The interaction between vascular endothelial cells (ECs) and cancer cells is of vital importance to understand tumor dissemination. A paradigmatic cancer to study cell-cell interactions is classical Hodgkin Lymphoma (cHL) due to its complex microenvironment.The role of the interplay between cHL and ECs remains poorly understood. Here, we identify canonical WNT pathway activity as important for the mutual interactions between cHL cells and EC.We demonstrate that local canonical WNT signaling activates cHL cell chemotaxis towards ECs, adhesion to EC layers and cell invasion using the Wnt-inhibitor Dickkopf, tankyrases and casein kinase inhibitors but also knock-down of the lymphocyte enhancer binding-factor 1 (LEF-1) and β-catenin in cHL cells. Furthermore, LEF-1 and β-catenin-regulated cHL secretome promoted EC migration, sprouting and vascular tube formation involving VEGF-A. Importantly, high VEGFA expression is associated with a worse overall survival of cHL patients.These findings strongly support the concept that WNTs might function as regulator of lymphoma dissemination by affecting cHL cell chemotaxis and promoting endothelial cell behavior and thus angiogenesis through paracrine interactions.

Macrophages (Mφ) are abundantly present in the tumor microenvironment and may predict outcome in solid tumors and defined lymphoma subtypes. Mφ heterogeneity, the mechanisms of their recruitment, and their differentiation into lymphoma‐promoting, alternatively activated M2‐like phenotypes are still not fully understood. Therefore, further functional studies are required to understand biological mechanisms associated with human tumor‐associated Mφ (TAM). Here, we show that the global mRNA expression and protein abundance of human Mφ differentiated in Hodgkin lymphoma (HL)‐conditioned medium (CM) differ from those of Mφ educated by conditioned media from diffuse large B‐cell lymphoma (DLBCL) cells or, classically, by macrophage colony‐stimulating factor (M‐CSF). Conditioned media from HL cells support TAM differentiation through upregulation of surface antigens such as CD40, CD163, CD206, and PD‐L1. In particular, RNA and cell surface protein expression of mannose receptor 1 (MRC1)/CD206 significantly exceed the levels induced by classical M‐CSF stimulation in M2‐like Mφ; this is regulated by interleukin 13 to a large extent. Functionally, high CD206 enhances mannose‐dependent endocytosis and uptake of type I collagen. Together with high matrix metalloprotease9 secretion, HL‐TAMs appear to be active modulators of the tumor matrix. Preclinical in ovo models show that co‐cultures of HL cells with monocytes or Mφ support dissemination of lymphoma cells via lymphatic vessels, while tumor size and vessel destruction are decreased in comparison with lymphoma‐only tumors. Immunohistology of human HL tissues reveals a fraction of cases feature large numbers of CD206‐positive cells, with high MRC1 expression being characteristic of HL‐stage IV. In summary, the lymphoma‐TAM interaction contributes to matrix‐remodeling and lymphoma cell dissemination.

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By this I declare that I independently authored the presented thesis "Hodgkin lymphoma secreted factors determine macrophage polarization and function " and that I did not use other auxiliary means than indicated. Paragraphs that are taken from other publications, by wording or by sense, are marked in every case with a specification of the literary source.Furthermore, I declare that I carried out the scientific experiments following the principles of Good Scientific Practice according to the valid "Richtlinien der Georg-August-Universität Göttingen zur Sicherung guter wissenschaftlicher Praxis".