PDCD1 and triple-negative breast carcinoma: Figure 1 depicts the regulatory relationships between specific miRNAs and the expression of PD-1, an immune checkpoint protein, in various cancer types including gastric cancer (GC), hepatocellular carcinoma (HCC), non-small cell lung cancer (NSCLC), melanoma, renal cell carcinoma (RCC) and triple-negative breast cancer (TNBC).