Specifically, Notably, in vitro experiments further reveal that cancer-associated fibroblasts trigger CD8+T cell apoptosis through the Fas (expressed on CD8+T cells) and FasL (expressed on cancer-associated fibroblasts) pathways and inactivate CD8+T cells through the PD-1 (expressed on CD8+T cells) and PD-L1 (expressed on cancer-associated fibroblasts) pathways (161). Here, PDCD1 is linked to cancer.