Inhibition of vascular endothelial growth factor (VEGF) signaling in cancer causes loss of endothelial fenestrations, regression of tumor vessels, and appearance of basement membrane ghosts

Adding Adjuvants to Fluoropyrimidine-based Neoadjuvant Chemoradiotherapy for Locally Advanced Rectal Cancer: An Option Worthy of Serious Consideration

The application of fluoropyrimidine-based neoadjuvant chemoradiotherapy (Fu-nCRT) of locally advanced rectal cancer (LARC) has become a common therapeutic regimen. In order to improve the efficacy and enable more patients to benefit from this treatment, an accumulation of studies have been carried out on the auxiliary use of other drugs with Fu-nCRT. However, due to specific challenges and the potential opportunities that coexist in this field, a more reasonable approach to the mode of treatment remains to be explored. In this review, we have summarized the results of the studies on the combination of Fu-nCRT with cytotoxic drugs, anti-tumor angiogenesis, and anti-EGFR agents, as well as the status of the application of immune checkpoint inhibitors in the neoadjuvant therapy of LARC patients.

Paying attention to tumor blood vessels: Cancer phototherapy assisted with nano delivery strategies

Cancer phototherapy has attracted increasing attention for its promising effectiveness and relative non-invasiveness. Over the past years, tremendous efforts have been made to develop better phototherapy strategies with various nano delivery systems. This review introduces cancer phototherapy strategies based on tumor blood vessels for improved therapeutic outcomes from the angle of direct tumor destruction and improved delivery process assisted with nano delivery designs. Latest directions and ideas of cancer phototherapy with translation potential are also discussed. Focusing on the double role of tumor vessels not only as an anti-tumor target but also as part of the delivery process, we highlight the crosstalk between photo-induced extensive effects and the complicated drug delivery process. Due to the heterogeneity of tumors, deeper investigations about the interconnection between tumor vessels and cancer phototherapy remain to be carried out. More delicate and intelligent nano delivery systems are expected to help realize the full potential of this therapeutic strategy.

A Window of Opportunity: Targeting Cancer Endothelium to Enhance Immunotherapy

Vascular abnormalities in tumors have a major impact on the immune microenvironment in tumors. The consequences of abnormal vasculature include increased hypoxia, acidosis, high intra-tumoral fluid pressure, and angiogenesis. This introduces an immunosuppressive microenvironment that alters immune cell maturation, activation, and trafficking, which supports tumor immune evasion and dissemination of tumor cells. Increasing data suggests that cancer endothelium is a major barrier for traveling leukocytes, ranging from a partial blockade resulting in a selective endothelial barrier, to a complete immune infiltration blockade associated with immune exclusion and immune desert cancer phenotypes. Failed immune cell trafficking as well as immunosuppression within the tumor microenvironment limits the efficacy of immunotherapeutic approaches. As such, targeting proteins with key roles in angiogenesis may potentially reduce immunosuppression and might restore infiltration of anti-tumor immune cells, creating a therapeutic window for successful immunotherapy. In this review, we provide a comprehensive overview of established as well as more controversial endothelial pathways that govern selective immune cell trafficking across cancer endothelium. Additionally, we discuss recent insights and strategies that target tumor vasculature in order to increase infiltration of cytotoxic immune cells during the therapeutic window of vascular normalization hereby improving the efficacy of immunotherapy.

Angiogenesis in gynecological cancers and the options for anti-angiogenesis therapy

Angiogenesis is required in cancer, including gynecological cancers, for the growth of primary tumors and secondary metastases. Development of anti-angiogenesis therapy in gynecological cancers and improvement of its efficacy have been a major focus of fundamental and clinical research. However, survival benefits of current anti-angiogenic agents, such as bevacizumab, in patients with gynecological cancer, are modest. Therefore, a better understanding of angiogenesis and the tumor microenvironment in gynecological cancers is urgently needed to develop more effective anti-angiogenic therapies, either or not in combination with other therapeutic approaches. We describe the molecular aspects of (tumor) blood vessel formation and the tumor microenvironment and provide an extensive clinical overview of current anti-angiogenic therapies for gynecological cancers. We discuss the different phenotypes of angiogenic endothelial cells as potential therapeutic targets, strategies aimed at intervention in their metabolism, and approaches targeting their (inflammatory) tumor microenvironment.

Pembrolizumab plus axitinib combination and the paradigm change in the treatment of advanced renal cell carcinoma

Sequential administration of single targeted agents has been challenged as the dominant treatment paradigm in patients with metastatic renal cell carcinoma by improved outcomes obtained with combination regimens based on immune checkpoint inhibitors. Most patients treated with sequential monotherapy eventually develop drug resistance and succumb to progressive disease, leading to the search for therapies that would overcome drug resistance and result in a more durable treatment response. Improved outcomes have been demonstrated in Phase III trials in comparison with sunitinib for the combinations of axitinib plus pembrolizumab, axitinib plus avelumab, bevacizumab plus atezolizumab and ipilimumab plus nivolumab. A statistically significant improvement of both progression-free and overall survival has been demonstrated for the axitinib plus pembrolizumab combination.

Vascular toxicity associated with anti-angiogenic drugs

Over the past two decades, the treatment of cancer has been revolutionised by the highly successful introduction of novel molecular targeted therapies and immunotherapies, including small-molecule kinase inhibitors and monoclonal antibodies that target angiogenesis by inhibiting vascular endothelial growth factor (VEGF) signaling pathways. Despite their anti-angiogenic and anti-cancer benefits, the use of VEGF inhibitors (VEGFi) and other tyrosine kinase inhibitors (TKIs) has been hampered by potent vascular toxicities especially hypertension and thromboembolism. Molecular processes underlying VEGFi-induced vascular toxicities still remain unclear but inhibition of endothelial NO synthase (eNOS), reduced nitric oxide (NO) production, oxidative stress, activation of the endothelin system, and rarefaction have been implicated. However, the pathophysiological mechanisms still remain elusive and there is an urgent need to better understand exactly how anti-angiogenic drugs cause hypertension and other cardiovascular diseases (CVDs). This is especially important because VEGFi are increasingly being used in combination with other anti-cancer dugs, such as immunotherapies (immune checkpoint inhibitors (ICIs)), other TKIs, drugs that inhibit epigenetic processes (histone deacetylase (HDAC) inhibitor) and poly (adenosine diphosphate-ribose) polymerase (PARP) inhibitors, which may themselves induce cardiovascular injury. Here, we discuss vascular toxicities associated with TKIs, especially VEGFi, and provide an up-to-date overview on molecular mechanisms underlying VEGFi-induced vascular toxicity and cardiovascular sequelae. We also review the vascular effects of VEGFi when used in combination with other modern anti-cancer drugs.

Clinical effect of conbercept on improving diabetic macular ischemia by OCT angiography

BACKGROUND

Varying degrees of macular ischemia generally occur in diabetic retinopathy (DR). This study aims to evaluate the effect of conbercept with 3+ pro re nata (PRN) on macular perfusion status in patients with diabetic macular edema (DME) and quantitatively assess changes in foveal avascular zone (FAZ) areas and capillary density in macular regions by applying optical coherence tomography angiography (OCTA).

METHODS

Fifty patients were divided into ischemic (n = 31) and non-ischemic (n = 19) groups according to the presence of ischemia on OCTA at baseline. All patients received intravitreal injections of 0.5 mg of conbercept with 3+ PRN principle. The FAZ areas and macular vessel density measured using OCTA were evaluated at baseline, 3 months, and 6 months after treatment in both groups.

RESULTS

At months 3 and 6, the FAZ area in the ischemic group changed from 0.510 ± 0.171 mm2 to 0.441 ± 0.158 mm2 then to 0.427 ± 0.153 mm2 (p = 0.003, p = 0.296); in the non-ischemic group, it remained stable (p = 0.269, p = 0.926). The superficial vessel density changed from 41.1 ± 4.1 to 42.5% ± 4.7% then to 42.6% ± 4.6% (p = 0.043, p = 0.812), and the deep vessel density changed from 40.7 ± 4.4 to 42.3% ± 3.6% then to 42.3% ± 4.7% (p = 0.072, p = 0.961) in the ischemic group. In the non-ischemic group, the superficial vessel density changed from 44.8 ± 3.2 to 46.0% ± 3.5% then to 45.7% ± 3.3% (p = 0.108, p = 0.666), whereas the deep vessel density changed from 43.6 ± 3.6 to 43.8% ± 3.2% then to 43.5% ± 4.5% (p = 0.882, p = 0.736). Reperfusion in macular nonperfusion areas was observed.

