Progesterone receptor isoform identification and subcellular localization in endometrial cancer

OBJECTIVE: These studies were undertaken to characterize the subcellular localization of the two major isoforms of progesterone receptors (PR), PRA and PRB, in endometrial cancer. METHODS: Immunohistochemistry, immunoprecipitation, and confocal microscopy were performed using Hec50co and KLE endometrial cancer cell models expressing PRA or PRB as a consequence of transduction. The location of PRB compared to PRA was determined, and antibodies were tested for specificity with respect to PR isoform recognition. Immunohistochemical analyses of PR expression and subcellular compartmentalization were also performed on 20 formalin-fixed endometrial cancer tumors. RESULTS: Morphological and biochemical evaluations demonstrated that PRA is localized to the nucleus, even in the absence of progesterone. In contrast, a large proportion of PRB is cytoplasmic in the absence of ligand, but is rapidly translocated to the nucleus in the presence of progesterone. The differential distribution of PRA and PRB proved to be a hallmark of malignant and nonmalignant epithelia in 20 samples of archival endometrial tissue from women with the pre-operative diagnosis of endometrial cancer. All endometrial cancer specimens demonstrated cytoplasmic PRB in 50% or more of the cells, and five of the seven tumors that were moderately to poorly differentiated demonstrated no PRB staining in the nuclei. Nuclear PRB was significantly associated with increasing tumor differentiation (P = 0.031). CONCLUSION: In the absence of ligand, PRA is nuclear and PRB is largely cytoplasmic. This suggests that PRA may exert ligand-independent nuclear effects, while PRB may have nongenomic cytoplasmic actions in endometrial cancer cells.     

Epidermal growth factor receptor signaling enhanced by long-term medroxyprogesterone acetate treatment in endometrial carcinoma

OBJECTIVE: Progestin is an effective endocrine treatment for patients with atypical hyperplasia or with endometrial carcinoma that is estrogen receptor (ER) positive and progesterone receptor (PR) positive. However, long-term progestin treatment may lead to resistance. We have studied the progestin resistance phenotype that frequently develops in endometrial carcinoma. METHODS: Ishikawa endometrial carcinoma cells were cultured for a long period (10 months) in the presence of the synthetic progestin medroxyprogesterone acetate (MPA), thereby generating a subline refractory to the growth-suppressive effects of MPA. RESULTS: The MPA-resistant subline showed growth stimulation rather than inhibition after MPA treatment. Immunocytochemical analysis showed reduced ER alpha and PR-B expression and increased ER beta expression in this subline compared with parental Ishikawa cells. Progestin-resistant Ishikawa cells also showed increased expression of transforming growth factor alpha (TGFalpha), the epidermal growth factor receptor (EGFR), and EGFR tyrosine kinase (EGFR-TK); MPA treatment further stimulated the expression of TGFalpha in these cells. Additionally, progestin-resistant Ishikawa cells were highly sensitive to growth stimulation by TGFalpha and to growth inhibition by the EGFR-TK-specific inhibitor AG1478, and they showed increased dependence on TGFalpha-EGFR signaling. CONCLUSIONS: Our results suggest that prolonged treatment of endometrial carcinoma cells with MPA induces resistance to the growth-suppressive effects of MPA and enhances cancer cell proliferation. The downregulation of ER alpha and PR-B, the upregulation of ER beta, and highly activated TGF-EGFR signaling are thus likely to contribute to progestin resistance in endometrial carcinoma. Therefore, an EGFR-TK-specific inhibitor might be useful in the treatment of progestin-resistant endometrial carcinoma.     

