Response and recurrence correlates in individuals treated with neoadjuvant anti-PD-1 therapy for resectable oral cavity squamous cell carcinoma.

Neoadjuvant PD-1 blockade may be efficacious in some individuals with high-risk, resectable oral cavity head and neck cancer. To explore correlates of response patterns to neoadjuvant nivolumab treatment and post-surgical recurrences, we analyzed longitudinal tumor and blood samples in a cohort of 12 individuals displaying 33% responsiveness. Pretreatment tumor-based detection of FLT4 mutations and PTEN signature enrichment favors response, and high tumor mutational burden improves recurrence-free survival. In contrast, preexisting and/or acquired mutations (in CDKN2A, YAP1, or JAK2) correlate with innate resistance and/or tumor recurrence. Immunologically, tumor response after therapy entails T cell receptor repertoire diversification in peripheral blood and intratumoral expansion of preexisting T cell clones. A high ratio of regulatory T to T helper 17 cells in pretreatment blood predicts low T cell receptor repertoire diversity in pretreatment blood, a low cytolytic T cell signature in pretreatment tumors, and innate resistance. Our study provides a molecular framework to advance neoadjuvant anti-PD-1 therapy for individuals with resectable head and neck cancer.

Brain-to-cervical lymph node signaling after stroke.

After stroke, peripheral immune cells are activated and these systemic responses may amplify brain damage, but how the injured brain sends out signals to trigger systemic inflammation remains unclear. Here we show that a brain-to-cervical lymph node (CLN) pathway is involved. In rats subjected to focal cerebral ischemia, lymphatic endothelial cells proliferate and macrophages are rapidly activated in CLNs within 24 h, in part via VEGF-C/VEGFR3 signalling. Microarray analyses of isolated lymphatic endothelium from CLNs of ischemic mice confirm the activation of transmembrane tyrosine kinase pathways. Blockade of VEGFR3 reduces lymphatic endothelial activation, decreases pro-inflammatory macrophages, and reduces brain infarction. In vitro, VEGF-C/VEGFR3 signalling in lymphatic endothelial cells enhances inflammatory responses in co-cultured macrophages. Lastly, surgical removal of CLNs in mice significantly reduces infarction after focal cerebral ischemia. These findings suggest that modulating the brain-to-CLN pathway may offer therapeutic opportunities to ameliorate systemic inflammation and brain injury after stroke.

Isolation of a Novel Anti-KDR3 Single-chain Variable Fragment Antibody from a Phage Display Library.

Vascular endothelial growth factor receptor 2 (VEGFR-2) is known as one of the important antigens playing a vital role in angiogenesis. In this study, phage display technology (PDT) was used to produce a single-chain variable fragment (scFv) antibody against a region of the domain 3 in VEGFR-2 called kinase insert domain receptor 3 (KDR3). After designing the KDR3 peptide and biopanning, a colony was chosen for scFv antibody expression. Following expression and purification; western blotting, dot blotting and immunofluorescence (IF) were used to evaluate the antibody function. Surface plasmon resonance (SPR) was also employed to measure affinity of produced antibody. Once a colony was selected and transferred to the expression host, the scFv antibody was expressed in the expected range of 28 kDa. Using a designed chromatography column, antibody purification was found to be about 95%. In this study, a novel scFv with the capability of binding to KDR3 was isolated and purified and its intracellular function was investigated and verified.

Neuroinflammation-induced lymphangiogenesis near the cribriform plate contributes to drainage of CNS-derived antigens and immune cells.

