Antiangiogenic and Antitumor Activities of Aflibercept, a Soluble VEGF Receptor-1 and -2, in a Mouse Model of Hepatocellular Carcinoma

Precision Culture Scaling to Establish High-Throughput Vasculogenesis Models

Hydrogel-based 3D cell cultures can recapitulate (patho)physiological phenomena ex vivo. However, due to their complex multifactorial regulation, adapting these tissue and disease models for high-throughput screening workflows remains challenging. In this study, a new precision culture scaling (PCS-X) methodology combines statistical techniques (design of experiment and multiple linear regression) with automated, parallelized experiments and analyses to customize hydrogel-based vasculogenesis cultures using human umbilical vein endothelial cells and retinal microvascular endothelial cells. Variations of cell density, growth factor supplementation, and media composition are systematically explored to induce vasculogenesis in endothelial mono- and cocultures with mesenchymal stromal cells or retinal microvascular pericytes in 384-well plate formats. The developed cultures are shown to respond to vasculogenesis inhibitors in a compound- and dose-dependent manner, demonstrating the scope and power of PCS-X in creating parallelized tissue and disease models for drug discovery and individualized therapies.

New Opportunities in the Systemic Treatment of Hepatocellular Carcinoma-Today and Tomorrow

Hepatocellular carcinoma (HCC) is the most common primary liver cancer. Liver cirrhosis, hepatitis B, hepatitis C, and non-alcoholic fatty liver disease represent major risk factors of HCC. Multiple different treatment options are available, depending on the Barcelona Clinic Liver Cancer (BCLC) algorithm. Systemic treatment is reserved for certain patients in stages B and C, who will not benefit from regional treatment methods. In the last fifteen years, the arsenal of available therapeutics has largely expanded, which improved treatment outcomes. Nevertheless, not all patients respond to these agents and novel combinations and drugs are needed. In this review, we aim to summarize the pathway of trials investigating the safety and efficacy of targeted therapeutics and immunotherapies since the introduction of sorafenib. Furthermore, we discuss the current evidence regarding resistance mechanisms and potential novel targets in the treatment of advanced HCC.

Lentiviral delivered aflibercept OXB-203 for treatment of neovascular AMD

Neovascular age-related macular degeneration (nAMD) is a leading cause of blindness in the aging population, with vascular endothelial growth factor (VEGF) playing a key role. Treatment with recombinant anti-VEGFs is the current standard of care; however, it is only effective for 1-2 months at a time and requires re-administration. Gene therapy could pave the way for stable, long-term expression of therapeutic anti-VEGF with a single dose, reducing the frequency of treatment and potentially improving clinical outcomes. As such, we have developed OXB-203, a lentiviral-based gene therapy encoding the anti-VEGF protein aflibercept. Aflibercept derived from OXB-203 exhibited comparable in vitro binding characteristics to VEGF as recombinant aflibercept. Furthermore, its biological potency was demonstrated by the equivalent inhibition of VEGF-induced human umbilical vein endothelial cell (HUVEC) proliferation and tubule formation as recombinant aflibercept. In a rat choroidal neovascularization (CNV) model of nAMD, a single subretinal administration of OXB-203 reduced laser-induced CNV lesion areas analogous to an intravitreal bolus of recombinant aflibercept. Finally, in a head-to-head comparative study, aflibercept derived from OXB-203 was shown to be expressed at significantly higher levels in ocular tissues than from an AAV8-aflibercept vector following a single subretinal delivery to rats. These findings support the therapeutic potential of OXB-203 for the management of nAMD.

