Pharmacological interference with the stemness-associated Notch-signaling pathway exerts an antiproliferative effect on the endometriotic 12Z cell line

Adult stem cells are thought to participate in endometrial regeneration during the reproductive phase of women. We have previously demonstrated dysregulated stem cell activity in endometriosis, a benign disease associated with unspecific pain symptoms and reduced fertility due to ectopic endometrial growth. We hypothesize that the unlimited proliferative potential of stem cells, along with their high differentiation capacity, contributes to the pathogenetic process. In the present study, we evaluated the effects of interference with the stemness-associated notch pathway on the properties of an epithelial endometriotic cell line (12Z). Pharmacological inhibition of notch signaling was achieved by in vitro treatment with a gamma-secretase inhibitor (GSI), which blocks proteolytic activation of the receptor. Furthermore, we employed siRNA-mediated depletion of two modulators of notch endocytosis, Msi-1 and Msi-2. Both GSI-treatment and Msi-knockdown rinhibited cell proliferation as determined by MTT assay, and ALDH1 activity, a surrogate marker of stem cell activity. Flow cytometric annexin V assays demonstrated increased apoptosis in 12Z cells subjected to notch inhibition. TaqMan low density PCR array analysis of GSI-treated endometriotic cells revealed a dysregulation of several stemness-associated factors. Among these, qPCR-analysis confirmed a significant downregulation of the stemness-associated factors LIFR, SOX2, PODXL and IFITM1 upon notch inhibition. Our data support the stem cell concept of endometriosis and suggest that pharmacological interference with the notch pathway may be a worthwhile future strategy for its treatment.