Human Endometrial Tumors Research Articles

K-Ras stabilization by estrogen via PKCδ is involved in endometrial tumorigenesis.

Estrogens are considered as a major risk factor of endometrial cancer. In this study, we identified a mechanism of tumorigenesis in which K-Ras protein is stabilized via estrogen signaling through the ER-α36 receptor. PKCδ was shown to stabilize K-Ras specifically via estrogen signaling. Estrogens stabilize K-Ras via inhibition of polyubiquitylation-dependent proteasomal degradation. Estrogen-induced cellular transformation was abolished by either K-Ras or PKCδ knockdown. The role of PKCδ in estrogen-induced tumorigenesis was confirmed in a mouse xenograft model by reduction of tumors after treatment with rottlerin, a PKCδ inhibitor. Finally, levels of PKCδ correlated with that of Ras in human endometrial tumor tissues. Stabilization of K-Ras by estrogen signaling involving PKCδ up-regulation provides a potential therapeutic approach for treatment of endometrial cancer.

Metabolic vulnerabilities in endometrial cancer.

Women with metabolic disorders, including obesity and diabetes, have an increased risk of developing endometrial cancer. However, the metabolism of endometrial tumors themselves has been largely understudied. Comparing human endometrial tumors and cells with their nonmalignant counterparts, we found that upregulation of the glucose transporter GLUT6 was more closely associated with the cancer phenotype than other hallmark cancer genes, including hexokinase 2 and pyruvate kinase M2. Importantly, suppression of GLUT6 expression inhibited glycolysis and survival of endometrial cancer cells. Glycolysis and lipogenesis were also highly coupled with the cancer phenotype in patient samples and cells. To test whether targeting endometrial cancer metabolism could be exploited as a therapeutic strategy, we screened a panel of compounds known to target diverse metabolic pathways in endometrial cells. We identified that the glycolytic inhibitor, 3-bromopyruvate, is a powerful antagonist of lipogenesis through pyruvylation of CoA. We also provide evidence that 3-bromopyruvate promotes cell death via a necrotic mechanism that does not involve reactive oxygen species and that 3-bromopyruvate impaired the growth of endometrial cancer xenografts.

Progesterone receptor membrane component 1 deficiency attenuates growth while promoting chemosensitivity of human endometrial xenograft tumors

Endometrial cancer is the leading gynecologic cancer in women in the United States with 52,630 women predicted to be diagnosed with the disease in 2014. The objective of this study was to determine if progesterone (P4) receptor membrane component 1 (PGRMC1) influenced endometrial cancer cell viability in response to chemotherapy in vitro and in vivo. A lentiviral-based shRNA knockdown approach was used to generate stable PGRMC1-intact and PGRMC1-deplete Ishikawa endometrial cancer cell lines that also lacked expression of the classical progesterone receptor (PGR). Progesterone treatment inhibited mitosis of PGRMC1-intact, but not PGRMC1-deplete cells, suggesting that PGRMC1 mediates the anti-mitotic actions of P4. To test the hypothesis that PGRMC1 attenuates chemotherapy-induced apoptosis, PGRMC1-intact and PGRMC1-deplete cells were treated in vitro with vehicle, P4 (1 µM), doxorubicin (Dox, 2 µg/ml), or P4 + Dox for 48 h. Doxorubicin treatment of PGRMC1-intact cells resulted in a significant increase in cell death; however, co-treatment with P4 significantly attenuated Dox-induced cell death. This response to P4 was lost in PGRMC1-deplete cells. To extend these observations in vivo, a xenograft model was employed where PGRMC1-intact and PGRMC1-deplete endometrial tumors were generated following subcutaneous and intraperitoneal inoculation of immunocompromised NOD/SCID and nude mice, respectively. Tumors derived from PGRMC1-deplete cells grew slower than tumors from PGRMC1-intact cells. Mice harboring endometrial tumors were then given three treatments of vehicle (1:1 cremophor EL: ethanol + 0.9% saline) or chemotherapy [Paclitaxel (15 mg/kg, i.p.) followed after an interval of 30 minutes by CARBOplatin (50 mg/kg)] at five day intervals. In response to chemotherapy, tumor volume decreased approximately four-fold more in PGRMC1-deplete tumors when compared with PGRMC1-intact control tumors, suggesting that PGRMC1 promotes tumor cell viability during chemotherapeutic stress. In sum, these in vitro and in vivo findings demonstrate that PGRMC1 plays a prominent role in the growth and chemoresistance of human endometrial tumors.

