Differential expression analysis showed that the expression levels of PD-1/PD-L1 and CTLA-4 in ovarian cancer were insignificant compared with normal ovarian tissues (Figures 1A–C), and the expression in advanced ovarian cancer tissues was significantly lower than that in early ovarian cancer tissues (Supplymentary Figures S1A–C). Here, CTLA4 is linked to ovarian cancer.