We demonstrated the ability of miRNAs to modulate PD-1 and PD-L1 expression in various cancer types, including gastrointestinal cancers, hepatocellular carcinoma, glioblastoma, breast cancers, cervical, ovarian, and endometrial cancer, diffuse large B cell lymphoma, melanoma, bladder, and prostate cancer. This evidence concerns the gene PDCD1 and breast cancer.