VWF RELEASE AND PLATELET-AGGREGATION IN HUMAN-MELANOMA AFTER PERFUSION WITH TNF-ALPHA

Twenty-nine stage IIIA/B melanoma patients treated by isolated limb pe rfusion (ILP) with a high dose of recombinant human tumour necrosis fa ctor alpha (rHuTNF alpha), interferon gamma (IFN gamma), and melphalan were histologically documented with emphasis on therapy-induced chang es of the tumour vasculature. Sequential biopsies were taken at Variou s intervals before and after the treatment to compare the morphologica l changes. In order to visualize microvascular changes, immunostaining was performed for von Willebrand factor (VWF), type IV collagen, a-sm ooth muscle actin, endothelial antigen PAL-E, tissue factor, CD41 (thr ombocyte marker), and fibrin. In biopsies prior to perfusion, necrosis , haemorrhage, and fibrin thrombi were not found. Within 3 h following triple combination therapy, a change in the distribution of VWF stain ing occurred, from a discrete endothelial pattern in the untreated les ions to a fuzzy perivascular and subepidermal pattern in the treated l esions. Within 24 h, this was accompanied by intravascular thrombocyte aggregation and erythrostasis, in the absence of tissue factor and fi brin deposits. These findings indicate that the thrombocyte aggregatio n observed is not caused by local procoagulant activity, but is rather the result of the therapy-associated vascular damage or haemostasis. Although it is difficult to derive the dynamics of this process from s tatic images, we assume that TNF alpha induced endothelial cell damage , leading to VWF release. Released VWF may play a role in the adhesion between thrombocytes and the damaged endothelium or the denuded suben dothelium. As a consequence, the blood flow is impaired, leading to co ngestion and oedema, compatible with an early stage of haemorrhagic in farction.