Showing papers by "Michael Detmar published in 2018"

Unexpected contribution of lymphatic vessels to promotion of distant metastatic tumor spread

Abstract: Tumor lymphangiogenesis is accompanied by a higher incidence of sentinel lymph node metastasis and shorter overall survival in several types of cancer. We asked whether tumor lymphangiogenesis might also occur in distant organs with established metastases and whether it might promote further metastatic spread of those metastases to other organs. Using mouse metastasis models, we found that lymphangiogenesis occurred in distant lung metastases and that some metastatic tumor cells were located in lymphatic vessels and draining lymph nodes. In metastasis-bearing lungs of melanoma patients, a higher lymphatic density within and around metastases and lymphatic invasion correlated with poor outcome. Using a transgenic mouse model with inducible expression of vascular endothelial growth factor C (VEGF-C) in the lung, we found greater growth of lung metastases, with more abundant dissemination to other organs. Our findings reveal unexpected contributions of lymphatics in distant organs to the promotion of growth of metastases and their further spread to other organs, with potential clinical implications for adjuvant therapies in patients with metastatic cancer.

Lymphatic exosomes promote dendritic cell migration along guidance cues.

Abstract: Lymphatic endothelial cells (LECs) release extracellular chemokines to guide the migration of dendritic cells. In this study, we report that LECs also release basolateral exosome-rich endothelial vesicles (EEVs) that are secreted in greater numbers in the presence of inflammatory cytokines and accumulate in the perivascular stroma of small lymphatic vessels in human chronic inflammatory diseases. Proteomic analyses of EEV fractions identified >1,700 cargo proteins and revealed a dominant motility-promoting protein signature. In vitro and ex vivo EEV fractions augmented cellular protrusion formation in a CX3CL1/fractalkine-dependent fashion and enhanced the directional migratory response of human dendritic cells along guidance cues. We conclude that perilymphatic LEC exosomes enhance exploratory behavior and thus promote directional migration of CX3CR1-expressing cells in complex tissue environments.

Antibody-mediated delivery of VEGF-C potently reduces chronic skin inflammation

Abstract: VEGF-C is an important mediator of lymphangiogenesis and has been shown to alleviate chronic inflammation in a variety of disease models. In this study, we investigated whether targeted delivery of VEGF-C to sites of inflammation and site-specific activation of lymphatic vessels would represent a clinically feasible strategy for treating chronic skin inflammation. To this end, we generated a fusion protein consisting of human VEGF-C fused to the F8 antibody (F8-VEGF-C), which is specific for the alternatively spliced, angiogenesis-marking extradomain A (EDA) of fibronectin. In two mouse models of psoriasis-like skin inflammation, mediated by transgenic VEGF-A overexpression or repeated application of imiquimod, intravenous treatment with F8-VEGF-C but not with untargeted VEGF-C significantly reduced ear skin edema and was as effective as the clinically used TNF-α receptor-Fc fusion protein (TNFR-Fc). Treatment with F8-VEGF-C led to a marked expansion of lymphatic vessels in the inflamed skin and significantly improved lymphatic drainage function. At the same time, treatment with F8-VEGF-C significantly reduced leukocyte numbers, including CD4+ and γδ T cells. In sum, our results reveal that targeted delivery of VEGF-C and site-specific induction of lymphatic vessels represent a potentially new and promising approach for the treatment of chronic inflammatory diseases.

Itch suppression in mice and dogs by modulation of spinal α2 and α3GABAA receptors

Abstract: Chronic itch is a highly debilitating condition affecting about 10% of the general population. The relay of itch signals is under tight control by inhibitory circuits of the spinal dorsal horn, which may offer a hitherto unexploited therapeutic opportunity. Here, we found that specific pharmacological targeting of inhibitory α2 and α3GABAA receptors reduces acute histaminergic and non-histaminergic itch in mice. Systemic treatment with an α2/α3GABAA receptor selective modulator alleviates also chronic itch in a mouse model of atopic dermatitis and in dogs sensitized to house dust mites, without inducing sedation, motor dysfunction, or loss of antipruritic activity after prolonged treatment. Transsynaptic circuit tracing, immunofluorescence, and electrophysiological experiments identify spinal α2 and α3GABAA receptors as likely molecular targets underlying the antipruritic effect. Our results indicate that drugs targeting α2 and α3GABAA receptors are well-suited to alleviate itch, including non-histaminergic chronic itch for which currently no approved treatment exists.

Alternative transcription of a shorter, non-anti-angiogenic thrombospondin-2 variant in cancer-associated blood vessels.

Abstract: Thrombospondin-2 (TSP2) is an anti-angiogenic matricellular protein that inhibits tumor growth and angiogenesis. Tumor-associated blood vascular endothelial cells (BECs) were isolated from human invasive bladder cancers and from matched normal bladder tissue by immuno-laser capture microdissection. Exon expression profiling analyses revealed a particularly high expression of a short TSP2 transcript containing only the last 9 (3') exons of the full-length TSP2 transcript. Using 5' and 3' RACE (rapid amplification of cDNA ends) and Sanger sequencing, we confirmed the existence of the shorter transcript of TSP2 (sTSP2) and determined its sequence which completely lacked the anti-angiogenic thrombospondin type 1 repeats domain. The largest open reading frame predicted within the transcript comprises 209 amino acids and matches almost completely the C-terminal lectin domain of full-length TSP2. We produced recombinant sTSP2 and found that unlike the full-length TSP2, sTSP2 did not inhibit vascular endothelial growth factor-A-induced proliferation of cultured human BECs, but in contrast when combined with TSP2 blocked the inhibitory effects of TSP2 on BEC proliferation. In vivo studies with stably transfected A431 squamous cell carcinoma cells revealed that full-length TSP2, but not sTSP2, inhibited tumor growth and angiogenesis. This study reveals that the transcriptional program of tumor stromal cells can change to transcribe a new version of an endogenous angiogenesis inhibitor that has lost its anti-angiogenic activity.

Visualization and Measurement of Lymphatic Function In Vivo.

Abstract: An increased research focus on the lymphatic system has necessitated the development of reliable in vivo assessments of lymphatic function in rodent models. Here, we provide three protocols for assays based upon near-infrared fluorescence imaging that were developed in our laboratory that can visualize and quantify different aspects of lymphatic function in mice. The first, a protocol for the tracking of the clearance of an injected intradermal bolus of a pegylated tracer, provides a measurement of lymphatic function in a specific region of the skin. The second assay allows noninvasive imaging of the contractility of collecting lymphatic vessels of the lower limb after injection of the pegylated tracer into the paw skin. This assay also enables real-time visualization of the routing of lymphatic flow from the paw to draining lymph nodes. The final protocol describes invasive imaging of the contractility and valve function of a collecting lymphatic vessel connecting the inguinal and axillary lymph nodes. This assay allows compounds to be added directly on the collecting lymphatic vessel and responses in contraction frequency and amplitude to be measured.