CONCLUSION

Anti-vascular endothelial growth factor treatment may have a positive effect on macular perfusion status. Furthermore, OCTA had advantages in quantifying and calculating blood flow index in the study of macular perfusion status.

A Custom-Made Semiautomatic Analysis of Retinal Nonperfusion Areas After Dexamethasone for Diabetic Macular Edema

Purpose

To evaluate the changes of retinal capillary nonperfusion areas and retinal capillary vessel density of the superficial capillary plexus (SCP) and deep capillary plexus in patients with diabetes with diabetic macular edema treated with an intravitreal dexamethasone implant (IDI).

Methods

We enrolled 28 patients with diabetic retinopathy and diabetic macular edema candidates to IDI. All patients underwent widefield optical coherence tomography angiography with PLEX Elite 9000 device with 15 × 9 mm scans centered on the foveal center at baseline, 1 month, 2 months, and 4 months after IDI. In all the patients, the variation of the retinal capillary nonperfusion areas and of the retinal vessel density of the SCP and deep capillary plexus were calculated using an automatic software written in Matlab (MathWorks, Natick, MA).

Results

During follow-up, SCP showed a statistically significant reduction of ischemic areas at 1 month after IDI (P = 0.04) and slightly increased not significantly thereafter (P = 0.15). The percentage of nonperfusion areas changed from 11.4% at baseline, to 6.3% at 1 month, 8.1%, at 2 months, and 10.2% at 4 months. The whole vessel density of SCP slightly increased (not significantly) from 35.30% at baseline to 38.00% at 1 month, and then decreased to 37.85% at 2 months and 36.04% at 4 months (P = 0.29). Retinal capillary nonperfusion areas and retinal vessel density at the deep capillary plexus did not change significantly (P = 0.31 and P = 0.73, respectively).

Conclusions

Widefield optical coherence tomography angiography showed a decrease in retinal capillary nonperfusion areas after dexamethasone implant suggesting a possible drug-related reperfusion of retinal capillaries particularly evident in the early period.

Translational Relevance

A custom-made automatic analysis of retinal nonperfusion areas may allow a better and precise evaluation of ischemic changes after intravitreal therapy.

VEGFR2 signaling drives meningeal vascular regeneration upon head injury

Upon severe head injury (HI), blood vessels of the meninges and brain parenchyma are inevitably damaged. While limited vascular regeneration of the injured brain has been studied extensively, our understanding of meningeal vascular regeneration following head injury is quite limited. Here, we identify key pathways governing meningeal vascular regeneration following HI. Rapid and complete vascular regeneration in the meninges is predominantly driven by VEGFR2 signaling. Substantial increase of VEGFR2 is observed in both human patients and mouse models of HI, and endothelial cell-specific deletion of Vegfr2 in the latter inhibits meningeal vascular regeneration. We further identify the facilitating, stabilizing and arresting roles of Tie2, PDGFRβ and Dll4 signaling, respectively, in meningeal vascular regeneration. Prolonged inhibition of this angiogenic process following HI compromises immunological and stromal integrity of the injured meninges. These findings establish a molecular framework for meningeal vascular regeneration after HI, and may guide development of wound healing therapeutics.

Severe head injury results in critical damage of blood vessels of the meninges and brain parenchyma. Here, the authors describe key pathways governing meningeal vascular regeneration following head injury, characterizing the differential roles of VEGFR2, Tie2, Dll4 and PDGFRβ signaling.

BMP9 signaling promotes the normalization of tumor blood vessels

The presence of an immature tumor vascular network contributes to cancer dissemination and the development of resistance to therapies. Strategies to normalize the tumor vasculature are therefore of significant therapeutic interest for cancer treatments. VEGF inhibitors are used clinically to normalize tumor blood vessels. However, the time frame and dosage of these inhibitors required to achieve normalization is rather narrow, and there is a need to identify additional signaling targets to attain vascular normalization. In addition to VEGF, the endothelial-specific receptor Alk1 plays a critical role in vascular development and promotes vascular remodeling and maturation. Therefore, we sought to evaluate the effects of the Alk1 ligand BMP9 on tumor vascular formation. BMP9 overexpression in Lewis Lung Carcinoma (LLC) tumors significantly delayed tumor growth. Blood vessels in BMP9-overexpressing LLC tumors displayed markers of vascular maturation and were characterized by increased perivascular cell coverage. Tumor vasculature normalization was associated with decreased permeability and increased perfusion. These changes in vascular function in BMP9-overexpressing LLC tumors resulted in significant alterations of the tumor microenvironment, characterized by a decrease in hypoxia and an increase in immune infiltration. In conclusion, we show that BMP9 promotes vascular normalization in LLC tumors that leads to changes in the microenvironment.

Turning liabilities into opportunities: Off-target based drug repurposing in cancer

Targeted drugs and precision medicine have transformed the landscape of cancer therapy and significantly improved patient outcomes in many cases. However, as therapies are becoming more and more tailored to smaller patient populations and acquired resistance is limiting the duration of clinical responses, there is an ever increasing demand for new drugs, which is not easily met considering steadily rising drug attrition rates and development costs. Considering these challenges drug repurposing is an attractive complementary approach to traditional drug discovery that can satisfy some of these needs. This is facilitated by the fact that most targeted drugs, despite their implicit connotation, are not singularly specific, but rather display a wide spectrum of target selectivity. Importantly, some of the unintended drug "off-targets" are known anticancer targets in their own right. Others are becoming recognized as such in the process of elucidating off-target mechanisms that in fact are responsible for a drug's anticancer activity, thereby revealing potentially new cancer vulnerabilities. Harnessing such beneficial off-target effects can therefore lead to novel and promising precision medicine approaches. Here, we will discuss experimental and computational methods that are employed to specifically develop single target and network-based off-target repurposing strategies, for instance with drug combinations or polypharmacology drugs. By illustrating concrete examples that have led to clinical translation we will furthermore examine the various scientific and non-scientific factors that cumulatively determine the success of these efforts and thus can inform the future development of new and potentially lifesaving off-target based drug repurposing strategies for cancers that constitute important unmet medical needs.

Tumour vessel remodelling: new opportunities in cancer treatment

Tumour growth critically depends on a supportive microenvironment, including the tumour vasculature. Tumour blood vessels are structurally abnormal and functionally anergic which limits drug access and immune responses in solid cancers. Thus, tumour vasculature has been considered an attractive therapeutic target for decades. However, with time, anti-angiogenic therapy has evolved from destruction to structural and functional rehabilitation as understanding of tumour vascular biology became more refined. Vessel remodelling or normalisation strategies which alleviate hypoxia are now coming of age having been shown to have profound effects on the tumour microenvironment. This includes improved tumour perfusion, release from immune suppression and lower metastasis rates. Nevertheless, clinical translation has been slow due to challenges such as the transient nature of current normalisation strategies, limited in vivo monitoring and the heterogeneity of primary and/or metastatic tumour environments, calling for more tailored approaches to vascular remodelling. Despite these setbacks, harnessing vascular plasticity provides unique opportunities for anti-cancer combination therapies in particular anti-angiogenic immunotherapy which are yet to reach their full potential.

Remodeling of reactive lymph nodes: Dynamics of stromal cells and underlying chemokine signaling

Lymph nodes (LNs) are secondary immune organs dispersed throughout the body. They are primarily composed of lymphocytes, "transient passengers" that are only present for a few hours. During this time, they extensively interact with a meshwork of stromal cells. Although these cells constitute less than 5% of all LN cells, they are integral to LN function: Stromal cells create a three-dimensional network that provides a rigid backbone for the transport of lymph and generates "roads" for lymphocyte migration. Beyond structural support, the LN stroma also produces survival signals for lymphocytes and provides nutrients, soluble factors, antigens, and immune cells collectively required for immune surveillance and the generation of adaptive immune responses. A unique feature of LNs is their ability to considerably and rapidly change size: the volume and cellularity of inflamed LNs can increase up to 20-fold before returning to homeostatic levels. This cycle will be repeated many times during life and is accommodated by stromal cells. The dynamics underlying this dramatic remodeling are subject of this review. We will first introduce the main types of LN stromal cells and explain their known functions. We will then discuss how these cells enable LN growth during immune responses, with a particular focus on underlying cellular mechanisms and molecular cues. Similarly, we will elaborate on stromal dynamics mediating the return to LN homeostasis, a process that is mechanistically much less understood than LN expansion.

