RRM2 and cancer: Interestingly, the 5 hub nodes RRM2, AURKB, DTL, CCNB1, CCNB2 identified from the PPI network constructed by148 shared DEGs were all associated with cell cycle and mitosis, and down-regulated in the ectopic lesions in our analysis while always up-regulated in cancer tissues (Wang et al., 1997; Kolesar et al., 2009; Takashima et al., 2014; Kobayashi et al., 2015; Chieffi, 2018), thus promoting excessive proliferation, which suggested limited and controlled proliferative activity in EMs endometriotic lesions, distinct from cancerous proliferation feature.