ERBB2 and cancer: In addition to tumor cells, the presence of cancer‐associated fibroblasts (CAFs), endothelial cells (ECs), and immune cells were included in the system to better reproduce the tumor microenvironment.[81] This advanced breast CoC model enabled the recapitulation of human epidermal growth factor 2 (HER2) overexpression in HER2‐positive breast cancers, a key target for TCT.[81] Another breast CoC identified the epidermal growth factor receptor (EGFR) as a key target for anticancer treatment and inhibiting growth and migration.[89]