Models of endometriosis and their utility in studying progression to ovarian clear cell carcinoma

PURE vs. mixed clear cell ovarian carcinomas: Is there any impact on survival?

OBJECTIVE

Our primary aim in this study is to define the clinical characteristics of patients with clear-cell ovarian carcinoma and evaluate the prognostic factors affecting survival.

STUDY DESIGN

Records of 85 patients, operated between 2000 and 2018, for an adnexal mass and whose final pathology reported clear cell ovarian carcinoma were reviewed. The study considered demographic data, clinical characteristics of the patients, as well as pure and mixed-type clear cell histology. The patients' follow-up time, disease-free and overall survival recorded. The primary outcomes were disease-free survival (DFS) and overall survival (OS).

RESULTS

The median age of the patients at diagnosis was 52. In 64.7 % of the cases, clear cell histology was pure, while the others (35.3 %) were mixed. Patients with ovarian endometriosis constituted 27.1 % of the whole population. The median OS for the entire population was 92 months (95 %CI:72-124). On univariate and multivariate analyses, advanced age was found to have a significant independent impact on OS and DFS (p < 0.05) and, was associated with a worse prognosis. Also, the multivariate analyses showed that the presence of endometriosis has a significant independent impact on OS (p < 0.05). When examining the relationship between the histological origin (mixed vs. pure) and 5-year survival, the mixed type showed longer OS and DFS rates (76.8 % vs. 69.8 %, 61.5 % vs. 53.8 %), the difference was not statistically significant (p > 0.05).

CONCLUSION

This retrospective study showed that although mixed type histological origin was associated with higher OS and DFS rates compared to pure type in patients with CCOC, the difference was not statistically significant. Advanced age and the presence of endometriosis was found to have a significant independent effect on OS and DFS and was associated with a worse prognosis. Overall, this study provides useful insights into the clinical characteristics of patients with CCOC and identifies important prognostic factors affecting survival.

Case report: A germline CHEK1 c.613 + 2T>C leads to a splicing error in a family with multiple cancer patients

Background

Genome instability plays a crucial role in promoting tumor development. Germline mutations in genes responsible for DNA repair are often associated with familial cancer syndromes. A noticeable exception is the CHEK1 gene. Despite its well-established role in homologous recombination, germline mutations in CHEK1 are rarely reported.

Case presentation

In this report, we present a patient diagnosed with ovarian clear cell carcinoma who has a family history of cancer. Her relatives include a grandfather with esophageal cancer, a father with gastric cancer, and an uncle with a brain tumor. The patient carried a typical genomic profile of clear cell carcinoma including mutations in KRAS, PPP2R1A, and PIK3R1. Importantly, her paired peripheral blood cells harbored a germline CHEK1 mutation, CHEK1 exon 6 c.613 + 2T>C, which was also found in her father. Unfortunately, the CHEK1 status of her grandfather and uncle remains unknown due to the unavailability of their specimens. Further evaluation via RT-PCR confirmed a splicing error in the CHEK1 gene, resulting in truncation at the kinase domain region, indicative of a loss-of-function mutation.

Conclusion

This case highlights a rare germline CHEK1 mutation within a family with a history of cancer. The confirmed splicing error at the mRNA level underscores the functional consequences of this mutation. Documenting such cases is vital for future evaluation of inheritance patterns, clinical penetrance of the mutation, and its association with specific cancer types.

From clinical management to personalized medicine: novel therapeutic approaches for ovarian clear cell cancer

Ovarian clear-cell cancer is a rare subtype of epithelial ovarian cancer with unique clinical and biological features. Despite optimal cytoreductive surgery and platinum-based chemotherapy being the standard of care, most patients experience drug resistance and a poor prognosis. Therefore, novel therapeutic approaches have been developed, including immune checkpoint blockade, angiogenesis-targeted therapy, ARID1A synthetic lethal interactions, targeting hepatocyte nuclear factor 1β, and ferroptosis. Refining predictive biomarkers can lead to more personalized medicine, identifying patients who would benefit from chemotherapy, targeted therapy, or immunotherapy. Collaboration between academic research groups is crucial for developing prognostic outcomes and conducting clinical trials to advance treatment for ovarian clear-cell cancer. Immediate progress is essential, and research efforts should prioritize the development of more effective therapeutic strategies to benefit all patients.

Diminished Ovarian Reserve in Endometriosis: Insights from In Vitro, In Vivo, and Human Studies-A Systematic Review

Endometriosis, a prevalent disorder in women of reproductive age, is often associated with undesired infertility. Ovarian reserve, an essential measure of ovarian function that is crucial for maintaining fecundity, is frequently diminished in women with endometriosis. Though the causative relationship between endometriosis and reduced ovarian reserve is not fully understood due to the lack of standardized and precise measurements of ovarian reserve, there is ongoing discussion regarding the impact of interventions for endometriosis on ovarian reserve. Therefore, in this review, we investigate articles that have related keywords and which were also published in recent years. Thereafter, we provide a comprehensive summary of evidence from in vitro, in vivo, and human studies, thereby shedding light on the decreased ovarian reserve in endometriosis. This research consolidates evidence from in vitro, in vivo, and human studies on the diminished ovarian reserve associated with endometriosis, as well as enhances our understanding of whether and how endometriosis, as well as its interventions, contribute to reductions in ovarian reserve. Furthermore, we explore potential strategies to modify existing therapy options that could help prevent diminished ovarian reserve in patients with endometriosis.

A phase 2 study of dasatinib in recurrent clear cell carcinoma of the ovary, fallopian tube, peritoneum or endometrium: NRG oncology/gynecologic oncology group study 0283

OBJECTIVE

Gynecologic cancers are traditionally managed according to their presumed site of origin, without regard to the underlying histologic subtype. Clear cell histology is associated with chemotherapy refractoriness and poor survival. Mutations in SWI/SNF chromatin remodeling complex member ARID1A, which encodes for BAF250a protein, are common in clear cell and endometriosis-associated endometrioid carcinomas. High-throughput cell-based drug screening predicted activity of dasatinib, a tyrosine kinase inhibitor, in ARID1A-mutant clear cell carcinoma.

METHODS

We conducted a phase 2 clinical trial of dasatinib 140 mg once daily by mouth in patients with recurrent or persistent ovarian and endometrial clear cell carcinoma. Patients with measurable disease were enrolled and then assigned to biomarker-defined populations based on BAF250a immunohistochemistry. The translational endpoints included broad next-generation sequencing to assess concordance of protein expression and treatment outcomes.

