SummaryBackground Fumaric acid esters (FAEs) are recommended in international guidelines for induction and long-term treatment of adults with moderate-to-severe chronic plaque psoriasis. The fixed combination Fumaderm â is approved in Ger-

Fumaric acid esters, mainly dimethylfumarate (DMF), have been successfully used to treat psoriasis. Based on previous observations that DMF inhibited expression of several TNF-induced genes in endothelial cells, we wished to explore the molecular basis of DMF function in greater detail. In first experiments we analyzed DMF effects on tissue factor expression in human endothelial cells in culture, because tissue factor is expressed by two independent sets of transcription factors, by NF-κB via TNF and by early gene response-1 transcription factor via vascular endothelial growth factor (VEGF). We show that DMF inhibits TNF-induced tissue factor mRNA and protein expression as well as TNF-induced DNA binding of NF-κB proteins, but not VEGF-induced tissue factor protein, mRNA expression, or VEGF-induced early gene response-1 transcription factor/DNA binding. To determine where DMF interferes with the TNF/NF-κB signaling cascade, we next analyzed DMF effects on IκB and on the subcellular distribution of NF-κB. DMF does not inhibit TNF-induced IκBα phosphorylation and IκB degradation; thus, NF-κB is properly released from IκB complexes even in the presence of DMF. Importantly, DMF inhibits the TNF-induced nuclear entry of NF-κB proteins, and this effect appears selective for NF-κB after the release from IκB, because the constitutive shuttling of inactive NF-κB/IκB complexes into and out from the nucleus is not blocked by DMF. Moreover, DMF does not block NF-κB/DNA binding. In conclusion, DMF appears to selectively prevent the nuclear entry of activated NF-κB, and this may be the basis of its beneficial effect in psoriasis.

Dimethylfumarate (DMF) inhibits signals transmitted by Rel proteins and is used for the treatment of inflammatory skin diseases such as psoriasis, but potential effects of DMF on tumor progression have yet not been analyzed. We show that DMF reduced melanoma growth and metastasis in severe combined immunodeficient mouse models. To identify targets of DMF action, we analyzed mRNA expression in DMF-treated melanomas by gene chip arrays. Using BiblioSphere software for data analysis, significantly regulated genes were mapped to Gene Ontology terms cell death, cell growth, and cell cycle. Indeed, we found that DMF inhibited proliferation of human melanoma cells A375 and M24met in vitro. The cell cycle was arrested at the G 2 -M boundary. Moreover, DMF was proapoptotic, as shown by cell cycle analysis and by Annexin V and Apo2.7 staining. These results were confirmed in vivo. DMF reduced proliferation rates of tumor cells as assessed by Ki-67 immunostaining and increased apoptosis as assessed by terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling staining. In conclusion, DMF is antiproliferative and proapoptotic and reduces melanoma growth and metastasis in animal models. (Cancer Res 2006; 66(24): 11888-96)

Factors determining lymphatic differentiation in the adult organism are not yet well characterized. We have made the observation that mixed primary cultures of dermal blood endothelial cells (BEC) and lymphatic endothelial cells (LEC) grown under standard conditions change expression of markers during subculture: After passage 6, they uniformly express LEC-specific markers Prox-1 and podoplanin. Using sorted cells, we show that LEC but not BEC constitutively express IL-3, which regulates Prox-1 and podoplanin expression in LEC. The addition of IL-3 to the medium of BEC cultures induces Prox-1 and podoplanin. Blocking IL-3 activity in LEC cultures results in a loss of Prox-1 and podoplanin expression. In conclusion, endogenous IL-3 is required to maintain the LEC phenotype in culture, and the addition of IL-3 to BEC appears to induce transdifferentiation of BEC into LEC.

