IDO2 and cervical cancer: Cervical cancers often express elevated levels of various immunosuppressive molecules, including interleukin (IL) 6 [52, 53], IL10 [53–55], indoleamine-2,3-dioxygenase (IDO) [56–59], programmed death ligand 1 (PD-L1) [60, 61], hypoxia-inducible factor 1 (HIF-1α) [62], vascular endothelial growth factor (VEGF) [63, 64], and transforming growth factor beta (TGF-β) [55, 65].