Analysis of interleukin-13 receptor α2 expression in human pediatric brain tumors

BACKGROUND. Compared with normal brain tissue cells, human malignant glioma cells express higher levels of interleukin-13 receptor (IL-13R). However, whether this receptor is expressed in situ has not been carefully examined. With IL-13R-targeted cytotoxin (IL13-PE38QQR, comprising IL-13 and a mutated form of Pseudomonas exotoxin [PE]) being tested in three Phase I/II clinical trials for the treatment of adult human glioma, and with pediatric studies being planned, the authors set out to analyze pediatric brain tumor tissue specimens for the expression of IL-13R. METHODS. Using in situ hybridization and immunohistochemical staining, the authors examined 58 pediatric brain tumor specimens for expression of the predominant IL-13 binding and internalizing protein (IL-13Rα2) chain at the mRNA and protein levels. RESULTS. Overall, approximately 83% of pediatric brain tumor samples expressed IL-13Rα2. One hundred percent (11 of 11) high-grade astrocytoma, 79% (26 of 33) low-grade astrocytoma, 67% (4 of 6) medulloblastoma, and 67% (2 of 3) ependymoma samples were positive for IL-13Rα2. Among IL-13Rα2-positive samples, 88% (42 of 48 samples) had positive expression in ≥ 50% of all tumor fields. The results obtained using both assays were consistent with each other. CONCLUSIONS. The current study established that pediatric brain tumor specimens expressed the IL-13Rα2 chain. Because the IL-13Rα2 chain is a major binding component of the IL-13R complex, these results suggest that the targeting of IL-13R may represent a useful approach for the treatment of pediatric brain tumors.