Abstract 4211: Protein kinase C alpha (PKCα) signaling in endometrial cancer

Abstract Endometrial cancer is the most common gynecological malignancy in the US and the fourth most common cancer in women. Despite its high incidence, there is limited knowledge of the molecular etiology of this disease. With obesity being a major risk factor, the incidence of endometrial cancer has been on a steady incline and is expected to become an increasing cause of cancer mortality in future years. Thus, improved understanding of endometrial tumorigenesis is of critical importance. Our analysis of human endometrial tumors identified loss of the signaling molecule PKCα in approximately 60% of endometrioid (Type I) tumors. Loss of PKCα trends with increasing tumor grade and is associated with aggressive disease features such as lymphovascular involvement and myometrial invasion, pointing to an important role for this molecule in regulating endometrial cancer progression. Inactivation of the tumor suppressor PTEN and deregulation of the PI3K/AKT pathway are key drivers of Type I endometrial cancer. Thus, mice with allele-specific knock-in of cancer-related Pten mutants (i.e., PtenΔ4-5, PtenC124R, and PtenG120E) offer unique models for the disease. Precancerous endometrial hyperplasias arising in these mice show loss of PTEN and increased AKT activity. While PKCα is expressed in the normal murine endometrial epithelium at all phases of the estrus cycle, the enzyme is uniformly lost in these precancerous lesions. Thus, disruption of PKCα signaling can occur early in endometrial tumorigenesis. In human endometrial cancer cell lines, low PKCα levels also correlate with PTEN loss; however, shRNA-mediated knockdown of PTEN in PTEN expressing cells did not affect PKCα expression indicating that downregulation of the kinase is not the direct result of changes in PTEN activity. Notably, PKC agonists suppress AKT activity in cells expressing high levels PKCα (HEC-1-A, HEC-50) but not in PKCα-low cells (Ishikawa, RL95-2). Collectively, these data suggest that, in addition to PTEN inactivation, loss of PKCα is required for full activation of the PI3K/AKT signaling pathway during endometrial carcinogenesis. Analysis of the molecular basis for loss of PKCα expression in endometrial tumors identified multiple regulatory mechanisms. PKCα protein expression in tumors generally parallels that of its mRNA and promoter activity assays point to transcriptional mechanisms for PKCα downregulation. Differential mRNA and protein stability were identified as additional levels of regulation of PKCα expression in endometrial cancer. Taken together, our findings indicate that 1) PKCα signaling regulates the PI3K/AKT pathway in the endometrial epithelium; 2) concomitant loss of PKCα and PTEN may act in a co-operative manner in regulation of endometrial turmorigenesis; and 3) loss of PKCα can occur by multiple mechanisms, as often seen with tumor suppressive molecules during neoplastic progression. Supported by NIH grants CA036727, CA016056, and DK60632. Citation Format: Alice H. Hsu, Kathryn J. Curry, Kang-Sup Shim, Peter Frederick, Carl D. Morrison, Baojing Chen, Subodh M. Lele, Gustavo Leone, Adrian R. Black, Jennifer D. Black. Protein kinase C alpha (PKCα) signaling in endometrial cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4211. doi:10.1158/1538-7445.AM2014-4211

CGRRF1 as a novel biomarker of tissue response to metformin in the context of obesity

ObjectiveObesity-associated hyperestrogenism and hyperinsulinemia contribute significantly to the pathogenesis of endometrial cancer. We recently demonstrated that metformin, a drug long used for treatment of type 2 diabetes, attenuates both insulin- and estrogen-mediated proliferative signaling in the obese rat endometrium. In this study, we sought to identify tissue biomarkers that may prove clinically useful to predict tissue response for both prevention and therapeutic studies. We identified CGRRF1 (cell growth regulator with ring finger domain 1) as a novel metformin-responsive gene and characterized its possible role in endometrial cancer prevention. MethodsCGRRF1 mRNA expression was evaluated by RT-qPCR in the endometrium of obese and lean rats, and also in normal and malignant human endometrium. CGRRF1 levels were genetically manipulated in endometrial cancer cells, and its effects on proliferation and apoptosis were evaluated by MTT and Western blot. ResultsCGRRF1 is significantly induced by metformin treatment in the obese rat endometrium. In vitro studies demonstrate that overexpression of CGRRF1 inhibits endometrial cancer cell proliferation. Analysis of human endometrial tumors reveals that CGRRF1 expression is significantly lower in hyperplasia, Grade 1, Grade 2, Grade 3, MMMT, and UPSC endometrial tumors compared to normal human endometrium (p<0.05), suggesting that loss of CGRRF1 is associated with the presence of disease. ConclusionCGRRF1 represents a novel, reproducible tissue marker of metformin response in the obese endometrium. Furthermore, our preliminary data suggests that up-regulation of CGRRF1 expression may prove clinically useful in the prevention or treatment of endometrial cancer.