There are no conventional lymphatic vessels within the CNS parenchyma, although it has been hypothesized that lymphatics near the cribriform plate or dura maintain fluid homeostasis and immune surveillance during steady-state conditions. However, the role of these lymphatic vessels during neuroinflammation is not well understood. We report that lymphatic vessels near the cribriform plate undergo lymphangiogenesis in a VEGFC - VEGFR3 dependent manner during experimental autoimmune encephalomyelitis (EAE) and drain both CSF and cells that were once in the CNS parenchyma. Lymphangiogenesis also contributes to the drainage of CNS derived antigens that leads to antigen specific T cell proliferation in the draining lymph nodes during EAE. In contrast, meningeal lymphatics do not undergo lymphangiogenesis during EAE, suggesting heterogeneity in CNS lymphatics. We conclude that increased lymphangiogenesis near the cribriform plate can contribute to the management of neuroinflammation-induced fluid accumulation and immune surveillance.

Attenuated Joint Tissue Damage Associated With Improved Synovial Lymphatic Function Following Treatment With Bortezomib in a Mouse Model of Experimental Posttraumatic Osteoarthritis.

OBJECTIVE: To investigate the roles of the synovial lymphatic system in the severity and progression of joint tissue damage and functional responses of synovial lymphatic endothelial cells (LECs) to macrophage subsets, and to evaluate the therapeutic potential of the proteasome inhibitor bortezomib (BTZ) in a mouse model of experimental posttraumatic osteoarthritis (OA). METHODS: C57BL/6J wild-type mice received a meniscal ligamentous injury to induce posttraumatic knee OA. Lymphangiogenesis was blocked by a vascular endothelial growth factor receptor 3 (VEGFR-3) neutralizing antibody. Synovial lymphatic drainage was examined by near-infrared imaging. Joint damage was assessed by histology. RNA-sequencing and pathway analyses were applied to synovial LECs. Macrophage subsets in the mouse synovium were identified by flow cytometry and immunofluorescence staining. M1 and M2 macrophages were induced from mouse bone marrow cells, and their effects on LECs were examined in cocultures in the presence or absence of BTZ. The effects of BTZ on joint damage, LEC inflammation, and synovial lymphatic drainage were examined. RESULTS: Injection of a VEGFR-3 neutralizing antibody into the joints of mice with posttraumatic knee OA reduced synovial lymphatic drainage and accelerated joint tissue damage. Synovial LECs from the mouse OA joints had dysregulated inflammatory pathways and expressed high levels of inflammatory genes. The number of M1 macrophages was increased in the knee joints of mice with posttraumatic OA, thereby promoting the expression of inflammatory genes by LECs; this effect was blocked by BTZ. Treatment with BTZ decreased cartilage loss, reduced the expression of inflammatory genes by LECs, and improved lymphatic drainage in the knee joints of mice with posttraumatic OA. CONCLUSION: Experimental posttraumatic knee OA is associated with decreased synovial lymphatic drainage, increased numbers of M1 macrophages, and enhanced inflammatory gene expression by LECs, all of which was improved by treatment with BTZ. Intraarticular administration of BTZ may represent a new therapy for the restoration of synovial lymphatic function in subjects with posttraumatic knee OA.

Anti-metastatic Efficacy of Traditional Chinese Medicine (TCM) Ginsenoside Conjugated to a VEFGR-3 Antibody on Human Gastric Cancer in an Orthotopic Mouse Model.

Background/Aim: The aim of the present study was to investigate the efficacy of a traditional Chinese medicine (TCM), VEGFR-3 antibody-conjugated ginsenoside Rg 3 nanoemulsion (VRIN), targeting lymphangiogenesis, on the inhibition of tumor growth and metastasis in an orthotopic mouse model of human gastric cancer. Materials and Methods: An orthotopic nude-mouse model of gastric cancer was established with the red fluorescent protein (RFP)-expressing human gastric cancer cell line NUGC-4-RFP. The tumor-bearing mice were treated with vehicle (0.2 ml normal saline every other day, iv), 5-FU (20 mg/kg once a week, i.p.) and VRIN (1 mg/kg every other day, i.v.). Real-time fluorescence imaging was performed to assess tumor inhibition in each group. Metastasis was evaluated by open fluorescence imaging at autopsy. The expression of lymphangiogenesis-related factors VEGF-C, VEDF-D and VEGFR-3 in the tumors were analyzed by immunohistochemistry and real-time RCP. Results: VRIN and 5-FU significantly inhibited primary tumor growth as compared to vehicle control (p<0.05). However, significant inhibition of lymph-node metastasis was only found in the VRIN-treated group (p<0.05). The expression of VEGF-C, VEGF-D and VEGFR-3 in the tumor was suppressed by VRIN treatment (p<0.05). Expression of VEGF-D and VEGFR-3 in the 5-FU-treated group was not significantly increased (p>0.05). No obvious toxicity was found in VRIN- and 5-FU-treated groups. Conclusion: Lymphangiogenesis-targeted ginsenoside Rg 3 immune-nanoemulsion inhibited tumor growth and reduced lymphatic metastasis by suppressing expression of VEGF-C, VEGF-D and VEGFR-3 in an orthotopic mouse model of human gastric cancer. Our study demonstrates the potential of TCM as an effective targeted treatment for metastatic gastric cancer.