RESULTS

Twenty-eight patients, 15 of whom had tumors with retained BAF250a and 13 with loss of BAF250a were evaluable for treatment response and safety. The most common grade 3 adverse events were anemia, fatigue, dyspnea, hyponatremia, pleural effusion, and vomiting. One patient had a partial response, eight (28%) had stable disease, and 15 (53.6%) had disease progression. Twenty-three patients had next-generation sequencing results; 13 had a pathogenic ARID1A alteration. PIK3CA mutations were more prevalent in ARID1A-mutant tumors, while TP53 mutations were more prevalent in ARID1A wild-type tumors.

CONCLUSIONS

Dasatinib was not an effective single-agent treatment for recurrent or persistent ovarian and endometrial clear cell carcinoma. Studies are urgently needed for this rare gynecologic subtype.

Establishment of a novel model of endometriosis-associated ovarian cancer by transplanting uterine tissue from Arid1a/Pten knockout mice

Although endometriosis is primarily benign, it has been identified as a risk factor for endometriosis-associated ovarian cancer (EAOC). Genetic alterations in ARID1A, PTEN, and PIK3CA have been reported in EAOC; however, an appropriate EAOC animal model has yet to be established. Therefore, the present study aimed to create an EAOC mouse model by transplanting uterine pieces from donor mice, in which Arid1a and/or Pten was conditionally knocked out (KO) in Pax8-expressing endometrial cells by the administration of doxycycline (DOX), onto the ovarian surface or peritoneum of recipient mice. Two weeks after transplantation, gene KO was induced by DOX and endometriotic lesions were thereafter removed. The induction of only Arid1a KO did not cause any histological changes in the endometriotic cysts of recipients. In contrast, the induction of only Pten KO evoked a stratified architecture and nuclear atypia in the epithelial lining of all endometriotic cysts, histologically corresponding to atypical endometriosis. The induction of Arid1a; Pten double-KO evoked papillary and cribriform structures with nuclear atypia in the lining of 42 and 50% of peritoneal and ovarian endometriotic cysts, respectively, which were histologically similar to EAOC. These results indicate that this mouse model is useful for investigating the mechanisms underlying the development of EAOC and the related microenvironment.

Friend or foe? The prognostic role of endometriosis in women with clear cell ovarian carcinoma. A UK population-based cohort study

PURPOSE

The prognostic role of endometriosis amongst women with ovarian clear cell carcinoma (OCCC) remains debatable. The aim of this study was to ascertain the effect of endometriosis on the prognosis of OCCC.

METHODS

A retrospective review of the medical records of 94 women diagnosed and treated for OCCC at a tertiary gynaecological cancer centre in the UK, spanning the period 2010-2019. Women were divided into two groups according to the presence of endometriosis. Clinico-pathological characteristics, progression-free survival (PFS) and overall survival (OS) were collated between the two groups.

RESULTS

Forty-six cases of endometriosis-free OCCC (Ef-OCCC) were collated with 48 cases of endometriosis-related OCCC (Er-OCCC). There was no significant difference between the two groups regarding age (p-value = 0.2), FIGO stage (p-value = 0.8), residual disease (RD) (p-value = 0.07), adjuvant chemotherapy agent (p-value = 0.4) or chemo-resistance (p-value = 0.9). The presence of endometriosis did not significantly affect either OS or PFS. The median OS in the Ef-OCCC and Er-OCCC was 55.00 (95% CI 32.00-189.00) and 71.00 (95% CI 47.00-97.00; log rank = 1.35, p-value = 0.2) months. The median PFS in the Ef-OCCC and Er-OCCC group was 39.00 (95% CI 19.00-143.00) and 39.00 (95% CI 19.00-62.00; log rank = 0.7, p-value = 0.4) months. Survival differences between the two groups were not significant after stratification analysis for independent prognosticators.

CONCLUSION

Endometriosis was not independently associated with the prognosis of OCCC either in crude analysis or after stratification for stage and RD. Further larger, well-designed prospective studies are warranted to draw firmer conclusions on the intrinsic link between endometriosis and OCCC.

Ribosome Biogenesis Serves as a Therapeutic Target for Treating Endometriosis and the Associated Complications

Ribosome biogenesis is a cellular process critical for protein homeostasis during cell growth and multiplication. Our previous study confirmed up-regulation of ribosome biogenesis during endometriosis progression and malignant transition, thus anti-ribosome biogenesis may be effective for treating endometriosis and the associated complications. A mouse model with human endometriosis features was established and treated with three different drugs that can block ribosome biogenesis, including inhibitors against mTOR/PI3K (GSK2126458) and RNA polymerase I (CX5461 and BMH21). The average lesion numbers and disease frequencies were significantly reduced in treated mice as compared to controls treated with vehicle. Flow cytometry analyses confirmed the reduction of small peritoneal macrophage and neutrophil populations with increased large versus small macrophage ratios, suggesting inflammation suppression by drug treatments. Lesions in treated mice also showed lower nerve fiber density which can support the finding of pain-relief by behavioral studies. Our study therefore suggested ribosome biogenesis as a potential therapeutic target for treating endometriosis.

Effects of iron-related compounds and bilirubin on redox homeostasis in endometriosis and its malignant transformations

OBJECTIVES

The balance between oxidative stress and antioxidant defense has been reported to differ between women with endometriosis and patients with its malignant transformation. The aim of this study is to investigate changes in redox balance in endometriosis and endometriosis-related ovarian cancer (EAOC) by simultaneously measuring iron-related compounds and bilirubin.

METHODS

This study included 235 patients with a histopathologically confirmed diagnosis of endometriosis (n=178) and EAOC (n=57). Cyst fluid samples were collected in Nara Medical University hospital from January 2013 to May 2019. The levels of iron-related compounds (total iron, heme iron, free iron, oxyhemoglobin [oxyHb], methemoglobin [metHb], and metHb/oxyHb ratio) and bilirubin were measured.

RESULTS

Total iron, heme iron, free iron, metHb/oxyHb ratio, and bilirubin were significantly elevated in endometriosis compared to EAOC. In both endometriosis and EAOC, iron-related compounds in the cyst were correlated with each other. There was no statistically significant difference in oxyHb and metHb levels between the two groups, but the metHb/oxyHb ratio was significantly higher in endometriosis than in EAOC. Bilirubin was positively correlated with total iron and free iron in EAOC, but there was no correlation between bilirubin and iron-related compounds in endometriosis.