Involvement of Akt isoforms in chemoresistance of endometrial carcinoma cells

ObjectiveIn tumors, upstream regulation of Akt is affected by oncogenic events which lead to its constitutive activation and promote cell survival. Since studies have demonstrated that the three Akt isoforms exhibit different physiological functions, Akt isoforms may contribute differently in chemoresistance. The objective of the study was to determine the role of each Akt isoforms in chemoresistance.MethodsWe stably transfected the chemoresistant KLE endometrial carcinoma cells with specific shRNAs for Akt1, Akt2 or Akt3. Alternatively, we stably transfected the chemosensitive Hec-1-A endometrial carcinoma cells, in which no Akt activity is detected, with constitutively active Akt expression vectors for each isoform.ResultsWe demonstrated that Akt1 and Akt2 downregulation by RNAi highly sensitizes KLE cells to cisplatin by inducing the activation of pro-apoptotic factors such as the cleavage of caspases-3, -6, -9 and PARP; downregulation of all Akt isoforms leads to increased sensitivity to doxorubicin while only Akt1–2 downregulation increases taxol sensitivity. Proliferation of Akt1, and mostly Akt2 deficient cells was affected by cisplatin treatment. Constitutive Akt1 or Akt2 expression led to an increased resistance to apoptosis. Akt isoforms have been shown to influence migration in other cancer cells. We showed that Akt2 blocks cell motility, while Akt1–3 had less effect on our endometrial cancer cell models.ConclusionOur findings highlight the contribution of Akt1 and Akt2 in the molecular mechanisms that govern chemoresistance of endometrial carcinomas. Furthermore, Akt isoform-specific transfectants will provide a strong model to determine the involvement of each Akt isoform in tumor progression and metastasis.     

Progesterone-mediated regulation of catechol-O-methyl transferase expression in endometrial cancer cells

The effects of estrogen and progesterone on the expression of estrogen-metabolizing enzymes such as catechol-O-methyl transferase (COMT) are not known. COMT converts genotoxic catecholestrogens to anticarcinogenic methoxyestrogens in the endometrium. The aim of this study is to investigate the effect of progesterone on COMT expression in well-differentiated endometrial cancer cells. The wild-type Ishikawa cell line as well as progesterone receptor A- or progesterone receptor B-transfected Ishikawa cells were used for in vitro studies. The regulation of COMT expression by progesterone was studied using Western blots, Hoechst dye DNA proliferation studies, and wild-type and/or site-directed mutagenesis of COMT promoter 1-luciferase reporter gene. Progesterone upregulated COMT protein expression in Ishikawa cells through progesterone receptor A isoform. COMT promoter activity was differentially regulated by the 3 half-site progesterone response elements in the COMT promoter. High doses of 2-ME2 inhibited Ishikawa cell proliferation. These data suggest that COMT expression is hormonally regulated in well-differentiated human endometrial cancer cells. COMT regulation and 2-ME2 production in the endometrium may affect endometrial carcinogenesis.     

Progestin suppresses matrix metalloproteinase production in endometrial cancer

OBJECTIVES: Endometrial carcinoma (EC) is one of the few cancers where there is a clear relationship between excessive hormone stimulation and malignant transformation. In this study we have analyzed the effects of the female sex steroids estrogen and progesterone on matrix metalloproteinases (MMP-9 and -2) production in primary EC cells and EC cell lines. MMPs are implicated in cancer invasion via mechanisms including extracellular matrix degradation and the processing of a range of molecules, including growth factors and cytokines. METHODS: Cells were isolated from biopsies collected from three cancer patients undergoing hysterectomy for grade 1 endometrial adenocarcinoma and two patients undergoing procedures unrelated to EC. These cells plus the EC cell lines Ishikawa and HEC-1A were cultured without hormones or with medroxyprogesterone acetate (MPA), estradiol (E(2)), or these hormones in combination. Gelatin and reverse zymography were used to analyze MMPs and TIMPs, respectively, in culture medium. RT-PCR was used to characterize steroid receptor expression. RESULTS: Cell lines differed from primary cells in the range and abundance of MMPs secreted. Treatment with MPA significantly reduced proMMP-9, proMMP-2, and MMP-2 release from primary EC cancer and stromal cells. Treatment with E(2) alone or MPA + E(2) had no significant effect on MMP expression. Primary EC and stromal cells also showed a loss of the progesterone B receptor isoform. CONCLUSION: EC cells retain the suppression of MMPs by progesterone, seen in normal endometrial cells. These data provide a rationale for the use of progestin therapy in the treatment of early stage grade 1 endometrial carcinomas.     

