Advances in Brief ERBB Receptor Signaling Promotes Ependymoma Cell Proliferation and Represents a Potential Novel Therapeutic Target for This Disease

Purpose: This study was designed to investigate the biological and therapeutic significance of ERBB1, ERBB2, ERBB3, and ERBB4 in childhood ependymoma. Experimental Design: The expression frequency and clinical significance of ERBB1–4 was analyzed in a large cohort of pediatric ependymoma (n 121) using immunohistochemistry, Western blotting, and reverse transcriptionPCR analysis. Histological markers of anaplasia (necrosis, microvascular proliferation, and Ki-67 proliferative index) were also determined. Functional assessment of ERBBdependent cell signaling and proliferation, in addition to novel therapeutic inhibition of these processes, was conducted using short-term cultures of human ependymoma cells. Results: Coexpression of ERBB2 and ERBB4 was identified in over 75% of tumors. High-level coexpression of these receptors was significantly related to tumor proliferative activity [P < 0.05; Ki-67 labeling index (LI)] and, in combined survival analysis of clinical (degree of surgical resection) and molecular (ERBB2/ERBB4 expression status and Ki-67 LI) factors, enabled a greater resolution of patient prognosis than any individual variable alone. Ligand-dependent activation of ERBB receptor-signaling in cultured ependymoma cells resulted in AKT phosphorylation and cellular proliferation that was significantly blocked in a dose-dependent manner using WAY-177820, a novel inhibitor of ERBB2 tyrosine kinase activity. Conclusions: This study suggests that ERBB receptor signaling results in aggressive disease behavior in ependymoma by promoting tumor cell proliferation. An analysis of ERBB2 and ERBB4 expression, in association with Ki-67 LI and the degree of surgical resection, may provide an accurate tool for assessing disease risk in children with this disease. In addition, these receptors may serve as a target for novel therapeutic approaches in ependymoma.