SAR131675, a potent and selective VEGFR-3-TK inhibitor with antilymphangiogenic, antitumoral, and antimetastatic activities

Vegfr3 activation of Pkd2l1+ CSF-cNs triggers the neural stem cell response in spinal cord injury

Activating adult neural stem cells (NSCs) located within the spinal cord niche is considered a promising therapeutic approach for treating spinal cord injury (SCI). Cerebrospinal fluid (CSF)-contacting neurons expressing Pkd2l1 exhibit phenotypic and molecular traits similar to those of adult NSCs. However, the mechanism responsible for regulating the activation of Pkd2l1+ CSF-cNs still needs to be discovered. This research demonstrated that Pkd2l1+ CSF-cNs have a high concentration of vascular endothelial growth factor receptor 3 (Vegfr3) and that SCI results in elevated Vegfr3 levels. The overexpression of Vegfr3 in Pkd2l1+CSF-cNs induced potential NSC activation. Blocking Vegfr3 led to a significant reduction in the percentage of active Pkd2l1+ CSF-cNs, suggesting that Vegfr3 is involved in controlling the shift from dormancy to activation in these cells. In vivo, the downregulation of Vegfr3 by SAR131475 inhibited Pkd2l1+CSF-cN proliferation and maintained self-renewal. Injection of vascular endothelial growth factor C (Vegf-C) into the lateral ventricle of adult mice confirmed the involvement of Vegfr3 in activating Pkd2l1+ CSF-cNs. Vegf-C administration significantly increased the number of activated Pkd2l1+ CSF-cNs. Mechanistically, Vegfr3 primed quiescent Pkd2l1+ CSF-cNs for cell cycle reentry by enabling the activation of PI3K/Akt signaling. The activation of Vegfr3 may enhance SCI outcomes by promoting neuronal survival and facilitating the recovery of motor function in mice. Together, our findings highlight that Vegfr3 is a crucial functional regulator of Pkd2l1+ CSF-cNs, governing the transition from NSC quiescence to activation.

Lymphangiogenesis orchestrating tumor microenvironment: Face changing in immunotherapy

In the era of immunotherapy, the lymphatic system has garnered significant attention from researchers. Increasing evidence highlights the complex regulation of lymphatic vessels (LVs) within the tumor microenvironment, unveiling a paradox in tumor progression: while LVs enhance immune surveillance, they simultaneously foster immune suppression. This review summarizes the regulatory factors of lymphangiogenesis, discusses the intricate effects of LVs on immunotherapy, and emphasizes the potential connection between lymphangiogenesis and tertiary lymphoid structure. Additionally, current therapeutic strategies targeting lymphangiogenesis are critically evaluated, with a forward-looking perspective on future research directions and regulatory approaches to achieve precise targeting and optimize immunotherapy paradigms.

Metabolic expression profiling analysis reveals pyruvate-mediated EPHB2 upregulation promotes lymphatic metastasis in head and neck squamous cell carcinomas

Lymphatic metastasis is a well-known factor for initiating distant metastasis of head and neck squamous cell carcinoma (HNSCC), which caused major death in most patients with cancer. Meanwhile, metabolic reprogramming to support metastasis is regarded as a prominent hallmark of cancers. However, how metabolic disorders drive in HNSCC remains unclear. We firstly established a new classification of HNSCC patients based on metabolism gene expression profiles from the TCGA and GEO database, and identified an enriched carbohydrate metabolism subgroup which was significantly associated with lymphatic metastasis and worse clinical outcome. Moreover, we found that highly activated pyruvate metabolism endowed tumors with EPHB2 upregulation and promoted tumor lymphangiogenesis independently of VEGF-C/VEGFR3 signaling pathway. Mechanically, high nuclear acetyl-CoA production from pyruvate metabolism promoted histone acetylation, which in turn transcriptionally upregulated EPHB2 expression and secretion in tumor cells. EPHB2 bound with EFNB1 in lymphatic endothelial cells promoted YAP/TAZ cytoplasmic retention, which alleviated YAP/TAZ-mediated prospero homeobox protein 1 (PROX1) transcriptional repression, and then triggered tumor lymphangiogenesis. Importantly, combined treatment with EFNB1-Fc and VEGFR3 inhibitor synergistic abrogated lymphangiogenesis in vitro and in vivo, suggesting that targeting EPHB2 might be a potential strategy to patients with no or slight response to VEGFR3 inhibitor. These findings uncover the mechanism by which pyruvate metabolism is linked to lymphatic metastasis of tumor and provides a promising therapeutic strategy for the prevention of HNSCC metastasis.

Compensatory lymphangiogenesis is required for edema resolution in zebrafish

Edema, characterized by the accumulation of interstitial fluid, poses significant challenges in various pathological conditions. Lymphangiogenesis is critical in edema clearance, and delayed or inadequate lymphatic responses significantly hinder healing processes. However, real-time observation of dynamic changes in lymphangiogenesis during tissue repair in animal models has been challenging, leaving the mechanisms behind compensatory lymphatic activation for edema clearance largely unexplored. To address this gap, we subjected zebrafish larvae to osmotic stress using hypertonic (375 mOsm/L) and isotonic (37.5 mOsm/L) solutions to induce osmotic imbalance and subsequent edema formation. Intravital imaging of vascular transgenic larvae revealed significant lymphatic vessel remodeling during tissue edema. The observed increase in lymphatic endothelial progenitor cells, alongside the sustained expansion and remodeling of primary lymphatics, indicates active lymphangiogenesis during the recovery phase. We developed a novel method employing translating ribosome affinity purification to analyze the translatome of lymphatic and venous endothelial cells in vivo, which uncovered the upregulation of key pro-lymphangiogenic genes, particularly vegfr2 and vegfr3, during tissue recovery. Inhibition of compensatory lymphangiogenesis impaired edema fluid clearance and tissue recovery. Our findings establish a new model for in vivo live imaging of compensatory lymphangiogenesis and provide a novel approach in investigating lymphatic activation during edema resolution.

Synergistic effects of mTOR inhibitors with VEGFR3 inhibitors on the interaction between TSC2-mutated cells and lymphatic endothelial cells

Lymphangioleiomyomatosis (LAM) is a rare neoplastic disease affecting the lung, kidney, and lymphatic system with a molecular mechanism of tuberous sclerosis complex 2 (TSC2) mutations. Vascular endothelial growth factor D (VEGF-D), a ligand for vascular endothelial growth factor receptor 3 (VEGFR3), is a diagnostic biomarker of LAM and is associated with lymphatic circulation abnormalities. This study explored the interaction between LAM cells and lymphatic endothelial cells (LECs) and the effects of rapamycin on this interaction, which may help to identify new targets for LAM treatment. This study used direct and indirect cocultures of TSC2-null cells and LECs. The xenograft model was applied to explore the therapeutic feasibility. Single-cell sequencing revealed increased LECs in the lungs of LAM patients through activation of pathways involved in lymphangiogenesis. TSC2-null cells attracted LECs and promoted tube formation. VEGF-D/VEGFR3 was a key mediator of the above interaction. Rapamycin can directly inhibit recruitment but not the tube formation of LECs in vitro. The combination of rapamycin with VEGFR3 inhibitors not only enhanced the effect of rapamycin but also inhibited lymphatic related manifestations including the tube formation and the lymphatic metastasis. Our findings demonstrated that LAM cells recruit LECs and promote tube formation via VEGF-D/VEGFR3. Rapamycin only partially blocked this interaction. The synergistic effects of rapamycin and VEGFR3 inhibitors suggest a novel strategy for the treatment of LAM and other TSC2-mutated diseases.

Activation of VEGFR3 and MLC2 are Critical for GLP-2 Enhancement of Chylomicron Transport

Background and Aims

A significant proportion of absorbed dietary triglycerides (TGs) remain in various intracellular and extracellular intestinal compartments for many hours after fat ingestion, including in the lymphatic circulation. TGs retained in the intestine or lymphatics can be mobilized by the gut peptide glucagon-like peptide 2 (GLP-2) and other stimuli. Our previous published data demonstrated that GLP-2 enhances lymph flow by acting distal to the enterocyte, specifically by enhancing lacteal contractility, in an enteric nervous system-dependent fashion. The objective of the present study was to further explore various intermediates in the signaling pathway whereby GLP-2 enhances mesenteric lymph flow. In this study we focused on the roles of vascular endothelial growth factor receptor 3 (VEGFR3) and myosin light chain 2 (MLC2), known to play important roles in lymphangiogenesis and lymphatic contractility, respectively.

Methods

A rat lymph fistula model was utilized in this study. An intraduodenal lipid bolus was applied to the rats 5 hours before the following intraperitoneal (i.p.) administrations: 1) saline (placebo), 2) GLP-2, 3) GLP-2 + MAZ-51 (a VEGFR3 inhibitor), 4) GLP-2 + SAR131675 (a second VEGFR3 inhibitor), 5) GLP-2 + ML-7 (a MLCK inhibitor). Lymph flow and TG output were assessed for 60 minutes after the i.p. administrations. In another set of animals, post-i.p. administration, tissue samples were collected to quantify VEGFR3 and MLC2 activation (via phosphorylation).