Distinct functional differences of human progesterone receptors A and B on gene expression and growth regulation in two endometrial carcinoma cell lines

To study the functional differences between the two progesterone receptor isoforms (hPRA and hPRB) in human endometrial cancer, two new endometrial carcinoma cell lines were created-one expressing hPRA and one expressing hPRB.A well-differentiated, hPR-negative Ishikawa cell line was stably transfected with either hPRA or hPRB cDNA. Transfected cells were selected, and two cell lines expressing approximately equal amounts of receptor were isolated-one expressing hPRA (PRA-14) and one expressing hPRB (PRB-59).Cell growth experiments revealed a growth-inhibitory response to progestins (MPA and R5020) in the PRB-59 cells but not in the PRA-14 cells. Differences in expression of genes targeted by the two isoforms were studied using a cDNA expression array technique. A different set of genes appeared to be progesterone regulated in the PRA-14 cells than in the PRB-59 cells. None of the genes were regulated by both hPRA and hPRB. Insulin-like growth factor binding protein 3 expression was studied in more detail as an example of a gene regulated in PRB-59 cells but not in PRA-14 cells.We established a new model to study functional differences between the two hPR isoforms in human endometrial carcinoma cells. This model revealed distinctive differences in target gene regulation between the two hPR isoforms. Moreover, antiproliferative actions of progesterone on human endometrial cancer cells could be observed only in the PRB-expressing cell line.     

Expression of progesterone receptor A and B isoforms in low-grade endometrial stromal sarcoma.

The progesterone receptor (PR) exists as two isoforms, PRA and PRB. In vitro studies have shown that these proteins are functionally distinct, suggesting that their relative expression can influence progesterone response. Low-grade endometrial stromal sarcoma (LGESS) is an uncommon tumor that usually expresses PR. In normal endometrial stroma, both PR isoforms are present with PRA predominant throughout the menstrual cycle. The relative expression of PRA and PRB in LGESS has not been previously reported. All nine cases of primary LGESS (seven uterine, two extrauterine) expressed PRB. Eight tumors also contained PRA and it was the predominant isoform in seven cases. These tumors had similar histopathologic appearances, whereas a case with approximately equal PR isoform expression showed features of sex cord or smooth muscle differentiation. An extrauterine tumor expressing only PRB had myxoid stroma. Recurrent tumor in two cases, which expressed predominantly PRA in the primary, contained reduced levels of PR consisting predominantly or entirely of PRB after prolonged interval progestin therapy. Most primary LGESSs showed PR isoform expression similar to normal endometrial stroma, consistent with the highly differentiated phenotype of this tumor. Variant differentiation or disease recurrence was accompanied by an altered PR isoform profile that could impact on hormone response.     

Reevaluating the safety of fertility-sparing hormonal therapy for early endometrial cancer

OBJECTIVE: To evaluate the safety of fertility-sparing hormonal therapy for endometrial cancer in young patients. METHODS: Six patients diagnosed with endometrial adenocarcinoma grade I and had undergone progestin treatment were reviewed. Four patients failed progestin treatment and were then found at surgery to have both endometrial and ovarian cancers. A clonality assay using the human androgen receptor gene as the X-linked polymorphic marker and immunohistochemistry for steroid hormone receptor expression were used to delineate the relation between the endometrial and ovarian lesions and to explore possible causes of treatment failure. RESULTS: The patients were followed for a mean of 48.8 months. Four of the six responded to the treatment at a mean of 3.5 months. Two of these patients had a recurrence within a mean of 4.5 months after their initial response. Two patients did not respond to progestin treatment. At surgery in those 4, both endometrial and ovarian tumors were found. All 6 are still alive, and 2 successfully delivered healthy infants. The clonality assay revealed an independent cell origin for the endometrial and ovarian lesions in 2 of the 4 women who failed progestin treatment. Progesterone receptors were absent in both endometrial and ovarian tumors in 2 of these 4 patients. CONCLUSION: The absence of progesterone receptors may relate to the failure of progestin treatment. The use of progestin treatment for well-differentiated early endometrial carcinoma should be cautious and requires very careful clinical evaluation before and after treatment.     

