This recombinant immunotoxin consists of a circularly permutated IL-4 and a mutated form of Pseudomonas exotoxin [termed IL4 (38-37)-PE38KDEL, cpIL4-PE], which shows highly specific cytotoxicity to IL-4Rα-positive tumor cells in vitro [17, 26, 27]. This evidence concerns the gene IL4 and neoplasm.