Telmisartan Induces Growth Inhibition, DNA Double-Strand Breaks and Apoptosis in Human Endometrial Cancer Cells

Telmisartan, an angiotensin II receptor type 1 blocker, is often used as an antihypertension drug, and it has also been characterized as a peroxisome proliferator-activated receptor-gamma (PPARγ) ligand. The purpose of this study was to elucidate the antitumor effects of telmisartan on endometrial cancer cells. We treated three endometrial cancer cell lines with various concentrations of telmisartan, and we investigated the effects of the telmisartan on the cell proliferation, apoptosis, and their related measurements in vitro. We also administered telmisartan to nude mice with experimental tumors to determine its in vivo effects and toxicity. All three endometrial cancer cell lines were sensitive to the growth-inhibitory effect of telmisartan. The induction of apoptosis was confirmed in concert with the altered expression of genes and proteins related to the apoptosis. We also observed that DNA double-strand breaks (DSBs) were induced in HHUA (human endometrial cancer) cells by telmisartan treatment. In addition, experiments in nude mice showed that telmisartan significantly inhibited human endometrial tumor growth, without toxic side effects. Our results suggest that telmisartan might be a new therapeutic option for the treatment of endometrial cancers.

High expression of ecto-nucleotidases CD39 and CD73 in human endometrial tumors.

One of the strategies used by tumors to evade immunosurveillance is the accumulation of extracellular adenosine, which has immunosupressive and tumor promoting effects. The study of the mechanisms leading to adenosine formation at the tumor interstitium are therefore of great interest in oncology. The dominant pathway generating extracellular adenosine in tumors is the dephosphorylation of ATP by ecto-nucleotidases. Two of these enzymes acting sequentially, CD39 and CD73, efficiently hydrolyze extracellular ATP to adenosine. They have been found to play a crucial role in a variety of tumors, but there were no data concerning endometrial cancer, the most frequent of the invasive tumors of the female genital tract. The aim of the present work is to study the expression of CD39 and CD73 in human endometrial cancer. We have analyzed protein and gene expression, as well as enzyme activity, in type I endometrioid adenocarcinomas and type II serous adenocarcinomas and their nonpathological endometrial counterparts. High levels of both enzymes were found in tumor samples, with significantly increased expression of CD39 in type II serous tumors, which also coincided with the higher tumor grade. Our results reinforce the involvement of the adenosinergic system in cancer, emphasizing the relevance of ecto-nucleotidases as emerging therapeutic targets in oncology.

A Genetic Mouse Model of Invasive Endometrial Cancer Driven by Concurrent Loss of Pten and Lkb1 Is Highly Responsive to mTOR Inhibition

Signals from the tumor suppressors PTEN and LKB1 converge on mTOR to negatively regulate its function in cancer cells. Notably, both of these suppressors are attenuated in a significant fraction of human endometrial tumors. In this study, we generated a genetic mouse model of endometrial cancer driven by concomitant loss of these suppressors to gain pathophysiological insight into this disease. Dual loss of Pten and Lkb1 in the endometrial epithelium led to rapid development of advanced endometrioid endometrial tumors with 100% penetrance and short host survival. The tumors displayed dysregulated phosphatidylinositol 3-kinase (PI3K)/Akt and Lkb1/Ampk signaling with hyperactivation of mTOR signaling. Treatment with a dual PI3K/mTOR inhibitor, BEZ235, extended the time before tumor onset and prolonged overall survival. The PI3K inhibitor GDC-0941 used as a single agent reduced the growth rate of primary tumor implants in Pten/Lkb1-deficient mice, and the mTOR inhibitor RAD001 was unexpectedly as effective as BEZ235 in triggering tumor regression. In parallel, we also found that ectopic expression of LKB1 in PTEN/LKB1-deficient human endometrial cancer cells increased their sensitivity to PI3K inhibition. Together, our results demonstrated that Pten/Lkb1-deficient endometrial tumors rely strongly on deregulated mTOR signaling, and they provided evidence that LKB1 status may modulate the response of PTEN-deficient tumors to PI3K or mTOR inhibitors.