The vascular endothelial growth factor trap aflibercept induces vascular dysfunction and hypertension via attenuation of eNOS/NO signaling in mice

Aflibercept, as a soluble decoy vascular endothelial growth factor receptor, Which has been used as a first-line monotherapy for cancers. Aflibercept often causes cardiovascular toxicities including hypertension, but the mechanisms underlying aflibercept-induced hypertension remain unknown. In this study we investigated the effect of short-term and long-term administration of aflibercept on blood pressure (BP), vascular function, NO bioavailability, oxidative stress and endothelin 1 (ET-1) in mice and cultured endothelial cells. We showed that injection of a single-dose of aflibercept (18.2, 36.4 mg/kg, iv) rapidly and dose-dependently elevated BP in mice. Aflibercept treatment markedly impaired endothelial-dependent relaxation (EDR) and resulted in NADPH oxidases 1 (NOX1)- and NADPH oxidases 4 (NOX4)-mediated generation of ROS, decreased the activation of protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS) concurrently with a reduction in nitric oxide (NO) production and elevation of ET-1 levels in mouse aortas; these effects were greatly attenuated by supplementation of L-arginine (L-arg, 0.5 or 1.0 g/kg, bid, ig) before aflibercept injection. Similar results were observed in L-arg-pretreated cultured endothelial cells, showing markedly decreased ROS accumulation and AKT/eNOS/NO signaling impairment induced by aflibercept. In order to assess the effects of long-term aflibercept on hypertension and to evaluate the beneficial effects of L-arg supplementation, we administered these two drugs to WT mice for up to 14 days (at an interval of two days). Long-term administration of aflibercept resulted in a sustained increase in BP and a severely impaired EDR, which are associated with NOX1/NOX4-mediated production of ROS, increase in ET-1, inhibition of AKT/eNOS/NO signaling and a decreased expression of cationic amino acid transporter (CAT-1). The effects caused by long-term administration were greatly attenuated by L-arg supplementation in a dose-dependent manner. We conclude that aflibercept leads to vascular dysfunction and hypertension by inhibiting CAT-1/AKT/eNOS/NO signaling, increasing ET-1, and activating NOX1/NOX4-mediated oxidative stress, which can be suppressed by supplementation of L-arg. Therefore, L-arg could be a potential therapeutic agent for aflibercept-induced hypertension.

Network analysis and the impact of Aflibercept on specific mediators of angiogenesis in HUVEC cells

Angiogenesis, inflammation and endothelial cells’ migration and proliferation exert fundamental roles in different diseases. However, more studies are needed to identify key proteins and pathways involved in these processes. Aflibercept has received the approval of the US Food and Drug Administration (FDA) for the treatment of wet AMD and colorectal cancer. Moreover, the effect of Aflibercept on VEGFR2 downstream signalling pathways has not been investigated yet. Here, we integrated text mining data, protein‐protein interaction networks and multi‐experiment microarray data to specify candidate genes that are involved in VEGFA/VEGFR2 signalling pathways. Network analysis of candidate genes determined the importance of the nominated genes via different centrality parameters. Thereupon, several genes—with the highest centrality indexes—were recruited to investigate the impact of Aflibercept on their expression pattern in HUVEC cells. Real‐time PCR was performed, and relative expression of the specific genes revealed that Aflibercept modulated angiogenic process by VEGF/PI3KA/AKT/mTOR axis, invasion by MMP14/MMP9 axis and inflammation‐related angiogenesis by IL‐6‐STAT3 axis. Data showed Aflibercept simultaneously affected these processes and determined the nominated axes that had been affected by the drug. Furthermore, integrating the results of Aflibercept on expression of candidate genes with the current network analysis suggested that resistance against the Aflibercept effect is a plausible process in HUVEC cells.

Cytokine Profiles and the Effect of Intravitreal Aflibercept Treatment on Experimental Choroidal Neovascularization

PURPOSE

The purpose of our study was to investigate the profiles of inflammatory cytokines and the macrophage polarization gene in a choroidal neovascularization (CNV) mouse model before and after intravitreal aflibercept treatment.