Results

We showed that GLP-2 treatment acutely activated VEGFR3 and MLC2, and that inhibition of VEGFR3 (via MAZ-51/SAR131675) and MLC2 (via ML-7) abolished GLP-2-induced lymph flow and TG output. Furthermore, VEGFR3 inhibition blocked MLC2 activation.

Conclusion

Our data suggest that the activation of VEGFR3 and MLC2 play critical roles in GLP-2's enhancement of chylomicron secretion and that VEGFR3 activation is an important intermediary step in GLP-2's activation of MLC2.

Simvastatin alleviates glymphatic system damage via the VEGF-C/VEGFR3/PI3K-Akt pathway after experimental intracerebral hemorrhage

Current clinical practice primarily relies on surgical intervention to remove hematomas in patients with intracerebral hemorrhage (ICH), given the lack of effective drug therapies. Previous research indicates that simvastatin (SIM) may enhance hematoma absorption and resolution in the acute phase of ICH, though the precise mechanisms remain unclear. Recent findings have highlighted the glymphatic system (GS) as a crucial component in intracranial cerebrospinal fluid circulation, playing a significant role in hematoma clearance post-ICH. This study investigates the link between SIM efficacy in hematoma resolution and the GS. Our experimental results show that SIM alleviates GS damage in ICH-induced rats, resulting in improved outcomes such as reduced brain edema, neuronal apoptosis, and degeneration. Further analysis reveals that SIM's effects are mediated through the VEGF-C/VEGFR3/PI3K-Akt pathway. This study advances our understanding of SIM's mechanism in promoting intracranial hematoma clearance and underscores the potential of targeting the GS for ICH treatment.

VEGFD signaling balances stability and activity-dependent structural plasticity of dendrites

Mature neurons have stable dendritic architecture, which is essential for the nervous system to operate correctly. The ability to undergo structural plasticity, required to support adaptive processes like memory formation, is still present in mature neurons. It is unclear what molecular and cellular processes control this delicate balance between dendritic structural plasticity and stabilization. Failures in the preservation of optimal dendrite structure due to atrophy or maladaptive plasticity result in abnormal connectivity and are associated with various neurological diseases. Vascular endothelial growth factor D (VEGFD) is critical for the maintenance of mature dendritic trees. Here, we describe how VEGFD affects the neuronal cytoskeleton and demonstrate that VEGFD exerts its effects on dendrite stabilization by influencing the actin cortex and reducing microtubule dynamics. Further, we found that during synaptic activity-induced structural plasticity VEGFD is downregulated. Our findings revealed that VEGFD, acting on its cognate receptor VEGFR3, opposes structural changes by negatively regulating dendrite growth in cultured hippocampal neurons and in vivo in the adult mouse hippocampus with consequences on memory formation. A phosphoproteomic screening identified several regulatory proteins of the cytoskeleton modulated by VEGFD. Among the actin cortex-associated proteins, we found that VEGFD induces dephosphorylation of ezrin at tyrosine 478 via activation of the striatal-enriched protein tyrosine phosphatase (STEP). Activity-triggered structural plasticity of dendrites was impaired by expression of a phospho-deficient mutant ezrin in vitro and in vivo. Thus, VEGFD governs the equilibrium between stabilization and plasticity of dendrites by acting as a molecular brake of structural remodeling.

Preventing periprosthetic osteolysis in aging populations through lymphatic activation and stem cell-associated secretory phenotype inhibition

With increases in life expectancy, the number of patients requiring joint replacement therapy and experiencing periprosthetic osteolysis, the most common complication leading to implant failure, is growing or underestimated. In this study, we found that osteolysis progression and osteoclast differentiation in the surface of the skull bone of adult mice were accompanied by significant expansion of lymphatic vessels within bones. Using recombinant VEGF-C protein to activate VEGFR3 and promote proliferation of lymphatic vessels in bone, we counteracted excessive differentiation of osteoclasts and osteolysis caused by titanium alloy particles or inflammatory cytokines LPS/TNF-α. However, this effect was not observed in aged mice because adipogenically differentiated mesenchymal stem cells (MSCs) inhibited the response of lymphatic endothelial cells to agonist proteins. The addition of the JAK inhibitor ruxolitinib restored the response of lymphatic vessels to external stimuli in aged mice to protect against osteolysis progression. These findings suggest that inhibiting SASP secretion by adipogenically differentiated MSCs while activating lymphatic vessels in bone offers a new method to prevent periprosthetic osteolysis during joint replacement follow-up.

Piezo1 regulates meningeal lymphatic vessel drainage and alleviates excessive CSF accumulation

Piezo1 regulates multiple aspects of the vascular system by converting mechanical signals generated by fluid flow into biological processes. Here, we find that Piezo1 is necessary for the proper development and function of meningeal lymphatic vessels and that activating Piezo1 through transgenic overexpression or treatment with the chemical agonist Yoda1 is sufficient to increase cerebrospinal fluid (CSF) outflow by improving lymphatic absorption and transport. The abnormal accumulation of CSF, which often leads to hydrocephalus and ventriculomegaly, currently lacks effective treatments. We discovered that meningeal lymphatics in mouse models of Down syndrome were incompletely developed and abnormally formed. Selective overexpression of Piezo1 in lymphatics or systemic administration of Yoda1 in mice with hydrocephalus or Down syndrome resulted in a notable decrease in pathological CSF accumulation, ventricular enlargement and other associated disease symptoms. Together, our study highlights the importance of Piezo1-mediated lymphatic mechanotransduction in maintaining brain fluid drainage and identifies Piezo1 as a promising therapeutic target for treating excessive CSF accumulation and ventricular enlargement.

Decorin suppresses tumor lymphangiogenesis: A mechanism to curtail cancer progression

The complex interplay between malignant cells and the cellular and molecular components of the tumor stroma is a key aspect of cancer growth and development. These tumor-host interactions are often affected by soluble bioactive molecules such as proteoglycans. Decorin, an archetypical small leucine-rich proteoglycan primarily expressed by stromal cells, affects cancer growth in its soluble form by interacting with several receptor tyrosine kinases (RTK). Overall, decorin leads to a context-dependent and protracted cessation of oncogenic RTK activity by attenuating their ability to drive a prosurvival program and to sustain a proangiogenic network. Through an unbiased transcriptomic analysis using deep RNAseq, we identified that decorin down-regulated a cluster of tumor-associated genes involved in lymphatic vessel (LV) development when systemically delivered to mice harboring breast carcinoma allografts. We found that Lyve1 and Podoplanin, two established markers of LVs, were markedly suppressed at both the mRNA and protein levels, and this suppression correlated with a significant reduction in tumor LVs. We further identified that soluble decorin, but not its homologous proteoglycan biglycan, inhibited LV sprouting in an ex vivo 3D model of lymphangiogenesis. Mechanistically, we found that decorin interacted with vascular endothelial growth factor receptor 3 (VEGFR3), the main lymphatic RTK, and its activity was required for the decorin-mediated block of lymphangiogenesis. Finally, we identified that Lyve1 was in part degraded via decorin-evoked autophagy in a nutrient- and energy-independent manner. These findings implicate decorin as a biological factor with antilymphangiogenic activity and provide a potential therapeutic agent for curtailing breast cancer growth and metastasis.

Anti-lymphangiogenesis for boosting drug accumulation in tumors

The inadequate tumor accumulation of anti-cancer agents is a major shortcoming of current therapeutic drugs and remains an even more significant concern in the clinical prospects for nanomedicines. Various strategies aiming at regulating the intratumoral permeability of therapeutic drugs have been explored in preclinical studies, with a primary focus on vascular regulation and stromal reduction. However, these methods may trigger or facilitate tumor metastasis as a tradeoff. Therefore, there is an urgent need for innovative strategies that boost intratumoral drug accumulation without compromising treatment outcomes. As another important factor affecting drug tumor accumulation besides vasculature and stroma, the impact of tumor-associated lymphatic vessels (LVs) has not been widely considered. In the current research, we verified that anlotinib, a tyrosine kinase inhibitor with anti-lymphangiogenesis activity, and SAR131675, a selective VEGFR-3 inhibitor, effectively decreased the density of tumor lymphatic vessels in mouse cancer models, further enhancing drug accumulation in tumor tissue. By combining anlotinib with therapeutic drugs, including doxorubicin (Dox), liposomal doxorubicin (Lip-Dox), and anti-PD-L1 antibody, we observed improved anti-tumor efficacy in comparison with monotherapy regimens. Meanwhile, this strategy significantly reduced tumor metastasis and elicited stronger anti-tumor immune responses. Our work describes a new, clinically transferrable approach to augmenting intratumoral drug accumulation, which shows great potential to address the current, unsatisfactory efficacies of therapeutic drugs without introducing metastatic risk.

