Tumor-infiltrating CD8+ T cells from advanced HCC tumor samples displayed significantly impaired secretion of the cytolytic enzymes perforin, granzyme A, and granzyme B. Specifically, Tregs extracted from patients with HCC were capable of significantly suppressing CD8+ T cells’ production of these cytolytic enzymes, in addition to inhibiting the secretion of the key anti-tumor cytokines IFN-γ and TNF-α in vitro (139). This evidence concerns the gene PRF1 and neoplasm.