Lymphangiogenesis is a feature of acute GVHD, and VEGFR-3 inhibition protects against experimental GVHD.

Lymph vessels play a crucial role in immune reactions in health and disease. In oncology the inhibition of lymphangiogenesis is an established therapeutic concept for reducing metastatic spreading of tumor cells. During allogeneic tissue transplantation, the inhibition of lymphangiogenesis has been successfully used to attenuate graft rejection. Despite its critical importance for tumor growth, alloimmune responses, and inflammation, the role of lymphangiogenesis has not been investigated during allogeneic hematopoietic stem cell transplantation (allo-HSCT). We found that acute graft-versus-host disease (aGVHD) is associated with lymphangiogenesis in murine allo-HSCT models as well as in patient intestinal biopsies. Inhibition of aGVHD-associated lymphangiogenesis by monoclonal antibodies against vascular endothelial growth factor receptor 3 (VEGFR-3) ameliorated aGVHD and improved survival in murine models. The administration of anti-VEGFR-3 antibodies did not interfere with hematopoietic engraftment and improved immune reconstitution in allo-HSCT recipients with aGVHD. Anti-VEGFR-3 therapy had no significant impact on growth of malignant lymphoma after allo-HSCT. We conclude that aGVHD is associated with lymphangiogenesis in intestinal lesions and in lymph nodes. Our data show that anti-VEGFR-3 treatment ameliorates lethal aGVHD and identifies the lymphatic vasculature as a novel therapeutic target in the setting of allo-HSCT.

Immunoexpression of VEGFR-3, but not the immunoexpression of VEGF-C or lymphatic density, is correlated with metastasis in lower lip squamous cell carcinoma.

The purpose of this study was to evaluate the immunoexpression of vascular endothelial growth factor C (VEGF-C) and VEGF receptor 3 (VEGFR-3) and their correlation with intratumoural lymphatic density (ILD) and peritumoural lymphatic density (PLD) in metastatic and non-metastatic lower lip squamous cell carcinoma (LLSCC). Twenty-five LLSCC with regional nodal metastasis and 25 LLSCC without metastasis were selected. The percentages of VEGF-C and VEGFR-3 staining in each tumour core and at the deep invasive front were assessed. PLD and ILD were determined using anti-podoplanin antibody. Immunohistochemical findings were correlated with nodal metastasis, clinical staging, local recurrence, clinical outcome, and histological grade. Cytoplasmic immunoexpression of VEGFR-3 in the tumour core was associated with metastasis (P=0.009), patient death (P=0.008), and histological grade (P<0.005). PLD, ILD, and VEGF-C expression showed no significant associations with clinicopathological parameters (P>0.05). PLD and ILD were not significantly correlated with the immunoexpression of VEGF-C or VEGFR-3 (P>0.05). There was a significant positive correlation between PLD and ILD (P=0.004), and between cytoplasmic immunoreactivity of VEGF-C and VEGFR-3 (P=0.011). These results suggest an important role for VEGFR-3 in the progression of LLSCC, and highlight the possible influence of its expression on the prognosis of these tumours. ILD and PLD may not be associated with lymph node metastasis in LLSCC.