The role of tumor-derived exosomes in tumor angiogenesis and tumor progression

Exosomes, belonging to the group of extracellular bodies, are released by healthy as well as cancerous cells and serve as a communication pathway. Tumor-derived exosomes (TEX) possess the capacity to reprogram the function of normal cells owing to their genetic and molecular cargo. Such exosomes target endothelial cells (among others) in the tumor microenvironment to promote angiogenesis. Blood supply is essential in solid tumor growth and metastasis. The potential of pro-angiogenic changes is enhanced by an increased amount of circulating tumor-derived exosomes in the body fluids of cancer patients. A vascular network is important, since the proliferation, as well as the metastatic spread of cancer cells depends on an adequate supply of oxygen and nutrients, and the removal of waste products. New blood vessels and lymphatic vessels are formed through processes called angiogenesis and lymphangiogenesis, respectively. Angiogenesis is regulated by both activator and inhibitor molecules. Thousands of patients have received anti-angiogenic therapy to date. Despite their theoretical efficacy, anti-angiogenic treatments have not proved beneficial in terms of long-term survival. Tumor-derived exosomes carrying pro-angiogenic factors might be a target for new anti-cancer therapy.

The role of exercise in the reversal of IGF-1 deficiencies in microvascular rarefaction and hypertension

Hypertension has been linked with peripheral and central reductions in vascular density, and with devastating effects on brain function. However, the underlying mechanisms in the relationship between blood pressure and cognitive impairment have yet to be fully elucidated. Here, we review compelling evidence from two lines of inquiry: one that links microvascular rarefaction with insulin-like growth factor 1 (IGF-1) deficiencies, and another which posits that vascular dysfunction precedes hypertension. Based on the findings from experimental and clinical studies, we propose that these lines of evidence converge, and suggest that age-related declines in IGF-1 concentrations precede microvascular rarefaction, initiate an increase in vascular resistance, and therefore are causally linked to onset of hypertension. Physical exercise provides a relevant model for supporting our premise, given the well-established effects of exercise in attenuating vascular dysfunction, hypertension, IGF-1 deficiency, and cognitive decline. We highlight here the role of exercise-induced increases in blood flow in improving vascular integrity and enhancing angiogenesis via the actions of IGF-1, resulting in reversal of rarefaction and hypertension, and enhancement of cerebral blood flow and cognition.

Intravital imaging of vascular anomalies and extracellular matrix remodeling in orthotopic pancreatic tumors

Pancreatic cancers, both adenocarcinomas and endocrine tumors are characterized by varying levels of aberrant angiogenesis and fibrotic microenvironment. The difficulty to deliver drugs and treat the disease has been attributed in part to the vascular architecture and tissue/ECM density. Here we present longitudinal three-dimensional intravital imaging of vascular and tumor microenvironment remodeling in spontaneous transgenic tumors (RIP1-Tag2 insulinomas) and orthotopically injected tumors (KPC adenocarcinomas). Analysis of the data acquired in insulinomas revealed major differences in tumor blood vessel branching, fraction volume, number of branch points segments, vessel straightness and length compared to the normal tissue. The aggressive adenocarcinoma presented widespread peritumoral vascular remodeling and heterogeneous vascular distribution. Longitudinal imaging was used to acquire sequential vascular remodeling data during tumor progression. This work demonstrates the potential for using a pancreatic intravital imaging window for direct visualization of the tumor heterogenic microenvironments during tumor progression.

Protocol development for discovery of angiogenesis inhibitors via automated methods using zebrafish

Their optical clarity as larvae and embryos, small size, and high fecundity make zebrafish ideal for whole animal high throughput screening. A high-throughput drug discovery platform (HTP) has been built to perform fully automated screens of compound libraries with zebrafish embryos. A Tg(kdrl:EGFP) line, marking endothelial cell cytoplasm, was used in this work to help develop protocols and functional algorithms for the system, with the intent of screening for angiogenesis inhibitors. Indirubin 3’ Monoxime (I3M), a known angiogenesis inhibitor, was used at various concentrations to validate the protocols. Consistent with previous studies, a dose dependant inhibitory effect of I3M on angiogenesis was confirmed. The methods and protocols developed here could significantly increase the throughput of drug screens, while limiting human errors. These methods are expected to facilitate the discovery of novel anti-angiogenesis compounds and can be adapted for many other applications in which samples have a good fluorescent signal.

Combination Radioimmunotherapy Strategies for Solid Tumors

Combination radioimmunotherapy is an emerging approach for the treatment of solid tumors where radio immunotherapy alone has proven to be reasonably ineffective. Radioimmunotherapy (RIT) using monoclonal antibodies (mAbs) labeled with radionuclides is an attractive approach for cancer treatment because tumor-associated mAbs with cytotoxic radionuclides can selectively bind to tumor antigens. However, due to various limitations, mAbs cannot reach solid tumors, consequently reducing RIT efficacy. Combination RIT is a pragmatic approach through which the addition of drugs or other agents not only help mAbs to reach the targeted site but also improves its efficacy. Thus, the combination of drugs or moieties with RIT can be applied to overcome the barriers that RIT faces for solid tumors. This review covers the RIT approach, along with the mechanism of action of mAb used in RIT, limitations of solid tumors, and strategies that can be used in combination RIT to enhance the treatment regimen for solid tumors.

Increase in Blood Pressure Associated With Tyrosine Kinase Inhibitors Targeting Vascular Endothelial Growth Factor

Objectives

This study quantified the change in blood pressure (BP) during antivascular endothelial growth factor (VEGF) tyrosine kinase inhibitor (TKI) therapy, compared BPs between TKIs, and analyzed change in BP during antihypertensive therapy.

Background

TKIs targeting VEGF are associated with hypertension. The absolute change in BP during anti-VEGF TKI treatment is not well characterized outside clinical trials.

Methods

A retrospective single-center study included patients with metastatic renal cell carcinoma who received anti-VEGF TKIs between 2007 and 2018. Mixed models analyzed 3,088 BPs measured at oncology clinics.

Results

In 228 patients (baseline systolic blood pressure [SBP] 130.2 ± 16.3 mm Hg, diastolic blood pressure [DBP] 76.8 ± 9.3 mm Hg), anti-VEGF TKIs were associated with mean increases in SBP of 8.5 mm Hg (p < 0.0001) and DBP of 6.7 mm Hg (p <0.0001). Of the anti-VEGF TKIs evaluated, axitinib was associated with the greatest BP increase, with an increase in SBP of 12.6 mm Hg (p < 0.0001) and in DBP of 10.3 mm Hg (p < 0.0001) relative to baseline. In pairwise comparisons between agents, axitinib was associated with greater SBPs than cabozantinib by 8.4 mm Hg (p = 0.004) and pazopanib by 5.1 mm Hg (p = 0.01). Subsequent anti-VEGF TKI courses were associated with small increases in DBP, but not SBP, relative to the first course. During anti-VEGF TKI therapy, calcium-channel blockers and potassium-sparing diuretic agents were associated with the largest BP reductions, with decreases in SBP of 5.6 mm Hg (p < 0.0001) and 9.9 mm Hg (p = 0.007), respectively.

Conclusions

Anti-VEGF TKIs are associated with increased BP; greatest increases are observed with axitinib. Calcium-channel blockers and potassium-sparing diuretic agents were associated with the largest reductions in BP.

[68Ga]RGD Versus [18F]FDG PET Imaging in Monitoring Treatment Response of a Mouse Model of Human Glioblastoma Tumor with Bevacizumab and/or Temozolomide

PURPOSE

The aim of this study was to evaluate positron emission tomography (PET) imaging with [⁶⁸Ga]NODAGA-c(RGDfK) ([⁶⁸Ga]RGD), in comparison with 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG), for early monitoring of the efficacy of an antiangiogenic agent associated or not with chemotherapy, in a mouse model of glioblastoma (GB).

