IL13RA1 and neoplasm: Interestingly, IL-13Rα1, which is not overexpressed in great abundance compared to IL-13Rα2 in solid tumors, is another binding protein to its ligand IL-13 that has recently been observed to co-exist with Kirsten rat sarcoma KRAS in pancreatic cancer cells supporting a pro-tumorigenic tumor microenvironment [27].