsatile flow, with a perfused transcapillary co-culture system. Notch and hedgehog signaling was examined by immunocytochemistry, immunoblot, and real-time PCR.

RESULTS

Notch and hedgehog proteins were present in BRECs and BRPs in vitro and in human retinal vasculature in vivo. Inhibition of hedgehog with cyclopamine and Notch with DAPT decreased hedgehog target gene levels and Notch intracellular receptor expression, respectively, concomitant with an increase in BREC and BRP apoptosis. Sonic hedgehog (Shh) mediated upregulation of Notch1 receptor levels was attenuated after cyclopamine treatment in both cell types. Exposure of co-cultured BRECs and BRPs to pulsatile flow increased apoptosis in the BRPs while concurrently decreasing apoptosis in the BRECs. These changes were concomitant with increased expression of Notch and hedgehog signaling components in the BRECs and reduced expression in the BRPs. The flow-induced decrease in apoptosis in the BRECs was associated with increased Notch receptor expression and was reversed after inhibition of hedgehog signaling with cyclopamine and inhibition of Notch signaling after ectopic expression of the CBF-1/RBP-Jκ-binding protein, RPMS-1.

CONCLUSIONS

Pulsatile flow promotes BREC survival and enhances BRP apoptosis through modulation of Notch and hedgehog pathways. These interactions have important implications for the pathogenesis of retinopathies.

TGF-β signaling is required for maintenance of retinal ganglion cell differentiation and survival

PURPOSE

To determine the role of TGF-β1 in the maintenance of retinal ganglion cell line (RGC-5) differentiation and integrity.

METHODS

RGC-5 cells were differentiated in media conditioned by human non-pigmented ciliary epithelial cells (HNPE) for 4 days before treatment with TGF-β1 for 24 h. Cells were examined for morphological changes and harvested for western blot and real-time PCR analysis. For study of apoptosis, differentiated RGC-5 cells were grown in serum-free medium for 24 h in the presence or absence of TGF-β1 and collected for Annexin V/Propidium iodide FACs analysis. The role of MAPK pathways in TGF-β1-dependent signaling was determined by treatment with specific inhibitors of ERK, JNK and p38.

RESULTS

Differentiation of RGC-5 cells in HNPE-conditioned media (CM) increased the neural cell markers, Brn-3c, NF-160, Thy1.2, Tau and PGP9.5. Treatment with TGF-β1 significantly increased the length of neurites extended by differentiated RGC-5s, concomitant with increased expression of NF-160 and PGP9.5, but not Brn-3c, Thy1.2 or Tau. TGF-β1 also decreased RGC-5 cell apoptosis in serum-free medium. p38 phosphorylation, but not smad2/3, JNK or ERK phosphorylation, was increased in TGF-β1 treated cells. Specific inhibition of p38 signaling reversed TGF-β1 induced neurite growth.

CONCLUSIONS

These findings demonstrate the induction of RGC-5 cell differentiation by HNPE-derived CM and illustrate a role for TGF-β1 in maintaining RGC-5 cell survival and promoting neurite outgrowth through p38 MAPK.

The role of pulsatile flow in controlling microvascular retinal endothelial and pericyte cell apoptosis and proliferation

AIMS

Aberrant retinal blood flow is a hallmark of various retinopathies and may be a causative factor in the pathology associated with these conditions. We examined the effects of pulsatile flow on bovine retinal endothelial cell (BREC) and bovine retinal pericyte (BRP) apoptosis and proliferation.

METHODS AND RESULTS

Co-cultured BRECs and BRPs were exposed to low (0.3 mL/min) or high (25 mL/min) pulsatile flow for 72 h using a perfused transcapillary culture system. Pulsatile flow increased BREC nitric oxide synthase (eNOS) and cyclooxygenase-2 (COX-2) expression and activity concomitant with a significant decrease in pre-pro-endothelin-1 (ET-1) mRNA and peptide. BREC apoptosis was significantly attenuated following exposure to high flow. The inhibition of NOS, COX, and ET receptors significantly reduced the pro-survival effects of flow on BREC. In contrast, BRP apoptosis was significantly enhanced following exposure to high flow. The inhibition of COX and ET receptors significantly attenuated the high flow-induced increase in BRP apoptosis when compared with untreated controls. Treatment of static BREC with NO donor (S-nitroso-N-acetylpenicillamine, SNAP), ET-1, or iloprost inhibited serum deprivation-induced apoptosis, whereas treatment of BRP with ET-1 and iloprost, but not SNAP, was ineffective. High pulsatile flow decreased BRP proliferation, in the absence of any changes in BREC proliferation.

