CD8A and neoplasm: To corroborate whether the BTC tumor microenvironment can induce the upregulation of common checkpoint receptors and ER stress in CD8+ T cells, we treated CD8+ T cells isolated from the peripheral blood of healthy people with conditioned media collected from two human BTC cell lines (GBC-SD, HCCC-9810) and a normal bile duct cell line (HIBEpiC, as a control).