(2) Therapeutic antibody synergy: CAR-NK cells targeting HER2, when combined with trastuzumab, achieved a 75% increase in clearance of HER2-low breast cancer cells relative to monotherapy groups, mediated through the synergistic interplay of CD16-dependent ADCC and CAR-mediated killing [56], thereby broadening the antigen expression threshold for targeted therapy. This evidence concerns the gene ERBB2 and breast cancer.