CONCLUSIONS

Iron-induced oxidative stress in endometriosis may exceed bilirubin-dependent antioxidant capability, while redox homeostasis in EAOC can be maintained by at least bilirubin.

Endometriosis-associated Ovarian Clear Cell Carcinoma: A Special Entity?

Endometriosis is an estrogen-dependent disease, which serves as a precursor of ovarian cancer, especially clear cell carcinoma (OCCC) and endometrial carcinoma. Although micro-environmental factors such as oxidative stress, immune cell dysfunction, inflammation, steroid hormones, and stem cells required for malignant transformation have been found in endometriosis, the exact carcinogenic mechanism remains unclear. Recent research suggest that many putative driver genes and aberrant pathways including ARID1A mutations, PIK3CA mutations, MET activation, HNF-1β activation, and miRNAs dysfunction, play crucial roles in the malignant transformation of endometriosis to OCCC. The clinical features of OCCC are different from other histological types. Patients usually present with a large, unilateral pelvic mass, and occasionally have thromboembolic vascular complications. OCCC patients are easier to be resistant to chemotherapy, have a worse prognosis, and are usually difficult to treat. To improve the survival of OCCC patients, it is necessary to better understand its specific carcinogenic mechanism and explore new treatment strategy, including molecular target.

Molecular dysregulations underlying the pathogenesis of endometriosis

Endometriosis is a crippling disease characterized by the presence of endometrium-like tissue or scar outside the uterine cavity, commonly confined to the peritoneal and serosal surfaces of the pelvic organs. 10-15% of women in reproductive age are estimated to be affected by endometriosis. Most of these patients present with infertility and suffer from pelvic pain. The benign disease rarely progresses to malignancy. Regardless of its high prevalence, the pathogenesis of the disease is not fully understood. Treatment options for endometriosis are limited and are often based on a symptomatic approach. The unavailability of proper diagnostic approaches, fewer therapeutic options, and sparse understanding of molecular alterations are responsible for the continued disease burden. Exploring the molecular elements causing the pathogenesis of endometriosis may lead to a number of breakthroughs in the treatment of the illness, such as the discovery of new biomarkers for diagnosis and therapeutic targets that can be a guide to better prognosis and reduced recurrence. The goal of this review is to provide the reader a critical understanding of the disease by summarizing the genetic, immunological, hormonal, and epigenetic deregulations that support the molecular basis for development of endometriotic cyst, with a special focus on the study models needed to analyze these changes in the endometriotic microenvironment.

Clinical characteristics and prognosis of ovarian clear cell carcinoma: a 10-year retrospective study

Background

Ovarian clear cell carcinoma (OCCC) is a special pathological type of epithelial ovarian carcinoma (EOC). We conducted this research to investigate the clinical characteristics and outcomes of OCCC and to provide additional supporting evidence to aid in the clinical diagnosis and management.

Methods

This was a retrospective study investigating the clinical characteristics and survival outcomes of 86 patients with OCCC treated at our center between January 2010 and March 2020. Survival analysis was also performed on 179 patients with OCCC obtained from the Surveillance, Epidemiology and End Results (SEER) cancer registry database.

Results

The median age of participants was 49.21 ± 9.91 years old, and 74.42% of them were diagnosed at early stage. The median CA125 level was 601.48 IU/mL, while 19.77% of the patients had normal CA125 levels. Sixteen patients (18.60%) had co-existing endometriosis and 8 patients (9.3%) developed venous thromboembolism (VTE). There were 5 patients received suboptimal cytoreduction. Sixty-six patients (76.74%) underwent lymphadenectomy, and only 3 (4.55%) patients had positive lymph nodes. Patients diagnosed at an early stage had higher 3-year overall survival (OS) and progression-free survival (PFS) rates than those with advanced stage OCCC. CA19–9 (P = 0.025) and ascites (P = 0.001) were significantly associated with OS, while HE4 (P = 0.027) and ascites (P = 0.001) were significantly associated with PFS. Analysis of data from the SEER database showed that positive lymph nodes is also an independent prognostic factor for OS (P = 0.001).

Conclusions

OCCC often presents at an early stage and young age with a mildly elevated CA125. CA19–9, HE4, massive ascites, and positive lymph node are independent prognostic factors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08061-7.

Disturbed progesterone signalling in an advanced preclinical model of endometriosis

RESEARCH QUESTION

Do human endometriosis organoids recapitulate aberrant progesterone signalling in the disease to serve as advanced experimental models for uncovering epigenetic mechanisms involved in attenuated progesterone response in endometriosis?

DESIGN

Initially, the organoids were established from acquired biopsies (women with and without endometriosis) and characterized by morphological, histological and immunostaining analyses.

RESULTS

A panel of endometriosis-related genes showed a pattern of expressions in cytochrome c oxidase subunit II (COX2), matrix metalloproteinase 2 (MMP2), MMP9, tissue inhibitor of metalloproteinase-3 (TIMP3), transforming growth factor beta 1 (TGF-β1), and zinc finger E-box binding homeobox 1 (ZEB1), and a contradictory expression pattern for cadherin (CDH1), POU class 5 homeobox 1 (POU5F1; also known as OCT4), and Nanog homeobox (NANOG) in the endometriosis organoids that is concordant with published research. These endometriosis organoids failed to upregulate 17β-Hydroxysteroid dehydrogenase 2 (17HSDβ2), progestogen associated endometrial protein (PAEP), secreted phosphoprotein 1 (SPP1), and leukaemia inhibitory factor (LIF) in response to progesterone at the level observed in control endometrium organoids. Progesterone receptor B (PRB) gene expression significantly decreased in both eutopic and ectopic organoids compared with control endometrium organoids. DNA hypermethylation, as an epigenetic mechanism for suppression of transcription, was detected at the PRB promoter in the eutopic, but not ectopic, organoids. Therefore, other epigenetic mechanisms, such as histone modifications and microRNAs, may be responsible for PRB downregulation in ectopic organoids.

CONCLUSIONS

Endometriosis organoids are powerful preclinical models that can be used to investigate the molecular mechanisms involved in endometriosis-associated progesterone resistance.