AKT involvement in cisplatin chemoresistance of human uterine cancer cells

OBJECTIVE: The aim of this study was to investigate the possible involvement of Akt activity and specific isoforms (Akt1, Akt2, and Akt3) in the resistance of human uterine cancer cells to cisplatin. METHODS: Two different endometrial (HEC-1-A and KLE) and one cervical (HeLa) cancer cell lines all known as wild-type PTEN (tumor suppressor phosphatase tensin homologue, a lipid phosphatase involved in the negative regulation of Akt activity) were used for these studies. RESULTS: Basal levels of Akt1, Akt2, and Akt3 mRNAs were determined by real-time quantitative RT-PCR studies and Western blot analyses were carried out to determine protein abundance of each isoforms. Akt1 mRNA and protein were present in all cell lines studied. Akt2 and Akt3 mRNAs and proteins were strongly expressed in KLE cells. Surprisingly, Akt phosphorylation was found in KLE expressing high levels of wild-type PTEN protein. KLE cells remained resistant to PI 3-K inhibitor, indicating that Akt phosphorylation might be, in part, independent of PI 3-K in this cell line. Cisplatin induced apoptosis in HeLa and HEC-1-A cells, but KLE cells expressing Akt2 and Akt3 remained more resistant to cisplatin. Knockout of Akt isoforms using specific siRNA technology increased the sensitivity of KLE cells toward cisplatin and caused a significant induction of cell death. CONCLUSION: Taken together, these results suggest that specific Akt isoforms such as Akt2 and Akt3 might be involved in chemoresistance to cisplatin and that these isoforms could be putative targets for gene therapy in uterine cancers.     

Models representing type I and type II human endometrial cancers: Ishikawa H and Hec50co cells

OBJECTIVE: Endometrial cancer models are critical to the advancement of investigation, and Ishikawa H and Hec50co cells have been used as research tools. The purpose of these studies is to verify the degree to which these commonly used cell models share the molecular characteristics of the two major in vivo endometrial cancer subtypes, I and II. METHODS: The studies reported include an analysis of pathologic features, tumor suppressor mutations, detailed karyotyping, and cell cycle regulation. RESULTS: Ishikawa H cells are hormone responsive and have lost PTEN expression. In addition they have lost RB1 expression due to a deletion in exon 9. Hec50co cells have lost p53 expression due to a deletion at the junction of exon 6 and intron 6-7. Compared to Ishikawa H cells, Hec50co cells harbor many more chromosomal rearrangements (29 versus seven), and the doubling time is more rapid. The percent of cells in each phase of the cell cycle is reported and linked to cell cycle regulators. CONCLUSION: We present extensive data indicating that Ishikawa H cells are excellent models for type I endometrial cancers, and Hec50co cells faithfully replicate the molecular characteristics of type II endometrial cancers. These studies allow testing of new therapeutic regimens using appropriate cell models.     

The association of transforming growth factor-beta 1 with myometrial invasion of endometrial carcinomas through effects on matrix metalloproteinase

OBJECTIVE: The association of transforming growth factor-beta 1 (TGF-beta 1) with a matrix metalloproteinase (MMP) and a tissue inhibitor of metalloproteinase (TIMP), as well as myometrial invasion of endometrial cancer was studied. METHODS: The effects of TGF-beta 1 on cellular invasiveness, gelatinase activity, and expression of TIMP-1 were examined in 2 endometrial adenocarcinoma cell lines, KLE and Ishikawa. Plasma was obtained from 8 endometrial cancer patients with Stage-Ia disease, from 6 with Stage-Ib disease, and from 4 with Stage-Ic disease, and the levels of TGF-beta 1 were measured by enzyme immunoassays. The immunohistochemical expression of MMP-9, TIMP-1, TGF-beta 1, and TGF-beta receptor Type I in tumor tissue from the same patients also was detected. RESULTS: Invasiveness, gelatinase activity, and the expression of TIMP-1 were higher in KLE cells than in Ishikawa cells, and they were increased by treatment with rTGF-beta 1. The expression of TGF-beta receptor Type I was higher in KLE cells than in Ishikawa cells, which were unresponsive to exogenous TGF-beta 1. The plasma levels of TGF-beta 1 were greater in Stage-Ib and Stage-Ic patients than in Stage-Ia patients. MMP-9 and TGF-beta receptor Type I were expressed mainly in tumor cells, while TIMP-1 and TGF-beta 1 were localized in both tumor epithelial cells and stromal cells. MMP-9 and TIMP-1 were expressed only in Stage-Ib and Stage-Ic patients, although TGF-beta 1 and TGF-beta receptor Type I were ubiquitous. CONCLUSIONS: Myometrial invasion of endometrial cancers involves an increase in gelatinase activity, regulated to some extent by TGF-beta 1 in an autocrine or paracrine fashion.     