METHODS

The CNV mouse model was conducted by laser photocoagulation. A total of 58 cytokines were measured by the multiplex mouse cytokine antibody array. The macrophage polarization genes were tested by reverse transcription polymerase chain reaction. The relationship between the cytokines and the CNV lesion area was analyzed by correlation.

RESULTS

MIP-1a on day 3 after laser photocoagulation, MCP-5 and Fas-L on day 7, and IL-15 and IL-7 on day 14 were significantly upregulated (p < 0.001, fold change >10.0). After the intravitreal aflibercept treatment, GM-CSF and MCP-1 on day 3 and TIMP-1 on days 7 and 14 were the most significantly upregulated cytokines (p < 0.001, fold change >10.0). MIP-1 on day 3, IL-13 and Fas-L on day 7, and Fas-L on day 14 were the most significantly downregulated cytokines after intravitreal aflibercept treatment (p < 0.001, fold change >5.0). M2 polarization and VEGFA genes were significantly increased in the CNV formation, whereas aflibercept suppressed M2 polarization and VEGFA genes. IL-7 was negatively related to the CNV lesion area on day 14 after intravitreal aflibercept treatment (r = -0.938, p = 0.006).

CONCLUSION

The inflammatory cytokines and the M1/M2 macrophage genes significantly changed in the CNV mouse model. This result suggests that inflammatory cytokines and macrophages play a critical role in the physiopathology of CNV.

Anti-VEGF DNA-based aptamers in cancer therapeutics and diagnostics

The vascular endothelial growth factor (VEGF) family and its receptors play fundamental roles not only in physiological but also in pathological angiogenesis, characteristic of cancer progression. Aiming at finding putative treatments for several malignancies, various small molecules, antibodies, or protein-based drugs have been evaluated in vitro and in vivo as VEGF inhibitors, providing efficient agents approved for clinical use. Due to the high clinical importance of VEGF, also a great number of anti-VEGF nucleic acid-based aptamers-that is, oligonucleotides able to bind with high affinity and specificity a selected biological target-have been developed as promising agents in anticancer strategies. Notable research efforts have been made in optimization processes of the identified aptamers, searching for increased target affinity and/or bioactivity by exploring structural analogues of the lead compounds. This review is focused on recent studies devoted to the development of DNA-based aptamers designed to target VEGF. Their therapeutic potential as well as their significance in the construction of highly selective biosensors is here discussed.

Activated FGF2 signaling pathway in tumor vasculature is essential for acquired resistance to anti-VEGF therapy

Anti-vascular endothelial growth factor (VEGF) therapy shows antitumor activity against various types of solid cancers. Several resistance mechanisms against anti-VEGF therapy have been elucidated; however, little is known about the mechanisms by which the acquired resistance arises. Here, we developed new anti-VEGF therapy-resistant models driven by chronic expression of the mouse VEGFR2 extracellular domain fused with the human IgG4 fragment crystallizable (Fc) region (VEGFR2-Fc). In the VEGFR2-Fc-expressing resistant tumors, we demonstrated that the FGFR2 signaling pathway was activated, and pericytes expressing high levels of FGF2 were co-localized with endothelial cells. Lenvatinib, a multiple tyrosine kinase inhibitor including VEGFR and FGFR inhibition, showed marked antitumor activity against VEGFR2-Fc-expressing resistant tumors accompanied with a decrease in the area of tumor vessels and suppression of phospho-FGFR2 in tumors. Our findings reveal the key role that intercellular FGF2 signaling between pericytes and endothelial cells plays in maintaining the tumor vasculature in anti-VEGF therapy-resistant tumors.

Strong Antitumor Activity of Bevacizumab and Aflibercept in Neuroendocrine Carcinomas: In-Depth Preclinical Study

BACKGROUND

Neuroendocrine carcinoma (NEC) is a rare and very aggressive tumor. It has been greatly understudied, and very little is known about optimal treatment strategy for patients with this disease. The purpose of this study was to evaluate in vivo whether anti-vascular endothelial growth factor (VEGF) drugs could be a therapeutic alternative for these tumors with a poor prognosis.