SAR131675 exhibits anticancer activity on human ovarian cancer cells through inhibition of VEGFR-3/ERK1/2/AKT signaling pathway

Vascular endothelial growth factor receptor-3 (VEGFR-3) is known to participate in tumorigenesis and lymphangiogenesis, and as such, has the potential to serve as a molecular target for cancer therapy. SAR131675 is a highly selective VEGFR-3 antagonist that has an inhibitive effect on lymphatic cell growth. However, the anticancer effects and underlying mechanisms of SAR131675 in ovarian cancer remain poorly understood. In this study, we investigated the pathological role of VEGFR-3, and the effects of SAR131675 on proliferation, cell cycle, migration, and apoptosis in ovarian cancer cells. Our results showed that the mRNA and protein of VEGFR-3 were expressed in OVCAR3 and SKOV3 ovarian cancer cells, and this receptor was activated following stimulation with 50 ng/ml VEGF-C Cys156Ser (VEGF-CS), a selective ligand for VEGFR-3. Enhancing VEGFR-3 phosphorylation by treatment of ovarian cancer cells with VEGF-CS resulted in increased levels of phosphorylated extracellular signal-regulated kinases 1/2 (ERK1/2) and AKT. Moreover, our data demonstrated that SAR131675 inhibited VEGF-CS-mediated proliferation, colony formation, and migration of cancer cells in a dose-dependent manner. In addition, inhibition of VEGFR-3 activation with SAR131675 significantly increased cell cycle arrest and promoted apoptosis in both OVCAR3 and SKOV3 cells. Mechanistically, SAR131675 effectively suppressed the VEGF-CS-induced phosphorylation of VEGFR-3 and its downstream effectors including activated ERK1/2 and AKT in ovarian cancer cells. Our results reveal an anticancer activity of SAR131675 on the growth and migration of ovarian cancer cells, which may be through inhibiting VEGFR-3/ERK1/2/AKT pathway. SAR131675 may serve as an effective targeted drug for ovarian cancer.

Dual FGFR and VEGFR inhibition synergistically restrain hexokinase 2-dependent lymphangiogenesis and immune escape in intrahepatic cholangiocarcinoma

BACKGROUND

Therapies for cholangiocarcinoma are largely limited and ineffective. Herein, we examined the role of the FGF and VEGF pathways in regulating lymphangiogenesis and PD-L1 expression in intrahepatic cholangiocarcinoma (iCCA).

METHODS

The lymphangiogenic functions of FGF and VEGF were evaluated in lymphatic endothelial cells (LECs) and iCCA xenograft mouse models. The relationship between VEGF and hexokinase 2 (HK2) was validated in LECs by western blot, immunofluorescence, ChIP and luciferase reporter assays. The efficacy of the combination therapy was assessed in LECs and xenograft models. Microarray analysis was used to evaluate the pathological relationships of FGFR1 and VEGFR3 with HK2 in human lymphatic vessels.

RESULTS

FGF promoted lymphangiogenesis through c-MYC-dependent modulation of HK2 expression. VEGFC also upregulated HK2 expression. Mechanistically, VEGFC phosphorylated components of the PI3K/Akt/mTOR axis to upregulate HIF-1α expression at the translational level, and HIF-1α then bound to the HK2 promoter region to activate its transcription. More importantly, dual FGFR and VEGFR inhibition with infigratinib and SAR131675 almost completely inhibited lymphangiogenesis, and significantly suppressed iCCA tumor growth and progression by reducing PD-L1 expression in LECs.

CONCLUSIONS

Dual FGFR and VEGFR inhibition inhibits lymphangiogenesis through suppression of c-MYC-dependent and HIF-1α-mediated HK2 expression, respectively. HK2 downregulation decreased glycolytic activity and further attenuated PD-L1 expression. Our findings suggest that dual FGFR and VEGFR blockade is an effective novel combination strategy to inhibit lymphangiogenesis and improve immunocompetence in iCCA.

Decorin suppresses tumor lymphangiogenesis: A mechanism to curtail cancer progression

The complex interplay between malignant cells and the cellular and molecular components of the tumor stroma is a key aspect of cancer growth and development. These tumor-host interactions are often affected by soluble bioactive molecules such as proteoglycans. Decorin, an archetypical small leucine-rich proteoglycan primarily expressed by stromal cells, affects cancer growth in its soluble form by interacting with several receptor tyrosine kinases (RTK). Overall, decorin leads to a context-dependent and protracted cessation of oncogenic RTK activity by attenuating their ability to drive a pro-survival program and to sustain a pro-angiogenic network. Through an unbiased transcriptomic analysis using deep RNAseq, we discovered that decorin downregulated a cluster of tumor-associated genes involved in lymphatic vessel development when systemically delivered to mice harboring breast carcinoma allografts. We found that Lyve1 and Podoplanin, two established markers of lymphatic vessels, were markedly suppressed at both the mRNA and protein levels and this suppression correlated with a significant reduction in tumor lymphatic vessels. We further discovered that soluble decorin, but not its homologous proteoglycan biglycan, inhibited lymphatic vessel sprouting in an ex vivo 3D model of lymphangiogenesis. Mechanistically, we found that decorin interacted with VEGFR3, the main lymphatic RTK, and its activity was required for the decorin-mediated block of lymphangiogenesis. Finally, we discovered that Lyve1 was in part degraded via decorin-evoked autophagy in a nutrient- and energy-independent manner. These findings implicate decorin as a new biological factor with anti-lymphangiogenic activity and provide a potential therapeutic agent for curtailing breast cancer growth and metastasis.

VEGFR-3 signaling restrains the neuron-macrophage crosstalk during neurotropic viral infection

Upon recognizing danger signals produced by virally infected neurons, macrophages in the central nervous system (CNS) secrete multiple inflammatory cytokines to accelerate neuron apoptosis. The understanding is limited about which key effectors regulate macrophage-neuron crosstalk upon infection. We have used neurotropic-virus-infected murine models to identify that vascular endothelial growth factor receptor 3 (VEGFR-3) is upregulated in the CNS macrophages and that virally infected neurons secrete the ligand VEGF-C. When cultured with VEGF-C-containing supernatants from virally infected neurons, VEGFR-3+ macrophages suppress tumor necrosis factor α (TNF-α) secretion to reduce neuron apoptosis. Vegfr-3ΔLBD/ΔLBD (deletion of ligand-binding domain in myeloid cells) mice or mice treated with the VEGFR-3 kinase inhibitor exacerbate the severity of encephalitis, TNF-α production, and neuron apoptosis post Japanese encephalitis virus (JEV) infection. Activating VEGFR-3 or blocking TNF-α can reduce encephalitis and neuronal damage upon JEV infection. Altogether, we show that the inducible VEGF-C/VEGFR-3 module generates protective crosstalk between neurons and macrophages to alleviate CNS viral infection.

Role of LGMN in tumor development and its progression and connection with the tumor microenvironment

Legumain (LGMN) has been demonstrated to be overexpressed not just in breast, prostatic, and liver tumor cells, but also in the macrophages that compose the tumor microenvironment. This supports the idea that LGMN is a pivotal protein in regulating tumor development, invasion, and dissemination. Targeting LGMN with siRNA or chemotherapeutic medicines and peptides can suppress cancer cell proliferation in culture and reduce tumor growth in vivo. Furthermore, legumain can be used as a marker for cancer detection and targeting due to its expression being significantly lower in normal cells compared to tumors or tumor-associated macrophages (TAMs). Tumor formation is influenced by aberrant expression of proteins and alterations in cellular architecture, but the tumor microenvironment is a crucial deciding factor. Legumain (LGMN) is an in vivo-active cysteine protease that catalyzes the degradation of numerous proteins. Its precise biological mechanism encompasses a number of routes, including effects on tumor-associated macrophage and neovascular endothelium in the tumor microenvironment. The purpose of this work is to establish a rationale for thoroughly investigating the function of LGMN in the tumor microenvironment and discovering novel tumor early diagnosis markers and therapeutic targets by reviewing the function of LGMN in tumor genesis and progression and its relationship with tumor milieu.

Interaction of tumor‑associated macrophages with stromal and immune components in solid tumors: Research progress (Review)

Tumor‑associated macrophages (TAMs) are crucial cells of the tumor microenvironment (TME), which belong to the innate immune system and regulate primary tumor growth, immunosuppression, angiogenesis, extracellular matrix remodeling and metastasis. The review discusses current knowledge of essential cell‑cell interactions of TAMs within the TME of solid tumors. It summarizes the mechanisms of stromal cell (including cancer‑associated fibroblasts and endothelial cells)‑mediated monocyte recruitment and regulation of differentiation, as well as pro‑tumor and antitumor polarization of TAMs. Additionally, it focuses on the perivascular TAM subpopulations that regulate angiogenesis and lymphangiogenesis. It describes the possible mechanisms of reciprocal interactions of TAMs with other immune cells responsible for immunosuppression. Finally, it highlights the perspectives for novel therapeutic approaches to use combined cellular targets that include TAMs and other stromal and immune cells in the TME. The collected data demonstrated the importance of understanding cell‑cell interactions in the TME to prevent distant metastasis and reduce the risk of tumor recurrence.

Lymphatic vessels in bone support regeneration after injury

Blood and lymphatic vessels form a versatile transport network and provide inductive signals to regulate tissue-specific functions. Blood vessels in bone regulate osteogenesis and hematopoiesis, but current dogma suggests that bone lacks lymphatic vessels. Here, by combining high-resolution light-sheet imaging and cell-specific mouse genetics, we demonstrate presence of lymphatic vessels in mouse and human bones. We find that lymphatic vessels in bone expand during genotoxic stress. VEGF-C/VEGFR-3 signaling and genotoxic stress-induced IL6 drive lymphangiogenesis in bones. During lymphangiogenesis, secretion of CXCL12 from proliferating lymphatic endothelial cells is critical for hematopoietic and bone regeneration. Moreover, lymphangiocrine CXCL12 triggers expansion of mature Myh11+ CXCR4+ pericytes, which differentiate into bone cells and contribute to bone and hematopoietic regeneration. In aged animals, such expansion of lymphatic vessels and Myh11-positive cells in response to genotoxic stress is impaired. These data suggest lymphangiogenesis as a therapeutic avenue to stimulate hematopoietic and bone regeneration.

