Identification of Interleukin-9 Producing Immune Cells in Endometrial Carcinoma and Establishment of a Prognostic Nomogram.

Background: Interleukin-9 (IL9) plays a critical role in immunity and the pathogenesis of endometrial cancer (EC), especially endometrioid EC (EEC). This study aimed to identify the IL9+ immune cell subsets and their pleiotropic functions and establish an optimized prognostic nomogram towards the promotion of personalized treatment of EEC. Methods: 1,417 EC patients were involved in the present study. 143 patients from the tertiary gynecology centers in Shanghai between 2013 and 2019 were recruited, and the study protocol was approved by the Institutional Review Board (IRB) of Shanghai First Maternity and Infant Hospital. The genomic data of the other 1,274 patients were extracted from the TCGA and the MSKCC datasets, respectively. Immune and stromal scores were calculated using the ESTIMATE R tool, and the tumor infiltration of immune cells was analyzed using the TIMER platform. Metascape and GEPIA datasets were used for bioinformatic analysis. P < 0.05 was considered statistically significant. All statistical analyses were performed with GraphPad Prism and R studio. Results: 552 genes that were correlated with leukocyte infiltration, lymphocyte activation, and regulation of innate immune response were up-regulated in the high immune score group. More IL9+ cell infiltration was detected in the highly and moderately differentiated EC (p = 0.04). High IL9+ lymphocyte infiltration was related to a better overall survival (p = 0.0027). IL9 positive cell clusters included ILC2s, Vδ2 γδT cells, mast cells, macrophages, and Th9 cells. Parameters such as FIGO stage, IL9 score, Vδ2 + γδT cell infiltration, classification of differentiation, and diabetes mellitus were assigned a weighted number of points in the nomogram for a specific predicted 3-, 5- and 10-year overall survival (OS). IL9-IL9R axis played a vital role in EEC, IL9R positive cell subgroups were also identified, and the related function was analyzed in the present study. Additionally, PR (Progesterone Receptor, or PGR) expression was relevant to a higher density of IL9+ lymphocyte infiltration. However, PGRMC1 (Progesterone Receptor Membrane Component 1) was negatively relevant to IL9R (p = 4.26e-8). Conclusion: We observed a significant infiltration of IL9+ cells and the overrepresentation of IL-9R in tissue specimens of patients in EC cases. The nomogram incorporating the IL9 could accurately predict individualized survival probability in EEC. Additionally, this study not only established a prognostic nomogram but also assist in the firmer understanding of the relevance of the IL9-IL9R axis and IL9-producing cells in EC immunity.

Estrogen-ERα signaling and DNA hypomethylation co-regulate expression of stem cell protein PIWIL1 in ERα-positive endometrial cancer cells.

BACKGROUND: We previously identified PIWIL1 as an oncogene involved in endometrial carcinogenesis. However, the mechanism of Piwil1 mediated regulation of tumorigenesis remains poorly understood. METHODS: The expression levels of target genes in endometrial cancer cells were detected by quantitative reverse transcription-PCR (RT-qPCR) and western blotting. Up- or down-regulation of ERα or PIWIL1 was achieved by transient transfection with expressing plasmids or short hairpin RNA (shRNA). Dual-luciferase reporter assays and chromatin immunoprecipitation (ChIP) were used to demonstrate the ERα bound to the half estrogen response element (half-ERE) located in PIWIL1 promoter. The expression of PIWIL1 and ERα in endometrial carcinoma tissues were investigated using immunohistochemistry and RT-qPCR. The proliferation ability of cancer cells were evaluated by MTT. Methylation status of the PIWIL1 promoter was detected by bisulfite sequencing PCR (BSP). RESULTS: In the present study, we found that PIWIL1 mediated E2-stimulated cancer cell proliferation. In ERα-positive endometrial cancer cells, we demonstrated that estrogen-ERα signaling significantly up-regulated the expression of PIWIL1, which was mediated by binding of the ERα onto the PIWIL1 promoter. Furthermore, we found that a half-ERE in the PIWIL1 promoter was essential for ERα binding. The PIWIL1 promoter was hypomethylated in ERα-positive endometrial cancer cells. Treatment with 5-aza-deoxycytidine (5-aza-dC) could up-regulate PIWIL1 expression. CONCLUSIONS: These findings uncover a novel molecular mechanism by which estrogen-ERα signaling and DNA hypomethylation co-regulate PIWIL1 expression. These findings provide novel insights into the hormonal regulation of PIWIL1 in endometrial cancer and the PIWIL1's role in estrogen-stimulated endometrial carcinogenesis. Video Abstract. (MP4 41319 kb).