PROCEDURES

Mice bearing U87MG human GB cells line were parted into five groups of five mice each. One group was imaged at baseline before the treatment phase; another group was treated with bevacizumab (BVZ), another group with temozolomide (TMZ), another group with both agents, and the last one was the control group. Tumors growth and biological properties were evaluated by caliper measurements and PET imaging at three time points (baseline, during treatment t1 = 4-6 days and t2 = 10-12 days). At the end of the study, tumors were counted and analyzed by immunohistochemistry (CD31 to evaluate microvessel density).

RESULTS

The tumor volume assessed by caliper measurements was significantly greater at t1 in the control group than in the TMZ + BVZ-treated group or in the BVZ-treated group. At t2, tumor volume of all treated groups was significantly smaller than that of the control group. [¹⁸F]FDG PET failed to reflect this efficacy of treatment. In contrast, at t1, the [⁶⁸Ga]RGD tumor uptake was concordant with tumor growth in controls and in treated groups. At t2, a significant increase in tumor uptake of [⁶⁸Ga]RGD vs. t1 was only observed in the TMZ-treated group, reflecting a lack of angiogenesis inhibition, whereas TMZ + BVZ resulted in a dramatic tumor arrest, reduction in microvessel density and stable tumor [⁶⁸Ga]RGD uptake.

CONCLUSIONS

[⁶⁸Ga]RGD is a useful PET agent for in vivo angiogenesis imaging and can be useful for monitoring antiangiogenic treatment associated or not with chemotherapy.

Early Post-stroke Activation of Vascular Endothelial Growth Factor Receptor 2 Hinders the Receptor 1-Dependent Neuroprotection Afforded by the Endogenous Ligand

Vascular endothelial growth factor (VEGF) has long been connected to the development of tissue lesion following ischemic stroke. Contradictory findings either situate VEGF as a promoter of large infarct volumes or as a potential attenuator of damage due to its well documented neuroprotective capability. The core of this discrepancy mostly lies on the substantial number of pleiotropic functions driven by VEGF. Mechanistically, these effects are activated through several VEGF receptors for which various closely related ligands exist. Here, we tested in an experimental model of stroke how the differential activation of VEGF receptors 1 and 2 would modify functional and histological outcomes in the acute phase post-ischemia. We also assessed whether VEGF-mediated responses would involve the modulation of inflammatory mechanisms and how this trophic factor acted specifically on neuronal receptors. We produced ischemic infarcts in adult rats by transiently occluding the middle cerebral artery and induced the pharmacological inhibition of VEGF receptors by i.c.v. administration of the specific VEGFR2 inhibitor SU1498 and the pan-VEGFR blocker Axitinib. We evaluated the neurological performance of animals at 24 h following stroke and the occurrence of brain infarctions analyzed at the gross metabolic and neuronal viability levels. We also assessed the induction of peripheral pro- and anti-inflammatory cytokines in the cerebrospinal fluid and blood and assessed the polarization of activated microglia. Finally, we studied the direct involvement of cortical neuronal receptors for VEGF with in vitro assays of excitotoxic damage. Preferential VEGFR1 activation by the endogenous ligand promotes neuronal protection and prevents the presentation of large volume infarcts that highly correlate with neurological performance, while the concomitant activation of VEGFR2 reduces this effect, even in the presence of exogenous ligand. This process partially involves the polarization of microglia to the state M2. At the cellular level, neurons also responded better to the preferential activation of VEGFR1 when challenged to N-methyl-D-aspartate-induced excitotoxicity. Endogenous activation of VEGFR2 hinders the neuroprotective mechanisms mediated by the activation of VEGFR1. The selective modulation of these concurrent processes might enable the development of therapeutic approaches that target specific VEGFR1-mediated signaling during the acute phase post-stroke.

Vascular Dysfunction in Alzheimer's Disease: A Prelude to the Pathological Process or a Consequence of It?

Alzheimer's disease (AD) is the most prevalent form of dementia. Despite decades of research following several theoretical and clinical lines, all existing treatments for the disorder are purely symptomatic. AD research has traditionally been focused on neuronal and glial dysfunction. Although there is a wealth of evidence pointing to a significant vascular component in the disease, this angle has been relatively poorly explored. In this review, we consider the various aspects of vascular dysfunction in AD, which has a significant impact on brain metabolism and homeostasis and the clearance of β-amyloid and other toxic metabolites. This may potentially precede the onset of the hallmark pathophysiological and cognitive symptoms of the disease. Pathological changes in vessel haemodynamics, angiogenesis, vascular cell function, vascular coverage, blood-brain barrier permeability and immune cell migration may be related to amyloid toxicity, oxidative stress and apolipoprotein E (APOE) genotype. These vascular deficits may in turn contribute to parenchymal amyloid deposition, neurotoxicity, glial activation and metabolic dysfunction in multiple cell types. A vicious feedback cycle ensues, with progressively worsening neuronal and vascular pathology through the course of the disease. Thus, a better appreciation for the importance of vascular dysfunction in AD may open new avenues for research and therapy.

Distinct Tumor Microenvironment at Tumor Edge as a Result of Astrocyte Activation Is Associated With Therapeutic Resistance for Brain Tumor

Tumor vasculatures and hypoxia are critical tumor micro-environmental factors associated with tumor response to the therapy and heterogeneous in both time- and location-dependent manner. Using a murine orthotopic anaplastic astrocytoma model, ALTS1C1, this study showed that brain tumor edge had a very unique microenvironment, having higher microvascular density (MVD) and better vessel function than the tumor core, but on the other hand was also positive for hypoxia markers, such as pimonidazole (PIMO), hypoxia inducible factor-1α (HIF-1α), and carbonic anhydrase IV (CAIX). The hypoxia at tumor edge was transient, named as peripheral hypoxia, and caused by different mechanisms from the chronic hypoxia in tumor core. The correlation of CAIX staining with astrocyte activation marker, glial fibrillary acid protein (GFAP), at the tumor edge indicated the involvement of astrocyte activation on the development of peripheral hypoxia. Peripheral hypoxia was a specific trait of orthotopic brain tumors at tumor edge, regardless of tumor origin. The hypoxic cells were resistant to the therapy, regardless of their location. Surviving cells, particularly those at the hypoxic region of tumor edge, are likely the cause of tumor recurrence after the therapy. New therapeutic platform that targets cells in tumor edge is likely to achieve better treatment outcomes.

Tumor-induced neoangiogenesis and receptor tyrosine kinases - Mechanisms and strategies for acquired resistance

BACKGROUND

Angiogenesis is essential for tumor growth, proliferation and metastasis. Tumor-related angiogenesis is complex and involves multiple signaling pathways. Controlling angiogenesis is a promising strategy for limiting cancer progression.

SCOPE OF REVIEW

Several receptor tyrosine kinases influence the angiogenic response via multiple signaling molecules and pathways. Understanding the functional interaction of kinases in the angiogenic process and development of resistance to kinase inhibition is essential for future successful therapeutic strategies.

MAJOR CONCLUSIONS

Strategies that target receptor tyrosine kinases and other tumor microenvironment factors simultaneously, or sequentially, are required for achieving an efficient and robust anti-angiogenic response.

GENERAL SIGNIFICANCE

Understanding the molecular mechanism of angiogenesis has improved, and has led, to the clinical development and approval of anti-angiogenic drugs. While many patients have benefited from these agents, their limited efficacy and the development of resistance remains a challenge. This review highlights current therapies and challenges associated with targeting angiogenesis in cancer.

Tumor Neovascularization and Developments in Therapeutics

Tumors undergo fast neovascularization to support the rapid proliferation of cancer cells. Vasculature in tumors, unlike that in wound healing, is immature and affects the tumor microenvironment, resulting in hypoxia, acidosis, glucose starvation, immune cell infiltration, and decreased activity, all of which promote cancer progression, metastasis, and drug resistance. This innate defect of tumor vasculature can however represent a useful therapeutic target. Angiogenesis inhibitors targeting tumor vascular endothelial cells important for angiogenesis have attracted attention as cancer therapy agents that utilize features of the tumor microenvironment. While angiogenesis inhibitors have the advantage of targeting neovascularization factors common to all cancer types, some limitations to their deployment have emerged. Further understanding of the mechanism of tumor angiogenesis may contribute to the development of new antiangiogenic therapeutic approaches to control tumor invasion and metastasis. This review discusses the mechanism of tumor angiogenesis as well as angiogenesis inhibition therapy with antiangiogenic agents.