2D, 3D-QSAR study and docking of vascular endothelial growth factor receptor 3 (VEGFR3) inhibitors for potential treatment of retinoblastoma

Background: Retinoblastoma is currently the most common malignant tumor seen in newborns and children's eyes worldwide, posing a life-threatening hazard. Chemotherapy is an integral part of retinoblastoma treatment. However, the chemotherapeutic agents used in clinics often lead to drug resistance. Thus there is a need to investigate new chemotherapy-targeted agents. VEGFR3 inhibitors are anti-tumour-growth and could be used to develop novel retinoblastoma-targeted agents. Objective: To predict drug activity, discover influencing factors and design new drugs by building 2D, 3D-QSAR models. Method: First, linear and non-linear QSAR models were built using heuristic methods and gene expression programming (GEP). The comparative molecular similarity indices analysis (COMISA) was then used to construct 3D-QSAR models through the SYBYL software. New drugs were designed by changing drug activity factors in both models, and molecular docking experiments were performed. Result: The best linear model created using HM had an R², S², and R²cv of 0.82, 0.02, and 0.77, respectively. For the training and test sets, the best non-linear model created using GEP had correlation coefficients of 0.83 and 0.72 with mean errors of 0.02 and 0.04. The 3D model designed using SYBYL passed external validation due to its high Q² (0.503), R² (0.805), and F-value (76.52), as well as its low standard error of SEE value (0.172). This demonstrates the model's reliability and excellent predictive ability. Based on the molecular descriptors of the 2D model and the contour plots of the 3D model, we designed 100 new compounds using the best active compound 14 as a template. We performed activity prediction and molecular docking experiments on them, in which compound 14.d performed best regarding combined drug activity and docking ability. Conclusion: The non-linear model created using GEP was more stable and had a more substantial predictive power than the linear model built using the heuristic technique (HM). The compound 14.d designed in this experiment has the potential for anti-retinoblastoma treatment, which provides new design ideas and directions for retinoblastoma-targeted drugs.

Aiphanol, a multi-targeting stilbenolignan, potently suppresses mouse lymphangiogenesis and lymphatic metastasis

The high incidence of lymphatic metastasis is closely related to poor prognosis and mortality in cancers. Potent inhibitors to prevent pathological lymphangiogenesis and lymphatic spread are urgently needed. The VEGF-C-VEGFR3 pathway plays a vital role in driving lymphangiogenesis and lymph node metastasis. In addition, COX2 in tumor cells and tumor-associated macrophages (TAMs) facilitates lymphangiogenesis. We recently reported that aiphanol, a natural stilbenolignan, attenuates tumor angiogenesis by repressing VEGFR2 and COX2. In this study, we evaluated the antilymphangiogenic and antimetastatic potency of aiphanol using in vitro, ex vivo and in vivo systems. We first demonstrated that aiphanol directly bound to VEGFR3 and blocked its kinase activity with an half-maximal inhibitory concentration (IC50) value of 0.29 μM in an in vitro ADP-GloTM kinase assay. Furthermore, we showed that aiphanol (7.5-30 μM) dose-dependently counteracted VEGF-C-induced proliferation, migration and tubular formation of lymphatic endothelial cells (LECs), which was further verified in vivo. VEGFR3 knockdown markedly mitigated the inhibitory potency of aiphanol on lymphangiogenesis. In 4T1-luc breast tumor-bearing mice, oral administration of aiphanol (5 and 30 mg· kg-1 ·d-1) dose-dependently decreased lymphatic metastasis and prolonged survival time, which was associated with impaired lymphangiogenesis, angiogenesis and, interestingly, macrophage infiltration. In addition, we found that aiphanol decreased the COX2-dependent secretion of PGE2 and VEGF-C from tumor cells and macrophages. These results demonstrate that aiphanol is an appealing agent for preventing lymphangiogenesis and lymphatic dissemination by synergistically targeting VEGFR3 and inhibiting the COX2-PGE2-VEGF-C signaling axis.

The Lymphatic Endothelium in the Context of Radioimmuno-Oncology

The study of lymphatic tumor vasculature has been gaining interest in the context of cancer immunotherapy. These vessels constitute conduits for immune cells' transit toward the lymph nodes, and they endow tumors with routes to metastasize to the lymph nodes and, from them, toward distant sites. In addition, this vasculature participates in the modulation of the immune response directly through the interaction with tumor-infiltrating leukocytes and indirectly through the secretion of cytokines and chemokines that attract leukocytes and tumor cells. Radiotherapy constitutes the therapeutic option for more than 50% of solid tumors. Besides impacting transformed cells, RT affects stromal cells such as endothelial and immune cells. Mature lymphatic endothelial cells are resistant to RT, but we do not know to what extent RT may affect tumor-aberrant lymphatics. RT compromises lymphatic integrity and functionality, and it is a risk factor to the onset of lymphedema, a condition characterized by deficient lymphatic drainage and compromised tissue homeostasis. This review aims to provide evidence of RT's effects on tumor vessels, particularly on lymphatic endothelial cell physiology and immune properties. We will also explore the therapeutic options available so far to modulate signaling through lymphatic endothelial cell receptors and their repercussions on tumor immune cells in the context of cancer. There is a need for careful consideration of the RT dosage to come to terms with the participation of the lymphatic vasculature in anti-tumor response. Here, we provide new approaches to enhance the contribution of the lymphatic endothelium to radioimmuno-oncology.

Targeting Tumor Angiogenesis with the Selective VEGFR-3 Inhibitor EVT801 in Combination with Cancer Immunotherapy

The receptor tyrosine kinase VEGFR-3 plays a crucial role in cancer-induced angiogenesis and lymphangiogenesis, promoting tumor development and metastasis. Here, we report the novel VEGFR-3 inhibitor EVT801 that presents a more selective and less toxic profile than two major inhibitors of VEGFRs (i.e., sorafenib and pazopanib). As monotherapy, EVT801 showed a potent antitumor effect in VEGFR-3–positive tumors, and in tumors with VEGFR-3–positive microenvironments. EVT801 suppressed VEGF-C–induced human endothelial cell proliferation in vitro and tumor (lymph)angiogenesis in different tumor mouse models. In addition to reduced tumor growth, EVT801 decreased tumor hypoxia, favored sustained tumor blood vessel homogenization (i.e., leaving fewer and overall larger vessels), and reduced important immunosuppressive cytokines (CCL4, CCL5) and myeloid-derived suppressor cells (MDSC) in circulation. Furthermore, in carcinoma mouse models, the combination of EVT801 with immune checkpoint therapy (ICT) yielded superior outcomes to either single treatment. Moreover, tumor growth inhibition was inversely correlated with levels of CCL4, CCL5, and MDSCs after treatment with EVT801, either alone or combined with ICT. Taken together, EVT801 represents a promising anti(lymph)angiogenic drug for improving ICT response rates in patients with VEGFR-3 positive tumors.

Significance:

The VEGFR-3 inhibitor EVT801 demonstrates superior selectivity and toxicity profile than other VEGFR-3 tyrosine kinase inhibitors. EVT801 showed potent antitumor effects in VEGFR-3–positive tumors, and tumors with VEGFR-3–positive microenvironments through blood vessel homogenization, and reduction of tumor hypoxia and limited immunosuppression. EVT801 increases immune checkpoint inhibitors’ antitumor effects.

Structure-Activity Relationship Studies Based on 3D-QSAR CoMFA/CoMSIA for Thieno-Pyrimidine Derivatives as Triple Negative Breast Cancer Inhibitors

Triple-negative breast cancer (TNBC) is defined as a kind of breast cancer that lacks estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptors (HER2). This cancer accounts for 10-15% of all breast cancers and has the features of high invasiveness and metastatic potential. The treatment regimens are still lacking and need to develop novel inhibitors for therapeutic strategies. Three-dimensional quantitative structure-activity relationship (3D-QSAR) analyses, based on a series of forty-seven thieno-pyrimidine derivatives, were performed to identify the key structural features for the inhibitory biological activities. The established comparative molecular field analysis (CoMFA) presented a leave-one-out cross-validated correlation coefficient q² of 0.818 and a determination coefficient r² of 0.917. In comparative molecular similarity indices analysis (CoMSIA), a q² of 0.801 and an r² of 0.897 were exhibited. The predictive capability of these models was confirmed by using external validation and was further validated by the progressive scrambling stability test. From these results of validation, the models were determined to be statistically reliable and robust. This study could provide valuable information for further optimization and design of novel inhibitors against metastatic breast cancer.

Lymphangiogenesis contributes to exercise-induced physiological cardiac growth

BACKGROUND

Promoting cardiac lymphangiogenesis exerts beneficial effects for the heart. Exercise can induce physiological cardiac growth with cardiomyocyte hypertrophy and increased proliferation markers in cardiomyocytes. However, it remains unclear whether and how lymphangiogenesis contributes to exercise-induced physiological cardiac growth. We aimed to investigate the role and mechanism of lymphangiogenesis in exercise-induced physiological cardiac growth.

