HEC1A Endometrial Cancer Cells Research Articles

Estrogen-dependent expression and subcellular localization of the tight junction protein claudin-4 in HEC-1A endometrial cancer cells.

Endometrial cancer is the most common female reproductive cancer in the United States and is associated with deregulated tight junction protein expression. Given the highly estrogen-responsive nature of this tissue, we investigated the effects of estrogen and its agonist, 4-OH TAM, on the expression and subcellular localization of the tight junction protein claudin-4 (CLDN-4), in HEC-1A endometrial cancer cells. In untreated HEC-1A cells, we observed dramatic overexpression of claudin-4 protein. In addition, differential detergent extraction analysis indicated that claudin-4 was localized primarily in the membrane but also found in the cytosolic, nuclear and cytoskeletal fractions. Upon exposure of HEC-1A to estradiol (E2), we observed a biphasic effect both on the overall expression of claudin-4 protein and on its cytosolic and cytoskeletal presence as demonstrated by immunoblot analysis. Immunofluorescence analysis also revealed a biphasic effect of E2 on claudin-4 expression. In contrast, we observed no changes in expression levels nor in the subcellular distribution patterns of claudin-4 in HEC-1A cells treated with different concentrations of 4-OHTAM. The intracellular presence of CLDN-4 coupled with the biphasic effects of E2 on CLDN-4 expression in the cytoskeleton suggest that this protein may be involved in cell signaling to and from TJs.

Nidogen 1 and Nuclear Protein 1: novel targets of ETV5 transcription factor involved in endometrial cancer invasion

Endometrial cancer is the most frequent malignancy of the female genital tract in western countries. Our group has previously characterized the upregulation of the transcription factor ETV5 in endometrial cancer with a specific and significant increase in those tumor stages associated with myometrial invasion. We have shown that ETV5 overexpression in Hec1A endometrial cancer cells induces epithelial to mesenchymal transition resulting in the acquisition of migratory and invasive capabilities. In the present work, we have identified Nidogen 1 (NID1) and Nuclear Protein 1 (NUPR1) as direct transcriptional targets of ETV5 in endometrial cancer cells. Inhibition of NID1 and NUPR1 in ETV5 overexpressing cells reduced cell migration and invasion in vitro and reduced tumor growth and dissemination in an orthotopic endometrial cancer model. Importantly, we confirmed a significant increase of NUPR1 and NID1 protein expression in the invasion front of the tumor compared to their paired superficial zone, concomitant to ETV5 overexpression. Altogether, we conclude that NID1 and NUPR1 are novel targets of ETV5 and are actively cooperating with ETV5 at the invasion front of the tumor in the acquisition of an invasive phenotype to jointly drive endometrial cancer invasion.

A requirement for wild-type Ras isoforms in mutant KRas-driven signalling and transformation

The mutant forms of KRas, NRas and HRas drive the initiation and progression of a number of human cancers, but less is known about the role of WT (wild-type) Ras alleles and isoforms in cancer. We used zinc-finger nucleases targeting HRas and NRas to modify both alleles of these genes in the mutant KRas-driven Hec1A endometrial cancer cell line, which normally expresses WT copies of these genes. The disruption of either WT isoform of Ras compromised growth-factor-dependent signalling through the ERK (extracellular-signal-regulated kinase) pathway. In addition, the disruption of HRas hindered the activation of Akt and subsequent downstream signalling. This was associated with decreased proliferation, increased apoptosis and decreased anchorage-independent growth in the HRas-disrupted cells. However, xenograft tumour growth was not significantly affected by the disruption of either NRas or HRas. As expected, deleting the mutant allele of KRas abolished tumour growth, whereas deletion of the remaining WT copy of KRas increased the tumorigenic properties of these cells; deleting a single copy of either HRas or NRas did not mimic this effect. The present study demonstrates that the WT copies of HRas, NRas and KRas play unique roles in the context of mutant KRas-driven tumours.

Abstract 2032: Inhibition of signal transducers and activators of transcription 3 in human endometrial cancer, using a novel STAT3 inhibitor.

