Evaluation of osteopontin as a potential biomarker for central nervous system embryonal tumors

Osteopontin (OPN) is a protein linked to tumor growth, progression and metastasis of cancers. However, its role in the progression of central nervous system (CNS) embryonal tumors such as atypical teratoid/rhabdoid tumor (AT/RT), medulloblastoma (MB) and primitive neuroepithelial tumors (PNET) remains elusive. In this study, we investigated the value of OPN staining in differential diagnosis of AT/RT from MB and PNET, and assessed the correlation between OPN expression and patients' prognosis. This retrospective study was conducted on tissue sections obtained from children cases with CNS embryonal tumors treated in Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine from 2006 to 2012 by immunohistochemistry (IHC). 49 cases were collected (11 AT/RTs, 25 MBs, and 13 PNETs), with a median follow-up time of 28.9 months. OPN expression in AT/RT was significantly higher than MB and PNET with the positive rates of 100, 32, and 23 %, respectively (P < 0.01). The specificity and sensitivity of OPN staining in diagnosing AT/RT are 97.4 and 90.9 %, respectively, as judged by strong OPN IHC staining level (+++). Patients who had positive OPN staining have increased risks of poorer median overall survival (hazard risk 5.54, 95 % CI 1.87-16.38) and tumor progression (hazard risk 14.47, 95 % CI 4.47-46.85). OPN is a valuable biomarker to aid in the differential diagnosis between AT/RT and MB/PNET. Moreover, OPN is a potential novel prognostic marker for CNS embryonal tumors.