Additionally, as the mouse IL‐4R/IL‐4 interaction is species‐specific in that mouse IL‐4 does cross‐react with human IL‐4R, we were unable to perform cytotoxicity assays with DABIL‐4, either against human breast cancer cell lines in vitro or with in vivo murine models of human breast cancer. The gene discussed is IL4R; the disease is breast carcinoma.