PDCD1 and neoplasm: Tregs suppress antitumor immunity through interactions involving CTLA4 and PD-1/PD-L1 (Knochelmann et al., 2018; Noack & Miossec, 2014); MDSCs promote tumor progression and metastatic niche formation, and confer resistance to immunotherapy via suppression of T and NK cells (Gomez et al., 2020; Law, Valdes-Mora & Gallego-Ortega, 2020); and CAFs, central players in liver fibrosis within both pre-malignant and tumor microenvironments, drive HCC progression (Affo, Yu & Schwabe, 2017).