METHODS

Adult C57BL6/J mice were subjected to 3 weeks of swimming exercise to induce physiological cardiac growth. Oral treatment with vascular endothelial growth factor receptor 3 (VEGFR3) inhibitor SAR131675 was used to investigate whether cardiac lymphangiogenesis was required for exercise-induced physiological cardiac growth by VEGFR3 activation. Furthermore, human dermal lymphatic endothelial cell (LEC)-conditioned medium was collected to culture isolated neonatal rat cardiomyocytes to determine whether and how LECs could influence cardiomyocyte proliferation and hypertrophy.

RESULTS

Swimming exercise induced physiological cardiac growth accompanied by a remarkable increase of cardiac lymphangiogenesis as evidenced by increased density of lymphatic vessel endothelial hyaluronic acid receptor 1-positive lymphatic vessels in the heart and upregulated LYVE-1 and Podoplanin expressions levels. VEGFR3 was upregulated in the exercised heart, while VEGFR3 inhibitor SAR131675 attenuated exercise-induced physiological cardiac growth as evidenced by blunted myocardial hypertrophy and reduced proliferation marker Ki67 in cardiomyocytes, which was correlated with reduced lymphatic vessel density and downregulated LYVE-1 and Podoplanin in the heart upon exercise. Furthermore, LEC-conditioned medium promoted both hypertrophy and proliferation of cardiomyocytes and contained higher levels of insulin-like growth factor-1 and the extracellular protein Reelin, while LEC-conditioned medium from LECs treated with SAR131675 blocked these effects. Functional rescue assays further demonstrated that protein kinase B (AKT) activation, as well as reduced CCAAT enhancer-binding protein beta (C/EBPβ) and increased CBP/p300-interacting transactivators with E (glutamic acid)/D (aspartic acid)-rich-carboxylterminal domain 4 (CITED4), contributed to the promotive effect of LEC-conditioned medium on cardiomyocyte hypertrophy and proliferation.

CONCLUSION

Our findings reveal that cardiac lymphangiogenesis is required for exercise-induced physiological cardiac growth by VEGFR3 activation, and they indicate that LEC-conditioned medium promotes both physiological hypertrophy and proliferation of cardiomyocytes through AKT activation and the C/EBPβ-CITED4 axis. These results highlight the essential roles of cardiac lymphangiogenesis in exercise-induced physiological cardiac growth.

Lymphatic vessels in cancer

The lymphatic system, composed of initial and collecting lymphatic vessels as well as lymph nodes that are present in almost every tissue of the human body, acts as an essential transport system for fluids, biomolecules and cells between peripheral tissues and the central circulation. Consequently, it is required for normal body physiology but is also involved in the pathogenesis of various diseases, most notably cancer. The important role of tumor-associated lymphatic vessels and lymphangiogenesis in the formation of lymph node metastasis has been elucidated during the last two decades, whereas the underlying mechanisms and the relation between lymphatic and peripheral organ dissemination of cancer cells are incompletely understood. Lymphatic vessels are also important for tumor-host communication, relaying molecular information from a primary or metastatic tumor to regional lymph nodes and the circulatory system. Beyond antigen transport, lymphatic endothelial cells, particularly those residing in lymph node sinuses, have recently been recognized as direct regulators of tumor immunity and immunotherapy responsiveness, presenting tumor antigens and expressing several immune-modulatory signals including PD-L1. In this review, we summarize recent discoveries in this rapidly evolving field and highlight strategies and challenges of therapeutic targeting of lymphatic vessels or specific lymphatic functions in cancer patients.

Anti-Angiogenetic and Anti-Lymphangiogenic Effects of a Novel 2-Aminobenzimidazole Derivative, MFB

Background and Purpose

Benzimidazoles have attracted much attention over the last few decades due to their broad-spectrum pharmacological properties. Increasing evidence is showing the potential use of benzimidazoles as anti-angiogenic agents, although the mechanisms that impact angiogenesis remain to be fully defined. In this study, we aim to investigate the anti-angiogenic mechanisms of MFB, a novel 2-aminobenzimidazole derivative, to develop a novel angiogenesis inhibitor.

Experimental Approach

MTT, BrdU, migration and invasion assays, and immunoblotting were employed to examine MFB’s effects on vascular endothelial growth factor (VEGF)-induced endothelial cell proliferation, migration, invasion, as well as signaling molecules activation. The anti-angiogenic effects of MFB were analyzed by tube formation, aorta ring sprouting, and matrigel plug assays. We also used a mouse model of lung metastasis to determine the MFB’s anti-metastatic effects.

Key Results

MFB suppressed cell proliferation, migration, invasion, and endothelial tube formation of VEGF-A-stimulated human umbilical vascular endothelial cells (HUVECs) or VEGF-C-stimulated lymphatic endothelial cells (LECs). MFB suppressed VEGF-A and VEGF-C signaling in HUVECs or LECs. In addition, MFB reduced VEGF-A- or tumor cells-induced neovascularization in vivo. MFB also diminished B16F10 melanoma lung metastasis. The molecular docking results further showed that MFB may bind to VEGFR-2 rather than VEGF-A with high affinity.

Conclusions and Implications

These observations indicated that MFB may target VEGF/VEGFR signaling to suppress angiogenesis and lymphangiogenesis. It also supports the role of MFB as a potential lead in developing novel agents for the treatment of angiogenesis- or lymphangiogenesis-associated diseases and cancer.

SAR131675, a VEGRF3 Inhibitor, Modulates the Immune Response and Reduces the Growth of Colorectal Cancer Liver Metastasis

Most patients with colorectal cancer (CRC) develop metastases, predominantly in the liver (CLM). Targeted therapies are being investigated to improve current CLM treatments. This study tested the effectiveness of SAR131675, a selective VEGFR-3 tyrosine kinase inhibitor, to inhibit CLM in a murine model. Following intrasplenic induction of CLM, mice were treated daily with SAR131675. Tumor growth and immune infiltrates into tumor and liver tissues were assessed at 10-, 16- and 22-days post tumor induction by stereology, IHC and flow cytometry. SAR151675 treatment significantly reduced tumor burden and F4/80+ macrophages in the liver tissues. Analysis of immune cell infiltrates in liver showed tissue that at day 22, had the proportion of CD45+ leukocytes significantly reduced, particularly myeloid cells. Analysis of myeloid cells (CD11b+ CD45+) indicated that the proportion of F4/80- Ly6Clow was significantly reduced, including a predominate PD-L1+ subset, while CD3+ T cells increased, particularly CD8+ PD1+, reflected by an increase in the CD8+:CD4+ T cell ratio. In the tumor tissue SAR11675 treatment reduced the predominant population of F4/80+ Ly6Clo and increased CD4+ T cells. These results suggest that SAR131675 alters the immune composition within tumor and the surrounding liver in the later stages of development, resulting in a less immunosuppressive environment. This immunomodulation effect may contribute to the suppression of tumor growth.

Lymphatics in Tumor Progression and Immunomodulation

The lymphatic system consists of a unidirectional hierarchy of vessels responsible for fluid homeostasis, lipid absorption, and the transport of immune cells and antigens to secondary lymphoid organs. In cancer, lymphatics play complex and heterogenous roles that can promote or inhibit tumor growth. While lymphatic proliferation and remodeling promote tumor dissemination, functional lymphatics are necessary for generating an effective immune response. Recent reports have noted lymphatic-dependent effects on the efficacy of immunotherapy. These findings suggest that the impact of lymphatic vessels on tumor progression is organ- and context-specific and that a greater understanding of the interaction of tumor cells, lymphatics, and the tumor microenvironment can unveil novel therapies.

Discovery, Synthesis, and Evaluation of Highly Selective Vascular Endothelial Growth Factor Receptor 3 (VEGFR3) Inhibitor for the Potential Treatment of Metastatic Triple-Negative Breast Cancer

We herein report the identification, structural optimization, and structure-activity relationship of thieno[2,3-d]pyrimidine derivatives as a novel kind of selective vascular endothelial growth factor receptor 3 (VEGFR3) inhibitors. N-(4-Chloro-3-(trifluoromethyl)phenyl)-4-(6-(4-(4-methylpiperazin-1-yl)phenyl)thieno[2,3-d]pyrimidin-4-yl)piperazine-1-carboxamide (38k) was the most potent VEGFR3 inhibitor (IC50 = 110.4 nM) among developed compounds. Compared with VEGFR1 and VEGFR2, VEGFR3 was approximately 100 times more selective. Here, compound 38k significantly inhibited proliferation and migration of VEGF-C-induced human dermal lymphatic endothelial cells (HDLEC), MDA-MB-231, and MDA-MB-436 cells by inactivating the VEGFR3 signaling pathway. Additionally, 38k induced cell apoptosis and a prolonged G1/S-phase in MDA-MB-231 and MDA-MB-436 cells. It also presented acceptable pharmacokinetic characteristics in Sprague-Dawley (SD) rats with an oral bioavailability of 30.9%. In the xenograft model in vivo, 38k effectively inhibited breast cancer growth by suppressing the VEGFR3 signaling pathway. 38k pronouncedly resisted the formation of pulmonary metastatic nodules in mice. Collectively, 38k may be a promising therapeutic agent of metastatic breast cancer.

