Osteopontin Expression is a Marker of Poor Prognosis in Patients with Clear Cell Renal Cell Carcinoma.

Osteopontin (OPN) is a phosphorylated glycoprotein that is secreted into the extracellular matrix by a variety of cell types and has diverse functions which include enhancement of tumourogenesis and tumour progression in a variety of human tumours. Here, Matusan and colleagues examine the expression of OPN in human clear cell renal cell carcinoma (RCC).

The authors performed immunohistochemistry for OPN on 171 specimens of clear cell RCC. Of note, OPN is expressed by the distal tubular epithelium in the normal kidney. Mean tumour size was 7 cm, median follow up was 85 months (range 1-165), and 68.4% of tumours were organ confined. The authors found that OPN expression was increased in 35.7% of patients with clear cell RCC and was associated with increased tumour size (p less than 0.001), higher grade (p less than 0.001), advanced tumour stage (p=0.011), and a higher Ki67 proliferation index (less than 0.001). The 5 year overall survival was 71% for patients without OPN staining, and only 40% for patients that were positive for OPN (p=0.004). Despite these findings, only pathologic stage (p=0.013) predicted survival in their multivariate analysis. The authors conclude that OPN is a marker of progression in clear cell RCC and that overexpression may be involved in the molecular events that result in RCC progression. (Source: Journal of Surgical Oncology : December 2006.)