CTLA4 and digestive system neoplasm: We compared the H-score of the five immune checkpoints in liver metastases and its paired primary tumor, and found that there existed a significantly positive correlation of the five immune checkpoint expressions between the liver metastases and its paired primary tumor (PD1, R = 0.826, P < 0.001; TIM3, R = 0.779, P < 0.001; TIGIT, R = 0.577, P = 0.007; LAG3, R = 0.779, P < 0.001; CTLA4, R = 0.458, P = 0.038) (Fig. 5B), but the expressions were significantly lower in the liver metastases (Fig. 5C).