Individualised proteome profiling of human endometrial tumours improves detection of new prognostic markers

Background:The individual features of tumours are often disregarded in cohort studies. As these features may represent a source for individualised cancer treatment, it is important to develop a novel approach for their assessment.Methods:We used proteomics, systems biology, and immunohistochemistry to explore protein expression in human endometrial tumours, to identify deregulated regulatory mechanisms, and to validate observed changes in protein expression using tissue microarrays.Results:Compared with the evaluation of common tumour features, the evaluation of individual tumour features gave a more comprehensive and detailed overview of the regulatory processes in endometrial tumours. Systemic analysis of the individual proteome profiles showed that endometrial tumours employed different proteins to regulate similar functions. Comparison of our data with publicly available data sets of molecular profiling of human endometrial tumours confirmed that individual tumour features are not simply irrelevant individual variations, but are indeed important in endometrial tumorigenesis. Validation through tissue microarray investigation of MST1 and PKN1 proteins confirmed the usefulness of this approach, and suggested that MST1 and PKN1 may be considered as predictive biomarkers of endometrial cancer.Conclusion:We show that individualised profiling of endometrial tumours may deliver better insights into a tumour's physiology, thereby giving a better prediction of tumour development. Individual tumour features may also be used to tailor cancer treatment.

Silencing of ghrelin receptor expression inhibits endometrial cancer cell growth in vitro and in vivo

Ghrelin is a 28-amino acid peptide hormone produced predominantly in the stomach but also in a range of normal cell types and tumors, where it has endocrine, paracrine, and autocrine roles. Previously, we have demonstrated that ghrelin has proliferative and antiapoptotic effects in endometrial cancer cell lines, suggesting a potential role in promoting tumor growth. In the present study, we investigated the effect of ghrelin receptor, GHSR, and gene silencing in vitro and in vivo and characterized ghrelin and GHSR1a protein expression in human endometrial tumors. GHSR gene silencing was achieved in the Ishikawa and KLE endometrial cancer cell lines, using a lentiviral short-hairpin RNA targeting GHSR. The effects of GHSR1a knockdown were further analyzed in vivo using the Ishikawa cell line in a NOD/SCID xenograft model. Cell proliferation was reduced in cultured GHSR1a knockdown Ishikawa and KLE cells compared with scrambled controls in the absence of exogenously applied ghrelin and in response to exogenous ghrelin (1,000 nM). The tumor volumes were reduced significantly in GHSR1a knockdown Ishikawa mouse xenograft tumors compared with scrambled control tumours. Using immunohistochemistry, we demonstrated that ghrelin and GHSR1a are expressed in benign and cancerous glands in human endometrial tissue specimens, although there was no correlation between the intensity of staining and cancer grade. These data indicate that downregulation of GHSR expression significantly inhibits endometrial cancer cell line and mouse xenograft tumour growth. This is the first preclinical evidence that downregulation of GHSR may be therapeutic in endometrial cancer.

Abstract 4892: Hypoxia enhances tumor vascularization by endothelial differentiation of endometrial cancer stem cells.

