Tie2-dependent deletion of α6 integrin subunit in mice reduces tumor growth and angiogenesis

In vitro inhibition of cancer angiogenesis and migration by a nanobody that targets the orphan receptor Tie1

The human signaling molecules Tie1 and Tie2 receptor tyrosine kinases (RTKs) play important pathophysiological roles in many diseases, including different cancers. The activity of Tie1 is mediated mainly through the downstream angiopoietin-1 (Ang1)-dependent activation of Tie2, rendering both Tie 1 and the Tie1/Tie2/Ang1 axis attractive putative targets for therapeutic intervention. However, the development of inhibitors that target Tie1 and an understanding of their effect on Tie2 and on the Tie1/Tie2/Ang1 axis remain unfulfilled tasks, due, largely, to the facts that Tie1 is an orphan receptor and is difficult to produce and use in the quantities required for immune antibody library screens. In a search for a selective inhibitor of this orphan receptor, we sought to exploit the advantages (e.g., small size that allows binding to hidden epitopes) of non-immune nanobodies and to simultaneously overcome their limitations (i.e., low expression and stability). We thus performed expression, stability, and affinity screens of yeast-surface-displayed naïve and predesigned synthetic (non-immune) nanobody libraries against the Tie1 extracellular domain. The screens yielded a nanobody with high expression and good affinity and specificity for Tie1, thereby yielding preferential binding for Tie1 over Tie2. The stability, selectivity, potency, and therapeutic potential of this synthetic nanobody were profiled using in vitro and cell-based assays. The nanobody triggered Tie1-dependent inhibition of RTK (Tie2, Akt, and Fak) phosphorylation and angiogenesis in endothelial cells, as well as suppression of human glioblastoma cell viability and migration. This study opens the way to developing nanobodies as therapeutics for different cancers associated with Tie1 activation.

Contribution of Endothelial Laminin-Binding Integrins to Cellular Processes Associated with Angiogenesis

Endothelial cells engage extracellular matrix and basement membrane components through integrin-mediated adhesion to promote angiogenesis. Angiogenesis involves the sprouting of endothelial cells from pre-existing vessels, their migration into surrounding tissue, the upregulation of angiogenesis-associated genes, and the formation of new endothelial tubes. To determine whether the endothelial laminin-binding integrins, α6β4, and α3β1 contribute to these processes, we employed RNAi technology in organotypic angiogenesis assays, as well in migration assays, in vitro. The endothelial depletion of either α6β4 or α3β1 inhibited endothelial sprouting, indicating that these integrins have non-redundant roles in this process. Interestingly, these phenotypes were accompanied by overlapping and distinct changes in the expression of angiogenesis-associated genes. Lastly, depletion of α6β4, but not α3β1, inhibited migration. Taken together, these results suggest that laminin-binding integrins regulate processes associated with angiogenesis by distinct and overlapping mechanisms.

Autophagy Alters Bladder Angiogenesis and Improves Bladder Hyperactivity in the Pathogenesis of Ketamine-Induced Cystitis in a Rat Model

Simple Summary

Long-term ketamine abuse may increase urinary frequency, nocturia, urgency, bladder pain, dysuria, and sometimes hematuria. Evaluation of the pathophysiological mechanism of bladder voiding dysfunction in ketamine-induced cystitis (KIC) patients is a critical step for therapy. This study uses autophagy inducer (rapamycin, mTOR inhibitor) and inhibitor (wortmannin, PI3K-III inhibitor) to identify the role of autophagy in bladder angiogenesis alteration and bladder hyperactivity improvement.

Abstract

The present study attempts to elucidate whether autophagy alters bladder angiogenesis, decreases inflammatory response, and ameliorates bladder hyperactivity—thereby influencing bladder function in ketamine-induced cystitis (KIC). In our methodology, female Sprague-Dawley (S-D) rats were randomly divided into the control group, the ketamine group, the ketamine+rapamycin group, and the ketamine+wortmannin group. The bladder function, contractile activity of detrusor smooth muscle, distribution of autophagosome and autolysosome, total white blood cells (WBCs) and leukocyte differential counts, the expressions of autophagy-associated protein, angiogenesis markers, and signaling pathway molecules involved in KIC were tested, respectively. The data revealed that treatment with ketamine significantly results in bladder overactivity, enhanced interstitial fibrosis, impaired endothelium, induced eosinophil-mediated inflammation, swelling, and degraded mitochondria and organelles, inhibited angiogenesis, and elevated the phosphorylation of Akt. However, treatment with rapamycin caused an inhibitory effect on vascular formation, removed ketamine metabolites, decreased the eosinophil-mediated inflammation, and ameliorated bladder hyperactivity, leading to improve bladder function in KIC. Moreover, wortmannin treatment reduced basophil-mediated inflammatory response, improved bladder angiogenesis by increasing capillary density and VEGF expression, to reverse antiangiogenic effect to repair KIC. In conclusion, these findings suggested that autophagy could modulate inflammatory responses and angiogenesis, which improved bladder function in KIC.

