Effects of synthetic urokinase inhibitors on local invasion and metastasis in a murine mammary tumor model

Abstract

Urokinase-type plasminogen activator (uPA) initiates an extracellular proteolytic cascade with which invasive cells eliminate barriers to movement. We have evaluated the antiinvasive and antimetastatic properties of two recently developed synthetic uPA inhibitors, B428 and B623, in a BALB/c mouse mammary carcinoma model. We used the F3II and M3 tumor cell lines, previously described by our laboratory. In vitro, noncytotoxic concentrations of B428 or B623 inhibited secreted and cell-associated uPA activity produced by tumor cells and blocked uPA-mediated whole tumor cell degradation of fibronectin, allowing deposition of extracellular fibronectin fibrils. In vivo, administration of compounds was not associated with overt toxic effects. Daily i.p. treatment with B428 (20 mg/kg/day) or B623 (7.5 mg/kg/day) for 2 weeks, beginning after tumor take, markedly blocked the invasion of the muscle and adipose layers of the subcutis and dermis in mice bearing highly invasive F3II tumors. However, these compounds neither inhibited tumor-induced angiogenesis nor reduced the incidence of spontaneous lung metastasis. Moreover, B623 enhanced the formation of experimental lung metastasis. Our results suggest that synthetic uPA inhibitors act as potent antiinvasiveness agents in vivo but may be unable to control progression of the metastatic disease in the present mammary tumor model.

Fibronectin is distinctly downregulated in murine mammary adenocarcinoma cells with high metastatic potential

“…We had previously found, in coincidence with the present results, that MM3 tumor secretes about 3-to 4-fold more uPA than M3 (14). Furthermore, the critical role of uPA in the invasive phenotype of this mammary tumor model was also demonstrated in vivo (31). The present analysis revealed that several members of the TGFßs/TßRs system [TGFß2, TGFß receptor 1 (TßR-1), TGFß receptor type III] were coordinately upregulated in MM3 adenocarcinoma.…”

Modulation of urokinase-type plasminogen activator and metalloproteinase activities in cultured mouse mammary-carcinoma cells: Enhancement by paclitaxel and inhibition by nocodazole

“…Secreted tumor-derived protease activity was investigated in conditioned media, as reported (Alonso et al, 1996a). Semiconfluent tumor cells grown in 24-well plates were cultured for 24 hr in MEM plus 5% FBS, in the presence and the absence of paclitaxel (4 µM) or nocodazole (1 µM).…”

“…The radial caseinolytic assay, using plasminogen-rich caseinagarose plates, described by Saksela (1981), was employed to quantify uPA activity in conditioned media, as described in detail (Alonso et al, 1996a). Secreted uPA activity was referenced to a standard urokinase curve (0.2 to 50 IU/ml) and normalized to 10 6 cells and to a 24-hr or 1-hr incubation period.…”

Regulation of hepatocyte growth factor-mediated urokinase plasminogen activator secretion by MEK/ERK activation in human stomach cancer cell lines

“…In addition, studies performed with both in vitro and in vivo experimental models have demonstrates that the levels of uPA are closely associated with the degree of tumor cell invasion (Xing et al, 1996). Blocking uPA expression or disruption of uPA binding to uPAR has been found to significantly inhibit tumor cell invasion and metastasis in various tumor models (Alonso et al, 1996;Kriiger et al, 2000). From these facts, it is apparent that uPA plays a key role in tumor progression and metastasis.…”