Abstract Emerging evidence has shown that a small subpopulation of cancer cells plays critical roles in tumorigenesis, establishing the cancer stem cells (CSCs) theory. CSCs have properties of tumorigenesis, self-renewal and multilineage differentiation. Previous our study demonstrated that CD133+ enodometrial cancer cells showed tumorigenic and self-renewal ability, suggesting that CD133 was a potential CSC marker in endometrial cancer. In this study, we focused on multilineage differentiation and investigated an ability of endothelial differentiation in endometrial CSCs. Immunohistochemistry of subcutaneous xenografts showed that human endometrial tumors contained human vessels labeled by human-specific anti-CD31 and vWF antibodies. Endothelial tube formation assay (in vitro angiogenesis) revealed that isolated CD133+ endometrial cancer cells could show tube formation while CD133- cells could not. CD133+ cells expressed CD31 and VEGFR-1 higher than CD133- cells. In some cell types of endometrial cancer cells, flow cytometric analysis showed expression of CD31 was high ratio under hypoxia compared to normoxia. Furthermore, in vitro angiogenesis assay demonstrated hypoxic condition could promote and keep tube formation in CD133+ cells, but not CD133- cells. These results suggest that CSCs have potential of endothelial differentiation and hypoxia enhances endothelial differentiation of CSCs. These findings shed light on the establishment of new target therapy for endometrial cancer. Citation Format: Mitsuhiro Nakamura, Xiuzhi Zhang, Masahiro Takakura, Yoshiko Maida, Yasunari Mizumoto, Yukiko Bono, Toshiyuki Sasagawa, Satoru Kyo. Hypoxia enhances tumor vascularization by endothelial differentiation of endometrial cancer stem cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4892. doi:10.1158/1538-7445.AM2013-4892

Treatment with Tie2-siRNA in combination with carboplatin suppresses the growth of Ishikawa human endometrial carcinoma cell xenografts in vivo

It is well-known that tumor angiogenesis is important in cancer development, and studies on blocking angiogenesis to treat tumors have become one of the most promising and active fields in anticancer research. The present study investigated the effect of siRNA targeting the tyrosine kinase receptor 2 (Tie2) gene in combination with carboplatin in a mouse model of endometrial carcinoma in an attempt to elucidate the role of Tie2 in the carcinogenesis and progression of endometrial carcinoma via angiogenesis, in order to establish a basis for the development of complementary molecule targeting and chemotherapeutic actions. Ishikawa cells were used to establish a human endometrial carcinoma nude mouse tumor xenograft model. Tie2-siRNA (20 μg/mouse) and/or carboplatin (25.0 mg·kg−1) were administered as the treatment strategy. Real-time PCR and western blotting were used to evaluate the expression levels of Tie2 mRNA and protein and immunohistochemistry was used to assess the vessel density of the tumor tissues. The present data demonstrated that Tie2-siRNA and/or carboplatin were able to suppress the growth of endometrial xenografts in vivo and attenuate the expression of Tie2 mRNA and protein, as assessed by real-time PCR and western blotting. Furthermore, immunohistochemical assessment showed that the vessel density of the tumors decreased with treatment. The present results suggest that treatment with Tie2-siRNA or carboplatin alone was able to inhibit the growth of human endometrial carcinoma nude mouse xenografts markedly and decrease the expression of Tie2. The combination of Tie2-siRNA and carboplatin increased the therapeutic effect of carboplatin which may eliminate the tumor microenvironment, increase the apoptosis of tumor cells, normalize the abnormal tumor vessels and increase the efficiency of chemotherapy for endometrial carcinoma with carboplatin. The synergy of Tie2-siRNA in combination with carboplatin may involve the regulation of other angiogenesis and metastasis pathways.

The Role of LEF1 in Endometrial Gland Formation and Carcinogenesis

Endometrial carcinoma is the most common gynecologic cancer, yet the mechanisms underlying this disease process are poorly understood. We hypothesized that Lef1 is required for endometrial gland formation within the uterus and is overexpressed in endometrial cancer. Using Lef1 knockout (KO) mice, we compared uterine gland development to wild-type (WT) controls, with respect to both morphology and expression of the Lef1 targets, cyclin D1 and MMP7. We characterized the dynamics of Lef1 protein expression during gland development and the mouse estrus cycle, by immunostaining and Western blot. Finally, we investigated the roles of cyclin D1 and MMP7 in gland and cancer formation in the mouse, and assessed the relevance of Lef1 to human cancer by comparing expression levels in cancerous and normal endometrial tissues. Lef1 upregulation in mouse endometrium correlates with the proliferative stages of the estrus cycle and gland development during the neonatal period. WT mice endometrial glands began to develop by day 5 and were easily identified by day 9, whereas Lef1 KO mice endometrial glands had not developed by day 9 although the endometrial lining was intact. We found that during gland development cyclin D1 is elevated and localized to the gland buds, and that this requires the presence of Lef1. We also noted that Lef1 protein was expressed at higher levels in endometrial cancers within mice and humans when compared to normal endometrium. Our loss-of-function data indicate that Lef1 is required for the formation of endometrial glands in the mouse uterus. Lef1 protein elevation corresponds to gland formation during development, and varies cyclically with the mouse estrus cycle, in parallel with gland regeneration. Finally, Lef1 is overexpressed in human and mouse endometrial tumors, consistent with it playing a role in gland proliferation.

