Indeed, blockade, invalidation, or inhibition of PD-1 in melanoma (Kleffel et al.)[4] and HCC (Li et al. [5]) reduced tumor growth, while the blockade of PD-1 in lung and colon cancer cells promoted tumor growth (Du et al. [6], Wang et al. [8]). The gene discussed is PDCD1; the disease is malignant colon neoplasm.