CD274 and ovarian cancer: They concluded that changes in the immune system activity caused by the elevated expression of PD-1 and PD-L1 on T cells may be an important factor in the early steps of EMS development, which is similar to the mechanism observed in cancer (e.g., ovarian cancer), where tumour cells can evade the immune response via the upregulation of the PD-1/PD-L1/PD-L2 axis [29].