CONCLUSION

Increased pulsatile flow promotes BREC survival and enhances BRP apoptosis through the activation of endothelial-derived vasoactive substances. Altered pulsatile flow does not alter BREC proliferation in co-culture with BRP, whereas BRP proliferation was significantly decreased at high flow rates. These interactions have important implications for vessel growth and regression during retinal vascular pathogenesis.

RhoA/ROCK signaling is essential for multiple aspects of VEGF-mediated angiogenesis

The small GTPase RhoA and its downstream effectors, ROCK1 and ROCK2, regulate a number of cellular processes, including cell motility, proliferation, survival, and permeability. Pharmacological inhibitors of the Rho pathway reportedly block angiogenesis; however, the molecular details of this inhibition are largely unknown. We demonstrate that vascular endothelial growth factor-A (VEGF) rapidly induces RhoA activation in endothelial cells (ECs). Moreover, the pharmacological inhibition of ROCK1/2 using 10 microM Y-27632 (the IC(50) for this compound in ECs) strongly disrupts vasculogenesis in pluripotent embryonic stem cell cultures, VEGF-mediated regenerative angiogenesis in ex vivo retinal explants, and VEGF-mediated in vitro EC tube formation. Furthermore, using small interfering RNA knockdown and mouse heterozygote knockouts of ROCK1 and ROCK2, we provide data indicating that VEGF-driven angiogenesis is largely mediated through ROCK2. These data demonstrate that Rho/ROCK signaling is an important mediator in a number of angiogenic processes, including EC migration, survival, and cell permeability, and suggest that Rho/ROCK inhibition may prove useful for the treatment of angiogenesis-related disorders.

Inhibition of VEGF or TGF-{beta} signaling activates endothelium and increases leukocyte rolling

OBJECTIVE

Motivated by the central roles that vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-beta play in the assembly and maintenance of the vasculature, we examined the impact of systemic VEGF or TGF-beta signal inhibition on endothelial activation as detected by leukocyte-endothelial interactions.

METHODS AND RESULTS

VEGF or TGF-beta inhibition, accomplished using adenovirus expression of soluble Flt1 (Ad-sFlt1) or soluble endoglin (Ad-sEng), resulted in a significant increase in the number of leukocytes rolling along the mesenteric venous endothelium and a significant decrease in rolling velocity in Ad-sEng mice. Neutralization of VEGF or TGF-beta resulted in endothelial surface expression of P-selectin and impaired peripheral vasodilatation. Neither inhibition of VEGF nor TGF-beta was associated with platelet or leukocyte activation, as detected by the activation markers platelet P-selectin and the active integrin alphaIIbbetaIII, or by leukocyte expression of L-selectin. Soluble vascular cell adhesion molecule (VCAM)-1 and E-selectin were increased in sEng-expressing mice, indicating higher levels of these adhesion receptors.

CONCLUSIONS

VEGF or TGF-beta neutralization leads to impaired endothelium-mediated vasodilatation and elevated expression of surface adhesion molecules, resulting in increased leukocyte adhesion. These results indicate an essential role for both VEGF and TGF-beta in maintaining the endothelium in a nonactivated state and have implications for therapeutic approaches that neutralize VEGF or TGF-beta.

Endogenous VEGF is required for visual function: evidence for a survival role on müller cells and photoreceptors

Background

Vascular endothelial growth factor (VEGF) is well known for its role in normal and pathologic neovascularization. However, a growing body of evidence indicates that VEGF also acts on non-vascular cells, both developmentally as well as in the adult. In light of the widespread use of systemic and intraocular anti-VEGF therapies for the treatment of angiogenesis associated with tumor growth and wet macular degeneration, systematic investigation of the role of VEGF in the adult retina is critical.