Prognostic significance of immune landscape in tumour microenvironment of endometrial cancer.

Tumour microenvironment (TME) is crucial to tumorigenesis. This study aimed to uncover the differences in immune phenotypes of TME in endometrial cancer (EC) using Uterine Corpus Endometrial Carcinoma (UCEC) cohort and explore the prognostic significance. We employed GVSA enrichment analysis to cluster The Cancer Genome Atlas (TCGA) EC samples into immune signature cluster modelling, evaluated immune cell profiling in UCEC cohort (n = 538) and defined four immune subtypes of EC. Next, we analysed the correlation between immune subtypes and clinical data including patient prognosis. Furthermore, we analysed the expression of immunomodulators and DNA methylation modification. The profiles of immune infiltration in TCGA UCEC cohort showed significant difference among four immune subtypes of EC. Among each immune subtype, natural killer T cells (NKT), dendritic cells (DCs) and CD8+ T cells were significantly associated with EC patients survival. Each immune subtype exhibited specific molecular classification, immune cell characterization and immunomodulators expression. Moreover, the expression immunomodulators were significantly related to DNA methylation level. In conclusion, the identification of immune subtypes in EC tissues could reveal unique immune microenvironments in EC and predict the prognosis of EC patients.

Correction: AMF/PGI-mediated tumorigenesis through MAPK-ERK signaling in endometrial carcinoma.

[This corrects the article DOI: 10.18632/oncotarget.4708.].

POLE mutations improve the prognosis of endometrial cancer via regulating cellular metabolism through AMF/AMFR signal transduction.

BACKGROUND: The morbidity and mortality of endometrial tumors, a common type of malignant cancer in women, have increased in recent years. POLE encodes the DNA polymerase ε, which is responsible for the leading strand DNA replication. Somatic mutations of POLE have been acknowledged in numerous cancers, resulting in the accumulation of DNA errors, leading to ultra-mutated tumors. Mutations in the exonuclease domain of POLE have been reported to improve progression-free survival in endometrial cancer. However, the potential relationship and underlying mechanism between POLE mutations and the prognosis of endometrial cancer patients remains unclear. METHODS: The whole exome sequencing data, RNA sequencing data, and clinical information were obtained from the TCGA database and employed for the analyses in this study. The detailed mutational information was analyzed using whole exome sequencing data and the mutated genes were shown with OncoPlot. The survival curves and cox proportional hazards regression analysis were used to accessed patient prognosis, the association of clinical characteristics and prognosis. Differentially expressed genes were analyzed by the edgeR R/Bioconductor package, then the GSEA Pre-ranked tool was used for Gene Set Enrichment Analysis (GSEA) to estimate the function of genes. Expression values were clustered using hierarchical clustering with Euclidean distance and ward linkage by the dendextend R package. RESULTS: POLE mutational status was proven to be an independent prognostic factor for endometrial cancer patients. Patients with somatic POLE mutations presented a favorable prognosis. POLE mutations regulated glycolysis and cytokine secretion, affecting cell metabolism and immune response. Autocrine motility factor (AMF)/PGI and AMFR/gp78 exhibited higher expression levels in POLE mutant patients. The comprehensive high expressions of AMFR/gp78 and low expression of POLE were associated with the favorable prognosis of endometrial cancer patients. CONCLUSIONS: This study showed the POLE mutations a vital factor in endometrial cancer patients, leading to a higher expression of AMF/PGI and AMFR/gp78. These results suggested comprehensive consideration of the POLE mutations, expression of AMF/PGI and AMFR/gp78 may provide a more feasible and effective approach for the treatment of endometrial cancer, which might improve the prognosis.