Steroid-modulated proliferation of human endometrial carcinoma cell lines: any role for insulin-like growth factor signaling?

OBJECTIVES: Estrogen-stimulated proliferation of the normal and malignant human endometrium is balanced by the differentiating properties of progesterone. This study evaluated the role of insulin-like growth factor (IGF) signaling in steroid-induced modulation of endometrial cancer cell proliferation. METHODS: We used the human endometrial, estrogen-responsive ECC-1 and progesterone-responsive PRAB-36 cell lines. Proliferation studies with IGFs in combination with either estrogen or progesterone were conducted. Furthermore, the mRNA and protein expression of insulin-like growth factor-binding proteins (IGFBPs) was evaluated. RESULTS: Using the ECC-1 cell line, we observed that estrogen-induced proliferation is modulated via the IGF-receptor signaling pathway, and that IGF-1-induced stimulation of proliferation does not influence estrogen receptor signaling. Furthermore, expression of the main modulators of IGF action, the IGFBPs, was found to be regulated by estrogen and progesterone in both cell lines. IGFBP-4 was up-regulated by estrogen in the ECC-1 cell line, and IGFBP-3 and IGFBP-6 were down-regulated by progesterone in the PRAB-36 cell line. CONCLUSION: Estrogen-induced stimulation of proliferation of ECC-1 endometrial cancer cells is partly achieved via IGF signaling. Furthermore, the IGFBPs are regulated by estrogens as well as progestagens and could potentially play a role in the modulation of endometrial cancer cell proliferation.     

人类胰岛素样生长因子—I调控子宫内膜癌细胞系孕激素受体亚型表达的研究

目的 探讨不同剂量人类胰岛素样生长因子－I（IGF－I）对子宫内膜癌细胞系中孕激素受体亚型表达的动态变化的调控。方法 体外培养子宫内膜癌细胞系HEC－IB,以乳腺癌细胞系MCF－7为对照,采用蛋白印迹（Western blot)法观察不同剂量IGF－I对两种孕激素受体亚型表达的动态变化的调控。结果 （1）HEC－IB细胞中,IGF－I 10ng/ml作用24h,人孕激素受体B亚型（hPRB)表达有明显上调作用,随着剂量的增加、作用时间的延长,pPRB表达逐渐下调,IGF－I 20ng/ml作用72h及40ng/ml作用48h时,下调最明显。人孕激素受体A亚型（hPRA)表达的变化趋势与hPRB大致相同,IGF－I为20ng/ml作用48h时下调至最低。（2）MCF－7细胞中,IGF－I 10、40ng/ml对hPRA、hPRB表达均有上调的作用,在第24、48、72h时较为明显。IGF－I 20ng/ml作用24h对hPRB表达有上调的作用,但在48、72h出现明显的下调;而对hPRA表达均为下调作用。结果 （1）IGF－I对人孕激素受体亚型的调控具有细胞特异性、以及时间和剂量的依赖性。（2）HEC－IB细胞中,IGF－I 10ng/ml作用24h对hPRA、hPRB表达有上调作用,随着剂量的增加、作用时间的延长,hPRA、hPRB表达渐下调。     