Inhibition of Sphingosine Phosphate Receptor 1 Signaling Enhances the Efficacy of VEGF Receptor Inhibition

Inhibition of VEGFR signaling is an effective treatment for renal cell carcinoma, but resistance continues to be a major problem. Recently, the sphingosine phosphate (S1P) signaling pathway has been implicated in tumor growth, angiogenesis, and resistance to antiangiogenic therapy. S1P is a bioactive lipid that serves an essential role in developmental and pathologic angiogenesis via activation of the S1P receptor 1 (S1P1). S1P1 signaling counteracts VEGF signaling and is required for vascular stabilization. We used in vivo and in vitro angiogenesis models including a postnatal retinal angiogenesis model and a renal cell carcinoma murine tumor model to test whether simultaneous inhibition of S1P1 and VEGF leads to improved angiogenic inhibition. Here, we show that inhibition of S1P signaling reduces the endothelial cell barrier and leads to excessive angiogenic sprouting. Simultaneous inhibition of S1P and VEGF signaling further disrupts the tumor vascular beds, decreases tumor volume, and increases tumor cell death compared with monotherapies. These studies suggest that inhibition of angiogenesis at two stages of the multistep process may maximize the effects of antiangiogenic therapy. Together, these data suggest that combination of S1P1 and VEGFR-targeted therapy may be a useful therapeutic strategy for the treatment of renal cell carcinoma and other tumor types.

Is There a Direct Correlation Between Microvascular Wall Structure and k-Trans Values Obtained From Perfusion CT Measurements in Lymphomas?

RATIONALE AND OBJECTIVES

This study aimed to test the hypothesis that ultrastructural wall abnormalities of lymphoma vessels correlate with perfusion computed tomography (PCT) kinetics.

MATERIALS AND METHODS

Our local institutional review board approved this prospective study. Between February 2013 and June 2016, we included 23 consecutive subjects with newly diagnosed lymphoma, who were referred for computed tomography-guided biopsy (6 women, 17 men; mean age, 60.61 ± 12.43 years; range, 28-74 years) and additionally agreed to undergo PCT of the target lymphoma tissues. PCT was obtained for 40 seconds using 80 kV, 120 mAs, 64 × 0.6-mm collimation, 6.9-cm z-axis coverage, and 26 volume measurements. Mean and maximum k-trans (mL/100 mL/min), blood flow (BF; mL/100 mL/min) and blood volume (BV) were quantified using the deconvolution and the maximum slope + Patlak calculation models. Immunohistochemical staining was performed for microvessel density quantification (vessels/m²), and electron microscopy was used to determine the presence or absence of tight junctions, endothelial fenestration, basement membrane, and pericytes, and to measure extracellular matrix thickness.

RESULTS

Extracellular matrix thickness as well as the presence or absence of tight junctions, basal lamina, and pericytes did not correlate with computed tomography perfusion parameters. Endothelial fenestrations correlated significantly with mean BF_{deconvolution} (P = .047, r = 0.418) and additionally was significantly associated with higher mean BV_{deconvolution} (P < .005). Mean k-trans_Patlak correlated strongly with mean k-trans_{deconvolution} (r = 0.939, P = .001), and both correlated with mean BF_{deconvolution} (P = .001, r = 0.748), max BF_{deconvolution} (P = .028, r = 0.564), mean BV_{deconvolution} (P = .001, r = 0.752), and max BV_{deconvolution} (P = .001, r = 0.771). Microvessel density correlated with max k-trans_{deconvolution} (r = 0.564, P = .023). Vascular endothelial growth factor receptor-3 expression (receptor specific for lymphatics) correlated significantly with max k-trans_Patlak (P = .041, r = 0.686) and mean BF_{deconvolution} (P = .038, r = 0.695).

CONCLUSION

k-Trans values of PCT do not correlate with ultrastructural microvessel features, whereas endothelial fenestrations correlate with increased intra-tumoral BVs.

Endothelial Hypoxia-Inducible Factor-2α Is Required for the Maintenance of Airway Microvasculature

BACKGROUND

Hypoxia-inducible factors (HIFs), especially HIF-1α and HIF-2α, are key mediators of the adaptive response to hypoxic stress and play essential roles in maintaining lung homeostasis. Human and animal genetics studies confirm that abnormal HIF correlates with pulmonary vascular pathology and chronic lung diseases, but it remains unclear whether endothelial cell HIF production is essential for microvascular health. The large airway has an ideal circulatory bed for evaluating histological changes and physiology in genetically modified rodents.

METHODS

The tracheal microvasculature of mice, with conditionally deleted or overexpressed HIF-1α or HIF-2α, was evaluated for anatomy, perfusion, and permeability. Angiogenic signaling studies assessed vascular changes attributable to dysregulated HIF expression. An orthotopic tracheal transplantation model further evaluated the contribution of individual HIF isoforms in airway endothelial cells.

RESULTS

The genetic deletion of Hif-2α but not Hif-1α caused tracheal endothelial cell apoptosis, diminished pericyte coverage, reduced vascular perfusion, defective barrier function, overlying epithelial abnormalities, and subepithelial fibrotic remodeling. HIF-2α promoted microvascular integrity in airways through endothelial angiopoietin-1/TIE2 signaling and Notch activity. In functional tracheal transplants, HIF-2α deficiency in airway donors accelerated graft microvascular loss, whereas HIF-2α or angiopoietin-1 overexpression prolonged transplant microvascular perfusion. Augmented endothelial HIF-2α in transplant donors promoted airway microvascular integrity and diminished alloimmune inflammation.

CONCLUSIONS

Our findings reveal that the constitutive expression of endothelial HIF-2α is required for airway microvascular health.

Pericytes in Sarcomas and Other Mesenchymal Tumors

Tumors of mesenchymal origin are a diverse group, with >130 distinct entities currently recognized by the World Health Organization. A subset of mesenchymal tumors grow or invade in a perivascular fashion, and their potential relationship to pericytes is a matter of ongoing interest. In fact, multiple intersections exist between pericytes and tumors of mesenchymal origin. First, pericytes are the likely cell of origin for a group of mesenchymal tumors with a common perivascular growth pattern. These primarily benign tumors grow in a perivascular fashion and diffusely express canonical pericyte markers such as CD146, smooth muscle actin (SMA), platelet-derived growth factor receptor beta (PDGFR-β), and RGS5. These benign tumors include glomus tumor, myopericytoma, angioleiomyoma, and myofibroma. Second and as suggested by animal models, pericytes may give rise to malignant sarcomas. This is not a suggestion that all sarcomas within a certain subtype arise from pericytes, but that genetic modifications within a pericyte cell type may give rise to sarcomas. Third, mesenchymal tumors that are likely not a pericyte derivative co-opt pericyte markers in certain contexts. These include the PEComa family of tumors and liposarcoma. Fourth and finally, as "guardians" that enwrap the microvasculature, nonneoplastic pericytes may be important in sarcoma disease progression.

Role of the tumor microenvironment in digestive neuroendocrine tumors

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) represent a group of heterogeneous tumors whose incidence increased over the past few years. Around half of patients already present with metastatic disease at the initial diagnosis. Despite extensive efforts, cytotoxic and targeted therapies have provided only limited efficacy for patients with metastatic GEP-NETs, mainly due to the development of a certain state of resistance. One factor contributing to both the failure of systemic therapies and the emergence of an aggressive tumor phenotype may be the tumor microenvironment (TME), comprising dynamic and adaptative assortment of extracellular matrix components and non-neoplastic cells, which surround the tumor niche. Accumulating evidence shows that the TME can simultaneously support both tumor growth and metastasis and contribute to a certain state of resistance to treatment. In this review, we summarize the current knowledge of the TME of GEP-NETs and discuss the current therapeutic agents that target GEP-NETs and those that could be of interest in the (near) future.

Patterns, predictors and subsequent outcomes of disease progression in metastatic renal cell carcinoma patients treated with nivolumab

Background

Nivolumab is approved for the treatment of refractory metastatic renal cell carcinoma. Patterns and predictors of progressive disease (PD) on nivolumab, and outcomes in such patients are lacking.

