Several clinical studies have shown that a high rate of clinical benefits in patients with high-TMB tumors treated with immune checkpoint inhibitors (including anti-CTLA-4 treatment for melanoma [68], anti-PD-L1 treatment for uroepithelial cancer [69], and anti-PD-1 treatment for non-small cell lung and colorectal cancer [70,71]) might be associated with a high expression of immunoreactive neoplastic antigens in these tumors [70]. Here, PDCD1 is linked to colorectal cancer.