LPS Upregulated VEGFR-3 Expression Promote Migration and Invasion in Colorectal Cancer via a Mechanism of Increased NF-κB Binding to the Promoter of VEGFR-3.

BACKGROUND AND AIM: Lipopolysaccharide(LPS) could promote the progression of colorectal cancer, but the specific regulatory mechanisms are largely unknown. So, this study aim to clarify the mechanisms that LPS upregulated VEGFR-3, which promotes colorectal cancer cells migration and invasion with a mechanism of increased NF-κB bind to the promoter of VEGFR-3. METHODS: The present study examined the VEGFR-3 expression in colorectal cancer tissues and analyzed the relationship between the VEGFR-3 expression with clinical parameters. PCR, Western blot, CCK-8, colone formation assay, and Transwell assay detected that LPS promoted the migration and invasion and the role of VEGFR-3 in the process of colorectal carcinoma in vitro. Used the methods of promoter analysis, EMSA assay and ChIP assay to explore the mechanisms LPS increased the expression of VEGFR-3. RESULTS: VEGFR-3 was significantly high expression in the colorectal cancer tissues. And the high expression was associated with the TNM stage and lymph node metastasis of colorectal cancer. LPS could promote the migration and invasion, which could be blocked by the neutralizing antibody IgG of VEGFR-3. And found that -159 nt to +65 nt was the crucial region of VEGFR-3 promoter. And detected that the NF-κB was important transcription factor for the VEGFR-3 promoter. And LPS could increase NF-κB binding to VEGFR-3 promoter and upregulated the expression of VEGFR-3 to exert biological functions. CONCLUSION: We have elucidated the relationship between LPS and the VEGFR-3 expression and revealed that VEGFR-3 play very important role in the process of LPS promoting the migration and invasion of colorectal cancer cells. Further illuminated the mechanism that LPS upregulated VEGFR-3 expression via increased NF-κB bind to the promoter of VEGFR-3.

Phase 1 study of the anti-vascular endothelial growth factor receptor 3 monoclonal antibody LY3022856/IMC-3C5 in patients with advanced and refractory solid tumors and advanced colorectal cancer.

PURPOSE: Metastasis of solid tumors to regional lymph nodes is facilitated by tumor lymphangiogenesis, which is primarily mediated by the vascular endothelial growth factor receptor 3 (VEGFR-3). We conducted a phase 1 dose-escalation (part A) study of the VEGFR-3 human immunoglobulin G subclass 1 monoclonal antibody LY3022856 in advanced solid tumors, followed by a colorectal cancer (CRC) expansion (part B). METHODS: Part A evaluated the safety profile and maximum tolerated dose (MTD) of LY3022856 in patients treated intravenously at doses of 5-30 mg/kg weekly (qwk). Part B further evaluated tolerability in CRC patients treated with 30 mg/kg. Secondary objectives were pharmacokinetics, anti-tumor activity, and pharmacodynamics (exploratory). RESULTS: A total of 44 patients (23 in part A; 21 in part B) were treated; only one dose-limiting toxicity was observed at the lowest dose level. The MTD was not reached. Treatment-emergent adverse events (TEAEs) of any grade included in ≥15 % of all patients were: nausea (41 %), fatigue (32 %), vomiting (30 %), decreased appetite (27 %), pyrexia (25 %), peripheral edema (23 %), and urinary tract infection (UTI, 20 %). The most common grade 3/4 TEAEs included UTI and small intestinal obstruction (7 % each). No radiographic responses were noted. Median progression-free survival in part B was 6.3 weeks (95 % confidence interval: 5.1, 14.4), and a best overall response of stable disease was observed in 4 CRC patients (19.0 %). CONCLUSIONS: LY3022856 was well tolerated up to a dose of 30 mg/kg qwk, but with minimal anti-tumor activity in CRC. CLINICALTRIALS. GOV IDENTIFIER: NCT01288989.