Updates of Pathogenesis, Diagnostic and Therapeutic Perspectives for Ovarian Clear Cell Carcinoma

Ovarian clear cell carcinoma (OCCC) is a special pathological type of epithelial ovarian carcinoma (EOC) and has a high prevalence in Asia without specific molecular subtype classification. Endometriosis is a recognized precancerous lesion that carries 3-fold increased risk of OCCC. Ovarian endometrioid carcinoma, which also originates from endometriosis, shares several features with OCCC, including platinum resistance and younger age at diagnosis. Patients with OCCC have about a 2.5 to 4 times greater risk of having a venous thromboembolism (VTE) compared with other EOC, and OCCC tends to metastasize through lymphatic vesicular and peritoneal spread as opposed to hematogenous metastasis. There is only mild elevation of the conventional biomarker CA125. Staging surgery or optimal cytoreduction combined with chemotherapy is a common therapeutic strategy for OCCC. However, platinum resistance commonly portends a poor prognosis, so novel treatments are urgently needed. Targeted therapy and immunotherapy are currently being studied, including PARP, EZH2, and ATR inhibitors combined with the synthetic lethality of ARID1A-dificiency, and MAPK/PI3K/HER2, VEGF/bFGF/PDGF, HNF1β, and PD-1/PD-L1 inhibitors. Advanced stage, suboptimal cytoreduction, platinum resistance, lymph node metastasis, and VTE are major prognostic predictors for OCCC. We focus on update pathogenesis, diagnostic methods and therapeutic approaches to provide future directions for clinical diagnosis and treatment of OCCC.

Histopathology and ARID1A Expression in Endometriosis- Associated Ovarian Carcinoma (EAOC) Carcinogenesis Model with Endometrial Autoimplantation and DMBA Induction

BACKGROUND

Ovarian carcinoma is one of the most deadly malignancies in the gynecologic field. The cause is not yet known, and the clinical symptoms are not specific. Endometrioid carcinoma and ovarian clear cell carcinoma can originate from endometriosis and are known as endometriosis-related ovarian carcinoma (EAOC). Development of EAOC experimental animal models is needed for basic research and clinical preparation of human tissue tests. This study aimed to determine the role of the ARID1A gene mutation in the carcinogenetic process of EAOC in experimental animal models induced with DMBA.

METHODS

In this study, the EAOC experimental model was developed using the autoimplantation technique and DMBA induction. This study involved placebo surgery mice (sham), endometrial autoimplantation, and a combination of endometrial autoimplantation and DMBA induction, which were sacrificed at weeks 5, 10, and 20, respectively. Histopathological assessment and immunohistochemical ARID1A staining with an assessment of positive percentages were carried out on 200 cells.

RESULTS

This study produced 1 (20%) atypical endometriosis and 1 (20%) clear cell carcinoma at implantation and after 10 weeks of DMBA induction, and 100% endometrioid carcinoma in the DMBA-induced group. ARID1A staining did not show any significant difference (p = 0.313) in all groups.

CONCLUSION

The combination of endometrial autoimplantation techniques and DMBA induction in the ovary produced atypical endometriosis, clear cell carcinoma, and endometrioid carcinoma, where time is an important factor. There was no significant difference in ARID1A expression between the treatment and control groups.

Ovarian endometriosis, a precursor of ovarian cancer: Histological aspects, gene expression and microRNA alterations (Review)

Ovarian endometriosis is a frequent chronic gynecological disease with an uncertain evolution regarding its progression or association with ovarian malignant lesions. The present review summarized the histological aspects, gene expression and microRNA (miRNA/miR) alterations associated with ovarian endometriosis and cancer and their possible interaction. The endometriosis-ovarian cancer interaction has been proposed by certain researchers as a single entity. Histological results indicated that endometriosis has been in different circumstances coexisting with ovarian cancer, with reference to endometrioid and clear cell carcinoma. Endometriosis with moderate and severe atypia can influence cell proliferation and architecture, resulting in a possible malignant transformation. Gene expression analysis indicated that the pathologies of both endometriosis and ovarian cancer are characterized by genetic instability from a molecular point of view, as several important genetic mutations, including ARID1A, PI3KCA, PTEN, BRCA1, BRCA2, TP53 and KRAS genes, were identified. miRNA alterations have been implicated in the regulation of gene expression. Common dysregulated miRNAs, such as miR-331, miR-335, miR-891, miR-548, miR-124, miR-148, miR-215, miR-192, miR-337, miR-153, miR-155, miR-144, miR-221 and miR-3688 were extensively investigated in understanding endometriosis and ovarian cancer evolution. From a combined viewpoint including histological aspects, gene expression and miRNA alterations, it is reasonable to speculate that endometriosis is associated with ovarian cancer. Ovarian endometriosis lesions may present a risk for ovarian malignant lesions, which supports a model of endometriosis as a malignant precursor. However, the endometriosis-ovarian cancer association is not widely accepted in the literature and additional studies are required to validate this association.

Cross-Cancer Genome-Wide Association Study of Endometrial Cancer and Epithelial Ovarian Cancer Identifies Genetic Risk Regions Associated with Risk of Both Cancers

BACKGROUND

Accumulating evidence suggests a relationship between endometrial cancer and ovarian cancer. Independent genome-wide association studies (GWAS) for endometrial cancer and ovarian cancer have identified 16 and 27 risk regions, respectively, four of which overlap between the two cancers. We aimed to identify joint endometrial and ovarian cancer risk loci by performing a meta-analysis of GWAS summary statistics from these two cancers.

METHODS

Using LDScore regression, we explored the genetic correlation between endometrial cancer and ovarian cancer. To identify loci associated with the risk of both cancers, we implemented a pipeline of statistical genetic analyses (i.e., inverse-variance meta-analysis, colocalization, and M-values) and performed analyses stratified by subtype. Candidate target genes were then prioritized using functional genomic data.

RESULTS

Genetic correlation analysis revealed significant genetic correlation between the two cancers (rG = 0.43, P = 2.66 × 10-5). We found seven loci associated with risk for both cancers (P Bonferroni < 2.4 × 10-9). In addition, four novel subgenome-wide regions at 7p22.2, 7q22.1, 9p12, and 11q13.3 were identified (P < 5 × 10-7). Promoter-associated HiChIP chromatin loops from immortalized endometrium and ovarian cell lines and expression quantitative trait loci data highlighted candidate target genes for further investigation.