Autocrine motility factor promotes endometrial cancer progression by targeting GPER-1.

BACKGROUND: Autocrine motility factor (AMF) is a critical factor regulating aggressiveness of endometrial cancer (EC). Multiple pieces of evidence indicate that it is through G protein coupled estrogen receptor (GPER) signaling pathway that some growth factors promoted the migration and proliferation of tumor cells. The aim of this study is to explore the role of GPER-1 in AMF mediated regulatory mechanisms of EC recurrence and progression. METHODS: Real-Time Cell Analysis (RTCA) assays were performed to assess whether AMF depends on Autocrine motility factor recepter (AMFR) signaling in EC cells. A genome-wide expression microarray and Yeast Two-Hybrid assay were used to detect AMF and GPER-1 interaction in the context of AMFR depletion, and co-immunoprecipitation and immunofluorescence experiments were performed to confirm the physical interaction. Isobaric Tags for Relative and Absolute Quantification (iTRAQ) analysis was used for the identification of the target pathway activated by AMF-GPER-1 interaction. Cohorts of mice harboring xenografts derived from modified SPEC2 cell lines were treated with or without exogenous AMF to validate the results of previous experiments. Immunohistochemistry was performed to assess AMF and GPER-1 expression in endometrial cancer specimens and normal endometrium. RESULTS: Our data showed that GPER-1 binds to AMF and the formed complex translocates from the plasma membrane to the cytoplasm. Mechanistic investigations demonstrated that interaction between AMF and GPER-1 triggers phosphoinositide-3-kinase signaling and promotes EC cell growth. More importantly, through animal experiments and human tissue experiments, we found that AMF contributes to GPER-1-mediated EC progression, which is consistent with the above observations. CONCLUSIONS: Our work not only delineated the regulatory mechanisms of endometrial cancer progression by AMF-GPER-1-AKT signaling cascade but also laid the foundation of targeting this pathway for treating endometrial cancer.

Loss of exosomal miR-148b from cancer-associated fibroblasts promotes endometrial cancer cell invasion and cancer metastasis.

Cancer-associated fibroblasts (CAFs) play crucial roles in tumor progression, given the dependence of cancer cells on stromal support. Therefore, understanding how CAFs communicate with endometrial cancer cell in tumor environment is important for endometrial cancer therapy. Exosomes, which contain proteins and noncoding RNA, are identified as an important mediator of cell-cell communication. However, the function of exosomes in endometrial cancer metastasis remains poorly understood. In the current study we found that CAF-derived exosomes significantly promoted endometrial cancer cell invasion comparing to those from normal fibroblasts (NFs). We identified a significant decrease of miR-148b in CAFs and CAFs-derived exosomes. By exogenously transfect microRNAs, we demonstrated that miR-148b could be transferred from CAFs to endometrial cancer cell through exosomes. In vitro and in vivo studies further revealed that miR-148b functioned as a tumor suppressor by directly binding to its downstream target gene, DNMT1 to suppress endometrial cancer metastasis. In endometrial cancer DNMT1 presented a potential role in enhancing cancer cell metastasis by inducing epithelial-mesenchymal transition (EMT). Therefore, downregulated miR-148b induced EMT of endometrial cancer cell as a result of relieving the suppression of DNMT1. Taken together, these results suggest that CAFs-mediated endometrial cancer progression is partially related to the loss of miR-148b in the exosomes of CAFs and promoting the transfer of stromal cell-derived miR-148b might be a potential treatment to prevent endometrial cancer progression.

The role of lncRNAs in the development of endometrial carcinoma.

Endometrial carcinoma (EC) is one of the most common types of gynecological cancer. Long noncoding RNAs (lncRNAs) are associated with the carcinogenesis and progression of EC. In the following review, the emerging role of lncRNAs in EC initiation and progression is considered. The profile of lncRNAs is becoming higher as the contribution of lncRNAs to carcinogenesis through diverse mechanisms is being increasingly recognized, including in EC. A number of lncRNA-profiling studies have identified aberrantly expressed lncRNAs in EC tissue, and the regulatory network associated with these lncRNAs may be critical in EC progression. Additionally, certain lncRNAs may have diagnostic and/or prognostic significance. The potential function of lncRNAs as prospective therapeutic and prognostic targets in EC will be evaluated.