Mobilization of lymphatic endothelial precursor cells and lymphatic neovascularization in primary Sjögren's syndrome.

Although lymphatic neovascularization may be a key feature of chronic inflammation, it is almost unexplored in primary Sjögren's syndrome (pSS). A recent study revealed a pro-lymphangiogenic function of interleukin (IL)-17, a leading player in pSS pathogenesis. The aims of the study were to investigate lymphangiogenic mediators and lymphatic vasculature in pSS, as well as their possible association with IL-17. Circulating lymphatic endothelial precursor cells (LEPCs) and Th17 cells were enumerated in pSS patients and healthy donors. VEGF-C and IL-17 levels were assessed in paired serum samples. Lymphatic vasculature, VEGF-C/VEGF receptor (VEGFR)-3 and IL-17 were evaluated in pSS minor salivary glands (MSGs) and compared with normal and non-specific chronic sialadenitis (NSCS) MSGs. Circulating LEPCs were expanded in pSS and correlated with circulating Th17 cells, IL-17 and VEGF-C. In pSS MSGs, a newly formed lymphatic capillary network was found within periductal inflammatory infiltrates and the number of interlobular lymphatic vessels was significantly increased compared with normal and NSCS MSGs. Strong VEGF-C expression was detected in pSS ductal epithelial cells and periductal inflammatory cells. Numerous VEGFR-3(+) infiltrating mononuclear cells were exclusively observed in pSS MSGs. VEGFR-3 expression was strongly increased in lymphatic capillaries of pSS MSGs. IL-17(+) inflammatory cells were preferentially observed around lymphatic vessels in pSS MSGs. This study supports the notion that lymphvasculogenesis and lymphangiogenesis are active in pSS, thereby unmasking a novel aspect of disease pathogenesis. In addition, our results suggest another possible pathogenic role of IL-17 in pSS, further supporting its therapeutic targeting in this disease.

An orally administered DNA vaccine targeting vascular endothelial growth factor receptor-3 inhibits lung carcinoma growth.

Lung cancer is the leading cause of mortality and 5-year survival rate is very low worldwide. Recent studies show that vascular endothelial growth factor receptor-3 (VEGFR-3) signaling pathway contributes to lung cancer progression. So we hypothesize that an oral DNA vaccine that targets VEGFR-3 carried by attenuated Salmonella enterica serovar typhimurium strain SL3261 has impacts on lung cancer progression. In this study, the oral VEGFR-3-based vaccine-immunized mice showed appreciable inhibition of tumor growth and tumor lymphatic microvessels in lung cancer mice model. Moreover, the oral VEGFR-3-based vaccine-immunized mice showed remarkable increases in both VEGFR-3-specific antibody levels and cytotoxic activity. Furthermore, the oral VEGFR-3-based vaccine-immunized mice showed a significant increase in the levels of T helper type 1 (Th1) cell intracellular cytokine expression (IL-2, IFN-γ, and TNF-α). After inoculation with murine Lewis lung carcinoma (LLC) cells, CD4(+) or CD8(+) T cell numbers obviously declined in control groups whereas high levels were maintained in the oral VEGFR-3-based vaccine group. These results demonstrated that the oral VEGFR-3-based vaccine could induce specific humoral and cellular immune responses and then significantly inhibit lung carcinoma growth via suppressing lymphangiogenesis.

Simultaneous targeting of VEGF-receptors 2 and 3 with immunoliposomes enhances therapeutic efficacy.