CONCLUSIONS

Using cross-cancer GWAS meta-analysis, we have identified several joint endometrial and ovarian cancer risk loci and candidate target genes for future functional analysis.

IMPACT

Our research highlights the shared genetic relationship between endometrial cancer and ovarian cancer. Further studies in larger sample sets are required to confirm our findings.

Endometrial Organoids: A New Model for the Research of Endometrial-Related Diseases†

An ideal research model plays a vital role in studying the pathogenesis of a disease. At present, the most widely used endometrial disease models are cell lines and animal models. As a novel studying model, organoids have already been applied for the study of various diseases, such as disorders related to the liver, small intestine, colon, and pancreas, and have been extended to the endometrium. After a long period of exploration by predecessors, endometrial organoids (EOs) technology has gradually matured and maintained genetic and phenotypic stability after long-term expansion. Compared with cell lines and animal models, EOs have high stability and patient specificity. These not only effectively and veritably reflects the pathophysiology of a disease, but also can be used in preclinical drug screening, combined with patient derived xenografts (PDXs). Indeed, there are still many limitations for EOs. For example, the co-culture system of EOs with stromal cells, immune cell, or vascular cells is not mature, and endometrial cancer organoids have a lower success rate, which should be improved in the future. The investigators predict that EOs will play a significant role in the study of endometrium-related diseases.

The estrogen-regulated lncRNA H19/miR-216a-5p axis alters stromal cell invasion and migration via ACTA2 in endometriosis

Fibrotic tissue may contribute to the origin of some endometriosis-related symptoms, such as chronic pelvic pain and infertility. Alterations in the H19/miR-216a-5p/ACTA2 pathway may mediate the regulation of eutopic endometrial stromal cell (euESC) invasion and migration and may represent a potential mechanism underlying fibrous tissue formation or fibrosis in women with endometriosis. In this study, we aimed to determine the expression of H19 and ACTA2 in endometrial tissues of women with endometriosis. Two groups of 23 infertile women with endometriosis and 23 matched infertile women without endometriosis were investigated. Primary cultured cells of endometrial tissues were analyzed using RT-PCR and western blotting (WB) to determine expression of H19 and ACTA2. 5-Ethyl-2'-deoxyuridine, CCK8 and Transwell assays were used to study the functions of H19 and ACTA2. Human embryonic kidney 293 cells were used for luciferase assays to study miR-216a-5p binding sites with H19 and ACTA2. We found that H19 and ACTA2 levels were significantly higher in endometriosis euESCs than in control euESCs (P < 0.05) and were positively correlated in endometriosis euESCs. Luciferase assays indicated that H19 regulates ACTA2 expression via competition for inhibitory miR-216a-5p binding sites. Our results indicate that alterations in the estrogen/H19/miR-216a-5p/ACTA2 pathway regulated endometriosis euESC invasion and migration. Downregulation of H19 or ACTA2 inhibited endometriosis euESC invasion and migration; however, estrogen promoted endometriosis euESC invasion and migration via H19. The main limitation of our study was that experiments were conducted in vitro and further in vivo studies are required in the future. However, our study showed that primary cultured cells represented endometriosis cells more clearly than cell lines.

The establishment of a mouse model of deep endometriosis

STUDY QUESTION

Is it possible to establish a mouse model of deep endometriosis (DE)?

SUMMARY ANSWER

A mouse DE model that is macroscopically and microscopically similar to nodular lesions in humans can be constructed in as short as 3 weeks by intraperitoneal injection of uterine fragments along with the infusion of substance P (SP) and/or calcitonin gene-related peptide (CGRP).

WHAT IS KNOWN ALREADY

Although a baboon DE model was reported 5 years ago, its prohibitive cost and demand for facilities and expertise associated with the use of non-human primates put its use out of reach for most laboratories.

STUDY DESIGN, SIZE, DURATION

A total of 48 female Balb/C mice were used for this study. Among them, 16 were randomly selected as donors that contributed uterine fragments, and the remaining 32 were recipient mice. The mice with induced endometriosis were followed up for 3-4 weeks.

PARTICIPANTS/MATERIALS, SETTING, METHODS

One day before the induction of endometriosis by intraperitoneal injection of uterine fragments, osmotic pumps were inserted into equal groups of recipient mice to infuse either sterile saline, SP, CGRP, or both SP and CGRP. The hotplate test was administrated to all mice at the baseline and before and after induction of endometriosis. Four (3 for the SP+CGRP group) weeks after induction, all mice were sacrificed. Their endometriotic lesions were excised, weighed and processed for histopathologic examination, and histochemistry, immunohistochemistry and immunofluorescence analyses of markers of proliferation, angiogenesis, epithelial-mesenchymal transition (EMT), fibroblast-to-myofibroblast transdifferentiation (FMT), smooth muscle metaplasia (SMM), mesothelial-mesenchymal transition (MMT) and endothelial-mesenchymal transition (EndoMT) were done. The extent of lesional fibrosis was evaluated by Masson trichrome staining. To further evaluate surrounding organ/tissue invasion, the peritoneal areas adhesive to the lesions were excised for immunohistochemical analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

Endometriotic lesions in mice treated with SP and/or CGRP satisfied all requirements for DE, i.e. presence of endometrial epithelial and stromal cells, abundance of fibromuscular content, and encapsulation in surrounding tissues or organs. The lesion weight in the CGRP, SP and SP+CGRP groups was 1.62, 2.14 and 2.18-fold, respectively, heavier than that of control group. Concomitantly, the SP, CGRP and SP+CGRP groups had significantly shorter hotplate latency than that of control group. Lesions in mice treated with SP and/or CGRP, especially with SP+CGRP, exhibited characteristics consistent with EMT, FMT, SMM and extensive fibrosis, along with signs of MMT and EndoMT. Lesional invasion into surrounding tissues/organs was found to be 25.0, 75.0 and 87.5% in mice treated with CGRP, SP and SP+CGRP, but none in control mice.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

This study is limited by the use of histologic and immunohistochemistry analyses only and lacks molecular data.