Cross-talk between p21-activated kinase 4 and ERα signaling triggers endometrial cancer cell proliferation.

Cross-talk between estrogen receptor alpha (ERα) and signal transduction pathways plays an important role in the progression of endometrial cancer (EC). Here, we show that 17ß-estradiol (E2) stimulation increases p21-activated kinase 4 (Pak4) expression and activation in ER-positive EC cells. The estrogen-induced Pak4 activation is mediated via the PI3K/AKT pathway. Estrogen increases Pak4 and phosphorylated-Pak4 (p-Pak4) nuclear accumulation, and Pak4 in turn enhances ERα trans-activation. Depletion or functional inhibition of Pak4 abrogates EC cell proliferation induced by E2, whereas overexpression of Pak4 rescues cell proliferation decreased by inhibiting the estrogen pathway. Pak4 knockdown decreases cyclin D1 expression and induces G1-S arrest. Importantly, Pak4 suppression inhibits E2 induced EC tumor growth in vivo, in a mouse xenograft model. These data demonstrate that estrogen stimulation increases Pak4 expression and activation, which in turn enhances ERα transcriptional activity and ERα-dependent gene expression, resulting in increased proliferation of EC cells. Thus inhibition of Pak4-ERα signaling may represent a novel therapeutic strategy against endometrial carcinoma.

Dicer1 dysfunction promotes stemness and aggression in endometrial carcinoma.

Endometrial carcinoma is one of the most common gynecological malignancies, but the molecular events involved in the development and progression of endometrial carcinoma remain unclear. Dicer1 and cancer stem cells play important roles in cell motility and survival. This study investigated the role of the let-7 family and Dicer1 in the stemness of endometrial carcinoma cells. We profiled Dicer1 expression in clinical samples and explored its relationship with stem cell-associated markers and clinical parameters. We showed that Dicer1 dysfunction leads to the enrichment of tumor stemness features and tumor aggression both in vitro and in vivo. We also identified the mechanism related to this potential tumor-predisposing phenotype: loss of Dicer1 induced abnormal expression of the let-7 family, which comprises well-known tumor suppressors, thus regulating stemness in endometrial carcinoma cells.

Efficacy of Postoperative Hormone Replacement Therapy on Prognosis of Patients with Serous Ovarian Carcinoma.

BACKGROUND: Ovarian cancer is the most common cause of gynecological cancer-associated death. Iatrogenic menopause might adversely affect the quality of life and health outcomes in young female cancer survivors. We evaluated whether postoperative hormone replacement therapy (HRT) had a negative influence on the progression-free survival (PFS) of patients with papillary serous ovarian cancer (SOC). METHODS: We retrospectively reviewed the medical records of patients with papillary SOC, treated from January 1980 to December 2009, who suffered from menopause with or without HRT. Clinical characteristics of patients were compared between the two groups (HRT and non-HRT). Blood samples were collected from all the participants to detect serum cancer antigen (CA) 125. Hazard ratios with 95% confidential intervals for each variable were calculated by univariable and multivariable conditional Logistic regression analyses. RESULTS: Among 112 identified patients, 31 were HRT users and 81 were not. The two groups did not significantly differ in median age at diagnosis (t = 0.652, P = 0.513), International Federation of Gynecology and Obstetrics (FIGO) stage (χ2 = 0.565, P = 0.754), differentiation (χ2 = 1.728, P = 0.422), resection status (χ2 = 0.070, P = 0.791), relapse (χ2 = 0.109, P = 0.741), chemotherapy course (t = -1.079, P = 0.282), follow-up interval (t = 0.878, P = 0.382), or PFS (t = 0.580, P = 0.562). Median Kupperman score at the onset of HRT was 30.81 and 12.19 after the therapy (t = 3.302, P = 0.001). According to the analysis, the strongest independent variables in predicting PFS were FIGO stage and disease that was not optimally debulked. CONCLUSIONS: Postoperative HRT is not a prognostic factor for PFS of patients with papillary SOC. However, multicenter studies are needed to verify and extend our findings.