SummaryIncreased visceral fat is associated with a high risk of diabetes and metabolic syndrome and is in part caused by excessive glucocorticoids (GCs). However, the molecular mechanisms remain undefined. We now identify the GC-dependent gene LIM domain only 3 (LMO3) as being selectively upregulated in a depot-specific manner in human obese visceral adipose tissue, localizing primarily in the adipocyte fraction. Visceral LMO3 levels were tightly correlated with expression of 11β-hydroxysteroid dehydrogenase type-1 (HSD11B1), the enzyme responsible for local activation of GCs. In early human adipose stromal cell differentiation, GCs induced LMO3 via the GC receptor and a positive feedback mechanism involving 11βHSD1. No such induction was observed in murine adipogenesis. LMO3 overexpression promoted, while silencing of LMO3 suppressed, adipogenesis via regulation of the proadipogenic PPARγ axis. These results establish LMO3 as a regulator of human adipogenesis and could contribute a mechanism resulting in visceral-fat accumulation in obesity due to excess glucocorticoids.

Alterations in epidermal growth factor (EGF) expression are known to be of prognostic relevance in human melanoma, but EGF-mediated effects on melanoma have not been extensively studied. As lymph node metastasis usually represents the first major step in melanoma progression, we were trying to identify a potential role of primary tumor-derived EGF in the mediation of melanoma lymph node metastases. Stable EGF knockdown (EGFkd) in EGF-high (M24met) and EGF-low (A375) expressing melanoma cells was generated. Only in EGF-high melanoma cells, EGFkd led to a significant reduction of lymph node metastasis and primary tumor lymphangiogenesis in vivo, as well as impairment of tumor cell migration in vitro. Moreover, EGF-induced sprouting of lymphatic but not of blood endothelial cells was abolished using supernatants of M24met EGFkd cells. In addition, M24met EGFkd tumors showed reduced vascular endothelial growth factor-C (VEGF-C) expression levels. Similarly, in human primary melanomas, a direct correlation between EGF/VEGF-C and EGF/Prox-1 expression levels was found. Finally, melanoma patients with lymph node micrometastases undergoing sentinel node biopsy were found to have significantly elevated EGF serum levels as compared with sentinel lymph node-negative patients. Our data indicate that tumor-derived EGF is important in mediating melanoma lymph node metastasis.

Lymphatic vessels are essential for skin fluid homeostasis and immune cell trafficking. Whether the lymphatic vasculature is associated with hair follicle regeneration is, however, unknown. Here, using steady and live imaging approaches in mouse skin, we show that lymphatic vessels distribute to the anterior permanent region of individual hair follicles, starting from development through all cycle stages and interconnecting neighboring follicles at the bulge level, in a stem cell‐dependent manner. Lymphatic vessels further connect hair follicles in triads and dynamically flow across the skin. At the onset of the physiological stem cell activation, or upon pharmacological or genetic induction of hair follicle growth, lymphatic vessels transiently expand their caliber suggesting an increased tissue drainage capacity. Interestingly, the physiological caliber increase is associated with a distinct gene expression correlated with lymphatic vessel reorganization. Using mouse genetics, we show that lymphatic vessel depletion blocks hair follicle growth. Our findings point toward the lymphatic vasculature being important for hair follicle development, cycling, and organization, and define lymphatic vessels as stem cell niche components, coordinating connections at tissue‐level, thus provide insight into their functional contribution to skin regeneration.

Chemokines influence tumor metastasis by targeting tumor, stromal, and hematopoietic cells. Characterizing the chemokine mRNA expression profile of human primary melanoma samples, we found CXCL5 significantly up-regulated in stage T4 primary melanomas when compared to thin melanomas (T1 stage). To characterize the role of CXCL5 in melanoma progression, we established a metastasizing murine xenograft model using CXCL5-overexpressing human melanoma cells. CXCL5 had no effect on melanoma proliferation in vitro and on primary tumor growth in vivo, but CXCL5-overexpressing tumors recruited high amounts of neutrophils and exhibited significantly increased lymphangiogenesis in our severe combined immune-deficient mouse model. Recruited neutrophils were found in close proximity to or within lymphatic vessels, often in direct contact with melanoma cells. Clinically, CXCL5-overexpressing melanomas had significantly increased lymph node metastases. We were able to translate these findings to human patient samples and found a positive correlation between CXCL5 expression, numbers of neutrophils in stage T4 primary melanoma, and the occurrence of subsequent locoregional metastasis.