UROKINASE OVERPRODUCTION RESULTS IN INCREASED SKELETAL METASTASIS BY PROSTATE-CANCER CELLS IN-VIVO

We previously reported that urokinase (uPA) is produced by the human p rostate cancer cell line, PC-3, and could function as a growth factor for cells of the osteoblast phenotype. To examine the role of uPA in m etastasis to the skeleton and to extraskeletal sites, we have develope d a homologous model of uPA overexpression in a rat prostate cancer ce ll line. Full length cDNA encoding rat (r) uPA was isolated and subclo ned as a 1.4-kilobase, XbaI-BspHI fragment in the sense and antisense orientation into the Moloney murine leukemia retroviral vector pYN. Th e control (pYN) and experimental (pYN-ruPA, pYN-ruPA-AS) plasmids were transfected into Dunning R 3227, Mat LyLu rat prostate carcinoma cell s. Experimental clones expressing at least 5-fold higher (pYN-ruPA) or 3-fold lower (pYN-ruPA-AS) than controls were selected, and control a nd experimental cells were inoculated into the left ventricles of inbr ed male Copenhagen rats. Animals were sacrificed at timed intervals to examine the evolution of metastatic lesions. Control animals develope d metastases to the lumbar vertebrae resulting in spinal cord compress ion and hind limb paralysis at 20-21 days postinoculation. Animals ino culated with cells overexpressing uPA developed hind limb paralysis si gnificantly earlier (by day 14-15 postinoculation). Additionally, more widespread skeletal (ribs, scapula, and femora) metastases were seen. Serum from experimental animals showed a progressive elevation in alk aline phosphatase levels, and histological examination of lumbar metas tases revealed markedly increased osteoblastic activity over that obse rved in control animals. In contrast to this, animals inoculated with cells underexpressing uPA developed hind limb paralysis significantly later (days 25-29 postinoculation) and displayed decreased tumor metas tasis. These studies support a role for the catalytic domain of uPA in enhancing both skeletal and nonskeletal prostate cancer invasiveness and are consistent with a role for the growth factor domain of uPA in mediating an osteoblastic skeletal response.