Prevention of prostate‐cancer metastasis in vivo by a novel synthetic inhibitor of urokinase‐type plasminogen activator (uPA)

Abstract

Urokinase-type plasminogen activator (uPA) is a serine protease associated with tissue remodeling, cellular invasiveness, matrix degradation and tumor growth. Over-expression of uPA by the rat prostate-cancer cell line Dunning R3227, Mat LyLu, results in increased tumor metastasis to several non-skeletal and skeletal sites. Histological examination of these skeletal lesions has shown them to be primarily osteoblastic. In the present study we examined the capacity of a selective inhibitor of uPA enzymatic activity, 4-iodo benzo[b]thiophene-2-carboxamidine (B-428), to prevent the development of tumor growth and invasiveness in a syngeneic model of rat prostate cancer using a Dunning R3227 cell line over-expressing rat uPA. Male Copenhagen rats were inoculated s.c. with experimental cells into the right flank and continuously infused i.p. with either vehicle alone or uPA inhibitor for 2 to 3 weeks. Animals were killed at timed intervals and evaluated for the development of tumor growth and metastasis. Serum from these animals was collected to examine any signs of nephrotoxicity. Control animals receiving vehicle alone developed large tumors at the site of inoculation as well as macroscopic metastases in the lungs, kidney, spleen and lymph nodes. In contrast, experimental animals receiving uPA inhibitor showed a marked decrease in primary tumor volume and weight as well as in the development of tumor metastases. The occasional tumor metastases observed after infusion of B-428 were significantly smaller than those observed in vehicle controls. These effects of B-428 were found to be dose-dependent without any adverse effects on the renal function of experimental animals. These studies demonstrate that uPA-specific inhibitors can decrease primary tumor volume and invasiveness as well as metastasis in a model of prostate cancer where uPA has been implicated as a major pathogenetic factor.

Suppression of EGF-R signaling reduces the incidence of prostate cancer metastasis in nude mice

“…uPA-R is the best known modulator of uPA activation and it is expressed both by invasive PCa cells and normal osteoblasts (Rabbani et al 1994). The basic importance of the uPA/uPA-R system in the determination of PCa bone metastases has been clearly demonstrated in experimental animal models by the use uPA and uPA-R inhibitors (Rabbani et al 1995, Margheri et al 2005. Recently, some authors have suggested an important correlation between the function of the uPA/uPA-R system and EGF-R activation.…”

Proteinase Activity in Human and Murine Saliva as a Biomarker for Proteinase Inhibitor Efficacy

“…As the third drug, we have used an inhibitor of a serine proteinase, the urokinase inhibitor B428 (12). Like the MMPIs, B428 has shown some antitumor efficacy in preclinical models (13,14). However, clear indications that any of these drugs do indeed inhibit their target proteinases when administered systemically have not previously been presented.…”

Plasminogen promotes sarcoma growth and suppresses the accumulation of tumor-infiltrating macrophages

“…The direct causal relationship between Plg activator expression and tumor progression was furthermore demonstrated in a number of studies using the chick chorio-allantoic membrane metastasis model, and the mouse spontaneous and experimental metastasis models. These studies have employed a variety of strategies to inhibit Plg activator function including antisense RNA techniques (Kook et al, 1994;Yu and Schultz, 1990), anti-catalytic Plg activator antibodies (Hearing et al, 1988;Kobayashi et al, 1994b;Ossowski, 1988;Ossowski and Reich, 1983), natural and synthetic Plg activator inhibitors or uPAR antagonists (Crowley et al, 1993;Kobayashi et al, 1994a;Min et al, 1996;Mueller et al, 1995;Rabbani et al, 1995), and, lately, also genetically engineered mice with targeted deficiencies in components of the PA system (Bugge et al, 1997(Bugge et al, , 1998Sabapathy et al, 1997;Shapiro et al, 1996). Collectively, these studies have firmly established the PA system as an important contributor to tumor progression.…”