Methods

A retrospective analysis of patients (pts) with metastatic clear cell renal cell carcinoma (ccRCC) who received nivolumab at Cleveland Clinic (2015–2017) was performed. PD was defined per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 or clinical progression as per treating physician. Univariate analyses (UVA) and multivariate analyses (MVA) were used to identify clinical and laboratory markers as potential predictors of progression-free survival (PFS).

Results

Ninety patients with mean age of 65, 74% men, and 83% good or intermediate International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) risk group were included. Median number of prior systemic treatments was 2 (range, 1–6). Median overall survival (OS) and PFS were 15.8 and 4.4 months, respectively. Fifty-seven patients (63%) had PD and 44% of patients with radiographic PD had new organ sites of metastases with brain (8/23, 35%) being the most common. Twelve patients received treatment beyond progression (TBP), and among 6 patients with available data, 3 (50%) had any tumor shrinkage (2 pts. with 17% shrinkage, one pt. with 29% shrinkage). Of 57 patients with PD, 28 patients (49%) were able to initiate subsequent treatment, mainly with axitinib and cabozantinib, while 40% of patients were transitioned to hospice after PD. In MVA, a higher baseline Neutrophil-to-Lymphocyte ratio (NLR) (HR, 1.86; 95% CI, 1.05–3.29; p = 0.033) was associated with an increased risk of progression, whereas higher (> 0.1 k/uL) baseline eosinophil count was associated with a lower risk of progression (HR, 0.54; 95% CI, 0.30–0.98; p = 0.042).

Conclusion

Brain was the most common site of PD in patients treated with nivolumab, and only half of patients progressing on nivolumab were able to initiate subsequent treatment. The risk of PD increased with a higher baseline NLR and reduced with a higher baseline eosinophil count.

Electronic supplementary material

The online version of this article (10.1186/s40425-018-0425-8) contains supplementary material, which is available to authorized users.

The Impact of Pazopanib on the Cardiovascular System

Pazopanib is an approved treatment for renal cell carcinoma and a second-line treatment for nonadipocytic soft-tissue sarcoma. However, its clinical efficacy is limited by its cardiovascular side effects. Pazopanib and other vascular endothelial growth factor receptor tyrosine kinase inhibitors have been associated with the development of hypertension, QT interval prolongation, and other cardiovascular events; however, these mechanisms are largely unknown. Gaining a deeper understanding of these mechanisms is essential for the development of appropriate surveillance strategies and possible diagnostic biomarkers to allow us to monitor patients and modulate therapy prior to significant cardiac insult. This approach will be vital in keeping patients on these life-saving therapies and may be applicable to other tyrosine kinase inhibitors as well. In this review, we provide a comprehensive overview of the preclinical and clinical side effects of pazopanib with a focus on the mechanisms responsible for its toxicity to the cardiovascular system.

Cellular Constituents of the Prostate Stroma: Key Contributors to Prostate Cancer Progression and Therapy Resistance

Reciprocal signaling between prostate stroma and its epithelium are fundamental to organ development and homeostasis. Similarly, interactions between tumor cells and stromal constituents are central to key aspects of carcinogenesis and malignancy growth involving tumor cell invasion, dissemination, and growth in distant sites. The prostate stroma is complex with several distinct resident cell types, infiltrating nonresident cell types and an amalgam of structural matrix factors, matricellular proteins, metabolites, growth factors, and cytokines. Of importance, the stroma is dynamic with changes in composition as a cause or consequence of intrinsic and extrinsic factors. In the context of epithelial neoplasia, the prostate stroma undergoes phenotypic changes with a loss of well-differentiated smooth muscle cell population and the expansion of cancer-associated fibroblast populations. This reactive stroma further coevolves with tumor progression. Recent studies show the role of tumor microenvironment components in therapy resistance and highlight the importance of a thorough knowledge of cross talk between tumor cells and microenvironment niches to develop new therapeutic strategies.

Customizable biomaterials as tools for advanced anti-angiogenic drug discovery

The inhibition of angiogenesis is a critical element of cancer therapy, as cancer vasculature contributes to tumor expansion. While numerous drugs have proven to be effective at disrupting cancer vasculature, patient survival has not significantly improved as a result of anti-angiogenic drug treatment. Emerging evidence suggests that this is due to a combination of unintended side effects resulting from the application of anti-angiogenic compounds, including angiogenic rebound after treatment and the activation of metastasis in the tumor. There is currently a need to better understand the far-reaching effects of anti-angiogenic drug treatments in the context of cancer. Numerous innovations and discoveries in biomaterials design and tissue engineering techniques are providing investigators with tools to develop physiologically relevant vascular models and gain insights into the holistic impact of drug treatments on tumors. This review examines recent advances in the design of pro-angiogenic biomaterials, specifically in controlling integrin-mediated cell adhesion, growth factor signaling, mechanical properties and oxygen tension, as well as the implementation of pro-angiogenic materials into sophisticated co-culture models of cancer vasculature.

Drug Resistance in Non-Small Cell Lung Cancer: A Potential for NOTCH Targeting?

Drug resistance is a major cause for therapeutic failure in non-small cell lung cancer (NSCLC) leading to tumor recurrence and disease progression. Cell intrinsic mechanisms of resistance include changes in the expression of drug transporters, activation of pro-survival, and anti-apoptotic pathways, as well as non-intrinsic influences of the tumor microenvironment. It has become evident that tumors are composed of a heterogeneous population of cells with different genetic, epigenetic, and phenotypic characteristics that result in diverse responses to therapy, and underlies the emergence of resistant clones. This tumor heterogeneity is driven by subpopulations of tumor cells termed cancer stem cells (CSCs) that have tumor-initiating capabilities, are highly self-renewing, and retain the ability for multi-lineage differentiation. CSCs have been identified in NSCLC and have been associated with chemo- and radiotherapy resistance. Stem cell pathways are frequently deregulated in cancer and are implicated in recurrence after treatment. Here, we focus on the NOTCH signaling pathway, which has a role in stem cell maintenance in non-squamous non-small lung cancer, and we critically assess the potential for targeting the NOTCH pathway to overcome resistance to chemotherapeutic and targeted agents using both preclinical and clinical evidence.

Vascular Endothelial Growth Factor remains unchanged in cerebrospinal fluid of patients with Alzheimer's disease and vascular dementia

Background

Increasing evidence suggests that cerebral vascular dysfunction is associated with the early stages of Alzheimer’s disease (AD). Vascular endothelial growth factor (VEGF) is one of the key players involved in the development and maintenance of the vasculature. Here, we hypothesized that VEGF levels in cerebrospinal fluid (CSF) may be altered in AD patients with vascular involvement, characterized by the presence of microbleeds (MB), and in vascular dementia (VaD) patients compared to controls.

Methods

VEGF levels were determined by electrochemilumiscence Meso Scale Discovery (MULTI-SPOT Assay System) in CSF from age-matched groups of controls with subjective cognitive decline (n = 21), AD without MB (n = 25), AD with MB (n = 25), and VaD (n = 21) patients.

Results

The average level of VEGF in the different groups was 2.8 ± 1 pg/ml CSF. Adjusted for age and gender, no significant differences were detected between groups (p > 0.5). However, we detected a significant correlation between the concentration of VEGF in the CSF and age (r = 0.22, p = 0.03). In addition, males (n = 54) revealed higher VEGF levels in their CSF compared to females (n = 38) (males = 3.08 ± 0.769 pg/ml (mean ± SD), females = 2.6 ± 0.59; p = 0.006), indicating a gender-related regulation.

Conclusion

Our study suggests that VEGF levels in the CSF do not reflect the cerebral vascular alterations in either AD or VaD patients. The observed associations of VEGF with age and gender may indicate that VEGF reflects normal aging and that males and females may differ in their aging process.

Electronic supplementary material

The online version of this article (10.1186/s13195-018-0385-8) contains supplementary material, which is available to authorized users.

