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Nature. 2014 Mar 6;507(7490):109-13. doi: 10.1038/nature13111. Epub 2014 Feb 26.

Ultraviolet-radiation-induced inflammation promotes angiotropism and metastasis in melanoma.

Author information

Laboratory of Experimental Dermatology, Department of Dermatology and Allergy, University of Bonn, 53115 Bonn, Germany.
Molecular Immunology and Cell Biology, Life and Medical Sciences Institute, University of Bonn, 53115 Bonn, Germany.
Unit for RNA Biology, Department of Clinical Chemistry and Clinical Pharmacology, University of Bonn, 53105 Bonn, Germany.
Institute for Dental Research and Oral Musculoskeletal Biology, Center for Biochemistry, Medical Faculty, University of Cologne, D-50931 Cologne, Germany.
Immunology and Environment, Life and Medical Sciences Institute, University of Bonn, 53115 Bonn, Germany.
Institute for Physiology I, Life & Brain Center, University of Bonn, 53105 Bonn, Germany.
Department of Dermatology, University Hospital Essen, 45122 Essen, Germany.
Institute of Cardiovascular Research and Sport Medicine, Department of Molecular and Cellular Sport Medicine, German Sport University Cologne, 50933 Cologne, Germany.
Division of Genetics and Cell Biology, San Raffaele University and Scientific Institute, 20132 Milan, Italy.
Department of Pathology and Laboratory Medicine, Jonsson Comprehensive Cancer Center, University of California Los Angeles (UCLA) Medical Center, Los Angeles, California 90095, USA.
Institutes of Molecular Medicine and Experimental Immunology, University of Bonn, 53105 Bonn, Germany.


Intermittent intense ultraviolet (UV) exposure represents an important aetiological factor in the development of malignant melanoma. The ability of UV radiation to cause tumour-initiating DNA mutations in melanocytes is now firmly established, but how the microenvironmental effects of UV radiation influence melanoma pathogenesis is not fully understood. Here we report that repetitive UV exposure of primary cutaneous melanomas in a genetically engineered mouse model promotes metastatic progression, independent of its tumour-initiating effects. UV irradiation enhanced the expansion of tumour cells along abluminal blood vessel surfaces and increased the number of lung metastases. This effect depended on the recruitment and activation of neutrophils, initiated by the release of high mobility group box 1 (HMGB1) from UV-damaged epidermal keratinocytes and driven by Toll-like receptor 4 (TLR4). The UV-induced neutrophilic inflammatory response stimulated angiogenesis and promoted the ability of melanoma cells to migrate towards endothelial cells and use selective motility cues on their surfaces. Our results not only reveal how UV irradiation of epidermal keratinocytes is sensed by the innate immune system, but also show that the resulting inflammatory response catalyses reciprocal melanoma-endothelial cell interactions leading to perivascular invasion, a phenomenon originally described as angiotropism in human melanomas by histopathologists. Angiotropism represents a hitherto underappreciated mechanism of metastasis that also increases the likelihood of intravasation and haematogenous dissemination. Consistent with our findings, ulcerated primary human melanomas with abundant neutrophils and reactive angiogenesis frequently show angiotropism and a high risk for metastases. Our work indicates that targeting the inflammation-induced phenotypic plasticity of melanoma cells and their association with endothelial cells represent rational strategies to specifically interfere with metastatic progression.

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