Identification of interleukin-13 receptor 2 chain overexpression in situ in high-grade diffusely infiltrative pediatric brainstem glioma

¹ Tumor Vaccines and Biotechnology Branch, Division of Cellular and Gene Therapies, Office of Cellular, Tissue, and Gene Therapies, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Bethesda, MD, USA
² Division of Biostatistics and Epidemiology, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Bethesda, MD, USA
³ Brain Tumor Program, St. Jude Children's Research Hospital, Memphis, TN, USA

^* To whom correspondence should be addressed. E-mail: raj.puri{at}fda.hhs.gov.

	Abstract

Human malignant glioma cell lines and adult brain tumors overexpress high levels of interleukin-13 receptor 2 chain (IL-13R2). Because the IL-13R2 chain is an important target for cancer therapy and prognosis for patients with brainstem glioma (BSG) remains dismal, we investigated the expression of this receptor in specimens of diffusely infiltrative pediatric BSG relative to normal brain tissue. Twenty-eight BSG specimens and 15 normal brain specimens were investigated for IL-13R2 protein expression by immunohistochemical analysis (IHC) using two different antibodies in two different laboratories. Highly sensitive Q-dot-based IHC and in situ hybridization (ISH) assays were also developed to identify IL-13R2 protein and RNA in these specimens. The results were evaluated independently in two laboratories in a blinded fashion. By Q-dot IHC or a standard IHC assay, 17 of 28 (61%) tumor specimens showed modest to strong staining for IL-13R2, while 15 normal brain tissue samples showed weak expression for IL-13R2 protein. Significant interrater agreement between the two laboratories was seen in the assessment of IL-13R2 intensity. High-level IL-13R2 RNA expression was detected in tumor samples by Q-dot ISH, but only weak RNA expression was observed in normal brain. Significant agreement between ISH and IHC assays was observed (simple kappa [] estimate = 0.358, weighted = 0.89, p = 0.001). IL-13R2 protein and mRNA are expressed to significantly higher levels in BSG than in normal brain tissue. Both IHC and ISH represent robust methods to detect expression of the IL-13R2 receptor in BSG that could represent an important new drug target for treatment of this disease.

Key Words: brainstem glioma, IL-13 receptor 2, immunohistochemical analysis (IHC), in situ hybridization (ISH), pediatric tumors