METHODS

We have developed 2 xenograft models using either human cell line derived from lung (H460) or from colon (COLO320) NEC to assess the effect of 2 antiangiogenic drugs, aflibercept and bevacizumab, on tumor growth and their pathological characteristics. Additionally, tumors were subjected to immunohistochemistry staining and proteins were measured with Western blot and ELISA.

RESULTS

Both aflibercept and bevacizumab showed significant antitumor activity (p < 0.001). In the H460 model, aflibercept resulted in 94% tumor growth inhibition (TGI) and bevacizumab treatment resulted in 72.2% TGI. Similarly, in the COLO320 model, aflibercept and bevacizumab resulted in 89.3 and 84% TGI, respectively. Moreover, antitumor activity occurs early after treatment initiation. Using Tumor Control Index score, which address the kinetics of tumor growth in a way comparable to the methods used in human clinical studies, we confirmed that both drugs inhibit significantly tumor growth. When tumor stabilization was evaluated, aflibercept shows higher ability to stabilize NEC tumors than bevacizumab.

CONCLUSION

Results derived from this study strongly support anti-VEGF therapies, especially aflibercept, as a novel therapeutic option in NECs. Further studies are necessary, but our observations encourage the evaluation of antiangiogenics in clinical trials combined with standard chemotherapy.

Medical oncology management of advanced hepatocellular carcinoma 2019: a reality check

In terms of global cancer-related deaths, hepatocellular carcinoma (HCC) has the fourth highest mortality rate. Up until 2017, treatment of advanced HCC was largely limited to sorafenib, an oral tyrosine kinase inhibitor, with little to no success in the development of alternative treatment options. However, in the past two years, there has been an unprecedented increase in both the number and type of treatment options available for HCC. As of 2019, the US FDA has approved four oral tyrosine kinase inhibitors, two immune checkpoint inhibitors, and one anti-angiogenesis antibody for the treatment of HCC. Even with this new variety, systemic treatment of advanced HCC remains largely unsatisfactory, and the median survival rate stands at approximately one year. The expected breakthrough of using immune checkpoint inhibitors in advanced HCC did not materialize in 2019. The use of immune checkpoint inhibitors in conjunction with oral tyrosine kinase inhibitors or anti-angiogenesis medications is the current clinical research trend, the results of which are eagerly anticipated. Despite limited progress in survival, HCC research is currently experiencing a period of growth and innovation, and there is hope for significant advances in the treatment of advanced HCC as the field continues to develop.

Insights into the G-rich VEGF-binding aptamer V7t1: when two G-quadruplexes are better than one!

The G-quadruplex-forming VEGF-binding aptamer V7t1 was previously found to be highly polymorphic in a K⁺-containing solution and, to restrict its conformational preferences to a unique, well-defined form, modified nucleotides (LNA and/or UNA) were inserted in its sequence. We here report an in-depth biophysical characterization of V7t1 in a Na⁺-rich medium, mimicking the extracellular environment in which VEGF targeting should occur, carried out combining several techniques to analyse the conformational behaviour of the aptamer and its binding to the protein. Our results demonstrate that, in the presence of high Na⁺ concentrations, V7t1 behaves in a very different way if subjected or not to annealing procedures, as evidenced by native gel electrophoresis, size exclusion chromatography and dynamic light scattering analysis. Indeed, not-annealed V7t1 forms both monomeric and dimeric G-quadruplexes, while the annealed oligonucleotide is a monomeric species. Remarkably, only the dimeric aptamer efficiently binds VEGF, showing higher affinity for the protein compared to the monomeric species. These findings provide new precious information for the development of improved V7t1 analogues, allowing more efficient binding to the cancer-related protein and the design of effective biosensors or theranostic devices based on VEGF targeting.

