PDCD1 and ovarian carcinoma: Previous studies have identified surface markers such as C-X-C motif chemokine receptor 5, CD28, Slamf6 (Ly108) and C-C motif chemokine receptor 4 co-expressed with Tcf1 in TILs of gastric, lung, kidney, colorectal, liver and ovarian cancer to screen for stem-like exhausted (Tcf1+PD-1+) CD8+ T cells to some extent.