This new CAR4 construct has been reported to possess a potent anti-tumor efficiency against some solid tumor models, for examples, anti-FRα-CAR4 T cells in breast cancer (21), anti-MUC1-CAR4 T, anti-CD133-CAR4 T, and A20-CAR4 T cells in cholangiocarcinoma cells (18–20). This evidence concerns the gene MUC1 and cholangiocarcinoma.