Antiangiogenic therapy: Markers of response, "normalization" and resistance

Currently in cancer treatment, one premise is to use antiangiogenic therapies in association with chemotherapy or radiotherapy to augment their efficacy by benefiting from the vascular "normalization" induced by antiangiogenic therapy. This concept defines the time during which the tumor blood vessels adopt normal-like morphology and functionality, i.e. the blood vessels become more mature, the perfusion augments and hypoxia decreases. To date, there is such a diversity of treatment protocols where the type of antiangiogenic to adopt, its dose and duration of administration are different, that knowing when and how to treat is problematic. In this review, we analyzed thoroughly preclinical and clinical studies that use antiangiogenic treatments to benefit from the "normalization" and showed that the effects depend on the type of antiangiogenic administrated (anti-VEGF, anti-VEGFR, Multi-Kinase Inhibitor) and on the duration of treatment. Finally, biomarkers of "normalization" and resistance that could be used in the clinic are presented.

The complex ecosystem in non small cell lung cancer invasion

Many tumors are characterized by genetic instability, producing an assortment of genetic variants of tumor cells called subclones. These tumors and their surrounding environments form complex multi-cellular ecosystems, where subclones compete for resources and cooperate to perform multiple tasks, including cancer invasion. Our recent empirical studies revealed existence of such distinct phenotypes of cancer cells, leaders and followers, in lung cancer. These two cellular subclones exchange a complex array of extracellular signals demonstrating a symbiotic relationship at the cellular level. Here, we develop a computational model of the microenvironment of the lung cancer ecosystem to explore how the interactions between subclones can advance or inhibit invasion. We found that, due to the complexity of the ecosystem, invasion may have very different dynamics characterized by the different levels of aggressiveness. By altering the signaling environment, we could alter the ecological relationship between the cell types and the overall ecosystem development. Competition between leader and follower cell populations (defined by the limited amount of resources), positive feedback within the leader cell population (controlled by the focal adhesion kinase and fibronectin signaling), and impact of the follower cells to the leaders (represented by yet undetermined proliferation signal) all had major effects on the outcome of the collective dynamics. Specifically, our analysis revealed a class of tumors (defined by the strengths of fibronectin signaling and competition) that are particularly sensitive to manipulations of the signaling environment. These tumors can undergo irreversible changes to the tumor ecosystem that outlast the manipulations of feedbacks and have a profound impact on invasive potential. Our study predicts a complex division of labor between cancer cell subclones and suggests new treatment strategies targeting signaling within the tumor ecosystem.

Comparative Histologic and Molecular Analysis of 2 Recurrent Lesions Showing Different Magnetic Resonance Imaging Responses After Bevacizumab Treatment: Report of a Case of Anaplastic Astrocytoma

BACKGROUND

We report the case of a patient with anaplastic astrocytoma whose 2 recurrent lesions showed different imaging responses from one another after bevacizumab treatment. Histologic and genetic features of this patient are also described.

CASE DESCRIPTION

A 31-year-old patient with left temporal anaplastic astrocytoma had surgery, local radiotherapy, and chemotherapy. Recurrent lesions appeared in the cerebellar vermis and left cerebellar hemisphere, and the patient was started on biweekly bevacizumab. Subsequently, the 2 enhanced lesions showed different response patterns on magnetic resonance imaging. Although the lesion in the cerebellar vermis showed an enlargement of enhancing mass, the lesion in the left cerebellar hemisphere showed disappearance of enhancement. We resected the cerebellar vermis lesion and performed biopsy on the cerebellar hemisphere lesion. The specimens were investigated. Both recurrent lesions showed higher Ki-67 labeling indices and pericyte proliferation, and less angiogenesis compared with the initial specimen. Transmission electron microscopy showed a reduction in the distance between the endothelial cells and tumor cells in both recurrent lesions, compared with the initial lesion. However, the tight junctions in the vermian lesion were still disrupted compared with the initial lesion and the cerebellar hemispheric lesion. Genetic analysis of the initial specimen showed proneural signature; however, the recurrent vermian lesion exhibited decreased expression of proneural markers.

CONCLUSIONS

We report a case of anaplastic astrocytoma with 2 different imaging responses to bevacizumab. Our analysis suggests that differences in tight junctions possibly contributed to the changes on magnetic resonance imaging observed after bevacizumab treatment.

The dual blockade of MET and VEGFR2 signaling demonstrates pronounced inhibition on tumor growth and metastasis of hepatocellular carcinoma

BACKGROUND

The application of VEGF signaling inhibitors have been associated with more invasive or metastatic behavior of cancers including hepatocellular carcinoma (HCC). We explored the contribution of MET pathway to the enhanced HCC invasion and metastasis by VEGF signaling inhibition, and investigated the antitumor effects of NZ001, a novel dual inhibitor of MET and VEGFR2, in HCC.

METHODS

Immunocompetent orthotopic mice model of hepal-6 was established to investigate the effects of either VEGF antibody alone or in combination with the selective MET inhibitor on tumor aggressiveness. The antitumor effects of NZ001 were examined in cultured HCC cells as well as in vivo models. MET gene amplification was determined by SNP 6.0 assay. MET/P-MET expression was detected by IHC.

RESULTS

Selective VEGF signaling inhibition by VEGF antibody significantly reduced in vivo tumor growth of the orthotopic mice models, simultaneously also enhanced tumor invasion and metastasis, but inhibiting MET signaling attenuated this side-effect. Further study revealed that hypoxia caused by VEGF signaling inhibition induced HIF-1α nuclear accumulation, subsequently leading to elevated total-MET expression, and synergized with HGF in inducing invasion. NZ001, a novel dual inhibitor of MET and VEGFR2, markedly inhibited both tumor growth and metastasis of HCC, which showed obvious advantages over sorafenib in not inducing more invasive and metastatic behaviors. This effect is more pronounced in HCC with MET amplification and overexpression.

CONCLUSIONS

The activation of MET is responsible for the metastasis-promoting effects induced by VEGF inhibition. MET and VEGFR2 dual blockade, NZ001, has advantages over sorafenib in not inducing more invasive and metastatic behaviors; MET amplification and overexpression can be used to identify the subgroup of patients most likely to get the optimal benefit from NZ001 treatment.

Lysophosphatidic Acid Receptor 4 Activation Augments Drug Delivery in Tumors by Tightening Endothelial Cell-Cell Contact

Vascular normalization in tumors may improve drug delivery and anti-tumor immunity. Angiogenesis inhibitors induce hypoxia, which may facilitate malignant progression; therefore, we investigated other methods to promote vascular maturation. Here, we show that lysophosphatidic acid (LPA) enhances blood flow by promoting fine vascular networks, thereby improving vascular permeability and suppressing tumor growth when combined with anti-cancer drug treatment. Six different G protein-coupled receptors have been identified as LPA receptors (LPA1-6). In studies using mutant mice, we found that LPA4 is involved in vascular network formation. LPA4 activation induces circumferential actin bundling beneath the cell membrane and enhances linear adherens junction formation by VE-cadherin in endothelial cells. Therefore, we conclude that activation of LPA4 is a promising approach for vascular regulation.

Characterization of a drug-targetable allosteric site regulating vascular endothelial growth factor signaling

Vascular endothelial growth factors (VEGFs) regulate blood and lymph vessel development upon activation of three receptor tyrosine kinases (VEGFRs). The extracellular domain of VEGFRs consists of seven Ig-homology domains, of which D2-3 form the ligand-binding site, while the membrane proximal domains D4-7 are involved in homotypic interactions in ligand-bound receptor dimers. Based on low-resolution structures, we identified allosteric sites in D4-5 and D7 of vascular endothelial growth factor receptor 2 (VEGFR-2) accomplishing regulatory functions. Allosteric inhibition of VEGFR-2 signaling represents an attractive option for the treatment of neovascular diseases. We showed earlier that DARPin^® binders to domains D4 or D7 are potent VEGFR-2 inhibitors. Here we investigated in detail the allosteric inhibition mechanism of the domain D4 binding inhibitor D4b. The 2.38 Å crystal structure of D4b in complex with VEGFR-2 D4-5, the first high-resolution structure of this VEGFR-2 segment, indicates steric hindrance by D4b as the mechanism of inhibition of receptor activation. At the cellular level, D4b triggered quantitative internalization of VEGFR-2 in the absence of ligand and thus clearance of VEGFR-2 from the surface of endothelial cells. The allosteric VEGFR-2 inhibition was sufficiently strong to efficiently inhibit the growth of human endothelial cells at suboptimal dose in a mouse xenograft model in vivo, underlining the therapeutic potential of the approach.

Photoacoustic imaging of tumour vascular permeability with indocyanine green in a mouse model

Background

We analysed the haemodynamics of indocyanine green (ICG) in mouse organs and tumours and evaluated responses to anti-angiogenic agents in an allograft tumour mouse model by photoacoustic imaging.

