ESR1 and endometriosis: In addition, the use of dominant negative mutants of estrogen receptor (DN-ER) genes, delivered to endometriosis cells (from ovarian endometriomas) via an adenovirus vector (Ad-DN-ER), abrogated the estrogen action on these cells and decreased cell proliferation, induced apoptosis and decreased cytokine production such as monocyte chemotactic protein-1, vascular endothelial growth factor, and interleukin-6 [57].