The Tpl2-MEK pathway plays a critical role in spheroid-cultured endometriotic stromal cells

PROBLEM: Endometriosis is a proliferative disease characterized by cytokine-induced inflammation. The objective of this study was to assess cell growth and PGE2 production induced by TNF-α in endometriotic stromal cells (ESCs) in spheroid cell culture and to identify the signaling pathway involved with a view to finding new therapeutic targets for endometriosis. METHOD OF STUDY: Tissue samples were collected from patients with and without endometriosis. ESCs were isolated from ovarian endometrioma (OE). Gene expression was evaluated by real-time PCR and DNA microarray analysis, the proliferative effect on ESCs by WST-8 assay, and PGE2 production by ELISA. Protein phosphorylation was detected using western blotting. RESULTS: COX-2, aromatase and VEGFA mRNA expression and PGE2 production were significantly elevated in spheroid cell cultures compared to monolayer cell cultures. TNF-α receptor (TNFR) 1 and TNFR2 mRNA was also significantly increased. TNF-α promoted the proliferation and PGE2 production of ESCs in spheroid cell cultures significantly more than in monolayer cell cultures. TNF-α increased the expression of several genes related to the pathophysiology of endometriosis in spheroid ESCs. DNA microarray analysis revealed that the Tpl2 gene, which codes for a MAPK upstream of MEK, was upregulated in OE and endometrium with endometriosis compared to normal endometrium. TNF-α increased the phosphorylation and expression of Tpl2 and MEK, and Tpl2 and MEK inhibitors inhibited TNF-α-induced proliferation and PGE2 production in spheroid ESCs. CONCLUSION: The Tpl2-MEK signaling pathway may play a critical role in the cell growth and PGE2 production induced by TNF-α in spheroid ESCs.