Laminin-511 and α6 integrins regulate the expression of CXCR4 to promote endothelial morphogenesis

During angiogenesis, endothelial cells engage components of the extracellular matrix through integrin-mediated adhesion. Endothelial expression of laminin-411 and laminin-511 is known to promote vessel stability. However, little is known about the contribution of these laminins to endothelial morphogenesis. We used two organotypic cell culture angiogenesis assays, in conjunction with RNAi approaches, to demonstrate that depletion of either the α4 chain of laminin-411 (LAMA4) or the α5 chain of laminin-511 (LAMA5) from endothelial cells inhibits sprouting and tube formation. Depletion of α6 (ITGA6) integrins resulted in similar phenotypes. Gene expression analysis indicated that loss of either laminin-511 or α6 integrins inhibited the expression of CXCR4, a gene previously associated with angiogenic endothelial cells. Pharmacological or RNAi-dependent inhibition of CXCR4 suppressed endothelial sprouting and morphogenesis. Importantly, expression of recombinant CXCR4 rescued endothelial morphogenesis when α6 integrin expression was inhibited. Additionally, the depletion of α6 integrins from established tubes resulted in the loss of tube integrity and laminin-511. Taken together, our results indicate that α6 integrins and laminin-511 can promote endothelial morphogenesis by regulating the expression of CXCR4 and suggest that the α6-dependent deposition of laminin-511 protects the integrity of established endothelial tubes.

Gastric cancer increases transmigratory potential of peripheral blood monocytes by upregulation of β1- and β2-integrins

INTRODUCTION

Immune responses within the tumor depend on the ability of leukocytes to migrate from peripheral circulation into the local microenvironment. This process is controlled by mechanisms that guide leukocytes to the side of inflammation, allowing them to cross vascular endothelial barrier. Monocytes/macrophages are the predominant population of leukocyte infiltrate of many tumors, including, gastric cancer. However, to date mechanisms that control monocyte trafficking to the side of tumor growth are not fully elucidated.

AIM OF THE STUDY

It this study we aimed to evaluate transmigratory potential of peripheral blood monocytes from gastric cancer patients.

MATERIAL AND METHODS

By using multicolor flow cytometry we assessed expression of β1- and β2-integrins on peripheral blood monocytes from gastric cancer patients.

RESULTS

We found increased frequencies of VLA-4 and VLA-6 expressing monocytes and increased expression of analyzed β2-integrins in gastric cancer patients when compared to age matched controls.

CONCLUSIONS

In summary, this study revealed that gastric cancer increases transmigratory potential of peripheral blood monocytes.

The novel VEGF receptor 2 inhibitor YLL545 inhibits angiogenesis and growth in breast cancer

Their antiangiogenic effects make vascular endothelial growth factor receptor 2 (VEGFR2) inhibitors useful for cancer treatment. However, most of these drugs have unexpected adverse side effects. Here, we show that the novel VEGFR2 inhibitor YLL545 suppressed tumor angiogenesis and growth in triple-negative breast cancer without adverse effects. YLL545 treatment also markedly inhibited proliferation, migration, invasion, and tube formation by human umbilical vascular endothelial cells (HUVECs) in vitro. These effects of YLL545 were equal to or greater than those seen with sorafenib. In addition, YLL545 inhibited VEGF-induced phosphorylation of VEGFR2 and activation of downstream signaling regulators, such as phospho-STAT3 and phospho-ERK1/2, in HUVECs. Embryonic angiogenesis assays in zebrafish and Matrigel plug assays in mice demonstrated that YLL545 inhibits angiogenesis in vivo. YLL545 also inhibited proliferation and induced apoptosis in MDA-MB-231 breast cancer cells both in vitro and in vivo, and 50 mg/kg/d YLL545 inhibited human tumor xenograft growth by more than 50% in BALB/c nude mice. These observations suggest YLL545 is a potentially useful anticancer drug candidate.

