PDCD1 and hepatocellular carcinoma: Furthermore, Ma et al. described the different functions of highly and poorly heterogeneous (Div-high and -low, defined by the authors) HCC based on the analysis of the gene expression pattern, pathway enrichment, and T cell cluster distribution.86 Cytotoxic-related genes (e.g., GZMA and GZMB) and immune checkpoint molecules (IFNG, PDCD1, and NKG7) were highly expressed in Div-low compared to in Div-high HCC.