The specificity for IL13Rα2 (which is glioma-restricted) over the more broadly expressed IL13Rα1 is driven by a point mutation (E13Y) that gives a 50-fold higher affinity for IL13Rα2 and a 5-fold lower affinity for IL13Rα1/IL4Rα over wild-type IL13. This evidence concerns the gene IL13RA1 and central nervous system cancer.