BACKGROUND: Tumor progression depends on angiogenesis. Vascular endothelial growth factor (VEGF) receptors (VEGFRs) are the main signal transducers that stimulate endothelial cell migration and vessel sprouting. At present, only VEGFR2 is targeted in the clinical practice. PURPOSE: To develop new, anti-angiogenic nanoparticles (immunoliposomes, ILs), that redirect cytotoxic compounds to tumor-associated vascular cells. METHODS: Pegylated liposomal doxorubicin (PLD) was targeted against VEGFR2- and VEGFR3-expressing cells by inserting anti-VEGFR2 and/or anti-VEGFR3 antibody fragments into the lipid bilayer membrane of PLD. These constructs were tested in vitro, and in vivo in the Rip1Tag2 mouse model of human cancer. RESULTS: The combination treatment with anti-VEGFR2-ILs-dox and anti-VEGFR3-ILs-dox was superior to targeting only VEGFR2 cells and provides a highly efficient approach of depleting tumor-associated vasculature. This leads to tumor starvation and pronounced reduction of tumor burden. CONCLUSION: Nanoparticles against VEGFR2 and -3 expressing tumor-associated endothelial cells represent a promising and novel anti-cancer strategy.

Targeting tubulointerstitial remodeling in proteinuric nephropathy in rats.

Proteinuria is an important cause of tubulointerstitial damage. Anti-proteinuric interventions are not always successful, and residual proteinuria often leads to renal failure. This indicates the need for additional treatment modalities by targeting the harmful downstream consequences of proteinuria. We previously showed that proteinuria triggers renal lymphangiogenesis before the onset of interstitial inflammation and fibrosis. However, the interrelationship of these interstitial events in proteinuria is not yet clear. To this end, we specifically blocked lymphangiogenesis (anti-VEGFR3 antibody), monocyte/macrophage influx (clodronate liposomes) or lymphocyte and myofibroblast influx (S1P agonist FTY720) separately in a rat model to investigate the role and the possible interaction of each of these phenomena in tubulointerstitial remodeling in proteinuric nephropathy. Proteinuria was induced in 3-month old male Wistar rats by adriamycin injection. After 6 weeks, when proteinuria has developed, rats were treated for another 6 weeks by anti-VEGFR3 antibody, clodronate liposomes or FTY720 up to week 12. In proteinuric rats, lymphangiogenesis, influx of macrophages, T cells and myofibroblasts, and collagen III deposition and interstitial fibrosis significantly increased at week 12 vs week 6. Anti-VEGFR3 antibody prevented lymphangiogenesis in proteinuric rats, however, without significant effects on inflammatory and fibrotic markers or proteinuria. Clodronate liposomes inhibited macrophage influx and partly reduced myofibroblast expression; however, neither significantly prevented the development of lymphangiogenesis, nor fibrotic markers and proteinuria. FTY720 prevented myofibroblast accumulation, T-cell influx and interstitial fibrosis, and partially reduced macrophage number and proteinuria; however, it did not significantly influence lymphangiogenesis and collagen III deposition. This study showed that proteinuria-induced interstitial fibrosis cannot be halted by blocking lymphangiogenesis or the influx of macrophages. On the other hand, FTY720 treatment did prevent T-cell influx, myofibroblast accumulation and interstitial fibrosis, but not renal lymphangiogenesis and proteinuria. We conclude that tubulointerstitial fibrosis and inflammation are separate from lymphangiogenesis, at least under proteinuric conditions.

Vascular endothelial growth factor c/vascular endothelial growth factor receptor 3 signaling regulates chemokine gradients and lymphocyte migration from tissues to lymphatics.