Synthesis and Biological Evaluation of N-[2-(4-Hydroxyphenylamino)-pyridin-3-yl]-4-methoxy-benzenesulfonamide (ABT-751) Tricyclic Analogues as Antimitotic and Antivascular Agents with Potent in Vivo Antitumor Activity

Benzopyridothiadiazepine (2a) and benzopyridooxathiazepine (2b) were modified to produce tricyclic quinazolinone 15-18 or benzothiadiazine 26-27 derivatives. These compounds were evaluated in cytotoxicity and tubulin inhibition assays and led to potent inhibitors of tubulin polymerization. N-[2(4-Methoxyphenyl)ethyl]-1,2-dihydro-pyrimidino[2,1-b]quinazolin-6-one (16a) exhibited the best in vitro cytotoxic activity (GI50 10-66.9 nM) against the NCI 60 human tumor cell line and significant potency against tubulin assembly (IC50 0.812 μM). In mechanism studies, 16a was shown to block cell cycle in G2/M phase and to disrupt microtubule formation and displayed good antivascular properties as inhibition of cell migration, invasion, and endothelial tube formation. Compound 16a was evaluated in C57BL/6 mouse melanoma B16F10 xenograft model to validate its antitumor activity, in comparison with reference ABT-751 (1). Compound 16a displayed strong in vivo antitumor and antivascular activities at a dose of 5 mg/kg without obvious toxicity, whereas 1 needed a 10-fold higher concentration to reach similar effects.

Platelet integrin 61 controls lung metastasis through direct binding to cancer cell-derived ADAM9

Metastatic dissemination of cancer cells, which accounts for 90% of cancer mortality, is the ultimate hallmark of malignancy. Growing evidence suggests that blood platelets have a predominant role in tumor metastasis; however, the molecular mechanisms involved remain elusive. Here, we demonstrate that genetic deficiency of integrin α6β1 on platelets markedly decreases experimental and spontaneous lung metastasis. In vitro and in vivo assays reveal that human and mouse platelet α6β1 supports platelet adhesion to various types of cancer cells. Using a knockdown approach, we identified ADAM9 as the major counter receptor of α6β1 on both human and mouse tumor cells. Static and flow-based adhesion assays of platelets binding to DC-9, a recombinant protein covering the disintegrin-cysteine domain of ADAM9, demonstrated that this receptor directly binds to platelet α6β1. In vivo studies showed that the interplay between platelet α6β1 and tumor cell-expressed ADAM9 promotes efficient lung metastasis. The integrin α6β1-dependent platelet-tumor cell interaction induces platelet activation and favors the extravasation process of tumor cells. Finally, we demonstrate that a pharmacological approach targeting α6β1 efficiently impairs tumor metastasis through a platelet-dependent mechanism. Our study reveals a mechanism by which platelets promote tumor metastasis and suggests that integrin α6β1 represents a promising target for antimetastatic therapies.

Investigating the effect of tumor vascularization on magnetic targeting in vivo using retrospective design of experiment

Nanocarriers take advantages of the enhanced permeability and retention (EPR) to accumulate passively in solid tumors. Magnetic targeting has shown to further enhance tumor accumulation in response to a magnetic field gradient. It is widely known that passive accumulation of nanocarriers varies hugely in tumor tissues of different tumor vascularization. It is hypothesized that magnetic targeting is likely to be influenced by such factors. In this work, magnetic targeting is assessed in a range of subcutaneously implanted murine tumors, namely, colon (CT26), breast (4T1), lung (Lewis lung carcinoma) cancer and melanoma (B16F10). Passively- and magnetically-driven tumor accumulation of the radiolabeled polymeric magnetic nanocapsules are assessed with gamma counting. The influence of tumor vasculature, namely, the tumor microvessel density, permeability and diameter on passive and magnetic tumor targeting is assessed with the aid of the retrospective design of experiment (DoE) approach. It is clear that the three tumor vascular parameters contribute greatly to both passive and magnetically targeted tumor accumulation but play different roles when nanocarriers are targeted to the tumor with different strategies. It is concluded that tumor permeability is a rate-limiting factor in both targeting modes. Diameter and microvessel density influence passive and magnetic tumor targeting, respectively.

Breast Cancer-Derived Extracellular Vesicles: Characterization and Contribution to the Metastatic Phenotype

The study of extracellular vesicles (EVs) in cancer progression is a complex and rapidly evolving field. Whole categories of cellular interactions in cancer which were originally presumed to be due solely to soluble secreted molecules have now evolved to include membrane-enclosed extracellular vesicles (EVs), which include both exosomes and shed microvesicles (MVs), and can contain many of the same molecules as those secreted in soluble form but many different molecules as well. EVs released by cancer cells can transfer mRNA, miRNA, and proteins to different recipient cells within the tumor microenvironment, in both an autocrine and paracrine manner, causing a significant impact on signaling pathways, mRNA transcription, and protein expression. The transfer of EVs to target cells, in turn, supports cancer growth, immunosuppression, and metastasis formation. This review focuses exclusively on breast cancer EVs with an emphasis on breast cancer-derived exosomes, keeping in mind that breast cancer-derived EVs share some common physical properties with EVs of other cancers.