HLA-G and ovarian cancer: In the malignant environment where tumors occur, the expression of HLA-G in melanoma is first reported in 1998 (19), and then the abnormal expression of HLA-G is observed in a variety of malignant tumors, such as lung cancer (20–28), gastric cancer (29–37), ovarian cancer (OC) (38–47), breast cancer (48–54), and hematopoietic tumor (55–58).