Methods

Thirty-six male mice (aged 10–14 weeks; body weight 20–25 g) were used. Real-time photoacoustic imaging of organs and tumours after intravenous injection of ICG was conducted in mice until 10 min after ICG injection. ICG distribution in tumour tissues was assessed by immunohistochemical staining and observation of ICG-derived fluorescence. Vascular permeability changes induced by the vascular endothelial growth factor (VEGF)-blocking agent VEGF-trap on tumour photoacoustic signals were studied.

Results

The photoacoustic signals in salivary glands and tumours after intravenous injection of iCG (0.604 ± 0.011 and 0.994 ± 0.175 [mean ± standard deviation], respectively) were significantly increased compared with those in the liver, kidney, and great vessel (0.234 ± 0.043, 0.204 ± 0.058 and 0.127 ± 0.040, respectively; p < 0.010). In tumours, the photoacoustic signal increased within 30 s after ICG injection in a dose-dependent manner (r² = 0.899) and then decreased gradually. ICG was found to extravasate in tumour tissues. In VEGF-trap-treated mice, the photoacoustic signal in the tumour decreased at the early phase before inhibition of tumour growth was detected (0.297 ± 0.052 vs 1.011 ± 0.170 in the control; p < 0.001).

Conclusions

Photoacoustic imaging with ICG administration demonstrated extravasation of ICG in mouse organs and tumours, indicating the potential for early detection of changes in vascular permeability during cancer therapy.

The regulation of the mitochondrial apoptotic pathway by glucocorticoid receptor in collaboration with Bcl-2 family proteins in developing T cells

Glucocorticoids (GC) are important in the regulation of selection and apoptosis of CD4⁺CD8⁺ double-positive (DP) thymocytes. The pronounced GC-sensitivity of DP thymocytes, observed earlier, might be due to the combination of classical (genomic) and alternative (non-genomic) glucocorticoid receptor (GR) signaling events modifying activation or apoptotic pathways. In particular, the previously demonstrated mitochondrial translocation of activated GR in DP thymocytes offered a fascinating explanation for their pronounced GC-induced apoptosis sensitivity. However, the fine molecular details how the mitochondrial translocation of GR might regulate apoptosis remained unclear. Therefore, in the present study, we intended to examine which apoptotic pathways could be involved in GC-induced thymocyte apoptosis. Furthermore we investigated the potential relationship between the GR and Bcl-2 proteins. Using an in vitro test system, thymocytes from 4-week-old BALB/c mice, were treated with the GC-analogue dexamethasone (DX). Bax accumulated in mitochondria upon DX treatment. Mitochondrial GR showed association with members of the Bcl-2 family: Bak, Bim, Bcl-x_L. Elevated Cytochrome C, and active caspase-3, -8, and -9 levels were detected in thymocytes after DX treatment. These results support the hypothesis that in early phases of GC-induced thymocyte apoptosis, the mitochondrial pathway plays a crucial role, confirmed by the release of Cytochrome C and the activation of caspase-9. The activation of caspase-8 was presumably due to cross-talk between apoptotic signaling pathways. We propose that the GC-induced mitochondrial accumulation of Bax and the interaction between the GR and Bim, Bcl-x_L and Bak could play a role in the regulation of thymocyte apoptosis.

Randomized Phase II Trial of Parsatuzumab (Anti-EGFL7) or Placebo in Combination with Carboplatin, Paclitaxel, and Bevacizumab for First-Line Nonsquamous Non-Small Cell Lung Cancer

Lessons Learned.

The lack of efficacy associated with anti‐EGFL7 combined with standard bevacizumab and chemotherapy in this phase II trial in non‐small cell lung carcinoma is consistent with the lack of benefit observed in colorectal carcinoma, highlighting the challenge of enhancing the efficacy of VEGF inhibition in unselected populations.

Future efforts with agents like anti‐EGFL7 should be guided by advances in pharmacodynamic and predictive biomarker development for antiangiogenic agents.

Background.

Epidermal growth factor‐like domain 7 (EGFL7) is an extracellular matrix‐associated protein that is upregulated during angiogenesis and supports endothelial cell survival. This phase II trial evaluated the efficacy of the anti‐EGFL7 antibody, parsatuzumab, in combination with bevacizumab plus platinum‐based therapy for advanced or recurrent nonsquamous non‐small cell lung cancer (NS‐NSCLC).

Methods.

Patients (n = 104) were randomized to either placebo or parsatuzumab (600 mg) in combination with bevacizumab (15 mg/kg) and carboplatin/paclitaxel, administered on day 1 of each 21‐day cycle. Carboplatin and paclitaxel were administered for up to six cycles. Bevacizumab and parsatuzumab/placebo were administered for a maximum of 24 months.

Results.

The progression‐free survival (PFS) hazard ratio (HR) was 1.7 (95% confidence interval [CI], 1.0–2.8; p = .047). The median PFS was 6.7 months for the parsatuzumab arm versus 8.1 months for the placebo arm. The hazard ratio for overall survival (OS) was 1.1 (95% CI, 0.5–2.2; p = .847). The objective response rate (ORR) was 29% in the parsatuzumab arm and 56% in the placebo arm. Overall safety and tolerability were consistent with the established toxicity profile of bevacizumab.

Conclusion.

There was no evidence of efficacy for the addition of parsatuzumab to the combination of bevacizumab and chemotherapy for first‐line NS‐NSCLC.

Tumor refractoriness to anti-VEGF therapy

Vascular endothelial growth factor (VEGF) has been identified as the most potent cytokine involved in tumor angiogenesis and metastasis formation. Clinical results of anti-angiogenic therapies targeting VEGF and its receptors are very modest, resulting in a moderate improvement of overall survival. The clinical outcome is associated with the development of resistance and the increased risk of invasion and metastasis. In this article, I have analyzed the principal mechanisms of resistance to VEGF pathway inhibitors, including normalization of tumor blood vessels, hypoxia, recruitment of inflammatory cells and immature myeloid cells, alternative mechanisms of tumor vessel formation, genomic instability of tumor endothelial cells. In this context, the concept and strategies of anti-angiogenic therapies should be extensively re-considered and re-evaluated. In particular, rational combinations of anti-angiogenic agents based on pharmacokinetic and pharmacodynamics data are needed to overcome resistance and it is extremely important to determine the optimal duration and scheduling of anti-VEGF agents.

Anti-tumor effects of ONC201 in combination with VEGF-inhibitors significantly impacts colorectal cancer growth and survival in vivo through complementary non-overlapping mechanisms

Background

Small molecule ONC201 is an investigational anti-tumor agent that upregulates intra-tumoral TRAIL expression and the integrated stress response pathway. A Phase I clinical trial using ONC201 therapy in advanced cancer patients has been completed and the drug has progressed into Phase II trials in several cancer types. Colorectal cancer (CRC) remains one of the leading causes of cancer worldwide and metastatic disease has a poor prognosis. Clinical trials in CRC and other tumor types have demonstrated that therapeutics targeting the vascular endothelial growth factor (VEGF) pathway, such as bevacizumab, are effective in combination with certain chemotherapeutic agents.

Methods

We investigated the potential combination of VEGF inhibitors such as bevacizumab and its murine-counterpart; along with other anti-angiogenic agents and ONC201 in both CRC xenograft and patient-derived xenograft (PDX) models. We utilized non-invasive imaging and immunohistochemistry to determine potential mechanisms of action.

Results

Our results demonstrate significant tumor regression or complete tumor ablation in human xenografts with the combination of ONC201 with bevacizumab, and in syngeneic MC38 colorectal cancer xenografts using a murine VEGF-A inhibitor. Imaging demonstrated the impact of this combination on decreasing tumor growth and tumor metastasis. Our results indicate that ONC201 and anti-angiogenic agents act through distinct mechanisms while increasing tumor cell death and inhibiting proliferation.

Conclusion

With the use of both a murine VEGF inhibitor in syngeneic models, and bevacizumab in human cell line-derived xenografts, we demonstrate that ONC201 in combination with anti-angiogenic therapies such as bevacizumab represents a promising approach for further testing in the clinic for the treatment of CRC.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0671-0) contains supplementary material, which is available to authorized users.