Abstract OBJECTIVE: Signal transducer and activator of transcription 3 (Stat3) proteins have important roles in cancer cell survival and proliferation. Recent studies show constitutive activation of STAT3 is associated with tumor growth and oncogenic transformation in several human cancers, however, little is known about STAT3 expression in endometrial cancer. The objectives of this study were to examine the expression of the STAT family of proteins in endometrial cancer cell lines and to evaluate the efficacy of HO-3867, a novel STAT3 inhibitor. METHODS: Expression of STAT family proteins, cell cycle and apoptotic proteins were evaluated via western blot on Ishikawa, AN3-CA, RL95-2, HEC1B, HEC-1A, and SK-UT1B human endometrial cancer cell lines. Cell viability and proliferation of these cell lines were analyzed with MTT and nucleo counter assay after treatment with increasing concentrations of HO-3867. Cell cycle analysis and apoptosis were performed using flow cytometry and annexin V staining. An ubiquitination assay was used to examine the inhibition of CDK5 degradation. Finally, STAT3 over-expression or suppression experiments were performed using wild-type STAT3 cDNA. RESULTS: Expression of activated STAT1, 2, 5, and 6 was inconsistent among cell lines tested, while pSTAT3 Ser727 had consistently high expression. HO-3867 decreased cell viability through induced G2/M arrest and apoptosis within 24h of treatment. HO-3867 inhibits pSTAT3 Ser727 with no change in total STAT3. This was associated with an increase in cell cycle related proteins p53 and p21, a decrease in anti-apoptotic proteins Bcl2 and Bcl-XL, as well as increased cleavage of caspases. After 24h of treatment with HO-3867, 55-88% of cells were in apoptosis, as detected by Annexin. The downregulation of Ser727 was, at least in part, due to an accelerated inhibition of ubiquitin-dependent CDK5 degradation, as a positive regulator of STAT3 Ser727. Suppression of STAT3 expression with siRNA significantly reduced cell survival. In addition, we confirmed that over-expression of STAT3 cDNA provides resistance to HO-3867. CONCLUSION: Endometrial cancer cells express high levels of pSTAT3 Ser727. HO-3867 induces cell cycle arrest and apoptosis by targeting pSTAT3 Ser727. Our findings suggest a specific role of serine-phosphorylated STAT3 that is independent of tyrosine phosphorylation. HO-3867 may be a potential adjunct to chemotherapy and radiation in the treatment of endometrial cancer. Citation Format: Brent J. Tierney, Georgia A. McCann, Kellie S. Rath, Meryl Sudhakar, Shan Naidu, Periannan Kuppusamy, David E. Cohn, Karuppaiyah Selvendiran. Inhibition of signal transducers and activators of transcription 3 in human endometrial cancer, using a novel STAT3 inhibitor. [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 2032. doi:10.1158/1538-7445.AM2013-2032

Abstract 4897: Involvement of Akt isoforms in chemoresistance of carcinoma endometrial cells

Abstract Akt (also known as PKB) is a crucial survival kinase that is normally activated by growth factors, but in tumors, it is constitutively activated at a high frequency through oncogenic events affecting its upstream regulation. Since studies have demonstrated that the three Akt isoforms exhibit distinct physiological functions, we propose that Akt isoforms may contribute differently in chemoresistance of endometrial carcinoma cells. In order to determine the specific role of each Akt isoform, we have stably produced transfectants in which the expression of Akt is downregulated by specific shRNAs for Akt1, Akt2 and Akt3 using the KLE endometrial carcinoma cell line. This endometrial cell line is known to constitutively express the three Akt isoforms and to highly resist to chemotherapeutic treatment. In this study, we have demonstrated that the downregulation of Akt1 and Akt2 by RNA interference strongly sensitizes KLE cells to cisplatin, doxorubicin and taxol and affects cell proliferation. Moreover, cisplatin treatment of these cells induced the activation of pro-apoptotic factors such as the cleavage of caspase -3, -6, -9 and PARP and it also inhibited the expression of anti-apoptotic factors such as XIAP and Bcl-2. Alternatively, we used constitutively active Akt expression vectors for each isoform to produce stable transfectants using the chemosensitive Hec 1A endometrial cancer cell line, in which no Akt activity is detected. Constitutive Akt1 and Akt2 expression leads to an increase in cell proliferation, as well as resistance to apoptosis after chemotherapeutic treatment in these stable transfectants. Moreover, Akt isoforms contribute differently in other cancer cell processes, such as migration. We showed that Akt2 blocks cell motility, while the activation of Akt1 or Akt3 does not show any effect on our endometrial cancer cell model. Our findings highlight the contribution of Akt1 and Akt2 isoforms in the molecular mechanisms that govern chemoresistance of endometrial carcinoma. Furthermore, Akt isoform-specific transfectants will provide a solid model to determine the involvement of each Akt isoform in tumor progression and metastasis. 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 4897. doi:1538-7445.AM2012-4897

