Nogo-A expression in oligodendroglial tumors.

Nogo-A belongs to the reticulon protein family and is expressed in the inner and outer loops of myelin sheaths of oligodendrocytes. We analyzed the patterns of Nogo-A expression in human gliomas in an effort to identify a useful marker for the characterization of oligodendroglial tumors. We determined the expression of Nogo-A in a panel of 58 astrocytic and oligodendroglial tumors using immunohistochemistry and compared the expression of Nogo-A with Olig-2, a recently identified marker for oligodendrogliomas. To localize Nogo-A expression, immunofluorescent staining was performed using other glial markers (MAP-2 and GFAP). We also confirmed the overexpression of the Nogo-A protein in 53 astrocytic and oligodendroglial tumors using Western blot analysis. Based on immunohistochemical analysis, Nogo-A and Olig-2 had specificity in the detection of oligodendroglial tumors from astrocytic tumors (P=0.001). The level of Nogo-A staining was highly correlated with Olig-2 (P=0.001). The sensitivity and specificity of Nogo-A for oligodendroglial tumors was 86.9% and 57.1%, respectively. Nogo-A expression overlapped that of other oligodendroglial markers, but with different patterns of expression. Western blot analysis revealed that Nogo-A is predominantly expressed in 85.7% of oligodendroglioma cells and 93.7% of anaplastic oligodendroglioma cells. Like other oligodendroglial markers, Nogo-A is highly expressed in oligodendroglial tumors; however, it does not serve as a definite marker specific for oligodendroglial tumors.