Aflibercept regulates retinal inflammation elicited by high glucose via the PlGF/ERK pathway

Diabetic retinopathy (DR) is a secondary complication of diabetes. DR can cause irreversible blindness, and its pathogenesis is considered multifactorial. DR can progress from non-proliferative DR to proliferative DR, characterized by retinal neovascularization. The main cause of vision loss in diabetic patients is diabetic macular edema, caused by vessel leakage and blood retinal barrier breakdown. Currently, aflibercept is an anti-VEGF approved for diabetic macular edema. Aflibercept can bind several members of vascular permeability factors, namely VEGF-A, B, and PlGF. We analyzed the aflibercept-PlGF complex at molecular level, through an in silico approach. In order to explore the role of PlGF in DR, we treated primary human retinal endothelial cells (HRECs) and mouse retinal epithelial cells (RPEs) with aflibercept and an anti-PlGF antibody. We explored the hypothesis that aflibercept has anti-inflammatory action through blocking of PlGF signaling and the ERK axis in an in vitro and in vivo model of DR. Both aflibercept and the anti-PlGF antibody exerted protective effects on retinal cells, by inhibition of the ERK pathway. Moreover, aflibercept significantly decreased (p < 0.05) the expression of TNF-α in an in vitro and in vivo model of DR. Therefore, our data suggest that inhibition of PlGF signaling, or a selective blocking, may be useful in the management of early phases of DR when the inflammatory process is largely involved.

Therapy for Cancer: Strategy of Combining Anti-Angiogenic and Target Therapies

The concept that blood supply is required and necessary for cancer growth and spreading is intuitive and was firstly formalized by Judah Folkman in 1971, when he demonstrated that cancer cells release molecules able to promote the proliferation of endothelial cells and the formation of new vessels. This seminal result has initiated one of the most fascinating story of the medicine, which is offering a window of opportunity for cancer treatment based on the use of molecules inhibiting tumor angiogenesis and in particular vascular-endothelial growth factor (VEGF), which is the master gene in vasculature formation and is the commonest target of anti-angiogenic regimens. However, the clinical results are far from the remarkable successes obtained in pre-clinical models. The reasons of this discrepancy have been partially understood and well addressed in many reviews (Bergers and Hanahan, 2008; Bottsford-Miller et al., 2012; El-Kenawi and El-Remessy, 2013; Wang et al., 2015; Jayson et al., 2016). At present anti-angiogenic regimens are not used as single treatments but associated with standard chemotherapies. Based on emerging knowledge of the biology of VEGF, here we sustain the hypothesis of the efficacy of a dual approach based on targeting pro-angiogenic pathways and other druggable targets such as mutated oncogenes or the immune system.

Delivery of sFIT-1 engineered MSCs in combination with a continuous low-dose doxorubicin treatment prevents growth of liver cancer

One important process in liver cancer growth and progression is angiogenesis. Vascular endothelial growth factor (VEGF) has the significant role in liver cancer angiogenesis. sFlt1 (soluble Fms-like tyrosine kinase-1) is the promising inhibitor of VEGF and can be used as the new method of inhibiting angiogenesis. MSCs (Mesenchymal stem cells) can infiltrate into tumor tissue and function as the efficient transgene delivery mediator. Here, we engineered murine MSCs to express sFlt1 and examined the anti-tumor effect of MSC- sFlt1 in combination with continues low-dose doxorubicin treatment. We found that this combination therapy significantly inhibited liver cancer cells proliferation. Above all, HepG2 xenografts treated with this combination therapy went into remission. It is of note that this inhibition effect was not p53 binding and by increasing caspase8. This study suggests that this combination treatment has novel therapeutic potential for liver cancer because of significantly inhibiting cancer cells growth and anti-angiogenesis in vitro and in vivo.