WIDER IMPLICATIONS OF THE FINDINGS

The establishment of a mouse DE model supports the idea that endometriotic lesions are wounds undergoing repeated tissue injury and repair and underscores the importance of microenvironments in shaping the lesions' destiny. In addition, signs consistent with MMT and EndoMT indicate that there may be more culpable factors that still remain unidentified and should be pursued in the future. Moreover, the close correlation between the extent of lesional fibrosis and markers of EMT, MMT, EndoMT, FMT and SMM as shown here should facilitate our understanding of the molecular mechanisms underlying the DE pathophysiology. Since this DE model is based on a biologically plausible and evidence-backed theory, it should shed much needed insight into the molecular mechanisms underlying the pathophysiology of DE.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by Grants 81471434 (S.W.G.), 81530040 (S.W.G.), 81771553 (S.W.G.), 81671436 (X.S.L.) and 81871144 (X.S.L.) from the National Natural Science Foundation of China. None of the authors has any conflict of interest to disclose.

SWI/SNF Complex Mutations in Gynecologic Cancers: Molecular Mechanisms and Models

The SWI/SNF (mating type SWItch/Sucrose NonFermentable) chromatin remodeling complexes interact with histones and transcription factors to modulate chromatin structure and control gene expression. These evolutionarily conserved multisubunit protein complexes are involved in regulating many biological functions, such as differentiation and cell proliferation. Genomic studies have revealed frequent mutations of genes encoding multiple subunits of the SWI/SNF complexes in a wide spectrum of cancer types, including gynecologic cancers. These SWI/SNF mutations occur at different stages of tumor development and are restricted to unique histologic types of gynecologic cancers. Thus, SWI/SNF mutations have to function in the appropriate tissue and cell context to promote gynecologic cancer initiation and progression. In this review, we summarize the current knowledge of SWI/SNF mutations in the development of gynecologic cancers to provide insights into both molecular pathogenesis and possible treatment implications for these diseases.

Differential Expression of KRAS and SIRT1 in Ovarian Cancers with and Without Endometriosis

Accumulating research shows that ovarian cancer progression can be influenced by both gene mutations and endometriosis. However, the exact mechanism at hand is poorly understood. In the current study, we explored the expression of KRAS and SIRT1, two genes previously identified as altered in endometriosis and ovarian cancer. Human endometrial samples were obtained from regularly cycling women with endometriosis, ovarian cancer, and endometriosis-associated ovarian cancer between 18 and 50 of age undergoing hysterectomy, and immunohistochemical analyses were performed. The cytoplasmic expression of KRAS was low in eutopic endometrium from women without endometriosis or ovarian cancer; however, it was elevated in those who have been diagnosed with endometriosis, as well as ovarian cancer with or without the presence of endometriosis. Nuclear and cytoplasmic SIRT1 expression was also low within endometrium without either disease. However, nuclear SIRT1 expression was increased in those with endometriosis and ovarian cancer associated with endometriosis. Nuclear but not the cytoplasmic expression of SIRT1 correlated with KRAS expression in ovarian cancers associated with endometriosis. These results suggest roles of KRAS and SIRT1 in endometriosis and endometriosis-associated ovarian cancer. Cytoplasmic KRAS expression proves to be a key biomarker in both diseases, while nuclear SIRT1 may be a new biomarker specific to those with endometriosis and those with both endometriosis and ovarian cancer. Further research of these genes could aid in determining the pathogenesis of both diseases and help in clarifying the development of endometriosis-associated ovarian cancer.

A mouse model of endometriosis mimicking the natural spread of invasive endometrium

STUDY QUESTION

Is it possible to establish a genetically engineered mouse model (GEMM) of endometriosis that mimics the natural spread of invasive endometrium?

SUMMARY ANSWER

Endometriosis occurs in an ARID1A (AT-rich interactive domain-containing protein 1A) and PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha) mutant GEMM of endometrial dysfunction following salpingectomy.

WHAT IS KNOWN ALREADY

Although mouse models of endometriosis have long been established, most models rely on intraperitoneal injection of uterine fragments, steroid hormone treatments or the use of immune-compromised mice.

STUDY DESIGN, SIZE, DURATION

Mice harboring the lactotransferrin-Cre (LtfCre0/+), Arid1afl, (Gt)R26Pik3ca*H1047R and (Gt)R26mTmG alleles were subject to unilateral salpingectomies at 6 weeks of age. Control (n = 9), LtfCre0/+; (Gt)R26Pik3ca*H1047R; Arid1afl/+ (n = 8) and LtfCre0/+; (Gt)R26Pik3ca*H1047R; Arid1afl/fl (n = 9) were used for the study. The (Gt)R26mTmG allele was used for the purpose of fluorescent lineage tracing of endometrial epithelium. LtfCre0/+; (Gt)R26mTmG (n = 3) and LtfCre0/+; (Gt)R26Pik3ca*H1047R/mTmG; Arid1afl/fl (n = 4) were used for this purpose. Mice were followed until the endpoint of vaginal bleeding at an average time of 17 weeks of age.

PARTICIPANTS/MATERIALS, SETTING, METHODS

At 6 weeks of age, mice were subjected to salpingectomy surgery. Mice were followed until the time point of vaginal bleeding (average 17 weeks), or aged for 1 year in the case of control mice. At time of sacrifice, endometriotic lesions, ovaries and uterus were collected for the purpose of histochemical and immunohistochemical analyses. Samples were analyzed for markers of the endometriotic tissue and other relevant biomarkers.

MAIN RESULTS AND THE ROLE OF CHANCE

Following salpingectomy, LtfCre0/+; (Gt)R26Pik3ca*H1047R/mTmG; Arid1afl/fl mice developed endometriotic lesions, including lesions on the ovary, omentum and abdominal wall. Epithelial glands within lesions were negative for ARID1A and positive for phospho-S6 staining, indicating ARID1A-PIK3CA co-mutation status, and expressed EGFP (enhanced green fluorescent protein), indicating endometrial origins.

LARGE-SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

LtfCre0/+; (Gt)R26Pik3ca*H1047R; Arid1afl/fl mice develop vaginal bleeding as a result of endometrial dysfunction at an average age of 17 weeks and must be sacrificed. Furthermore, while this model mimics the natural spread of endometriotic tissue directly from the uterus to the peritoneum, the data presented do not reject current hypotheses on endometriosis pathogenesis.