Abstract 2802: Selective inhibition of signal transducers and activators of transcription 3 overexpressing endometrial cancer cells, using HO-3867, a novel STAT3 inhibitor

Abstract OBJECTIVE: Signal transducer and activator of transcription 3 (STAT3) proteins have important roles in cancer cell survival and proliferation. Recent studies show constitutive activation of STAT3 is associated with tumor growth and oncogenic transformation in several human cancers; however, little is known about STAT3 expression in endometrial cancer. The objectives of this study were to examine the expression of the STAT family of proteins in endometrial cancer cell lines and to evaluate the efficacy of HO-3867, a novel STAT3 inhibitor. METHODS: Expression of STAT family proteins, cell cycle and apoptotic proteins were evaluated via western blot on Ishikawa, AN3-CA, RL95-2, HEC1B, HEC-1A, and SK-UT1B human endometrial cancer cell lines. Cell viability and proliferation of these cell lines were analyzed with MTT and nucleo counter assay after treatment with increasing concentrations of HO-3867. Cell cycle analysis and apoptosis were performed using flow cytometry and annexin V staining. An ubiquitination assay was used to examine the inhibition of CDK5 degradation. Finally, STAT3 over-expression or suppression experiments were performed using wild-type STAT3 cDNA and STAT3 siRNA. RESULTS: Expression of activated STAT1, 2, 5, and 6 was inconsistent among cell lines tested, while pSTAT3 Ser727 had consistently high expression. HO-3867 decreased cell viability through induced G2/M arrest and apoptosis within 24h of treatment. HO-3867 inhibited pSTAT3 Ser727 with no change in total STAT3. This was associated with an increase in expression of cell cycle related proteins p53 and p21, a decrease in anti-apoptotic proteins Bcl2 and Bcl-XL, as well as increased cleavage of caspases. After 24h of treatment with HO-3867, 55-88% of cells were apoptotic. The downregulation of Ser727 was, at least in part, due to an accelerated inhibition of ubiquitin-dependent CDK5 degradation, as a positive regulator of STAT3 Ser727. Suppression of STAT3 expression with siRNA significantly reduced cell survival. In addition, we confirmed that over-expression of STAT3 cDNA provides resistance to HO-3867. CONCLUSION: Endometrial cancer cells express high levels of pSTAT3 Ser727. HO-3867 induces cell cycle arrest and apoptosis by targeting pSTAT3 Ser727. Our findings suggest a specific role of serine-phosphorylated STAT3 that is independent of tyrosine phosphorylation. HO-3867 may be a potential adjunct to chemotherapy and radiation in the treatment of 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 2802. doi:1538-7445.AM2012-2802

Acrp30 inhibits leptin-induced metastasis by downregulating the JAK/STAT3 pathway via AMPK activation in aggressive SPEC-2 endometrial cancer cells

Obesity is a well-established risk factor for endometrial cancer, due in part to the adipokines generated by adipose tissue, such as adiponectin (also known as Acrp30) and leptin, which are associated with many endocrine-related cancers. Recent reports suggested that Acrp30 inhibits leptin-stimulated cell proliferation in HEC-1A and RL95-2 endometrial cancer cell lines, and that the serum leptin/Acrp30 ratio plays an important role in endometrial cancer development. We explored whether Acrp30 could reverse the leptin-induced metastasis phenotype in the SPEC-2 endometrial cancer cell line. Transcripts for Acrp30 receptors (AdipoR1 and AdipoR2) and leptin receptor (Ob-Rb) were detected by quantitative real-time RT-PCR (qRT-PCR) in six endometrial cancer cell lines. Leptin (1µg/ml) treatment stimulated SPEC-2 cell proliferation by inducing cell cycle arrest and apoptosis, while Acrp30 (10µg/ml) treatment inhibited the growth of SPEC-2 cells. Importantly, Acrp30 was able to inhibit leptin-induced SPEC-2 cell proliferation. Leptin promoted SPEC-2 cell invasion in a Matrigel transwell assay, while Acrp30 partly suppressed the invasion stimulated by leptin. To investigate the molecular mechanism underlying this phenomenon, we monitored the AMPK and JAK/STAT3 signaling pathways by western blotting and cell immunofluorescence. Acrp30 reduced leptin-induced STAT3 phosphorylation and nuclear translocation via activation of the MAPK pathway. AG490 (JAK/STAT3 inhibitor) reduced MMP-2 and MMP-9 protein levels in cells treated with leptin, while IL-6 (JAK/STAT3 stimulator) and Compound C (AMPK inhibitor) elevated MMP-2 and MMP-9 protein levels in cells treated with Acrp30. In conclusion, we demonstrated that Acrp30 effectively reversed the invasion stimulated by leptin, and AMPK and JAK/STAT3 pathways mediated the invasive phenotype of SPEC-2 cells.

