Christoph C. Geilen

Sphingosine kinase activity counteracts ceramide-mediated cell death in human melanoma cells: role of Bcl-2 expression

While most of the pharmacological therapies for melanoma utilize the apoptotic machinery of the cells, the available therapeutic options are limited due to the ability of melanoma cells to resist programmed cell death. Human melanoma cell lines A-375 and M186 are sensitive to ceramide- and Fas-induced cell death, while Mel-2a and M221 are resistant. We have now found that Mel-2a and M221 cells have a significantly higher ceramide/sphingosine-1-phosphate (S1P) ratio than A-375 and M186 cells. As sphingosine kinase (SphK) type 1 plays a critical role in determining the dynamic balance between the proapoptotic sphingolipid metabolite ceramide and the prosurvival S1P, we examined its role in apoptosis of melanoma cells. Increasing SphK1 expression reduced the sensitivity of A-375 melanoma cells to Fas- and ceramide-mediated apoptosis. Conversely, downregulation of SphK1 with small interfering RNA decreased the resistance of Mel-2a cells to apoptosis. Importantly, overexpression of the prosurvival protein Bcl-2 in A-375 cells markedly stimulated SphK1 expression and activity, while downregulation of Bcl-2 reduced SphK1 expression. This link between Bcl-2 and SphK1 might be an additional clue to chemotherapy resistance of malignant melanoma.

New caspase-independent but ROS-dependent apoptosis pathways are targeted in melanoma cells by an iron-containing cytosine analogue

Chemotherapy resistance and related defects in apoptotic signaling are crucial for the high mortality of melanoma. Effective drugs are lacking, also due to the fact that apoptosis regulation in this tumor is essentially not understood. The cytosine analogue ferropoptoside (N69), which contains an iron carbonyl complex, resulted in strong induction of apoptosis in melanoma cells starting already after 2h, whereas cytotoxicity remained at a low level. Surprisingly, there was no indication for any caspase activation at early times, although cytochrome c was released from mitochondria. Indicative for new proapoptotic pathways was the production of reactive oxygen species (ROS) as an early effect, and the inhibition of apoptosis by the antioxidant vitamin E. Apoptosis was also blocked by exogenous Bcl-2 overexpression and by the pan-protease inhibitor zVAD. However, only zVAD also prevented ROS production, for which Bcl-2 remained without an effect. Thus, new proapoptotic pathways are described here for melanoma cells clearly related to ROS production. A cascade enclosing enhanced levels of intracellular iron, which lead to enhanced ROS production in a Fenton reaction, appears as suggestive. Whereas off-target effects of zVAD appear as upstream, Bcl-2 may exert its inhibitory activity downstream of ROS. New proapoptotic pathways are of particular interest for melanoma as they may open new options for targeting this highly therapy-refractory tumor.

Conditional expression of exogenous Bcl-XS triggers apoptosis in human melanoma cells in vitro and delays growth of melanoma xenografts

The Bcl‐2‐related proteins Bcl‐XL and Bcl‐XS represent alternative splice products and exert opposite activities in the control of apoptosis, but their significance for melanoma is not yet clear. Applying the tetracycline‐inducible expression system Tet‐On, we found overexpression of Bcl‐XS by itself sufficient to induce apoptosis in vitro in stably transfected human melanoma cell lines. Combination with proapoptotic agents such as etoposide, pamidronate, and ceramide resulted in additive proapoptotic effects, whereas Bcl‐XL protected from apoptosis caused via CD95/Fas stimulation. In nude mice growth of melanoma xenotransplants derived from stably transfected cells was significantly reduced after induction of Bcl‐XS by doxycycline. Our results indicate that Bcl‐X proteins are of major importance for control of apoptosis in malignant melanoma.

Angiolymphoid hyperplasia with eosinophilia—an incidental finding after surgical excision

SummaryAngiolymphoid hyperplasia with eosinophilia (ALHE) is a rare benign vasoproliferative lesion. Although it is a benign disease, lesions are often persistent and difficult to eradicate. ALHE typically presents clinically as papules or nodules, tan, brown, pink or dull red in colour, located predominantly in the head and neck region, especially around the ears and on the forehead and scalp.All races can be affected and no gender predominance exists. The disease also has nonspecific clinical features, hence it requires in most of the cases biopsy for accurate diagnosis. We present an uncommon clinical presentation of the disease, mimicking clinically a subcutaneous lipomatous mass, which has been treated successfully with surgical excision.ZusammenfassungDie angiolymphoide Hyperplasie mit Eosinophilie (ALHE) ist eine seltene, gutartige, vasoproliferative Krankheit. Obwohl sie gutartig ist, so persistieren die Veränderungen häufig und sind schwer, vollkommen zu beseitigen. Klinisch zeigt sich die ALHE typischerweise als bräunliche, rosa oder rötliche Papeln oder Knoten, die vorwiegend in der Kopf-Hals-Region, besonders periaurikulär, der Stirn und dem behaarten Kopf zu finden sind.Alle Rassen können betroffen sein und es exsistieren keine geschlechtsspezifischen Unterschiede. Da die Erkrankung auch klinisch unspezifisch in Erscheinung tritt, benötigt man in den meisten Fällen eine histologische Sicherung der Diagnose.Wir stellen hier eine ungewöhnliche klinische Manifestation der Erkrankung vor, die klinisch sich wie ein Lipom verhielt und erfolgreich durch chirurgische Exzision behandelt wurde.

Hepoxilin A3 (HXA3) synthase deficiency is causative of a novel ichthyosis form

Non‐bullous congenital ichthyosis erythroderma (NCIE) and lamellar ichthyosis (LI) are characterized by mutations in 12R‐lipoxygenase (12R‐LOX) and/or epidermal lipoxygenase 3 (eLOX3) enzymes. The eLOX3 lacks oxygenase activity, but is capable of forming hepoxilin‐type products from arachidonic acid‐derived hydroperoxide from 12R‐LOX, termed 12R‐hydroperoxyeicosa‐5,8,10,14‐tetraenoic acid (12R‐HpETE). Mutations in either of two enzymes lead to NCIE or LI. Moreover, 12R‐LOX‐deficient mice exhibit severe phenotypic water barrier dysfunctions. Here, we demonstrate that 12R‐HpETE can also be transformed to 8R‐HXA3 by hepoxilin A3 (HXA3) synthase (12‐lipoxygenase), which exhibits oxygenase activity. We also presented a novel form of ichthyosis in a patient, termed hepoxilin A3 synthase‐linked ichthyosis (HXALI), whose scales expressed high levels of 12R‐LOX, but were deficient of HXA3 synthase.