PDCD1 and neoplasm: Therefore, we verified the correlations between the tumour immune microenvironment and eight representative immune checkpoint genes, including PDCD1, CD274, PDCD1LG2, CTLA4, CD86, CD80, CD276, and VTCN1. The results showed that there was a significant positive correlation between immune microenvironment genes and all the immune checkpoint genes other than VTCN1. This suggested that these immune microenvironment genes might be potential immunotherapeutic targets.