No abstract

Equine melanoma shows striking features particularly with regard to clinical development in grey horses: in contrast to malignant melanoma in humans and in solid coloured horses that are characterized by early onset of metastasis, pigment cell tumours display almost benign clinical features in ageing grey horses. Through evolution, grey horses appear to be in a favourable position in regard to the biological behaviour of melanomas. Yet unknown factors inhibiting or retarding early melanoma metastasis may be responsible for this phenomenon. In this study, immunostaining profiles and histopathologic patterns of equine vs. human melanotic tumours were compared. In addition, the expression of melanoma markers currently used in human melanoma detection and characterization were evaluated for their applicability in equine melanoma diagnosis. Immunohistopathologic investigations revealed that benign grey horse melanomas share common features with human blue nevi and with human malignant desmoplastic melanomas, whereas their resemblance to other types of human cutaneous malignant melanomas is less pronounced. Our data equally underline that S-100, proliferating cell nuclear antigen (PCNA), HMB-45, Ki-67, T-311 and CD44 can serve as reliable markers for horse melanomas. Further investigations aiming at identifying factors retarding metastasis in affected grey horses are needed, as they may contribute to the development of novel treatment strategies for human malignant melanoma.

Abstract-Impaired response to catecholamines contributes to the altered hemodynamics in sepsis, which has been attributed to excessive NO formation. We have studied the systemic hemodynamic and local forearm responses and inducible NO synthase (iNOS) expression during experimental endotoxemia in humans. Escherichia coli endotoxin (lipopolysaccharide [LPS]) was administered at doses of 1 or 2 ng/kg to healthy volunteers. In 10 subjects, the systemic pressor effect of phenylephrine was assessed before and after the administration of LPS. In 9 further subjects, forearm blood flow responses to intra-arterial noradrenaline, acetylcholine, glyceryl trinitrate, and N G -monomethyl-L-arginine (L-NMMA) were studied at baseline and after LPS administration. Peripheral blood was collected and analyzed for iNOS mRNA and protein. Four hours after LPS, the response of systolic blood pressure (PϽ0.0005) and heart rate (PϽ0.05) to phenylephrine was significantly reduced. In the forearm, noradrenaline-induced vasoconstriction was also reduced by Ϸ50% (PϽ0.01), but L-NMMA responsiveness was unchanged. iNOS mRNA or protein was not increased. Marked vascular adrenoceptor hyporeactivity is detectable in the absence of increased NO activity or iNOS expression in endotoxemia, arguing against major involvement of vascular iNOS activity in the acute systemic vasodilation to LPS. Key Words: inducible nitric oxide synthase Ⅲ nitric oxide Ⅲ sepsis Ⅲ lipopolysaccharide Ⅲ adrenoceptors S epsis is still associated with a high mortality rate and remains a major therapeutic challenge despite improved intensive care therapy. 1 One of the key clinical aspects of sepsis, which is responsible for the poor hemodynamic state of these patients, is inappropriate vasodilation and impaired response to catecholamines, 2 resulting in hemodynamic instability and shock.A variety of substances and mediators is released by activated blood cells and endothelial cells during sepsis. 2,3 Many in vitro and in vivo animal experiments have indicated that excess formation of nitric NO in the vasculature may play the key role in the systemic vasodilation in sepsis and endotoxemia. These data suggest that most of the NO produced is formed after the induction of an inducible form of NO synthase (iNOS), which is not expressed in the vasculature under normal conditions. 4 iNOS can be induced in a variety of cells, such as vascular endothelial cells, vascular smooth muscle cells, and white blood cells (WBCs) after in vitro stimulation with endotoxin 5 and remains present for several days. Inhibition of NO synthesis in animals by NO synthase inhibitors reduces Escherichia coli endotoxin (lipopolysaccharide [LPS])-induced hypotension and vascular leakage and improves mortality. 6 -8 Experiments with iNOS knockout animals 9 and animals treated with iNOS antisense oligonucleotides 10 corroborated these pharmacological studies.Data on iNOS expression in humans are limited. A recent study did not detect iNOS in cells or vessels of the systemic circulation in septic patients but...

During past decades, knowledge of melanoma biology has increased considerably. Numerous therapeutic modalities based on this knowledge are currently under investigation. Advanced melanoma, nevertheless, remains a prime example of poor treatment response that may, in part, be the consequence of activated N-Ras oncoproteins. Besides oncogenic Ras, wild-type Ras gene products also play a key role in receptor tyrosine kinase growth factor signaling, known to be of importance in oncogenesis and tumor progression of a variety of human neoplasms, including malignant melanoma; therefore, it is reasonable to speculate that a pharmacological approach that curtails Ras activity may represent a sensible approach to inhibit melanoma growth. To test this concept, the antitumor activity of S-trans, trans-farnesylthiosalicylic acid (FTS), a recently discovered Ras antagonist that dislodges Ras from its membrane-anchoring sites, was evaluated. The antitumor activity of FTS was assessed both in vitro and in vivo in two independent SCID mouse xenotransplantation models of human melanoma expressing either wild-type Ras (cell line 518A2) or activated Ras (cell line 607B). We show that FTS (5-50 M) reduces the amounts of activated N-Ras and wild-type Ras isoforms both in human melanoma cells and Rat-1 fibroblasts, interrupts the Rasdependent extracellular signal-regulated kinase in melanoma cells, inhibits the growth of N-Ras-transformed fibroblasts and human melanoma cells in vitro and reverses their transformed phenotype. FTS also causes a profound and statistically significant inhibition of 518A2 (82%) and 607B (90%) human melanoma growth in SCID mice without evidence of drug-related toxicity. Our findings stress the notion that FTS may qualify as a novel and rational treatment approach for human melanoma and possibly other tumors that either carry activated ras genes or rely on Ras signal transduction more heavily than nonmalignant cells.A dvanced human melanoma is the most malignant type of skin cancer and remains a paradigm of poor treatment response intrinsically linked to poor prognosis (1, 2). Although a multitude of factors have been suspected to play a role in melanoma growth and progression (1-4), the most common specific gene defects identified in this tumor are activating mutations in ras genes. The 15% incidence of ras gene mutations in human melanoma represents predominantly alterations in N-ras at codon 61 (3-6), whereas Ha-ras and K-ras mutations are rare (3-6). The high frequency of this particular mutational hotspot (codon 61) in the N-ras gene basically excludes the possibility of its incidental nature and suggests the involvement of the constitutively active N-Ras protein encoded by the mutated gene in the oncogenesis of human melanoma (6). More recent studies have shown that activated N-Ras confers chemoresistance to human melanoma because expression decreases chemotherapy-induced apoptosis in melanoma xenotransplantation models (7). Because Ras proteins are regulators of multiple signaling pathways that contro...