The aim of this study was to investigate the effect of inhibiting αvβ(3)/α(v) 
β(5) integrins by cilengitide in experimentally induced breast cancer bone 
metastases using noninvasive imaging techniques. For this purpose, nude rats 
bearing established breast cancer bone metastases were treated with cilengitide, 
a small molecule inhibitor of αvβ(3) and αvβ(5) integrins (75 mg/kg, five days 
per week; n = 12 rats) and compared to vehicle-treated control rats (n = 12). In 
a longitudinal study, conventional magnetic resonance imaging (MRI) and flat 
panel volumetric computed tomography were used to assess the volume of the soft 
tissue tumor and osteolysis, respectively, and dynamic contrast-enhanced (DCE-) 
MRI was performed to determine functional parameters of the tumor vasculature 
reflecting blood volume and blood vessel permeability. In rats treated with 
cilengitide, VCT and MRI showed that osteolytic lesions and the respective bone 
metastatic soft tissue tumors progressed more slowly than in vehicle-treated 
controls. DCE-MRI indicated a decrease in blood volume and an increase in vessel 
permeability and immunohistology revealed increased numbers of immature vessels 
in cilengitide-treated rats compared to vehicle controls. In conclusion, 
treatment of experimental breast cancer bone metastases with cilengitide 
resulted in pronounced antiresorptive and antitumor effects, suggesting that 
αvβ(3)/αvβ(5) inhibition may be a promising therapeutic approach for bone 
metastases.