Enhanced glial fibrillary acidic protein-δ expression in human astrocytic tumor

Astrocytic tumor is one of the most common primary tumors of the adult brain. Although there are several biochemical markers for the categorization of astrocytic tumor, few markers are used for histopathological diagnosis. Therefore, we evaluated glial fibrillary acidic protein (GFAP)-δ, a product of alternative splicing variants of GFAP-α, as a diagnostic marker. GFAP-δ immunoreactive (GFAP-δ+) astrocyte was rarely detected in tissue samples from autopsy controls. In tissue samples from patients with low-grade astrocytic tumor (grades I and II), GFAP-δ+ cells appeared stellate, polygonal or round shape. In tissue samples from patients with high-grade astrocytic tumor (grades III and IV), GFAP-δ+ cells showed round or spindle shape. GFAP-δ immunoreactivities in grades III and IV astrocytic tumor cells were increased by 1.4- and 1.7-fold in comparison to grade I astrocytic tumor cells. GFAP-δ immunoreactivity was also observed in cell bodies along the margins of astrocytic tumor showing normal histological findings, even though astroglia had normal morphology (showing strong GFAP and glutamine synthase immunoreactivities and a stellate shape with well-developed processes). Furthermore, the malignancy of astrocytic tumor was directly correlated with the degree of GFAP-δ immunoreactivity. These findings suggest that GFAP-δ may be a useful diagnostic marker for the evaluation of functional cataplasia or proliferation of astrocytic tumor.