ESR1 and endometriosis: The use of chromatin immunoprecipitation (ChIP)-polymerase chain reaction made it possible to demonstrate hypoacetylation of H3/H4 within the promoter regions of candidate genes that are recognized as downregulated in endometriosis (e.g., HOXA10, ESR1, CDH1, and p21WAF1/Cip1) when comparing endometriotic lesions and control endometrium (219, 220).