The aim of this study is the characterisation of the expression of uPA, uPAR and PAI-1 in rat DS-sarcoma in vitro and in vivo (i.e., from tumour cell culture to the solid tumour), the identification of the main cellular source in solid DS-tumours and the examination of the dependency of uPA, uPAR and PAI-1 expression on micro-environmental factors such as oxygenation status. This evidence concerns the gene PLAU and neoplasm.