Positron Emission Tomography Imaging of Endometrial Cancer Using Engineered Anti-EMP2 Antibody Fragments

PurposeAs imaging of the cell surface tetraspan protein epithelial membrane protein-2 (EMP2) expression in malignant tumors may provide important prognostic and predictive diagnostic information, the goal of this study is to determine if antibody fragments to EMP2 may be useful for imaging EMP2 positive tumors.ProceduresThe normal tissue distribution of EMP2 protein expression was evaluated by immunohistochemistry and found to be discretely expressed in both mouse and human tissues. To detect EMP2 in tumors, a recombinant human anti-EMP2 minibody (scFv-hinge-CH3 dimer; 80 kDa) was designed to recognize a common epitope in mice and humans and characterized. In human tumor cell lines, the antibody binding induced EMP2 internalization and degradation, prompting the need for a residualizing imaging strategy. Following conjugation to DOTA (1,4,7,10-tetraazacyclododecane-N,N′,N′,N′″-tetraacetic acid), the minibody was radiolabeled with 64Cu (t 1/2 = 12.7 h) and evaluated in mice as a positron emission tomography (PET) imaging agent for human EMP2-expressing endometrial tumor xenografts.ResultsThe residualizing agent, 64Cu-DOTA anti-EMP2 minibody, achieved high uptake in endometrial cancer xenografts overexpressing EMP2 (10.2 ± 2.6, percent injected dose per gram (%ID/g) ± SD) with moderate uptake in wild-type HEC1A tumors (6.0 ± 0.1). In both cases, precise tumor delineation was observed from the PET images. In contrast, low uptake was observed with anti-EMP2 minibodies in EMP2-negative tumors (1.9 ± 0.5).ConclusionsThis new immune-PET agent may be useful for preclinical assessment of anti-EMP2 targeting in vivo. It may also have value for imaging of tumor localization and therapeutic response in patients with EMP2-positive malignancies.

Abstract 5199: Tumor vascularization by endothelial differentiation of endometrial cancer stem cells

Abstract Evidence for existence of cancer stem cells (CSCs) has been reported in several malignant tumors. CSCs have properties of self-renewal, tumorigenesis and multilineage differentiation. Many studies about CSCs have focused on self-renewal, tumorigenesis. However, it is unclear about multilineage differentiation. Our previous study showed CD133 was a CSC marker and a critical prognostic marker in endometrial cancer. In that study, we demonstrated that CD133+ cells were capable of generating both CD133+ and CD133- cells, whereas CD133 cells did not generate CD133+ cells, indicating that CD133+ CSCs have a differential ability. The present study investigated endothelial differentiation of endometrial cancer cells. We have established endometrial cancer cells from normal human endometrial epithelial cells by introduction of HPV16 E6/E7, hTERT and K-ras genes (EM-E6/E7/hTERT/K-ras cells). Histological findings of tumors formed from EM-E6/E7/hTERT/K-ras cells showed that tumors were composed of solid and vascular regions. Vascular regions were stained human-specific anti-CD31 antibody, suggesting that EM-E6/E7/hTERT/K-Ras cells are capable of differentiating to endothelial cells. Subcutaneous xenografts from clinical samples in endometrial cancer also demonstrated that human endometrial tumors contained human vessels labeled by human-specific anti-CD31 antibody. Endothelial tube formation assay (in vitro angiogenesis) revealed that isolated CD133+ endometrial cancer cells could show tube formation while CD133- cells could not, indicating that CD133+ endometrial cancer cells had an ability of endothelial differentiation. Furthermore, western blot analysis showed high expression of VEGFR1 in CD133+ cells. We demonstrated a new function of CSCs in endometrial cancer cells. These findings shed light on the establishment of new target therapy to endometrial cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5199. doi:1538-7445.AM2012-5199

The BRG1 chromatin remodeler protects against ovarian cysts, uterine tumors, and mammary tumors in a lineage-specific manner.

