Expression of phosphoprotein enriched in astrocytes 15 kDa (PEA-15) in astrocytic tumors: a novel approach of correlating malignancy grade and prognosis

Abstract

Phosphoprotein enriched in astrocytes 15 kDa (PEA-15) is a multifunctional protein that was first identified in brain astrocytes and that has subsequently been shown to be expressed in different tissues. Despite its many important roles, the clinical significance of PEA-15 expression levels in astrocytic tumors has yet to be properly defined. We studied the PEA-15 expression pattern of 65 patients [diagnosed according to World Health Organization (WHO) criteria] with diffuse astrocytoma (WHO grade II), anaplastic astrocytoma (grade III), and glioblastoma (grade IV). PEA-15 expression levels were immunohistochemically measured and categorized as no, low, or high expression. All tumors expressed PEA-15 in our study. Twenty-three (35.4%) and 42 (64.6%) tumors expressed low and high PEA-15 levels, respectively. In grade II astrocytoma (diffuse astrocytoma) and grade III astrocytoma (anaplastic astrocytoma), 100% and 88.9% of patients expressed high PEA-15 levels, respectively, while a smaller number (50%) of patients with grade IV astrocytoma (glioblastoma) expressed high PEA-15 levels. PEA-15 expression level was inversely associated with WHO grade (P = 0.0006). Next, we evaluated prognosis and PEA-15 expression levels in 43 patients with high-grade astrocytomas based on the following parameters: age, gender, WHO grade, surgical resection extent, MIB-1 labeling index (LI), and PEA-15 expression level. Multivariable analyses revealed that high PEA-15 expression level displayed a significant correlation with longer overall survival (OS) in high-grade astrocytomas (P = 0.0024). Patients with total resection survived significantly longer (P = 0.0044) than those with lower resection extent, while patients with MIB-1 labeling index ≤25% indicated significant (P = 0.0434) correlation with OS as well. In conclusion, PEA-15 expression level was inversely associated with WHO grade and may serve as an important prognostic factor for high-grade astrocytomas.