WIDER IMPLICATIONS OF THE FINDINGS

The idea that endometriosis is the result of abnormal endometrial tissue colonizing the peritoneum via retrograde menstruation has gained widespread support over the past century. However, most models of endometriosis take for granted this possibility, relying on the surgical removal of bulk uterine tissue and subsequent transplantation into the peritoneum. Growing evidence suggests that somatic mutations in ARID1A and PIK3CA are present in the endometrial epithelium. The establishment of a GEMM which mimics the natural spread of endometrium and subsequent lesion formation supports the hypothesis that endometriosis is derived from mutant endometrial epithelium with invasive properties.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by the American Cancer Society PF-17-163-02-DDC (M.R.W.), the Mary Kay Foundation 026-16 (R.L.C.) and the Ovarian Cancer Research Fund Alliance 457446 (R.L.C.). The authors declare no competing interests.

In-vitro models of human endometriosis

Endometriosis is one of the most common benign gynecological diseases in women of reproductive age worldwide. In past decades, a number of in-vitro models have been used to investigate the pathology and therapeutic methods for the treatment of endometriosis. The current review summarized the majority of currently available in-vitro models, which utilize a variety of cell or tissues types, including endometriotic cell lines, primary endometrial stromal cells, endometrial stem cells, endometrial explants, peritoneal explants and immune cells. These cells or tissues are cultured individually, co-cultured in 2D or 3D systems with various matrices or cultured in chicken chorioallantotic membranes and amniotic membranes culture systems. These models are able to represent one or more aspects of the process of endometriosis. These models are helpful and can be used to investigate the development of endometriosis and the underlying mechanisms of this disorder in detail, and help investigators select appropriate models for their experiments. Recently, the new concept of endometriosis as a fibrotic condition will lead research to investigate the differentiation of myofibroblasts and the development of fibrosis in endometriotic lesions, which will increase the development of novel models that can be used to investigate endometriotic fibrosis.

Patient-derived organoids from endometrial disease capture clinical heterogeneity and are amenable to drug screening

Endometrial disorders represent a major gynaecological burden. Current research models fail to recapitulate the nature and heterogeneity of these diseases, thereby hampering scientific and clinical progress. Here we developed long-term expandable organoids from a broad spectrum of endometrial pathologies. Organoids from endometriosis show disease-associated traits and cancer-linked mutations. Endometrial cancer-derived organoids accurately capture cancer subtypes, replicate the mutational landscape of the tumours and display patient-specific drug responses. Organoids were also established from precancerous pathologies encompassing endometrial hyperplasia and Lynch syndrome, and inherited gene mutations were maintained. Endometrial disease organoids reproduced the original lesion when transplanted in vivo. In summary, we developed multiple organoid models that capture endometrial disease diversity and will provide powerful research models and drug screening and discovery tools.

Galectin-3 plays an important role in endometriosis development and is a target to endometriosis treatment

This study aimed to analyze galectin-3 importance in endometriotic lesions development and the effect of recombinant Gal-3 carbohydrate recognition domain (Gal3C) in experimental endometriosis treatment. Experimental endometriosis was induced in WT and Gal-3-/- mice. Initially developed lesions were macroscopically and histologically analyzed, including immunohistochemical analysis. Then, WT mice were treated with Gal3C for 15 days. Gal-3 deficiency and Gal3C treatment significantly impaired endometriosis development. A significant decrease in lesions implantation and size, VEGF and VEGFR-2 expression, vascular density and macrophage distribution were observed in Gal-3 absence or inhibition. A greater presence of iNOS positive cells was observed in knockout mice lesions, while the presence of Arginase positive cells was higher in the WT animal lesions. In addition, COX-2 and TGFb1 were reduced by Gal3C treatment. Data showed here indicate a relevant role of Gal-3 in endometriosis development and highlight a target of endometriosis treatment using Gal-3 inhibitor.

The Endometriotic Tumor Microenvironment in Ovarian Cancer

Women with endometriosis are at increased risk of developing ovarian cancer, specifically ovarian endometrioid, low-grade serous, and clear-cell adenocarcinoma. An important clinical caveat to the association of endometriosis with ovarian cancer is the improved prognosis for women with endometriosis at time of ovarian cancer staging. Whether endometriosis-associated ovarian cancers develop from the molecular transformation of endometriosis or develop because of the endometriotic tumor microenvironment remain unknown. Additionally, how the presence of endometriosis improves prognosis is also undefined, but likely relies on the endometriotic microenvironment. The unique tumor microenvironment of endometriosis is composed of epithelial, stromal, and immune cells, which adapt to survive in hypoxic conditions with high levels of iron, estrogen, and inflammatory cytokines and chemokines. Understanding the unique molecular features of the endometriotic tumor microenvironment may lead to impactful precision therapies and/or modalities for prevention. A challenge to this important study is the rarity of well-characterized clinical samples and the limited model systems. In this review, we will describe the unique molecular features of endometriosis-associated ovarian cancers, the endometriotic tumor microenvironment, and available model systems for endometriosis-associated ovarian cancers. Continued research on these unique ovarian cancers may lead to improved prevention and treatment options.

Endometriosis does not confer improved prognosis in ovarian clear cell carcinoma: a retrospective study at a single institute

BACKGROUND

Considered as the precursor lesion of a subset of ovarian clear cell carcinoma (OCCC), the prognostic role of endometriosis in OCCC patients remains controversial. This study aimed to investigate the prognostic role of coexisting endometriosis in the survival of patients with OCCC, and also sought to identify other prognostic factors.

RESULTS

A total of 125 patients were diagnosed with OCCC during the study period. Of these, 55 (44.0%) patients had coexisting endometriosis. Patients with endometriosis were younger (p = 0.030), had smaller tumor diameter (p = 0.005) and lower preoperative CA125 levels (p = 0.005). More patients with endometriosis had International Federation of Gynecology and Obstetrics (FIGO) stage I disease (83.6% vs. 51.4%, p = 0.000) and exhibited sensitivity to platinum-based regimen (89.6% vs. 66.7%, p = 0.003). Univariate and multivariate analysis revealed that coexisting endometriosis was not a predictor of 5-year overall survival (OS) or progression-free survival (PFS) of OCCC patients. For OS, chemosensitivity was the only useful prognostic factor (Hazards ratio (HR) 109.33, 95% Confidence Interval (CI) 23.46-511.51; p = 0.000). For PFS, the useful prognostic factors were ascites (HR 2.78, 95% CI 1.21-6.47; p = 0.016), FIGO stage (HR 1.61, 95% CI 1.04-2.49; p = 0.033), and chemosensitivity (HR 101.60, 95% CI 29.45-350.49; p = 0.000). Moreover, higher FIGO stage was the only risk factor for resistance to platinum-based chemotherapy (Exp (B) = 0.292, 95% CI 0.123-0.693; p = 0.005).

