HMOX1 and ovarian cancer: The Nrf2/HO-1 axis is closely associated with multiple gynecological cancers, such as ovarian cancer and endometrial cancer [15], due to its regulation of cell proliferation, metastasis, the immune response, etc. To explore the role of the Nrf2/HO-1 axis, we firstly analyzed the protein–protein interaction (PPI) network across chemokines, adhesion molecules and heme metabolism-related factors on the basis of the STRING database (Figure 6A).