The BRG1 catalytic subunit of SWI/SNF-related complexes is required for mammalian development as exemplified by the early embryonic lethality of Brg1 null homozygous mice. BRG1 is also a tumor suppressor and, in mice, 10% of heterozygous (Brg1null/+) females develop mammary tumors. We now demonstrate that BRG1 mRNA and protein are expressed in both the luminal and basal cells of the mammary gland, raising the question of which lineage requires BRG1 to promote mammary homeostasis and prevent oncogenic transformation. To investigate this question, we utilized Wap-Cre to mutate both Brg1 floxed alleles in the luminal cells of the mammary epithelium of pregnant mice where WAP is exclusively expressed within the mammary gland. Interestingly, we found that Brg1Wap-Cre conditional homozygotes lactated normally and did not develop mammary tumors even when they were maintained on a Brm-deficient background. However, Brg1Wap-Cre mutants did develop ovarian cysts and uterine tumors. Analysis of these latter tissues showed that both, like the mammary gland, contain cells that normally express Brg1 and Wap. Thus, tumor formation in Brg1 mutant mice appears to be confined to particular cell types that require BRG1 and also express Wap. Our results now show that such cells exist both in the ovary and the uterus but not in either the luminal or the basal compartments of the mammary gland. Taken together, these findings indicate that SWI/SNF-related complexes are dispensable in the luminal cells of the mammary gland and therefore argue against the notion that SWI/SNF-related complexes are essential for cell survival. These findings also suggest that the tumor-suppressor activity of BRG1 is restricted to the basal cells of the mammary gland and demonstrate that this function extends to other female reproductive organs, consistent with recent observations of recurrent ARID1A/BAF250a mutations in human ovarian and endometrial tumors.

Omental Adipose Tissue–Derived Stromal Cells Promote Vascularization and Growth of Endometrial Tumors

Adipose tissue contains a population of tumor-tropic mesenchymal progenitors, termed adipose stromal cells (ASC), which engraft in neighboring tumors to form supportive tumor stroma. We hypothesized that intra-abdominal visceral adipose tissue may contain a uniquely tumor-promoting population of ASC to account for the relationship between excess visceral adipose tissue and mortality of intra-abdominal cancers. To investigate this, we isolated and characterized ASC from intra-abdominal omental adipose tissue (O-ASC) and characterized their effects on endometrial cancer progression as compared with subcutaneous adipose-derived mesenchymal stromal cells (SC-ASC), bone marrow-derived mesenchymal stromal cells (BM-MSC), and lung fibroblasts. To model chronic recruitment of ASC by tumors, cells were injected metronomically into mice bearing Hec1a xenografts. O-ASC expressed cell surface markers characteristic of BM-MSC and differentiated into mesenchymal lineages. Coculture with O-ASC increased endometrial cancer cell proliferation in vitro. Tumor tropism of O-ASC and SC-ASC for human Hec1a endometrial tumor xenografts was comparable, but O-ASC more potently promoted tumor growth. Compared with tumors in SC-ASC-injected mice, tumors in O-ASC-injected mice contained higher numbers of large tortuous desmin-positive blood vessels, which correlated with decreased central tumor necrosis and increased tumor cell proliferation. O-ASC exhibited enhanced motility as compared with SC-ASC in response to Hec1a-secreted factors. Visceral adipose tissue contains a population of multipotent MSCs that promote endometrial tumor growth more potently than MSCs from subcutaneous adipose tissue. We propose that O-ASCs recruited to tumors express specific factors that enhance tumor vascularization, promoting survival and proliferation of tumor cells.

The impact of the genetic background on the genome make‐up of tumor cells

Endometrial adenocarcinoma (EAC) is the most common form of malignancy in the female genital tract, ranking as the fourth leading form of invasive tumors that affect women. The BDII inbred rat strain has been used as a powerful tumor model in studies of the genetic background of EAC. Females from the BDII strain are prone to develop tumors with an incidence of more than 90%. Development of EAC in BDII female rats has similarities in pathogenesis, histopathological, and molecular properties to that of human, and thus represents a unique model for analysis of EAC tumorigenesis and for comparative studies in human EACs. In a previous study, a set of rat EAC cell lines derived from tumors developed in female crossprogenies between BDII and nonsusceptible rat strains were analyzed by spectral karyotyping (SKY). Here we present an analysis with specific focus on the impact of different genetic backgrounds on the rate and occurrence of genetic aberrations in experimental tumors using data presented in the previous report. We could reveal that the ploidy state, and the abundance and type of structural as well as numerical change differed between the two genetic setups. We have also identified chromosomes harboring aberrations independent of genetic input from the nonsusceptible strains, which provide valuable information for the identification of the genes involved in the development of EAC in the BDII model as well as in human endometrial tumors.

