We found that IL1R2‐neutralizing antibody pretreatment also inhibited BC cell tumorigenesis and BTIC population in vivo (Figure 6E–G; Figure S7D,E, Supporting Information), although the cell group pretreated with 3 μg mL−1 antibody showed no significant advantage over the 1 μg mL−1 pretreated group. Here, IL1R2 is linked to breast cancer.