ERVW-1 and carcinoma: Even if syncytin-1 was upregulated also in benign endometrial specimens, the highest expression was observed in carcinoma tissues, being induced by steroid hormones due to the presence of an hypomethylated estrogen responsive element (ERE) in ERVWE1 5′LTR (Strick et al., 2007; Strissel et al., 2012).