Dual-specificity Phosphatase 1 Deficiency Induces Endometrioid Adenocarcinoma Progression via Activation of Mitogen-activated Protein Kinase/Extracellular Signal-regulated Kinase Pathway.

BACKGROUND: Previously, we reported that dual-specificity phosphatase 1 (DUSP1) was differentially expressed in endometrioid adenocarcinoma (EEA). However, the role of DUSP1 in EEA progression and the relationship between DUSP1 and medroxyprogesterone (MPA) are still unclear. METHODS: The expression of DUSP1 in EEA specimens was detected by immunohistochemical analysis. The effect of DUSP1 on cell proliferation was analyzed by Cell Counting Kit 8 and colony formation assay, and cell migration was analyzed by transwell assay. MPA-induced DUSP1 expression in EEA cells was measured by Western blot. RESULTS: DUSP1 expression was deficient in advanced International Federation of Gynecology and Obstetrics stage, high-grade and myometrial invasive EEA. In EEA cell lines (Hec1A, Hec1B, RL952, and Ishikawa), the DUSP1 expression was substantially higher in Ishikawa cells than in other cell lines (P < 0.05). Knockdown of DUSP1 promoted Ishikawa cells proliferation, migration, and activation of mitogen-activated protein kinases/extracellular signal-regulated kinase (MAPK/Erk) pathway. MPA-induced DUSP1 expression and inhibited MAPK/Erk pathway in Ishikawa cells. CONCLUSIONS: Our data suggest that DUSP1 deficiency promotes EEA progression via MAPK/Erk pathway, which may be reversed by MPA, suggesting that DUSP1 may serve as a potential therapeutic target for the treatment of EEA.

Tumor-associated macrophage-derived CXCL8 could induce ERα suppression via HOXB13 in endometrial cancer.

PURPOSE: To elucidate the role of tumor-associated macrophage (TAM) in the loss of ERα in endometrial cancer (EC) and the underlying mechanism. MATERIALS AND METHODS: Tissue microarrays and immunohistochemistry assays were performed using endometrial cancer tissue along with coculture, immunofluorescence, invasion assays and ChIP-qPCR using a human endometrial cancer cell line. RESULTS: Compared with normal tissue, an increased number of TAM was found in EC tissue (34.0 ± 2.6 vs. 8.3 ± 1.1, respectively; p < 0.001), which may downregulate ERα (27.4%, p < 0.05 for HEC-1A and 16.9%, p < 0.05 for Ishikawa) and promote EC cell invasion (1.8-fold, p < 0.001 for HEC-1A and 2.0-fold, p < 0.001 for Ishikawa). Furthermore, we found that TAM-derived CXCL8 mediated the loss of ERα and cancer invasion via HOXB13. HOXB13 was highly expressed in the ERα-negative subtype (r = -0.204, p = 0.002) and low expression of ESR1 was associated with a poor prognosis for EC patients (log-rank p < 0.05). CONCLUSION: TAM-secreted CXCL8 downregulated the ERα expression of EC cells via HOXB13, which may be associated with cancer invasion, metastasis and poor prognosis.

Mutant p53 induces EZH2 expression and promotes epithelial-mesenchymal transition by disrupting p68-Drosha complex assembly and attenuating miR-26a processing.

The tumor suppressor p53 and the transcriptional repressor Enhancer of Zeste Homolog 2 (EZH2) have both been implicated in the regulation of epithelial-mesenchymal transition (EMT) and tumor metastasis via their impacts on microRNA expression. Here, we report that mutant p53 (mutp53) promotes EMT in endometrial carcinoma (EC) by disrupting p68-Drosha complex assembly. Overexpression of mutp53 has the opposite effect of wild-type p53 (WTp53), repressing miR-26a expression by reducing pri-miR-26a-1 processing in p53-null EC cells. Re-expression of miR-26a in mutp53 EC cells decreases cell invasion and promotes mesenchymal-epithelial transition (MET). Rescuing miR-26a expression also inhibits EZH2, N-cadherin, Vimentin, and Snail expression and induces E-cadherin expression both in vitro and in vivo. Moreover, patients with higher serum miR-26a levels have a better survival rate. These results suggest that p53 gain-of-function mutations accelerate EC tumor progression and metastasis by interfering with Drosha and p68 binding and pri-miR-26a-1 processing, resulting in reduced miR-26a expression and EZH2 overexpression.