Methods and Findings

Using immunohistochemistry and Lac-Z reporter mouse lines, we report that VEGF is produced by various cells in the adult mouse retina and that VEGFR2, the primary signaling receptor, is also widely expressed, with strong expression by Müller cells and photoreceptors. Systemic neutralization of VEGF was accomplished in mice by adenoviral expression of sFlt1. After 14 days of VEGF neutralization, there was no effect on the inner and outer retina vasculature, but a significant increase in apoptosis of cells in the inner and outer nuclear layers. By four weeks, the increase in neural cell death was associated with reduced thickness of the inner and outer nuclear layers and a decline in retinal function as measured by electroretinograms. siRNA-based suppression of VEGF expression in a Müller cell line in vitro supports the existence of an autocrine role for VEGF in Müller cell survival. Similarly, the addition of exogenous VEGF to freshly isolated photoreceptor cells and outer-nuclear-layer explants demonstrated VEGF to be highly neuroprotective.

Conclusions

These results indicate an important role for endogenous VEGF in the maintenance and function of adult retina neuronal cells and indicate that anti-VEGF therapies should be administered with caution.

The role of hypoxia in vascular injury and repair

Although the terms ischemia and hypoxia are often used interchangeably, they represent distinct processes that result in different modulatory effects at the cellular level. Hypoxia is a reduction in oxygen delivery below tissue demand, whereas ischemia is a lack of perfusion, characterized not only by hypoxia but also by insufficient nutrient supply. Hypoxia can be either acute or chronic, and both are centrally regulated by hypoxia-inducible factor, a transcription factor that governs the expression of key response genes such as vascular endothelial growth factor and erythropoietin. Whereas severe chronic hypoxia can cause cell death, less-severe hypoxia can protect against subsequent damage, a phenomenon known as hypoxic conditioning. Several important processes are characterized by hypoxia, including ischemia-reperfusion, tumor growth and progression, inflammation, myocardial ischemia, and a number of ocular pathologies.

VEGF and TGF-beta are required for the maintenance of the choroid plexus and ependyma

Although the role of vascular endothelial growth factor (VEGF) in developmental and pathological angiogenesis is well established, its function in the adult is less clear. Similarly, although transforming growth factor (TGF) β is involved in angiogenesis, presumably by mediating capillary (endothelial cell [EC]) stability, its involvement in quiescent vasculature is virtually uninvestigated. Given the neurological findings in patients treated with VEGF-neutralizing therapy (bevacizumab) and in patients with severe preeclampsia, which is mediated by soluble VEGF receptor 1/soluble Fms-like tyrosine kinase receptor 1 and soluble endoglin, a TGF-β signaling inhibitor, we investigated the roles of VEGF and TGF-β in choroid plexus (CP) integrity and function in adult mice. Receptors for VEGF and TGF-β were detected in adult CP, as well as on ependymal cells. Inhibition of VEGF led to decreased CP vascular perfusion, which was associated with fibrin deposition. Simultaneous blockade of VEGF and TGF-β resulted in the loss of fenestrae on CP vasculature and thickening of the otherwise attenuated capillary endothelium, as well as the disappearance of ependymal cell microvilli and the development of periventricular edema. These results provide compelling evidence that both VEGF and TGF-β are involved in the regulation of EC stability, ependymal cell function, and periventricular permeability.

Coordinated vascular endothelial growth factor expression and signaling during skeletal myogenic differentiation