Synergistic effects of sorafenib and celecoxib inhibit growth and VEGF expression in Hec-1A endometrial cancer cell line

목적 자궁내막암 세포주 Hec-1A에서 sorafenib과 celecoxib에 의한 세포증식억제 및 혈관내피성장인자(vascular endothelial growth factor, VEGF)의 발현 변화에 대해 연구하고자 하였다. 연구방법 Hec-1A 세포주에 대한 sorafenib과 celecoxib의 처치 농도와 시간에 따른 세포증식억제 작용을 (3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium, inner salt) assay로 측정하였으며, 또한 위 약제들을 단독 또는 병합투여시 VEGF, p53의 변화를 역전사-중합효소연쇄반응(reverse transcription-polymerase chain reaction)으로 측정하였다. 결과 Sorafenib과 celecoxib 각각을 자궁내막암 세포주인 Hec-1A에 처치 시, sorafenib의 농도를 5 ng/mL, 10 ng/mL, 20 ng/mL, 50 ng/mL로 증가시킬수록 모든 농도에서 의미 있게 점차적으로 세포들의 증식이 억제되었으며, celecoxib는 60 μmol/L의 농도에서부터 통계적으로 유의하게 차이가 났다. Sorafenib 10 ng/mL을 단독 처리하였을 때보다 celecoxib를 병합처리하였을 때 약제 간 상승 작용으로 세포증식억제의 차이가 통계적으로 의미 있게 나타났다(P＜0.0001). 혈관신생과 관련된 VEGF는 sorafenib과 celecoxib 두 가지 약제를 동시에 병합시 sorafenib 단독 처치보다 발현감소가 의미 있게 나타났다. 그러나 p53의 경우 sorafenib이나 celecoxib를 각각 또는 병합처리하며 시간과 농도를 다르게 하여도 약제들에 따른 발현의 변화는 나타나지 않았다. 결론 본 연구결과로 sorafenib과 celecoxib의 병합처치에 의해 Hec-1A자궁내막암 세포주의 증식과 VEGF의 발현이 억제되므로, 자궁내막암의 기존 치료요법에 위 약제들이 보조적인 역할을 할 수 있으리라 생각된다.

EGFR- and AKT-mediated reduction in PTEN expression contributes to tyrphostin resistance and is reversed by mTOR inhibition in endometrial cancer cells

Loss or mutation of the PTEN (phosphatase and tensin homologue deleted on chromosome 10) gene is associated with resistance to epidermal growth factor receptor (EGFR) inhibitors. However, the mechanism underlying remains elusive. In this study, we aimed to explore whether sensitivity to the EGFR tyrosine kinase inhibitor (TKI) is affected by PTEN status in endometrial cancer cells. PTEN siRNA and the PTEN gene were transfected into HEC-1A and Ishikawa endometrial cancer cells using lentiviral vectors. Cells were treated under various concentrations of RG14620 and rapamycin, which are EGFR and mammalian target of rapamycin (mTOR) inhibitors, respectively. The IC(50) of RG16420 was determined by using the MTT method. Cell apoptosis and the cell cycle were studied, and activation of EGFR, AKT, and p70S6 were detected by Western blot analysis. Loss of PTEN promoted cell proliferation and led to significant increases in the levels of EGFR, phospho-EGFR, AKT, phospho-AKT, and phospho-mTOR proteins. Ishikawa and HEC-1A(PTENkd) cells that displayed loss and inactivation of PTEN function were resistant to RG14620. HEC-1A and Ishikawa(PTEN) cells with intact PTEN were sensitive to RG14620. The combination of two inhibitors was more effective than both monotherapies, particularly in carcinoma cells with PTEN dysfunction. Decreased phospho-EGFR protein expression was observed in all cell lines that were sensitive to RG14620. Decreased phospho-AKT and phospho-p70S6 protein expression was observed in PTEN-intact cells that were sensitive to RG14620. PTEN loss results in resistance to EGFR TKI, which was reversed by PTEN reintroduction or mTOR inhibitor treatment. The combined treatment of EGFR TKI and the mTOR inhibitor provided a synergistic effect by promoting cell death in PTEN-deficient and PTEN-intact endometrial cancer cells, particularly in PTEN-deficient carcinoma cells with up-regulated EGFR activation.