雌激素受体相关受体α过度表达对雌激素受体阴性的子宫内膜癌细胞增殖的影响

目的探讨雌激素受体相关受体α（ERRα）在雌激素受体（ER）阴性及阳性的子宫内膜癌细胞中的作用。方法 将真核表达质粒pSG—ERRα（0．5、1．0、1．5、2．5μg）瞬时转染子宫内膜癌细胞株HEC-1A（ER阴性）、HEC-1B（ER阴性）、Ishikawa（ER阳性）,采用定量RT-PCR技术和蛋白印迹法（westernblot）检测ERRα mRNA和蛋白的表达情况;采用流式细胞仪分析细胞周期,并计数细胞的增殖情况。结果 转染pSG—ERRα质粒后,HEC-1A、HEC-1B、Ishikawa细胞在mRNA和蛋白水平均能检测到ERRet的表达增加。HEC-1B、HEC-1A、Ishikawa细胞未转染时ERRα mRNA的表达水平分别为2104．2、2870．6、1476．8copies／ng,转染后3者ERRα mRNA的表达水平分别为9835．3、9644．4、8008．6copies／ng,分别与各自未转染的细胞比较,差异均有统计学意义（P值分别为0．004、0．002、0．002）。HEC-1A、HEC-1B、Ishikawa细胞未转染时ERRα蛋白的表达水平分别为0．823、0．192、0．673,转染后3者ERRα蛋白的表达水平分别为1．128、1．104、1．008,分别与各自未转染的细胞比较,差异均有统计学意义（P〈0．05）。随着转染pSG—ERRα质粒质量的增加,HEC-1A、HEC-1B细胞的S期和G2／M期细胞比例明显上升（P〈0．01）。HEC-1B、HEC-1A细胞转染0．5、1．0μg pSG-ERRα质粒后,细胞在转染后24—96h间生长速度显著加快（P〈0．05）。结论ERRα过度表达是ER阴性的子宫内膜癌细胞株HEC-1A、HEC-1B的一种细胞增殖机制。     

PPARγ siRNA抑制子宫内膜腺癌细胞增殖与侵袭并诱导其凋亡

目的:应用siRNA技术沉默子宫内膜癌细胞PPARγ的表达,探讨其对子宫内膜癌细胞增殖、侵袭和凋亡的变化。方法:构建小干扰RNA重组质粒,用于转染KLE与HEC-1A细胞,W estern blotting检测沉默效应。沉默PPARγ后,MTT法观察两种细胞增殖能力的改变,Hoechst染色法观察细胞的凋亡情况,侵袭试验观察肿瘤细胞侵袭能力的变化。结果:转染干扰载体后48h,沉默效率可分别达到62.9%±3.3%、72.9%±10.29%;KLE与HEC-1A细胞增殖能力在转染后48h差异有统计学意义,72h后细胞增殖能力明显降低;细胞60h已表现出早期凋亡现象,72h凋亡明显增多;转染后48h细胞的侵袭能力已降低。结论:抑制PPARγ的表达可以抑制高表达PPARγ的子宫内膜样腺癌细胞KLE与HEC-1A的增殖,诱导其凋亡,同时降低细胞的侵袭能力,表明PPARγ在子宫内膜样腺癌细胞生长和侵袭生物学特征上发挥调控作用。     

7 Methyl indole ethyl isothiocyanate causes ROS mediated apoptosis and cell cycle arrest in endometrial cancer cells

Objective

Chemotherapy options for advanced endometrial cancer are limited and newer therapeutic agents are urgently needed. This study describes the therapeutic potential of 7 Methyl-indole ethyl isothiocyanate (7Me-IEITC) in endometrial cancer cell lines.

Methods

7Me-IEITC was synthesized in our laboratory. The cell viability of 7Me-IEITC treated ECC-1 and KLE endometrial cancer cell was determined by MTS assay. Morphology and apoptosis were further confirmed by DAPI-staining and TUNEL assay. The measurement of reactive oxygen species (ROS), mitochondrial transmembrane depolarization potential (ΔΨm) and cell cycle phase was determined by FACS analysis. Expression of proteins involved in apoptosis, survival and cell-cycle progression was analyzed by Western blotting.

