IL13RA2 and breast cancer: Recently, CHI3L1 has been shown to bind the IL‐13Rα2 receptor expressed on gastric and breast cancer cells, thereby promoting metastasis of these tumor cells.21 These investigators showed that the binding of CHI3L1 to IL‐13Rα2 results in the recruitment of AP (activator protein)‐1 family members, which include several transcription factors important for tumor invasiveness as well as matrix metalloproteases.