KDM4B and KDM4A promote endometrial cancer progression by regulating androgen receptor, c-myc, and p27kip1.

Epidemiological evidence suggests that elevated androgen levels and genetic variation related to the androgen receptor (AR) increase the risk of endometrial cancer (EC). However, the role of AR in EC is poorly understood. We report that two members of the histone demethylase KDM4 family act as major regulators of AR transcriptional activityin EC. In the MFE-296 cell line, KDM4B and AR upregulate c-myc expression, while in AN3CA cells KDM4A and AR downregulate p27kip1. Additionally, KDM4B expression is positively correlated with AR expression in EC cell lines with high baseline AR expression, while KDM4A and AR expression are positively correlated in low-AR cell lines. In clinical specimens, both KDM4B and KDM4A expression are significantly higher in EC tissues than that in normal endometrium. Finally, patients with alterations in AR, KDM4B, KDM4A, and c-myc have poor overall and disease-free survival rates. Together, these findings demonstrate that KDM4B and KDM4A promote EC progression by regulating AR activity.

AMF/PGI-mediated tumorigenesis through MAPK-ERK signaling in endometrial carcinoma.

Autocrine motility factor (AMF), which is also known as phosphoglucose isomerase (PGI), enhances tumor cell growth and motility. In this study, we found that AMF and its receptor were both highly expressed in Endometrial Carcinoma (EC) tissues compared to normal tissues. Levels of AMF were increased in serum of endometrial cancer patients. Downregulation of AMF by shRNA inhibited invasion, migration and proliferation as well as growth in a three-dimensional culture. AMF cytokine function, but not enzymatic activity of PGI, regulated tumorigenic activities of AMF. The MAPK-ERK1/2 pathway contributed to AMF-induced effects in EC cells. In agreement, Mek inhibitor decreased AMF-induced invasion, migration and proliferation of EC cells. In addition, in two mouse tumor metastasis models (EC cells delivered through left ventricle or intraperitoneally) AMF-silenced EC cells showed decreased tumor proliferative and metastatic capacities. We suggest that AMF/PGI is a potential therapeutic target in endometrial carcinoma.

Autocrine motility factor promotes epithelial-mesenchymal transition in endometrial cancer via MAPK signaling pathway.

Autocrine motility factor (AMF) as a cytokine and a growth factor, is known to regulate tumor cell growth and motility in the progress of various human malignant tumors, however, its role in endometrial cancer (EC) has not been fully studied. In the present study, using immunohistochemistry, we found that AMF was highly expressed in EC tissues compared with normal endometrial tissues and tissue micrioarray technology showed positive correlation between AMF expression and epithelial-to-mesenchymal transition (EMT) related markers E-cadherin, vimentin and Snail. Next, we detected that silencing of AMF by stable transfection with shRNA induced mesenchymal-to-epithelial transition phenotype in Ishikawa and HEC-1B cells by qRT-PCR, western blotting and immunofluorescence. Gene expression profile revealed that AMF silencing resulted in altered expression of EMT related molecular mediators including Snail and transforming growth factor ß receptor 1, and involvement of mitogen-activated protein kinase (MAPK) signaling pathway. Additionally, we found that EMT related markers were downregulated with pretreatment of the MAPK-specific inhibitor U0126 by western blotting. The present study is the first to support a role for AMF mediating EMT in endometrial cancer through MAPK signaling. Therefore, AMF may provide a potential prognostic and therapeutic target in preventing EC progression.

Piwil1 causes epigenetic alteration of PTEN gene via upregulation of DNA methyltransferase in type I endometrial cancer.