CONCLUSIONS

In this study, coexisting endometriosis was not a prognostic factor for the survival of OCCC patients. The most important predictor of both 5-year OS and PFS was chemosensitivity to platinum-based regimen, which decreased significantly with increase in FIGO stage.

Preclinical Models of Ovarian Cancer: Pathogenesis, Problems, and Implications for Prevention

Preclinical models are relatively underutilized and underfunded resources for modeling the pathogenesis and prevention of ovarian cancers. Several reviews have detailed the numerous published models of ovarian cancer. In this review, we will provide an overview of experimental model systems, their strengths and limitations, and use selected models to illustrate how they can be used to address specific issues about ovarian cancer pathogenesis. We will then highlight some of the preclinical prevention studies performed to date and discuss experiments needed to address important unanswered questions about ovarian cancer prevention strategies.

The ARID1A, p53 and ß-Catenin statuses are strong prognosticators in clear cell and endometrioid carcinoma of the ovary and the endometrium

Aim

The objective of this study was to evaluate the prognostic value of ARID1A, p53, p21, p16 and ß-Catenin in endometrioid and clear cell ovarian and endometrial carcinomas.

Materials and methods

97 tumors were available for analysis of ARID1A, p53, p21, p16 and ß-Catenin with the techniques of tissue microarray and immunohistochemistry. 32 were ovarian carcinomas and 65 were endometrial carcinomas.

Results

Endometrioid ovarian carcinomas showed negative staining for ARID1A (a) and p21 (b), aberrant expression of p53 (c) and p16 (d) and ß-Catenin positive nuclear expression (e) respectively in 19% (a), 100% (b), 28.6% (c), 52.4% (d) and 4.8% (e) of all cases. In the group of clear cell ovarian carcinomas it was 63.6% (a), 100% (b), 81.8% (c), 54.5% (d) and 0% (e). For endometrioid uterine carcinomas it was 75.7% (a), 94.9% (b), 30.5% (c), 52.1% (d) and 6.8% (e) and for clear cell uterine carcinomas it was 8.6% (a), 100% (b), 50% (c), 100% (d) and 0% (e). Survival analysis showed that negative expression of ARID1A, p53 aberrant expression and ß-Catenin nuclear positive staining are independent negative prognosticators in both, clear cell and endometrioid carcinoma, regardless of ovarian or uterine origin. Cox-Regression analysis showed them again as negative prognostic factors. Furthermore, we found a significant correlation between ARID1A and ß-Catenin expression in endometrioid uterine tumors.

Conclusion

The analyzed gynaecological carcinoma showed a distinct expression scheme of proteins that are associated with tumor suppression. We may conclude that ARID1A, p53 and ß-Catenin are the strongest prognostic factors by analyzing a subgroup of tumor suppressor genes in clear cell and endometrioid subtypes of ovarian and endometrial cancer and may be used along with traditional morphological and clinical characteristics for prognosis.

The disparate origins of ovarian cancers: pathogenesis and prevention strategies

Ovarian cancer is the fifth cause of cancer-related death in women and comprises a histologically and genetically broad range of tumours, including those of epithelial, sex cord-stromal and germ cell origin. Recent evidence indicates that high-grade serous ovarian carcinoma, clear cell carcinoma and endometrioid carcinoma primarily arise from tissues that are not normally present in the ovary. These histogenetic pathways are informing risk-reduction strategies for the prevention of ovarian and ovary-associated cancers and have highlighted the importance of the seemingly unique ovarian microenvironment.

Endometriosis: where are we and where are we going?

Endometriosis currently affects ~5.5 million reproductive-aged women in the U.S. with symptoms such as painful periods (dysmenorrhea), chronic pelvic pain, pain with intercourse (dyspareunia), and infertility. It is defined as the presence of endometrial tissue outside the uterine cavity and is found predominately attached to sites within the peritoneal cavity. Diagnosis for endometriosis is solely made through surgery as no consistent biomarkers for disease diagnosis exist. There is no cure for endometriosis and treatments only target symptoms and not the underlying mechanism(s) of disease. The nature of individual predisposing factors or inherent defects in the endometrium, immune system, and/or peritoneal cavity of women with endometriosis remains unclear. The literature over the last 5 years (2010-2015) has advanced our critical knowledge related to hormones, hormone receptors, immune dysregulation, hormonal treatments, and the transformation of endometriosis to ovarian cancer. In this review, we cover the aforementioned topics with the goal of providing the reader an overview and related references for further study to highlight the progress made in endometriosis research, while concluding with critical areas of endometriosis research that are urgently needed.

Animal and cellular models of human disease

In this eighteenth (2016) Annual Review Issue of The Journal of Pathology, we present a collection of 19 invited review articles that cover different aspects of cellular and animal models of disease. These include genetically-engineered models, chemically-induced models, naturally-occurring models, and combinations thereof, with the focus on recent methodological and conceptual developments across a wide range of human diseases.

An efficient model of human endometriosis by induced unopposed estrogenicity in baboons

Endometriosis is a chronic estrogen-dependent disease that occurs in approximately 10% of reproductive age women. Baboons offer a clear benefit for studying the initiation and progression of endometriosis since baboon is very close to humans phylogenetically. Progestins are used in the treatment of endometriosis. The therapeutic window of progestins depends on the ratio of its affinity towards progesterone receptor agonism verses antagonism. The present study is to determine the role of pure antiprogestin in baboon endometriosis. We hypothesize that pure antiprogestin will induce unopposed estrogenicity and spontaneous endometriosis in baboons. The rate of endometrial invasion and attachment through modeled peritoneum in the presence and absence of progesterone and antiprogestin was evaluated in this study. A baboon model of endometriosis induced by unopposed estrogenicity using progesterone receptor antagonist (EC304) was used in this study. We observed EC304 has induced unopposed estrogenicity that deregulated proteins involved in attachment, invasion, cell growth, and steroid hormone receptors in this model. Our data suggest that depleting progesterone levels in the endometrium will increase estrogen hyper-responsiveness that leads to increased endometriotic lesion progression in the baboon (Papio anubis) model. This study reports a refined model of human endometriosis in baboons that could potentially be used to develop new diagnostic and therapeutic strategies for the benefit of women suffering from endometriosis.