For example, PD-1 knockout in mesothelin-targeting CAR T cells was shown to increase cytokine production, improve tumor control, and prevent breast cancer in breast cancer [129], PD-1-disrupted GPC3-CAR T cells have shown enhanced in vivo anti-tumor activity for HCC by targeting GPC3-expressing tumor cells and overcoming immune suppression through PD-1 pathway disruption [130]. This evidence concerns the gene PDCD1 and breast cancer.