SAR131675 Receptor Tyrosine Kinase Inhibitor Induces Apoptosis through Bcl-2/Bax/Cyto c Mitochondrial Pathway in Human Umbilical Vein Endothelial Cells

BACKGROUND

Tyrosine kinase inhibitors (TKIs) can be used to inhibit cancer cell proliferation by targeting the vascular endothelial growth factor receptor (VEGFR) family. SAR131675 is a highly selective receptor tyrosine kinase inhibitor to VEGFR3 that reveals the inhibitory effect on proliferation in human lymphatic endothelial cells. However, the molecular mechanisms underlying this process are generally unclear.

OBJECTIVE

This study was performed to investigate the possible involvement of the Bcl-2/Bax/Cyto c apoptosis pathway in human umbilical vein endothelial cells (HUVECs). In addition, the role of reactive oxygen species (ROS) and mitochondrial membrane potential was evaluated.

METHODS

The effect of SAR131675 on HUVEC cell viability was evaluated by MTT assay. The activity of SAR131675 in inducing apoptosis was carried out through the detection of Annexin V-FITC/PI signal by flow cytometry. To determine the mechanisms underlying SAR131675 induced apoptosis, the mitochondrial membrane potential, ROS generation, the activity of caspase-3, and expression of apoptosis-related proteins such as Bcl-2, Bax, and cytochrome c were evaluated in HUVECs.

RESULTS

SAR131675 significantly inhibited cell viability and induced apoptosis in HUVECs in a dose-dependent manner. Moreover, SAR131675 induced mitochondrial dysfunction, ROS generation, Bcl-2 down-regulation, Bax up-regulation, cytochrome c release, and caspase-3 activation, which displays features of the mitochondria-dependent apoptosis signaling pathway.

CONCLUSION

Our present data demonstrated that SAR131675-induced cytotoxicity in HUVECs is associated with the mitochondria apoptotic pathway. These results suggest that further studies are required to fully elucidate the role of TKIs in these cellular processes.

Endothelial cell secreted VEGF-C enhances NSC VEGFR3 expression and promotes NSC survival

Although delivery of neural stem cell (NSC) as a therapeutic treatment for intracerebral hemorrhage (ICH) provides promise, NSC delivery typically has extremely low survival rates. Here, we investigate endothelial cell (EC) and pericyte (PC) interactions with NSC, where our results demonstrate that EC, and not PC, promote NSC cell proliferation and reduce cytotoxicity under glucose deprivation (GD). Additionally, NSC proliferation was increased upon treatment with EC conditioned media, inhibited with antagonism of VEGFR3. In an NSC + EC coculture we detected elevated levels of VEGF-C, not seen for NSC cultured alone. Exogenous VEGF-C induced NSC upregulation of VEGFR3, promoted proliferation, and reduced cytotoxicity. Finally, we delivered microbeads containing NSC + EC into a murine ICH cavity, where VEGF-C was increasingly present in the injury site, not seen upon delivery NSC encapsulated alone. These studies demonstrate that EC-secreted VEGF-C may promote NSC survival during injury, enhancing the potential for cell delivery therapies for stroke.

The Key Regulator of Necroptosis, RIP1 Kinase, Contributes to the Formation of Astrogliosis and Glial Scar in Ischemic Stroke

Necroptosis initiation relies on the receptor-interacting protein 1 kinase (RIP1K). We recently reported that genetic and pharmacological inhibition of RIP1K produces protection against ischemic stroke-induced astrocytic injury. However, the role of RIP1K in ischemic stroke-induced formation of astrogliosis and glial scar remains unknown. Here, in a transient middle cerebral artery occlusion (tMCAO) rat model and an oxygen and glucose deprivation and reoxygenation (OGD/Re)-induced astrocytic injury model, we show that RIP1K was significantly elevated in the reactive astrocytes. Knockdown of RIP1K or delayed administration of RIP1K inhibitor Nec-1 down-regulated the glial scar markers, improved ischemic stroke-induced necrotic morphology and neurologic deficits, and reduced the volume of brain atrophy. Moreover, knockdown of RIP1K attenuated astrocytic cell death and proliferation and promoted neuronal axonal generation in a neuron and astrocyte co-culture system. Both vascular endothelial growth factor D (VEGF-D) and its receptor VEGFR-3 were elevated in the reactive astrocytes; simultaneously, VEGF-D was increased in the medium of astrocytes exposed to OGD/Re. Knockdown of RIP1K down-regulated VEGF-D gene and protein levels in the reactive astrocytes. Treatment with 400 ng/ml recombinant VEGF-D induced the formation of glial scar; conversely, the inhibitor of VEGFR-3 suppressed OGD/Re-induced glial scar formation. RIP3K and MLKL may be involved in glial scar formation. Taken together, these results suggest that RIP1K participates in the formation of astrogliosis and glial scar via impairment of normal astrocyte responses and enhancing the astrocytic VEGF-D/VEGFR-3 signaling pathways. Inhibition of RIP1K promotes the brain functional recovery partially via suppressing the formation of astrogliosis and glial scar.

High ELK3 expression is associated with the VEGF-C/VEGFR-3 axis and gastric tumorigenesis and enhances infiltration of M2 macrophages

Aim: To assess the expression and effect of ELK3 in gastric cancer, along with its associations with the VEGF-C/VEGFR-3 axis, IC₅₀ of the VEGFR-3 inhibitor axitinib and immune infiltration of M2-polarized macrophages in gastric cancer, and to analyze the possible epigenetic regulation mechanism. Materials & methods: Expression profiles and methylation data from 1645 samples were obtained and examined from multi-institutional public datasets. The associations were assessed by multiple analysis methods. Results: Elevated ELK3 is associated with the VEGF-C/VEGFR-3 axis and tumorigenesis, reduces the effect of axitinib in vitro, enhances immune infiltration of M2 macrophages and affects clinical outcomes. Hypomethylation contributes to the upregulation of ELK3 in gastric cancer. Conclusions: ELK3 is a potential therapeutic target which reduces the effect of axitinib and enhances infiltration of M2-polarized macrophages.

Cellular Origins of the Lymphatic Endothelium: Implications for Cancer Lymphangiogenesis

The lymphatic system plays important roles in physiological and pathological conditions. During cancer progression in particular, lymphangiogenesis can exert both positive and negative effects. While the formation of tumor associated lymphatic vessels correlates with metastatic dissemination, increased severity and poor patient prognosis, the presence of functional lymphatics is regarded as beneficial for anti-tumor immunity and cancer immunotherapy delivery. Therefore, a profound understanding of the cellular origins of tumor lymphatics and the molecular mechanisms controlling their formation is required in order to improve current strategies to control malignant spread. Data accumulated over the last decades have led to a controversy regarding the cellular sources of tumor-associated lymphatic vessels and the putative contribution of non-endothelial cells to this process. Although it is widely accepted that lymphatic endothelial cells (LECs) arise mainly from pre-existing lymphatic vessels, additional contribution from bone marrow-derived cells, myeloid precursors and terminally differentiated macrophages, has also been claimed. Here, we review recent findings describing new origins of LECs during embryonic development and discuss their relevance to cancer lymphangiogenesis.

Vascular endothelial growth factor receptor-3 regulates astroglial glutamate transporter-1 expression via mTOR activation in reactive astrocytes following pilocarpine-induced status epilepticus

Recent evidence has shown that the vascular endothelial growth factor (VEGF) system plays a crucial role in several neuropathological processes. We previously reported an upregulation of VEGF-C and its receptor, VEGFR-3, in reactive astrocytes after the onset of status epilepticus (SE). However, it remains unknown, which molecules act as downstream signals following VEGFR-3 upregulation, and are involved in reactive astrogliosis after SE. Therefore, we investigated whether VEGFR-3 upregulation within reactive astrocytes is associated with the activation of mammalian target of rapamycin (mTOR) signaling, which we confirmed by assaying for the phosphorylated form of S6 protein (pS6), and whether VEGFR-3-mediated mTOR activation induces astroglial glutamate transporter-1 (GLT-1) expression in the hippocampus after pilocarpine-induced SE. We found that spatiotemporal expression of pS6 was consistent with VEGFR-3 expression in the hippocampus after SE, and that both pS6 and VEGFR-3 were highly expressed in SE-induced reactive astrocytes. Treatment with the mTOR inhibitor rapamycin decreased astroglial VEGFR-3 expression and GLT-1 expression after SE. Treatment with a selective inhibitor for VEGFR-3 attenuated astroglial pS6 expression as well as suppressed GLT-1 expression and astroglial reactivity in the hippocampus after SE. These findings demonstrate that VEGFR-3-mediated mTOR activation could contribute to the regulation of GLT-1 expression in reactive astrocytes during the subacute phase of epilepsy. In conclusion, the present study suggests that VEGFR-3 upregulation in reactive astrocytes may play a role in preventing hyperexcitability induced by continued seizure activity.

