In order to begin to understand why uPAR might be enriched in lymph node metastases, we directly compared uPAR overexpressing (uPAR+) cells with wild-type cells in vitro in assays designed to mimic some of the processes required for successful invasion We introduced uPAR into PC-3M cells by transient tranfection; this method produced a fraction of uPAR+ cells accompanied by a majority of wild-type uPAR-expressing PC-3M, which was analogous to our observation in the orthotopic tumor. This evidence concerns the gene PLAUR and neoplasm.