Piwil1, a member of the Piwi family, has been well demonstrated to mediate tumorigenesis associated with DNA hypermethylation. It has been reported that Piwil1 is overexpressed in various types of cancer, including endometrial cancer. However, the underlying mechanism of Piwil1 in endometrial cancer remains largely unclear. PTEN exerts an important tumor suppressor role in endometrial carcinogenesis. The present study aimed to investigate whether Piwil1 could regulate the expression of PTEN. Herein, we found that Piwil1 could promote the loss of PTEN expression and increase aberrant hypermethylation of PTEN gene promoter in Ishikawa cells. We also found that Piwil1 could regulate the expression of DNA methyltransferase 1 (DNMT1). Silencing DNMT1 gene could upregulate the PTEN gene expression and change the methylation status of PTEN gene promoter in Ishikawa cells. These results suggested that Piwil1 caused the loss of PTEN expression through DNMT1-mediated PTEN hypermethylation. Taken together, these data provide a novel regulatory mechanism of Piwil1 in endometrial cancer.

Interleukin 6 promotes endometrial cancer growth through an autocrine feedback loop involving ERK-NF-κB signaling pathway.

Interleukin (IL)-6 as an inflammation factor, has been proved to promote cancer proliferation in several human cancers. However, its role in endometrial cancer has not been studied clearly. Previously, we demonstrated that IL-6 promoted endometrial cancer progression through local estrogen biosynthesis. In this study, we proved that IL-6 could directly stimulate endometrial cancer cells proliferation and an autocrine feedback loop increased its production even after the withdrawal of IL-6 from the medium. Next, we analyzed the mechanism underlying IL-6 production in the feedback loop and found that its production and IL-6-stimulated cell proliferation were effectively blocked by pharmacologic inhibitors of nuclear factor-kappa B (NF-κB) and extra-cellular signal-regulated kinase (ERK). Importantly, activation of ERK was upstream of the NF-κB pathways, revealing the hierarchy of this event. Finally, we used an orthotopic nude endometrial carcinoma model to confirm the effects of IL-6 on the tumor progression. Taken together, these data indicate that IL-6 promotes endometrial carcinoma growth through an expanded autocrine regulatory loop and implicate the ERK-NF-κB pathway as a critical mediator of IL-6 production, implying IL-6 to be an important therapeutic target in endometrial carcinoma.

Activation of a positive feedback loop involving IL-6 and aromatase promotes intratumoral 17ß-estradiol biosynthesis in endometrial carcinoma microenvironment.

Tumor-stroma interactions contribute greatly to intratumoral estrogen biosynthesis in endometrial carcinoma, but the mechanisms involved remain largely unknown. Previous study demonstrated that intratumoral aromatase upregulation in stromal cells participated in this process, but the specific aromatase-regulators have not been reported. In the present study, we found that aromatase expression in intratumoral stroma, but not in tumor epithelium, correlated positively with interleukin 6 (IL-6) expression in cancer epithelial cells by immunohistochemistry, which was confirmed using laser capture microdissection/real-time reverse transcription-PCR. With stimulation by exogenous IL-6, aromarase expression was increased in stromal cells not but not in cancer cells. Aromatase mRNA levels in endometrial cancer cells were not influenced by cocultivation with intratumoral stromal cells. When cocultured with 17ß-estradiol (E2 )-treated cancer cells, aromatase mRNA in stromal cells was significantly elevated and increased IL-6 protein levels were detected in E2 -treated culture medium. Next, we demonstrated that E2 -induced IL-6 production was through cooperation between estrogen receptor α and nuclear factor-kappa B. Furthermore, an IL-6 receptor blocking antibody could attenuate the upregulation of aromatase expression in stromal cells and the E2 concentration in coculture systems of cancer and stromal cells. The results were confirmed by an orthotopic nude endometrial carcinoma model in vivo. These studies elucidated the activation of a positive feedback loop, that is, IL-6 stimulated by E2 in endometrial cancer cells induced aromatase expression in stromal cells, promoting enhanced intratumoral E2 synthesis. Blocking of this tumor-stroma interaction may be a therapeutic strategy to overcome in situ estrogen biosynthesis in endometrial carcinoma.