Expression of therapeutic targets in Ewing sarcoma family tumors

Abstract

Ewing sarcoma family tumor is an aggressive malignant tumor of bone and soft tissue in children and adolescents. Despite advances in modern therapy, metastasis occurs in 20% to 25% of cases and results in mortality in 80% of patients. Intracellular molecules mammalian target of rapamycin, Akt, vascular endothelial growth factor, nuclear factor κB, and BRAF are important kinases and transcription factors that regulate the proliferation of tumor cells. We studied the expression of these proteins in 72 Ewing sarcoma family tumors. Patients' survival data were available in 55 cases. Formalin-fixed, paraffin-embedded tumor sections were stained with antibodies against phosphorylated mammalian target of rapamycin, Akt, BRAF, vascular endothelial growth factor, and nuclear factor κB proteins. Stained sections were analyzed for percentage and strength of staining, and a composite score (0-200) was subsequently generated. Although most tumors expressed mammalian target of rapamycin, Akt, nuclear factor κB, and vascular endothelial growth factor, only 37%, 86%, 55%, and 12%, respectively, showed high expression (staining score ≥ 100). There was no significant correlation between mammalian target of rapamycin and Akt expression and clinical outcome. High nuclear factor κB expression was significantly associated with tumors in pelvic locations. Decreased vascular endothelial growth factor expression (score <100) was significantly associated with better prognosis (P < .05). BRAF was not expressed in most cases and showed negative or weak staining (score <100) in 97% of cases. Thus, except for BRAF, Ewing sarcoma family tumors may be amenable to treatment that targets the expressed proteins. High Akt expression suggests potential universal response to Akt-targeted therapy. BRAF kinase inhibitors are unlikely to be effective in the treatment of Ewing sarcoma family tumors.