ERV3-1 and endometrial carcinoma: Of interest is that during endometrial carcinoma progression, ERV3-1 ENV is co-expressed with six other ENV (HERV-W1, HERV-T, HERV-Fc2, HERV-H1-3, HERV-V1, HERV-E1) and showed significantly increased expression in more undifferentiated grade 3 tumors compared to differentiated grade 1 tumors (59).