Different mutation profiles between epithelium and stroma in endometriosis and normal endometrium

Abstract

STUDY QUESTION Are there common mutation profiles between epithelial and stromal cells in ovarian endometriotic tissue and the normal endometrium? SUMMARY ANSWER Our study revealed no common mutations between epithelial and stromal cells in ovarian endometriotic tissue and the normal endometrium. WHAT IS KNOWN ALREADY Epithelial cells in both ovarian endometriotic tissue and the normal endometrium harbor somatic mutations in cancer-associated genes such as phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) and KRAS proto-oncogene, GTPase (KRAS). STUDY DESIGN, SIZE, DURATION We performed a retrospective study to identify the mutation profiles of stromal cells in endometriotic tissue and the normal endometrium. We collected 11 endometriotic stroma samples and 10 normal endometrial stroma samples between 2013 and 2017 at a tertiary care center. PARTICIPANTS/MATERIALS, SETTING, METHODS The laser microdissection method was used to obtain stromal cells in ovarian endometriotic and normal endometrial tissues from patients with ovarian endometriosis and/or other non-invasive gynecological diseases. Target gene sequencing was performed to assess and compare the mutation profiles of stromal cells with those of epithelial cells obtained in our previous study. For target gene sequencing, 76 genes were selected based on previous genomic analyses for ovarian endometriosis, normal endometrium, endometriosis-related ovarian cancer and endometrial cancer. MAIN RESULTS AND THE ROLE OF CHANCE Stromal samples in ovarian endometrioma and normal endometrium harbor somatic mutations (18 mutations in 11 endometriosis samples and 16 mutations in 10 normal endometrial samples) but did not share any mutations with paired epithelial samples. The mutant allele frequency of stromal samples was significantly lower than that of epithelial samples in ovarian endometrioma (P = 6.0 × 10-11) and normal endometrium (P = 1.4 × 10-7). LIMITATIONS, REASONS FOR CAUTION The number of genes evaluated in the mutational analysis was limited. Additionally, the functional roles of somatic mutations in stromal cells remain unclear. WIDER IMPLICATIONS OF THE FINDINGS Different mutation profiles between paired epithelial and stromal cells in both ovarian endometrioma and normal endometrium suggest that origins of epithelial and stromal cells would be independent of each other in both normal endometrium and ovarian endometrioma; however, the theory of epithelial-mesenchymal transition is proposed in ovarian endometrioma. STUDY FUNDING/COMPETING INTEREST(S) This work was supported in part by the Japan Society for the Promotion of Science KAKENHI grant number JP15H02373 (Grant-in-Aid for Scientific Research A for I.I.), JP16H06267 (Grant-in-Aid for Young Scientists A for K.Y.), JP17K08688 (Grant-in-Aid for Scientific Research C for H.N.) and JP16H06279 (Grant-in-Aid for Scientific Research on Innovative Areas—Platforms for Advanced Technologies and Research Resources for H.N. and K.Y). There are no conflicts of interest to declare. TRIAL REGISTRATION NUMBER Not applicable.

Epithelial–Mesenchymal Transition in Endometriosis—When Does It Happen?

“…Subtle changes in the expression of cell–cell contacts and more pronounced changes in the presence of EMT markers suggest only a partial EMT occurring in the ectopic endometrium. This is further emphasized by the analysis of somatic mutations which clearly excluded a complete transition of endometrial epithelial to stromal cells [ 96 ], but not a partial EMT. We are inclined to assume that the partial EMT, which seems to be distinctly different in the three endometriotic entities, is a result of the interaction of the endometriotic implant with the different environments (e.g., peritoneal fluid, ovarian hormones, or different tissue environment) as suggested by Koninckx et al [ 98 , 99 ].…”

“…Further in line with our assumptions of a partial EMT in the pathogenesis of endometriosis are recent observations on somatic mutations in the eutopic and ectopic endometrium. The findings that endometrial stromata do not share mutations with the epithelium neither in the eutopic or in the ectopic endometrium [ 96 ] clearly suggest that endometrial epithelial cells do not transform into stromal cells. Our hypothesis of a partial EMT is in agreement with these observations, because we demonstrate that epithelial cells do not lose their epithelial phenotype and show only a partial gain of mesenchymal marker expression.…”

“…The distinct EMT patterns in the three endometriotic entities suggest that there might be differences such as inflammation or other factors in the distinct host tissues of women with endometriosis compared to healthy women, thereby causing EMT after implantation. Various aspects of the different microenvironments on the lesions [ 98 , 99 ], as well as the different rates of somatic mutations or genetic/epigenetic incidents of the endometriotic lesions compared to the eutopic endometrium [ 26 , 96 ], seem to be mainly responsible for their heterogeneity and, thus, for the clinical symptoms of endometriosis. In other words, we believe that we should focus more on characterization of the “soil” instead of the “seed” to treat women susceptible for endometriosis before they get the disease.…”

Clonal lineage from normal endometrium to ovarian clear cell carcinoma through ovarian endometriosis

“…The number of mutations shared with U decreased from E to AE to C. No mutations were shared by the stromal component of the carcinoma (S) and epithelial components (C), consistent with previous studies showing different mutation profiles between the epithelium and stroma in endometriosis and uterine endometrium. 18,25 The MAF of the shared mutations significantly increased from U to DE to AE to C ( Figure 3B). The MAF of these mutations in AE and C…”

What the Transcriptome of the Eutopic Endometrium from Women with Endometriosis tells us about the Disease Pathophysiology: A Brief Reflection

“…Despite their relevance to ovarian lesions (endometriomas), they do not appear to be crucial or significant in components of the eutopic endometrium. 30 Another interesting element is the importance of endometrial progenitor cells, or endometrial stem cells in their broadest concept. However, although admittedly associated with the development of the lesion at ectopic sites, 31 primary constitutive changes in these cells, when isolated from the eutopic endometrium, are still controversial.…”