Results

7Me-IEITC reduced the viability of the ECC-1 and KLE cancer cell-lines (IC₅₀ ~ 2.5-10 μM) in a dose dependent fashion. 7Me-IEITC treatment caused mitochondrial transmembrane potential reduction, elevated the production of ROS, leading to activation of apoptosis in endometrial cancer KLE and ECC-1 cells. 7Me-IEITC treatment activated Bad, suppressed Bcl2 phosphorylation followed by PARP-1 deactivation and caspase 3 and 7 activation. 7Me-IEITC treatment arrested the progression of KLE cells in S-phase and caused CDC25 and cyclin-D1 downregulation. Pre-treatment with ascorbic acid abrogated 7Me-IEITC induced apoptosis in ECC-1 and KLE cells, suggesting that 7Me-IEITC mediated cytotoxicity is primarily through ROS production.

Conclusion

7Me-IEITC demonstrated promising cytotoxic effects in endometrial cancer cell line model.     

子宫内膜癌细胞雌激素受体亚型的调控和功能的初步研究

目的初步建立子宫内膜癌雌激素受体（ER）亚型α或β弱表达的细胞模型,研究雌激素及他莫昔芬（TAM）与ER亚型的关系。方法分别设计针对ERα和ERβ的反义寡脱氧核苷酸（ODN）、正义ODN、错义ODN,并转染子宫内膜癌细胞株Ishikawa,将Ishikawa细胞分为4组,即未转染组、反义ODN组、正义ODN组及错义ODN组。蛋白印迹法测定转染后细胞ERα和ERβ蛋白的表达;四甲基偶氮唑蓝（MTT）法检测转染ODN后,17β雌二醇和TAM对Ishikawa细胞生长的影响。结果（1）分别针对ERα及ERβ的反义ODN可以选择性下调转染的Ishikawa细胞中ERα及ERβ蛋白的表达（分别下调45％和54％）。（2）17β雌二醇及TAM可以促进未转染组Ishikawa细胞的生长。转染ERα反义ODN后,可抑制17β雌二醇及TAM对Ishikawa细胞的促生长作用,以转染后的24、48及72h为著,反义ODN组各时间点分别与未转染、正义ODN、错义ODN组比较,差异均有统计学意义（P〈0．05）。（3）转染ERβ反义ODN后,17β雌二醇对Ishikawa细胞的促生长作用的改变不明显。转染ERβ反义ODN可抑制TAM对Ishikawa细胞的促生长作用,以转染后72h为著,反义ODN组分别与未转染、正义ODN、错义ODN组比较,差异有统计学意义（P〈0．05）。结论（1）反义核酸技术能够特异性地有效下调Ishikawa细胞中ERα和ERβ蛋白的表达,其可作为子宫内膜癌细胞中ER调控的一种有效的实验手段。（2）17β雌二醇促进子宫内膜癌细胞生长的作用主要通过ERβ介导;ERβ和ERβ均参与TAM促进子宫内膜癌细胞生长的作用。     

Up-regulation of DNA methyltransferase 3B expression in endometrial cancers

OBJECTIVE: To understand the role of epigenetic regulation in the pathogenesis of endometrial cancer, we have characterized DNA methyltransferase 3B (DNMT3B) gene expression in normal, Grade I and Grade III endometrioid cancers, and examined DNMT3B promoter activities in endometrial cancer cell lines. METHODS: DNMT3B expression was measured in normal, Grade I, and Grade III endometrioid cancer samples. Real-time PCR and Western blot analysis were performed to compare DNMT3B mRNA and protein levels. DNMT3B levels were also compared among endometrial cell lines including those for Ishikawa, KLE, AN3, RL-95, HEC-1A, and HEC-1B. DNMT3B promoter reporter plasmids were constructed. Promoter activities in well and poorly differentiated cell lines were compared by in vitro reporter gene transfection. RESULTS: DNMT3B was significantly up-regulated in both Grade I and Grade III cancers as compared to normal controls. Western blot analysis confirmed the increased DNMT3B protein expression in cancer tissues. It was also found that the well-differentiated endometrial cell line, Ishikawa, expressed lower levels of DNMT3B than the poorly differentiated KLE cells, the expression patterns similar to those observed in tumor specimens. CONCLUSION: The results suggest that DNMT3B overexpression may play a significant role in endometrial cancer development. In addition, the transfection experiments indicated that DNMT3B promoters are more active in the poorly differentiated endometrial cancer cell lines, suggesting that the in vitro assay provides a useful model for studying the DNMT3B transactivation mechanism related to tumor transformation.