Osteopontin: A Ras-Regulated Gene That Contributes to Tumor Metastasis

Osteopontin (OPN) is a secreted, integrin-binding protein, which has been implicated in a variety of 〉stress-responsive= pathologies. In this review, we focus primarily on the possible roles for OPN in cancer. We will not attempt to provide a comprehensive review of all aspects of OPN. We instead will summarize findings from our laboratory which implicate OPN in tumor progression and metastasis, and which suggest that OPN levels in both tumors and bloodplasma from cancer patients may have clinical value as a marker for metastasis and poor patient prognosis.