A selective anti-urokinase receptor (uPAR) antibody (ATN-658) blocks prostate cancer growth, migration, invasion and skeletal metastasis in vitro and in vivo Free

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Over expression of urokinase plasminogen activator (uPA) and its receptor (uPAR) have been strongly correlated with poor prognosis in many cancers including prostate cancer. uPAR is a multi-functional protein that interacts with uPA and integrins to activate various intracellular signaling pathways that mediate tumor cell proliferation, migration and invasion and promote the multi-step process of tumor growth and metastasis. We have developed and characterized a monoclonal anti-uPAR antibody (ATN-658), which is currently being humanized and will enter preclinical development in the near future, that does not block the binding of uPA to uPAR but affects uPAR-dependent downstream signaling cascades and tumor growth and metastasis.

In the current study we evaluated the ability of ATN-658 to effect prostate cancer growth, invasion and metastasis in various in vitro and in vivo models. Treatment of human prostate cancer cells PC-3 with ATN-658 resulted in a dose dependent inhibition of tumor cell proliferation, migration and invasion in vitro. Western blot analysis showed that ATN-658 treatment decreased the phosphorylation of MAPK, FAK and Vimentin without effecting total MAP and FAK expression. For in vivo studies, PC-3 cells (1x10⁵) were inoculated in the right flank or directly into the tibia of male BALB/c nu/nu mice. Animals were treated intraperitoneally with vehicle alone or ATN-658 (10mg/kg) twice weekly. Treatment with ATN-658 caused a significant decrease in tumor volume in both subcutaneous and intratibial tumors. However, ATN-658 was more effective in reducing the number and area of skeletal lesions as determined by X-ray analysis using Faxitron, µCT and bone histomorphometric analysis. Immunohistochemical analysis of control and experimental tumors showed a marked decrease in the levels of pMAPK, pFAK, and Vimentin without effecting total MAPK and FAK expression. Collectively these results provide compelling evidence for the continued development of ATN-658 as a potential therapeutic agent for patients with various malignancies associated with skeletal metastasis (breast, prostate) where the uPA/uPAR system plays a major role in tumor progression.