Diacylglycerol kinase α mediates 17-β-estradiol-induced proliferation, motility, and anchorage-independent growth of Hec-1A endometrial cancer cell line through the G protein-coupled estrogen receptor GPR30

Increased levels of endogenous and/or exogenous estrogens are one of the well known risk factors of endometrial cancer. Diacylglycerol kinases (DGKs) are a family of enzymes which phosphorylate diacylglycerol (DAG) to produce phosphatidic acid (PA), thus turning off and on DAG-mediated and PA-mediated signaling pathways, respectively. DGK α activity is stimulated by growth factors and oncogenes and is required for chemotactic, proliferative, and angiogenic signaling in vitro. Herein, using either specific siRNAs or the pharmacological inhibitor R59949, we demonstrate that DGK α activity is required for 17-β-estradiol (E2)-induced proliferation, motility, and anchorage-independent growth of Hec-1A endometrial cancer cell line. Impairment of DGK α activity also influences basal cell proliferation and growth in soft agar of Hec-1A, while it has no effects on basal cell motility. Moreover, we show that DGK α activity induced by E2, as well as its observed effects, are mediated by the G protein-coupled estrogen receptor GPR30 (GPER). These findings suggest that DGK α may be a potential target in endometrial cancer therapy.

Dysregulation of microRNA‐204 mediates migration and invasion of endometrial cancer by regulating FOXC1

MicroRNAs (miRNAs) regulate mRNA stability and protein expression, and certain miRNAs have been demonstrated to act either as oncogenes or tumor suppressors. Differential miRNA expression signatures have been documented in many human cancers but the role of miRNAs in endometrioid endometrial cancer (EEC) remains poorly understood. This study identifies significantly dysregulated miRNAs of EEC cells, and characterizes their impact on the malignant phenotype. We studied the expression of 365 human miRNAs using Taqman low density arrays in EECs and normal endometriums. Candidate differentially expressed miRNAs were validated by quantitative real-time PCR. Expression of highly dysregulated miRNAs was examined in vitro through the effect of anti-/pre-miRNA transfection on the malignant phenotype. We identified 16 significantly dysregulated miRNAs in EEC and 7 of these are novel findings with respect to EEC. Antagonizing the function of miR-7, miR-194 and miR-449b, or overexpressing miR-204, repressed migration, invasion and extracellular matrix-adhesion in HEC1A endometrial cancer cells. FOXC1 was determined as a target gene of miR-204, and two binding sites in the 3'-untranslated region were validated by dual luciferase reporter assay. FOXC1 expression was inversely related to miR-204 expression in EEC. Functional analysis revealed the involvement of FOXC1 in migration and invasion of HEC1A cells. Our results present dysfunctional miRNAs in endometrial cancer and identify a crucial role for miR-204-FOXC1 interaction in endometrial cancer progression. This miRNA signature offers a potential biomarker for predicting EEC outcomes, and targeting of these cancer progression- and metastasis-related miRNAs offers a novel potential therapeutic strategy for the disease.

ER-α36, a novel variant of estrogen receptor α, is involved in EGFR-related carcinogenesis in endometrial cancer

To explore the role of estrogen receptor-α36 (ER-α36) in epidermal growth factor receptor (EGFR)-related carcinogenesis in endometrial cancer. The expression of ER-α36, EGFR, and phospho-extracellular signal-regulated kinase was analyzed using immunohistochemistry in endometrial cancer samples. The cellular localization of ER-α36 and EGFR was determined using immunofluorescence in the endometrial cancer Hec1A cells. The level of phospho-extracellular signal-regulated kinase of Hec1A cells was determined using Western blotting after treatment with epidermal growth factor. Positive rate of ER-α36 was increased in high-stage (P = .03) and high-grade (P = .224) endometrial cancer; expression of ER-α36 and EGFR exhibited a significant positive correlation (r = 0.334, P = .025) and they showed substantial colocalization on the plasma membrane of glandular cells; phospho-extracellular signal-regulated kinase positive rate in ER-α36 positive group and EGFR positive group was higher than that of ER-α36 negative group (P = .014) and EGFR negative group (P = .016); finally, ER-α36 mediated epidermal growth factor-stimulated extracellular signal-regulated kinase activation in Hec1A cells. ER-α36 mediates EGFR-related extracellular signal-regulated kinase activation in endometrial cancer.

