However, considering that NFκB signaling plays an important role in BC progression16 and GO analysis showed that genes positively regulating NFκB signaling were enriched in PDX BTIC population (Figure S4A, Supporting Information), we speculated that IL1R2 regulated BTIC through an intracellular mechanism but not via its interruption to the IL1‐mediated NFκB signaling. Here, IL1A is linked to breast cancer.