Therapeutic potential of an anti-angiogenic multimodal biomimetic peptide in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major cause of cancer-related death worldwide. Due to inadequate screening methods and the common coexistence of limited functional liver reserves, curative treatment options are limited. Liver transplantation is the only curative treatment modality for early HCC. There are multidisciplinary treatment options like ablative treatments, radiation and systemic therapy available for more advanced patients or those that are inoperable. Treatment resistance and progression is inevitable for these HCC patients. Newer therapeutics need to be explored for better management of HCC. HCC is a hypervascular tumor and many pro-angiogenic proteins are found significantly overexpressed in HCC. Here we explored the therapeutic potential of the anti-angiogenic, anti-lymphangiogenic, and directly anti-tumorigenic biomimetic collagen IV-derived peptide developed by our group. Human HCC cell lines HuH7, Hep3b and HepG2 showed significant disruption of cell adhesion and migration upon treatment with the peptide. Consistent with previously described multimodal inhibitory properties, the peptide was found to inhibit both c-Met and IGF1R signaling in HepG2 cells and blocked HepG2 conditioned media stimulation of microvascular endothelial cell (MEC) tube formation. Furthermore, the peptide treatment of mouse HepG2 tumor xenografts significantly inhibited growth relative to untreated controls. The peptide was also found to improve the survival of autochthonous Myc-induced HCC in a transgenic mouse model. Mechanistically, we found that the peptide treatment reduced microvascular density in the autochthonous liver tumors with increased apoptosis. This study shows the promising therapeutic potential of our biomimetic peptide in the treatment of HCC.

Endothelial progenitor cells in multiple myeloma neovascularization: a brick to the wall

Multiple myeloma (MM) is characterized by the clonal expansion of plasma cells in the bone marrow that leads to events such as bone destruction, anaemia and renal failure. Despite the several therapeutic options available, there is still no effective cure, and the standard survival is up to 4 years. The evolution from the asymptomatic stage of monoclonal gammopathy of undetermined significance to MM and the progression of the disease itself are related to cellular and molecular alterations in the bone marrow microenvironment, including the development of the vasculature. Post-natal vasculogenesis is characterized by the recruitment to the tumour vasculature of bone marrow progenitors, known as endothelial progenitor cells (EPCs), which incorporate newly forming blood vessels and differentiate into endothelial cells. Several processes related to EPCs, such as recruitment, mobilization, adhesion and differentiation, are tightly controlled by cells and molecules in the bone marrow microenvironment. In this review, the bone marrow microenvironment and the mechanisms associated to the development of the neovasculature promoted by EPCs are discussed in detail in both a non-pathological scenario and in MM. The latest developments in therapy targeting the vasculature and EPCs in MM are also highlighted. The identification and characterization of the pathways relevant to the complex setting of MM are of utter importance to identify not only biomarkers for an early diagnosis and disease progression monitoring, but also to reveal intervention targets for more effective therapy directed to cancer cells and the endothelial mediators relevant to neovasculature development.

Tumor angiogenesis revisited: Regulators and clinical implications

Since Judah Folkman hypothesized in 1971 that angiogenesis is required for solid tumor growth, numerous studies have been conducted to unravel the angiogenesis process, analyze its role in primary tumor growth, metastasis and angiogenic diseases, and to develop inhibitors of proangiogenic factors. These studies have led in 2004 to the approval of the first antiangiogenic agent (bevacizumab, a humanized antibody targeting vascular endothelial growth factor) for the treatment of patients with metastatic colorectal cancer. This approval launched great expectations for the use of antiangiogenic therapy for malignant diseases. However, these expectations have not been met and, as knowledge of blood vessel formation accumulates, many of the original paradigms no longer hold. Therefore, the regulators and clinical implications of angiogenesis need to be revisited. In this review, we discuss recently identified angiogenesis mediators and pathways, new concepts that have emerged over the past 10 years, tumor resistance and toxicity associated with the use of currently available antiangiogenic treatment and potentially new targets and/or approaches for malignant and nonmalignant neovascular diseases.