These cells capture some of the hallmarks of endometriosis, such as over-secretion of the pro-inflammatory cytokine interleukin 1 beta (IL-1 β) (Mori et al., 1991), altered hormone sensitivity (Patel et al., 2017), increased prostaglandin and matrix metalloprotease (MMP) secretion (Banu et al., 2008), and a more invasive phenotype (Zeitvogel et al., 2001; Stejskalová et al., 2021) compared to primary endometrial epithelial and stromal cells isolated from the eutopic endometrium. The gene discussed is IL1B; the disease is endometriosis.