This is in line with previous studies showing higher IDO1 activity in the E-MenSCs (22) and enhanced KRAS gene expression in patients with endometriosis who have an SNP at the let-7 microRNA complementary site 6 (LCS6) in the 3′-UTR of the KRAS gene, which causes human endometrial stromal cells (hESC) to proliferate and invade more (43). Here, KRAS is linked to endometriosis.