ICIs function by blocking cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) or the programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) pathways, thereby relieving the inhibition of T cell and natural killer cell activity, restoring their anti-tumor activity, and ultimately suppressing tumor growth and metastasis. This evidence concerns the gene CTLA4 and neoplasm.