Abstract 3127: Expression and sub-cellular localization of claudin-4 in MCF-7 breast and HEC-1A endometrial cancer cell lines

Abstract The claudin (CLDN) family consists of 24 tetraspan membrane proteins that are essential for the formation of tight junctions (TJs). Members of the CLDN family display tissue-specific expression and are involved in multiple normal cellular processes. In addition, alterations in CLDN gene expression have been shown to be associated with a variety of cancers. For example, CLDN-3 and CLDN-4 have been found to be upregulated in prostate, ovarian and breast cancer. We have previously shown gross overexpression of CLDN-3 in the breast cancer cell lines MCF-7 and MDA-MB-415. Furthermore, using sequential protein extraction techniques we have consistently observed expression of CLDN-3 in all four subcellular fractions of MCF-7 cells with the bulk of expression in the membrane fraction. CLDN-3 and CLDN-4 genes are located within 50 kb on chromosome 7 and their coordinated regulation has been reported in normal, neoplastic tissues and various cancer cell lines. The present study reports the expression and sub-cellular localization of CLDN-4 in a panel of cancer cell lines using immunoblot analysis. Like CLDN-3, overexpression of claudin-4 was observed in the breast cancer cell lines MCF-7 and MDA-MB-415. In addition, we observed expression of CLDN-3 and CLDN-4 in both endometrial (HEC-1A and RL95-2) and prostate (DU-145) cancer cell lines. Sub-cellular localization analysis of MCF-7 cells demonstrated the expression of CLDN-4 in the membrane, nuclear, cytosolic and to a lesser extent in the cytoskeletal fractions. Currently we are investigating the sub-cellular localization of CLDN-3 and 4 in the endometrial and prostate cancer cell lines described above. Recent studies have shown CLNDs to be involved in signaling to and from TJs, conveying important chemical messages for cell proliferation and differentiation. The presence of CLDN-3 and 4 in the cytosol and nucleus observed in this study may indicate their involvement in cell signaling. Alternatively, their unusual localization may be a characteristic of breast cancer cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3127. doi:10.1158/1538-7445.AM2011-3127

Icaritin Causes Sustained ERK1/2 Activation and Induces Apoptosis in Human Endometrial Cancer Cells

Icaritin, a compound from Epimedium Genus, has selective estrogen receptor (ER) modulating activities, and posses anti-tumor activity. Here, we examined icaritin effect on cell growth of human endometrial cancer Hec1A cells and found that icaritin potently inhibited proliferation of Hec1A cells. Icaritin-inhibited cell growth was associated with increased levels of p21 and p27 expression and reduced cyclinD1 and cdk 4 expression. Icaritin also induced cell apoptosis accompanied by activation of caspases as evidenced by the cleavage of endogenous substrate Poly (ADP-ribose) polymerase (PARP) and cytochrome c release, which was abrogated by pretreatment with the pan-caspase inhibitor z-VAD-fmk. Icaritin treatment also induced expression of pro-apoptotic protein Bax with a concomitant decrease of Bcl-2 expression. Furthermore, icaritin induced sustained phosphorylation of extracellular signal-regulated kinase1/2 (the MAPK/ ERK1/2) in Hec1A cells and U0126, a specific MAP kinase kinase (MEK1/2) inhibitor, blocked the ERK1/2 activation by icaritin and abolished the icaritin-induced growth inhibition and apoptosis. Our results demonstrated that icaritin induced sustained ERK 1/2 activation and inhibited growth of endometrial cancer Hec1A cells, and provided a rational for preclinical and clinical evaluation of icaritin for endometrial cancer therapy.

Dysregulation of the expression of miR204 mediates migration and invasion of endometrial cancer by regulating FOXC1