Fibroblast Growth Factor 19-Mediated Up-regulation of SYR-Related High-Mobility Group Box 18 Promotes Hepatocellular Carcinoma Metastasis by Transactivating Fibroblast Growth Factor Receptor 4 and Fms-Related Tyrosine Kinase 4

BACKGROUND AND AIMS

The poor prognosis of patients with hepatocellular carcinoma (HCC) is mainly attributed to its high rate of metastasis and recurrence. However, the molecular mechanisms underlying HCC metastasis need to be elucidated. The SRY-related high-mobility group box (SOX) family proteins, which are a group of highly conserved transcription factors, play important roles in cancer initiation and progression. Here, we report on a role of SOX18, a member of the SOX family, in promoting HCC invasion and metastasis.

APPROACH AND RESULTS

The elevated expression of SOX18 was positively correlated with poor tumor differentiation, higher tumor-node-metastasis (TNM) stage, and poor prognosis. Overexpression of SOX18 promoted HCC metastasis by up-regulating metastasis-related genes, including fibroblast growth factor receptor 4 (FGFR4) and fms-related tyrosine kinase 4 (FLT4). Knockdown of both FGFR4 and FLT4 significantly decreased SOX18-mediated HCC invasion and metastasis, whereas the stable overexpression of FGFR4 and FLT4 reversed the decrease in cell invasion and metastasis that was induced by inhibition of SOX18. Fibroblast growth factor 19 (FGF19), which is the ligand of FGFR4, up-regulated SOX18 expression. A mechanistic investigation indicated that the up-regulation of SOX18 that was mediated by the FGF19-FGFR4 pathway relied on the phosphorylated (p)-fibroblast growth factor receptor substrate 2/p-glycogen synthase kinase 3 beta/β-catenin pathway. SOX18 knockdown significantly reduced FGF19-enhanced HCC invasion and metastasis. Furthermore, BLU9931, a specific FGFR4 inhibitor, significantly reduced SOX18-mediated HCC invasion and metastasis. In human HCC tissues, SOX18 expression was positively correlated with FGF19, FGFR4, and FLT4 expression, and patients that coexpressed FGF19/SOX18, SOX18/FGFR4, or SOX18/FLT4 had the worst prognosis.

CONCLUSIONS

We defined a FGF19-SOX18-FGFR4 positive feedback loop that played a pivotal role in HCC metastasis, and targeting this pathway may be a promising therapeutic option for the clinical management of HCC.

Identification of a Unique Resorcylic Acid Lactone Derivative That Targets Both Lymphangiogenesis and Angiogenesis

We synthesized 11 novel L-783277 derivatives, in which a structure rigidifying phenyl ring is incorporated into the 14-membered chiral resorcylic acid lactone system. The SAR study with these substances demonstrated that 17 possesses excellent kinase selectivity against a panel of 335 kinases in contrast to L-783277 and inhibits VEGFR3, VEGFR2, and FLT3 with single-digit nanomolar IC₅₀ values. Also, we found that 21, a stereoisomer of 17, has excellent potency (IC₅₀ = 9 nM) against VEGFR3 and selectivity over VEGFR2 and FLT3. 17, a potent dual VEGFR3 and VEGFR2 inhibitor, effectively suppresses both lymphangiogenesis and angiogenesis in a 3D-microfluidic tumor lymphangiogenesis assay and in vivo corneal assay while SAR131675 blocks only lymphangiogenesis. In addition, 17 blocks the endothelial tube formation and suppresses proliferation of PHE tumor vascular model. 17 will be a valuable templatefor developing therapeutically active and selective substances that target both lymphangiogenesis and angiogenesis.

Biomaterials for Modulating Lymphatic Function in Immunoengineering

Immunoengineering is a rapidly growing and interdisciplinary field focused on developing tools to study and understand the immune system, then employing that knowledge to modulate immune response for the treatment of disease. Because of its roles in housing a substantial fraction of the body's lymphocytes, in facilitating immune cell trafficking, and direct immune modulatory functions, among others, the lymphatic system plays multifaceted roles in immune regulation. In this review, the potential for biomaterials to be applied to regulate the lymphatic system and its functions to achieve immunomodulation and the treatment of disease are described. Three related processes-lymphangiogenesis, lymphatic vessel contraction, and lymph node remodeling-are specifically explored. The molecular regulation of each process and their roles in pathologies are briefly outlined, with putative therapeutic targets and the lymphatic remodeling that can result from disease highlighted. Applications of biomaterials that harness these pathways for the treatment of disease via immunomodulation are discussed.

Activation of the VEGFC/VEGFR3 Pathway Induces Tumor Immune Escape in Colorectal Cancer

Colorectal cancer is a major cause of cancer-related death in Western countries and is associated with increased numbers of lymphatic vessels (LV) and tumor-associated macrophages (TAM). The VEGFC/VEGFR3 pathway is regarded as the principal inducer of lymphangiogenesis and it contributes to metastases; however, no data are available regarding its role during primary colorectal cancer development. We found that both VEGFC and VEGFR3 were upregulated in human nonmetastatic colorectal cancer, with VEGFR3 expressed on both LVs and TAMs. With the use of three different preclinical models of colorectal cancer, we also discovered that the VEGFC/VEGFR3 axis can shape both lymphatic endothelial cells and TAMs to synergistically inhibit antitumor immunity and promote primary colorectal cancer growth. Therefore, VEGFR3-directed therapy could be envisioned for the treatment of nonmetastatic colorectal cancer. SIGNIFICANCE: The prolymphangiogenic factor VEGFC is abundant in colorectal cancer and activates VEGFR3 present on cancer-associated macrophages and lymphatic vessels; activation of VEGFR3 signaling fosters cancer immune escape, resulting in enhanced tumor growth.

Growth Factor Signaling Regulates Mechanical Nociception in Flies and Vertebrates

Mechanical sensitization is one of the most difficult clinical pain problems to treat. However, the molecular and genetic bases of mechanical nociception are unclear. Here we develop a Drosophila model of mechanical nociception to investigate the ion channels and signaling pathways that regulate mechanical nociception. We fabricated von Frey filaments that span the subthreshold to high noxious range for Drosophila larvae. Using these, we discovered that pressure (force/area), rather than force per se, is the main determinant of aversive rolling responses to noxious mechanical stimuli. We demonstrated that the RTK PDGF/VEGF receptor (Pvr) and its ligands (Pvfs 2 and 3) are required for mechanical nociception and normal dendritic branching. Pvr is expressed and functions in class IV sensory neurons, whereas Pvf2 and Pvf3 are produced by multiple tissues. Constitutive overexpression of Pvr and its ligands or inducible overexpression of Pvr led to mechanical hypersensitivity that could be partially separated from morphological effects. Genetic analyses revealed that the Piezo and Pain ion channels are required for mechanical hypersensitivity observed upon ectopic activation of Pvr signaling. PDGF, but not VEGF, peptides caused mechanical hypersensitivity in rats. Pharmacological inhibition of VEGF receptor Type 2 (VEGFR-2) signaling attenuated mechanical nociception in rats, suggesting a conserved role for PDGF and VEGFR-2 signaling in regulating mechanical nociception. VEGFR-2 inhibition also attenuated morphine analgesic tolerance in rats. Our results reveal that a conserved RTK signaling pathway regulates baseline mechanical nociception in flies and rats.SIGNIFICANCE STATEMENT Hypersensitivity to touch is poorly understood and extremely difficult to treat. Using a refined Drosophila model of mechanical nociception, we discovered a conserved VEGF-related receptor tyrosine kinase signaling pathway that regulates mechanical nociception in flies. Importantly, pharmacological inhibition of VEGF receptor Type 2 signaling in rats causes analgesia and blocks opioid tolerance. We have thus established a robust, genetically tractable system for the rapid identification and functional analysis of conserved genes underlying mechanical pain sensitivity.

Phomaketide A Inhibits Lymphangiogenesis in Human Lymphatic Endothelial Cells

Lymphangiogenesis is an important biological process associated with cancer metastasis. The development of new drugs that block lymphangiogenesis represents a promising therapeutic strategy. Marine fungus-derived compound phomaketide A, isolated from the fermented broth of Phoma sp. NTOU4195, has been reported to exhibit anti-angiogenic and anti-inflammatory effects. However, its anti-lymphangiogenic activity has not been clarified to date. In this study, we showed that phomaketide A inhibited cell growth, migration, and tube formation of lymphatic endothelial cells (LECs) without an evidence of cytotoxicity. Mechanistic investigations revealed that phomaketide A reduced LECs-induced lymphangiogenesis via vascular endothelial growth factor receptor-3 (VEGFR-3), protein kinase Cδ (PKCδ), and endothelial nitric oxide synthase (eNOS) signalings. Furthermore, human proteome array analysis indicated that phomaketide A significantly enhanced the protein levels of various protease inhibitors, including cystatin A, serpin B6, tissue factor pathway inhibitor (TFPI), and tissue inhibitor matrix metalloproteinase 1 (TIMP-1). Importantly, phomaketide A impeded tumor growth and lymphangiogenesis by decreasing the expression of LYVE-1, a specific marker for lymphatic vessels, in tumor xenograft animal model. These results suggest that phomaketide A may impair lymphangiogenesis by suppressing VEGFR-3, PKCδ, and eNOS signaling cascades, while simultaneously activating protease inhibitors in human LECs. We document for the first time that phomaketide A inhibits lymphangiogenesis both in vitro and in vivo, which suggests that this natural product could potentially treat cancer metastasis.

