IFNG and hepatocellular carcinoma: In functional assays in which T cells expanded from PD‐1+ and PD‐1‒ peripheral blood lymphocytes were incubated with autologous tumour cells from patients with metastatic melanoma, hepatocellular carcinoma (HCC), renal cell carcinoma (RCC), or non‐small‐cell lung cancer (NSCLC), IFN‐γ release was markedly increased in the PD‐1+ lymphocyte fraction, indicating enrichment of tumour‐reactive T cells in PD‐1+ cells.12