BACKGROUND: Circulation of leukocytes via blood, tissue and lymph is integral to adaptive immunity. Afferent lymphatics form CCL21 gradients to guide dendritic cells and T cells to lymphatics and then to draining lymph nodes (dLN). Vascular endothelial growth factor C and vascular endothelial growth factor receptor 3 (VEGFR-3) are the major lymphatic growth factor and receptor. We hypothesized these molecules also regulate chemokine gradients and lymphatic migration. METHODS: CD4 T cells were injected into the foot pad or ear pinnae, and migration to afferent lymphatics and dLN quantified by flow cytometry or whole mount immunohistochemistry. Vascular endothelial growth factor receptor 3 or its signaling or downstream actions were modified with blocking monoclonal antibodies (mAbs) or other reagents. RESULTS: Anti-VEGFR-3 prevented migration of CD4 T cells into lymphatic lumen and significantly decreased the number that migrated to dLN. Anti-VEGFR-3 abolished CCL21 gradients around lymphatics, although CCL21 production was not inhibited. Heparan sulfate (HS), critical to establish CCL21 gradients, was down-regulated around lymphatics by anti-VEGFR-3 and this was dependent on heparanase-mediated degradation. Moreover, a Phosphoinositide 3-kinase (PI3K)α inhibitor disrupted HS and CCL21 gradients, whereas a PI3K activator prevented the effects of anti-VEGFR-3. During contact hypersensitivity, VEGFR-3, CCL21, and HS expression were all attenuated, and anti-heparanase or PI3K activator reversed these effects. CONCLUSIONS: Vascular endothelial growth factor C/VEGFR-3 signaling through PI3Kα regulates the activity of heparanase, which modifies HS and CCL21 gradients around lymphatics. The functional and physical linkages of these molecules regulate lymphatic migration from tissues to dLN. These represent new therapeutic targets to influence immunity and inflammation.

Lymphangiogenesis is induced by mycobacterial granulomas via vascular endothelial growth factor receptor-3 and supports systemic T-cell responses against mycobacterial antigen.

Granulomatous inflammation is characteristic of many autoimmune and infectious diseases. The lymphatic drainage of these inflammatory sites remains poorly understood, despite an expanding understanding of lymphatic role in inflammation and disease. Here, we show that the lymph vessel growth factor Vegf-c is up-regulated in Bacillus Calmette-Guerin- and Mycobacterium tuberculosis-induced granulomas, and that infection results in lymph vessel sprouting and increased lymphatic area in granulomatous tissue. The observed lymphangiogenesis during infection was reduced by inhibition of vascular endothelial growth factor receptor 3. By using a model of chronic granulomatous infection, we also show that lymphatic remodeling of tissue persists despite resolution of acute infection and a 10- to 100-fold reduction in the number of bacteria and tissue-infiltrating leukocytes. Inhibition of vascular endothelial growth factor receptor 3 decreased the growth of new vessels, but also reduced the proliferation of antigen-specific T cells. Together, our data show that granuloma-up-regulated factors increase granuloma access to secondary lymph organs by lymphangiogenesis, and that this process facilitates the generation of systemic T-cell responses to granuloma-contained antigens.

Expression of vascular endothelial growth factor-C (VEGF-C) and its receptor (VEGFR-3) in the glial reaction elicited by human mesenchymal stem cell engraftment in the normal rat brain.

To determine whether vascular endothelial growth factor-C (VEGF-C) and its receptor (VEGFR-3) are involved in the glial reaction elicited by transplanted mesenchymal stem cells (MSCs), we examined the cellular localization of VEGF-C and VEGFR-3 proteins in the striatum of adult normal rats that received bone marrow-derived human MSCs. The MSC grafts were infiltrated with activated microglia/macrophages and astrocytes over a 2-week period post-transplantation, which appeared to parallel the loss of transplanted MSCs. VEGF-C/VEGFR-3 was expressed in activated microglia/macrophages recruited to the graft site, where the induction of VEGF-C protein was rather late compared with that of its receptor. VEGF-C protein was absent or very weak on day 3, whereas VEGFR-3 immunoreactivity was evident within the first three days. Furthermore, within three days, VEGF-C could be detected in the brain macrophages localized immediately adjacent to the needle track. At the same time, almost all the brain macrophages in both regions expressed VEGFR-3. Reactive astrocytes at the graft site expressed VEGFR-3, but not VEGF-C. These data demonstrated the characteristic time- and cell-dependent expression patterns for VEGF-C and VEGFR-3 within the engrafted brain tissue, suggesting that they may contribute to neuroinflammation in MSC transplantation, possibly through the recruitment and/or activation of microglia/macrophages and astrogliosis.