Two Birds, One Stone: Double Hits on Tumor Growth and Lymphangiogenesis by Targeting Vascular Endothelial Growth Factor Receptor 3

Vascular endothelial growth factor receptor 3 (VEGFR3) has been known for its involvement in tumor-associated lymphangiogenesis and lymphatic metastasis. The VEGFR3 signaling is stimulated by its main cognate ligand, vascular endothelial growth factor C (VEGF-C), which in turn promotes tumor progression. Activation of VEGF-C/VEGFR3 signaling in lymphatic endothelial cells (LECs) was shown to enhance the proliferation of LECs and the formation of lymphatic vessels, leading to increased lymphatic metastasis of tumor cells. In the past decade, the expression and pathological roles of VEGFR3 in tumor cells have been described. Moreover, the VEGF-C/VEGFR3 axis has been implicated in regulating immune tolerance and suppression. Therefore, the inhibition of the VEGF-C/VEGFR3 axis has emerged as an important therapeutic strategy for the treatment of cancer. In this review, we discuss the current findings related to VEGF-C/VEGFR3 signaling in cancer progression and recent advances in the development of therapeutic drugs targeting VEGF-C/VEGFR3.

Inhibition of lymphatic proliferation by the selective VEGFR-3 inhibitor SAR131675 ameliorates diabetic nephropathy in db/db mice

Recent studies have demonstrated that chronic inflammation-induced lymphangiogenesis plays a crucial role in the progression of various renal diseases, including diabetic nephropathy. SAR131675 is a selective vascular endothelial cell growth factor receptor-3 (VEGFR-3)-tyrosine kinase inhibitor that acts as a ligand for VEGF-C and VEGF-D to inhibit lymphangiogenesis. In this study, we evaluated the effect of SAR131675 on renal lymphangiogenesis in a mouse model of type 2 diabetes. Male C57BLKS/J db/m and db/db mice were fed either a regular chow diet or a diet containing SAR131675 for 12 weeks from 8 weeks of age. In addition, we studied palmitate-induced lymphangiogenesis in human kidney-2 (HK2) cells and RAW264.7 monocytes/macrophages, which play a major role in lymphangiogenesis in the kidneys. SAR131475 ameliorated dyslipidemia, albuminuria, and lipid accumulation in the kidneys of db/db mice, with no significant changes in glucose and creatinine levels and body weight. Diabetes-induced systemic inflammation as evidenced by increased systemic monocyte chemoattractant protein-1 and tumor necrosis factor-α level was decreased by SAR131475. SAR131475 ameliorated the accumulation of triglycerides and free fatty acids and reduced inflammation in relation to decreased chemokine expression and pro-inflammatory M1 macrophage infiltration in the kidneys. Downregulation of VEGF-C and VEGFR-3 by SAR131475 inhibited lymphatic growth as demonstrated by decreased expression of LYVE-1 and podoplanin that was further accompanied by reduced tubulointerstitial fibrosis, and inflammation in relation to improvement in oxidative stress and apoptosis. Treatment with SAR131475 improved palmitate-induced increase in the expression of VEGF-C, VEGFR-3, and LYVE-1, along with improvement in cytosolic and mitochondrial oxidative stress in RAW264.7 and HK2 cells. Moreover, the enhanced expression of M1 phenotypes in RAW264.7 cells under palmitate stress was reduced by SAR131475 treatment. The results suggest that modulation of lymphatic proliferation in the kidneys is a new treatment approach for type 2 diabetic nephropathy and that SAR131675 is a promising therapy to ameliorate renal damage by reducing lipotoxicity-induced lymphangiogenesis.

[Research on influence mechanism of G protein coupled receptor kinase interacting protein 1 on differentiation of bone marrow mesenchymal stem cells into endothelial cells]

Objective

To investigate the mechanism of G protein coupled receptor kinase interacting protein 1 (GIT1) affecting angiogenesis by comparing the differentiation of bone marrow mesenchymal stem cells (BMSCs) differentiated into endothelial cells between GIT1 wild type mice and GIT1 gene knockout mice.

Methods

Male and female GIT1 heterozygous mice were paired breeding, and the genotypic identification of newborn mice were detected by PCR. The 2nd generation BMSCs isolated from GIT1 wild type mice or GIT1 gene knockout mice were divided into 4 groups, including wild type control group (group A), wild type experimental group (group A1), GIT1 knockout control group (group B), and GIT1 knockout experimental group (group B1). The cells of groups A1 and B1 were cultured with the endothelial induction medium and the cells of groups A and B with normal cluture medium. The expressions of vascular endothelial growth factor receptor 2 (VEGFR-2), VEGFR-3, and phospho-VEGFR-2 (pVEGFR-2), and pVEGFR-3 proteins were detected by Western blot. The endothelial cell markers [von Willebrand factor (vWF), platelet-endothelial cell adhesion molecule 1 (PECAM-1), and vascular endothelial cadherin (VE-Cadherin)] were detected by flow cytometry. The 2nd generation BMSCs of GIT1 wild type mice were divided into 4 groups according to the different culture media: group Ⅰ, primary cell culture medium; group Ⅱ, cell culture medium containing SAR131675 (VEGFR-3 blocker); group Ⅲ, endothelial induction medium; group Ⅳ, endothelial induction medium containing SAR131675. The endothelial cell markers (vWF, PECAM-1, and VE-Cadherin) in 4 groups were also detected by flow cytometry.

Results

Western blot results showed that there was no obviously difference in protein expressions of VEGFR-2 and pVEGFR-2 between groups; and the expressions of VEGFR-3 and pVEGFR-3 proteins in group A1 were obviously higher than those in groups A, B, and B1. The flow cytometry results showed that the expressions of vWF, PECAM-1, and VE-Cadherin were significantly higher in group A1 than in groups A, B, and B1 ( P<0.05), and in group B1 than in groups A and B ( P<0.05); but no significant difference was found between groups A and B ( P>0.05). In the VEGFR-3 blocked experiment, the flow cytometry results showed that the expressions of vWF, PECAM-1, and VE-Cadherin were significantly higher in group Ⅲ than in groupsⅠ, Ⅱ, and Ⅳ, and in group Ⅳ than in groups Ⅰ and Ⅱ ( P<0.05); but no significant difference was found between groups Ⅰ and Ⅱ ( P>0.05).

Conclusion

GIT1 mediates BMSCs of mice differentiation into endothelial cells via VEGFR-3, thereby affecting the angiogenesis.

Induction of VEGFA and Snail-1 by meningitic Escherichia coli mediates disruption of the blood-brain barrier

Escherichia coli is the most common Gram-negative bacterium that possesses the ability to cause neonatal meningitis, which develops as circulating bacteria penetrate the blood-brain barrier (BBB). However, whether meningitic E. coli could induce disruption of the BBB and the underlying mechanisms are poorly understood. Our current work highlight for the first time the participation of VEGFA and Snail-1, as well as the potential mechanisms, in meningitic E. coli induced disruption of the BBB. Here, we characterized a meningitis-causing E. coli PCN033, and demonstrated that PCN033 invasion could increase the BBB permeability through downregulating and remodeling the tight junction proteins (TJ proteins). This process required the PCN033 infection-induced upregulation of VEGFA and Snail-1, which involves the activation of TLR2-MAPK-ERK1/2 signaling cascade. Moreover, production of proinflammatory cytokines and chemokines in response to infection also promoted the upregulation of VEGFA and Snail-1, therefore further mediating the BBB disruption. Our observations reported here directly support the involvement of VEGFA and Snail-1 in meningitic E. coli induced BBB disruption, and VEGFA and Snail-1 would therefore represent the essential host targets for future prevention of clinical E. coli meningitis.

Mir-126 is a conserved modulator of lymphatic development

Organ homeostasis relies upon cellular and molecular processes that restore tissue structure and function in a timely fashion. Lymphatic vessels help maintain fluid equilibrium by returning interstitial fluid that evades venous uptake back to the circulation. Despite its important role in tissue homeostasis, cancer metastasis, and close developmental origins with the blood vasculature, the number of molecular players known to control lymphatic system development is relatively low. Here we show, using genetic approaches in zebrafish and mice, that the endothelial specific microRNA mir-126, previously implicated in vascular integrity, regulates lymphatic development. In zebrafish, in contrast to mir-126 morphants, double mutants (mir-126a^-/-; mir-126b^-/-, hereafter mir-126^-/-) do not exhibit defects in vascular integrity but develop lymphatic hypoplasia; mir-126^-/- animals fail to develop complete trunk and facial lymphatics, display severe edema and die as larvae. Notably, following MIR-126 inhibition, human Lymphatic Endothelial Cells (hLECs) respond poorly to VEGFA and VEGFC. In this context, we identify a concomitant reduction in Vascular Endothelial Growth Factor Receptor-2 (VEGFR2) and Vascular Endothelial Growth Factor Receptor-3 (VEGFR3, also known as FLT4) expression upon MIR-126 inhibition. In vivo, we further show that flt4^+/- zebrafish embryos exhibit lymphatic defects after mild miR-126 knockdown. Similarly, loss of Mir-126 in Flt4^+/- mice results in embryonic edema and lethality. Thus, our results indicate that miR-126 modulation of Vegfr signaling is essential for lymphatic system development in fish and mammals.