PDCD1 and neoplasm: In this study, we demonstrated that SLC1A5, as an important modulator of ferroptosis, affects tumor immune microenvironment in HBV-related HCC via increasing the infiltrating Treg and macrophage cells, as well as up-regulating the levels of immune checkpoint-related genes (CTLA4, HAVCR2, LAG3, PDCD1, PDCD1LG2 and TIGIT).