ERBB2 and breast cancer: Xu et al. (2015) showed that intratumoral delivery of IL-21 effectively reprograms TAMs from M2 to the M1 phenotype in breast cancer models. This phenotype switch rapidly stimulates T-cell responses and dramatically enhances therapeutic efficacy against HER2-positive tumors, suggesting its potential application in TNBC treatment (Xu et al., 2015).