Restoration of natural killer cell cytotoxicity by VEGFR-3 inhibition in myelogenous leukemia.

Acute myeloid leukemia (AML) cells in vivo are constantly exposed to lymphangiogenic cytokines such as VEGF-C. However, it is poorly understood how the VEGF-C signaling modulates the immune functions in the tumor microenvironment. We have previously reported that natural killer (NK) cells in AML patients strongly upregulated VEGFR-3, the major VEGF-C receptor, and that the VEGFR-3 expression level in NK cells inversely correlates with their cytotoxic potential. These findings have led us to hypothesize that VEGFR-3 inhibition may reinstate the cytotoxic capacity of the AML-associated NK cells. To address this hypothesis, we employed a pharmaceutical approach to block the VEGFR-3 function in the murine model of syngeneic myelogenous leukemia. Using various molecular and cellular analyses, we assessed the correlation between VEGFR-3 inhibition and NK cell cytotoxicity. Indeed, we found that leukemic environment is highly enriched with lymphangiogenic stimuli, and that VEGFR-3 inhibition restored NK cell killing function with an increased IFN-γ level, providing a therapeutic implication of VEGFR-3 against AML. Together, we demonstrate the therapeutic value of functional modulation of NK cells by blocking VEGFR-3, and provide a possibility of advanced therapeutic approaches using immune cells against myelogenous leukemia.

Normal dendritic cell mobilization to lymph nodes under conditions of severe lymphatic hypoplasia.

To address the requirement for lymphatic capillaries in dendritic cell (DC) mobilization from skin to lymph nodes (LNs), we used mice bearing one inactivated allele of vascular endothelial growth factor receptor 3 (VEGFR3) where skin lymphatic capillaries are reported absent. Unexpectedly, DC mobilization from the back skin to draining LNs was similar in magnitude, and kinetics to control mice and humoral immunity appeared intact. By contrast, DC migration from body extremities, including ear and forepaws, was ablated. An evaluation in different regions of skin revealed rare patches of lymphatic capillaries only in body trunk areas where migration was intact. That is, whereas the ear skin was totally devoid of lymphatic capillaries, residual capillaries in the back skin were present though retained only at ∼10% normal density. This reduction in density markedly reduced the clearance of soluble tracers, indicating that normal cell migration was spared under conditions when lymphatic transport function was poor. Residual lymphatic capillaries expressed slightly higher levels of CCL21 and migration of skin DCs to LNs remained dependent on CCR7 in Chy mice. DC migration from the ear could be rescued by the introduction of a limited number of lymphatic capillaries through skin transplantation. Thus, the development of lymphatic capillaries in the skin of body extremities was more severely impacted by a mutant copy of VEGFR3 than trunk skin, but lymphatic transport function was markedly reduced throughout the skin, demonstrating that even under conditions when a marked loss in lymphatic capillary density reduces lymph transport, DC migration from skin to LNs remains normal.

Development of an AlphaScreen-based high-throughput screening assay for inhibitors of human vascular endothelial growth factor receptor-3.

Vascular endothelial growth factor receptor 3 (VEGFR-3, also known as Flt4), the receptor for vascular endothelial growth factors (VEGFs) C and D, is expressed on lymphatic endothelium and plays an important role in lymphangiogenesis. Recent studies indicate that VEGFR-3 may be involved in tumor angiogenesis and growth, and so VEGFR-3 is an attractive target for researchers seeking to prevent tumor growth and metastasis. Hence we expressed and purified the CD (catalytic domain) of VEGFR-3 (VEGFR-3-CD) in Escherichia coli expression system and established a new simple and effective HTS (high-throughput screening) assay based on AlphaScreen strategy for VEGFR-3 inhibitors. Then we identified a novel cobalt complex that inhibited the phosphorylation of VEGFR-3 in a dose-dependent manner with an IC(50) value of 338 nM. This compound could be a useful new angiogenesis inhibitor, which would be investigated further for its therapeutic potentials.