Abstract microRNAs (miRNAs) regulate gene expression and some have been shown to function as either oncogenes or tumor suppressors (oncomirs). Changes in miRNA expression have been observed in many human cancers but their role in endometrioid endometrial cancer (EEC) remains poorly understood. We studied the expression of 365 human miRNAs using Taqman low density arrays in 98 EECs as well as 60 normal endometria. Potentially interesting miRNAs were then validated by qRT-PCR. Expression of highly deregulated miRNAs on malignant cell properties was also examined in vitro using pre-/anti-miRNA transfection. Predicted mRNA targets for the miRNA of interest were also verified. We identified 16 significantly deregulated miRNAs in EEC and 7 of these are reported for the first time. Of these, miR-7, miR-194 and miR-449b knockdown and miR-204 induction repressed migration, invasion and extracellular matrix-adhesion in HEC1A endometrial cancer cells. For the cancer progression dysregulation of the expression of miR204 mediates migration and invasion of endometrial cancer by regulating FOXC1-related miR-204, FOXC1 was determined as its target gene possessing two miR-204-binding sites at the 3’-untranslated region. FOXC1 expression was inversely related to miR-204 expression in EEC. Functional analysis also revealed the involvement of FOXC1 in migration of HEC1A cells. We have identified dysfunctional miRNAs in endometrial cancer and elucidated the crucial role of miR-204-FOXC1 interaction in endometrial cancer progression. This work provides insight into miRNA-based diagnostic and therapeutic approaches for endometrial cancers.

Abstract 216: Role of Akt isoforms in chemoresistance of human endometrial carcinoma cells

Abstract AKT (also known as PKB) is a crucial survival kinase that is normally activated by growth factors but is constitutively activated at a high frequency in tumors through oncogenic events affecting its upstream regulation. Since studies have demonstrated that the three Akt isoforms exhibit distinct physiological functions, the aim of this study was to determine the isotype-specific functions for Akt in chemoresistance of endometrial carcinoma cells. In order to determine the role of Akt isoforms, we have stably produced transfectants in which the expression of Akt is downregulated by specific shRNAs for each isoforms using the KLE endometrial carcinoma cell line. This endometrial cell line is known to constitutively express the three Akt isoforms and to highly resist to chemotherapeutic treatment. In this study we have demonstrated that stably downregulation of Akt2 by RNA interference severely sensitized KLE cells to cisplatin and induced apoptosis. Moreover, cisplatin treatment of these cells induced the activation of pro-apoptotic factors such as caspase −3 and −9 but also inhibited the expression of anti-apoptotic factors such as XIAP and bcl-2. Alternatively, we used constitutively active Akt expression vectors for each isoform to produce stable transfectants using the chemosensitive Hec 1A endometrial cancer cell lines in which no Akt activity is detected. Constitutive Akt2 expression leads to increase cisplatin resistance in this stable transfectant. Our findings highlight the contribution of Akt2 isoform in the molecular mechanisms that govern chemoresistance of endometrial carcinoma. Furthermore, Akt isoform-specific transfectants will provide a strong model to determine the involvement of each Akt isoforms in chemoresistance of endometrial carcinoma cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 216.

ER-α36, a Variant of ER-α, Promotes Tamoxifen Agonist Action in Endometrial Cancer Cells via the MAPK/ERK and PI3K/Akt Pathways

BackgroundRecently, a novel variant of ER-α, ER-α36 was identified and cloned. ER-α36 lacks intrinsic transcription activity and mainly mediates nongenomic estrogen signaling. Here, we studied the role of nongenomic estrogen signaling pathways mediated by ER-α36 in tamoxifen resistance and agonist action.MethodologyThe cellular localization of ER-α36 was examined by immunofluorescence in MCF-7 cells and Hec1A cells. MCF-7 breast cancer cells, MCF-7 cells expressing recombinant ER-α36 (MCF-7/ER36), Hec1A endometrial cancer cells and Hec1A cells with siRNA knockdown of ER-α36 (Hec1A/RNAiER36) were treated with 17β-estradial (E2) and tamoxifen (TAM) in the absence and presence of kinase inhibitor U0126 and LY294002. We examined phosphorylation of signaling molecules and the expression of c-Myc by immunoblotting, and tumor cell growth by MTT assay.ConclusionsER variant ER-α36 enhances TAM agonist activity through activation of the membrane-initiated signaling pathways in endometrial cancer, and that ER-α36 is involved in de novo and acquired TAM resistance in breast cancer.

