Its elevated concentration has been shown in endometriotic stromal cells, as an effect of the action of E2 and TNF-α through NF-κB; remarkably, this increase is reversed by P4 treatment, indicating that P4 downregulation in endometriosis contributes to alteration of IL-8 expression during the pathogenesis of the disease (90). The gene discussed is NFKB1; the disease is endometriosis.