IDO1 and endometrial cancer: ERV3-2 expression was correlated with all three genes in ER− HER2− and HER2+ breast, colon, and endometrial cancers; and IDO-1 and IDO-2 (but not TDO-2) in ER+ HER2− breast, gastric, lung, prostate, cervical, and head-neck squamous cell cancers.