Angiogenesis is largely controlled by hypoxia-driven transcriptional up-regulation and secretion of vascular endothelial growth factor (VEGF) and its binding to the endothelial cell tyrosine receptor kinases, VEGFR1 and VEGFR2. Recent expression analysis suggests that VEGF is expressed in a cell-specific manner in normoxic adult tissue; however, the transcriptional regulation and role of VEGF in these tissues remains fundamentally unknown. In this report we demonstrate that VEGF is coordinately up-regulated during terminal skeletal muscle differentiation. We reveal that this regulation is mediated in part by MyoD homo- and hetero-dimeric transcriptional mechanisms. Serial deletions of the VEGF promoter elucidated a region containing three tandem CANNTG consensus MyoD sites serving as essential sites of direct interaction for MyoD-mediated up-regulation of VEGF transcription. VEGF-null embryonic stem (ES) cells exhibited reduced myogenic differentiation compared with wild-type ES cells, suggesting that VEGF may serve a role in skeletal muscle differentiation. We demonstrate that VEGFR1 and VEGFR2 are expressed at low levels in myogenic precursor cells and are robustly activated upon VEGF stimulation and that their expression is coordinately regulated during skeletal muscle differentiation. VEGF stimulation of differentiating C2C12 cells promoted myotube hypertrophy and increased myogenic differentiation, whereas addition of sFlt1, a VEGF inhibitor, resulted in myotube hypotrophy and inhibited myogenic differentiation. We further provide evidence indicating VEGF-mediated myogenic marker expression, mitogenic activity, migration, and prosurvival functions may contribute to increased myogenesis. These data suggest a novel mechanism whereby VEGF is coordinately regulated as part of the myogenic differentiation program and serves an autocrine function regulating skeletal myogenesis.

Vasospasm in Glaucoma: Clinical and Laboratory Aspects

During the last decade, the presumed etiology of glaucoma has moved from a pure pressure concept to a combined mechanical and vascular theory. Evidence of a localized vascular insufficiency leading to perfusion deficits of ocular structures, including the optic nerve head, the retina, the choroid, and the retrobulbar vessels, is now clear. This article evaluates the role of vasospasm as the primary cause of such a vascular failure. The role of both ocular and systemic vasospasms and their clinical correlations are discussed. At a cellular level, the function of the modulating role of the vascular endothelium is reviewed. Evidence of abnormalities of the vascular endothelium and its vasoactive peptides as a conduit for vasospasm is mounting. Herein lies exciting prospects for potential pharmacologic targets in future glaucoma management.

Pulsatile Flow Increases the Expression of eNOS, ET-1, and Prostacyclin in a Novel In Vitro Coculture Model of the Retinal Vasculature

PURPOSE

By the development of a novel retinal microvascular endothelial and pericyte cell coculture system, this study determined the effects of pulsatile flow on the activation of the endothelial cell markers nitric oxide (NO), prostacyclin (PGI2), and endothelin (ET)-1.

METHODS

Monocultured bovine retinal endothelial cells (BRECs) and cocultured BRECs with bovine retinal pericytes (BRPs) were exposed to low flow (flow rate, 0.3 mL/min; pulse pressure, 6 mmHg; shear stress, 0.5 dyne/cm2) or high flow (flow rate, 25 mL/min; pulse pressure, 56 mmHg; shear stress, 23 dynes/cm2) for 24 hours, by using a novel perfused transcapillary culture system. The cells were characterized by immunohistochemistry and electron and confocal microscopy. Endothelial nitric oxide synthase (eNOS) and phosphorylated-eNOSSer1179 (pp-eNOS) were determined by Western blot analysis. Nitrate, PGI2, and ET-1 levels were quantified in the medium perfusate by using fluorometric and enzyme-linked immunosorbent assays, respectively. Activation of cyclooxygenase (COX)-2 in BRECs was determined by measuring COX-2 promoter activity with a luciferase reporter assay.

RESULTS

The presence of BRPs and BRECs was confirmed by Western blot, immunocytochemistry, and scanning electron microscopy. Phosphorylated eNOS (pp-eNOS) protein levels in BRECs were significantly increased from low to high flow in both mono- and cocultures, concomitant with a significant increase in nitrate levels in the conditioned medium after exposure to pulsatile flow. In parallel cultures, PGI2 levels were also significantly enhanced concomitant with an increase in the transactivation of a COX-2 promoter BREC after exposure to pulsatile flow. ET-1 levels were also increased in both mono- and cocultured cells. conclusions. In this study a novel, functioning, in vitro model of retinal microvascular endothelial and pericyte cells that respond to changes in pulsatile flow was established.