Isoliquiritigenin inhibited cell proliferation and triggered apoptosis in human endometrial cancer cell line

Objective: To determine the anti-tumor effect of isoliquiritigenin (ISL) on endometrial cancer cell and to evaluate its effect on apoptosis in Hec1A endometrial cancer cell lines. Methods: Human endometrial cancer cell lines (Hec1A) and Ishikawa, and normal endometrial cell line (T-HESCS) were cultured in vitro. The viabilities of three cell lines on ISL were measured. Cell cycle distribution and induction of apoptosis were measured in Hec1A cells after ISL treatment. Results: ISL significantly reduced cell viabilities of endometrial cancer cell lines but not normal cell line in a dose-dependent manner. Cell cycle analysis indicated that ISL treatment increased the proportion of cells in the sub-G0/G1 phase. DNA frag- mentation and fluorometric TUNEL assays also revealed apoptotic cell death after ISL incubation. ISL treatment markedly up-regulated the expression of cyclin-dependent kinase inhibitor, p21 Cip1/Waf1 in a p53 independent manner and down regulated the expressions of cyclins and CDKs, with concomitant increase in FAS and cleavage of caspase 7, caspase 8, and caspase 9. In addition, elevation of caspase 3 activity also observed in a dose and time dependent manner. Conclusion: ISL inhibited cell proliferation and triggered apoptosis in human endometrial cancer cell line Hec1A. Hence, ISL can be used as a potentially potent clinical chemotherapeutic agent for treating endometrial cancer.

A novel variant of ER-alpha, ER-alpha36 mediates testosterone-stimulated ERK and Akt activation in endometrial cancer Hec1A cells

BackgroundEndometrial cancer is one of the most common gynecologic malignancies and its incidence has recently increased. Experimental and epidemiological data support that testosterone plays an important role in the pathogenesis of endometrial cancer, but the underlying mechanism has not been fully understood. Recently, we identified and cloned a variant of estrogen receptor (ER) alpha, ER-alpha36. The aim of the present study was to investigate the role of ER-alpha36 in testosterone carcinogenesis.MethodsThe cellular localization of ER-alpha36 was determined by immunofluorescence. Hec1A endometrial cancer cells (Hec1A/V) and Hec1A cells with siRNA knockdown of ER-alpha36 (Hec1A/RNAi) were treated with testosterone, ERK and Akt phosphorylation was assessed by Western blot analysis. Furthermore, the kinase inhibitors U0126 and LY294002 and the aromatase inhibitor letrozole were used to elucidate the pathway underlying testosterone-induced activities.ResultsImmunofluorescence shows that ER-alpha36 was localized on the plasma membrane of the both ER-alpha- and androgen receptor-negative endometrial cancer Hec1A cells. Testosterone induced ERK and Akt phosphorylation, which could be abrogated by ER-alpha 36 shRNA knockdown or the kinase inhibitors, U0126 and LY294002, and the aromatase inhibitor letrozole.ConclusionTestosterone induces ERK and Akt phosphorylation via the membrane-initiated signaling pathways mediated by ER-alpha36, suggesting a possible involvement of ER-alpha 36 in testosterone carcinogenesis.

Gonadotropin-releasing hormone (GnRH)-I and GnRH-II induce cell growth inhibition in human endometrial cancer cells: Involvement of integrin beta3 and focal adhesion kinase

Endometrial carcinoma is the most common neoplasm of the female genital tract, accounting for nearly one half of all gynecologic cancers in the Western world. Although intensive research on pathological phenomena of endometrial cancer is currently going on, but exact cause and biological aspects of this disease are not well described yet. In addition to well-documented roles of gonadotropin-releasing hormone (GnRH) in hypopituitary ovarian (HPO) axis, the agonistic or antagonistic analogs (or both) of GnRH have been shown to inhibit the proliferation of a variety of human gynecologic cancers. Thus, in the present study, we further examined the possibility that GnRH induces integrin beta3 and activation of focal adhesion kinase (FAK) through mitogen-activated protein kinases (MAPKs), ERK1/2 and p38, to inhibit the growth of HEC1A endometrial cancer cell line. As a result, both GnRH-I and GnRH-II resulted in a significant increase in integrin beta3 expression and evoked the activation of FAK in a time-dependent manner in these cells. In addition, these analogs induced an activation of ERK1/2 and p38 MAPK in a time-dependent manner as downstream pathways of FAK. It appears that GnRH-II has much greater effect on the activation of FAK, ERK1/2 and p38 compared to GnRH-I in these cells. Further, we demonstrated that the growth inhibition of HEC1A cells by GnRH-I or GnRH-II is involved in the activation of integrin-FAK and ERK1/2 and p38 MAPK pathways. Taken together, these results suggest that GnRH may be involved in the inhibition of endometrial cancer cell growth via activation of integrin beta3 and FAK as a direct effect. This knowledge could contribute to a better understanding of the mechanisms implicated in the therapeutic action of GnRH and its biomedical application for the treatment against endometrial cancer.