Abstract A230: Discovery and characterization of ARQ 092, an ATP-independent, potent and selective inhibitor of AKT kinases.

Abstract The AKT family of serine-threonine kinases is a critical signal transduction node serving a variety of cellular functions including survival, proliferation, protein synthesis, and glucose metabolism. Small molecule inhibitors of AKT are emerging as potential targeted agents to treat cancers that exhibit aberrant AKT pathway signaling. A screening strategy was employed to identify inhibitors which utilize the intrinsic negative regulatory function of hydrophobic clusters in the ATP-binding cleft to inhibit the kinase activity of AKT1. ARQ 092 was identified through this screening paradigm following in vitro and in vivo optimization and was selected for further development. Crystallographic studies provided evidence that this mechanism of inhibition of AKT had been achieved. ARQ 092 binds to inactive, unphosphorylated AKT1 with sub-nanomolar affinity (Kd = 0.28 nM measured by surface plasma resonance) and biochemically inhibits all three isoforms (IC50 values of 3 nM, 4.5 nM, and 5.5 nM respectively for AKT1, AKT2, and AKT3). ARQ 092 displayed inhibition kinetics against AKT1 which were not affected by ATP concentrations up to 1000 M. When screened against a panel of over 300 kinases, ARQ 092 inhibited only three kinases within 100-fold of its IC50 against AKT1. ARQ 092 potently inhibited AKT phosphorylation (Ser473 &amp; Thr308) in AN3CA human endometrial carcinoma cells (EC50 values of 39 nM and 61 nM, respectively for p-Ser473 &amp; p-Thr308) and demonstrated concentration-dependent inhibition of phosphorylation of the downstream AKT substrate PRAS40. ARQ 092 inhibited growth of AN3CA cells (GI50 = 555 nM), A2780 cells (GI50 = 400 nM), and IGROV-1 cells (GI50 = 66 nM), in addition to LNCaP, ZR-75–1, and BT-474 human cancer cell lines (GI50 values ranging from 1 to 4 μM). Following a single oral dose of ARQ 092, inhibition of AKT and PRAS40 phosphorylation was documented in vivo in both AN3CA human endometrial tumor and BT474 human breast tumor xenograft models. The growth of AN3CA tumor xenografts was markedly suppressed after daily oral administration of ARQ 092 for 10 days. Finally, ARQ 092 was shown to have good pharmaceutical properties and was advanced into preclinical development. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A230.

Predisposition to Cancer Caused by Genetic and Functional Defects of Mammalian Atad5

ATAD5, the human ortholog of yeast Elg1, plays a role in PCNA deubiquitination. Since PCNA modification is important to regulate DNA damage bypass, ATAD5 may be important for suppression of genomic instability in mammals in vivo. To test this hypothesis, we generated heterozygous (Atad5+/m) mice that were haploinsuffficient for Atad5. Atad5+/m mice displayed high levels of genomic instability in vivo, and Atad5+/m mouse embryonic fibroblasts (MEFs) exhibited molecular defects in PCNA deubiquitination in response to DNA damage, as well as DNA damage hypersensitivity and high levels of genomic instability, apoptosis, and aneuploidy. Importantly, 90% of haploinsufficient Atad5+/m mice developed tumors, including sarcomas, carcinomas, and adenocarcinomas, between 11 and 20 months of age. High levels of genomic alterations were evident in tumors that arose in the Atad5+/m mice. Consistent with a role for Atad5 in suppressing tumorigenesis, we also identified somatic mutations of ATAD5 in 4.6% of sporadic human endometrial tumors, including two nonsense mutations that resulted in loss of proper ATAD5 function. Taken together, our findings indicate that loss-of-function mutations in mammalian Atad5 are sufficient to cause genomic instability and tumorigenesis.