N-myc downstream-regulated gene 1/Cap43 may function as tumor suppressor in endometrial cancer

Purpose

N-myc downstream-regulated gene 1 (NDRG1) reportedly regulates tumor progression in various cancers. Our previous studies showed that NDRG1 was aberrantly overexpressed in human endometrial cancer tissues. The purpose of the present study was to investigate the role of NDRG1 in endometrial carcinogenesis.

Methods

A short hairpin RNA (shRNA)-mediated gene silencing strategy was employed to stably suppress the expression of NDRG1 in endometrial cancer Ishikawa cells. The influence of NDRG1 silencing on cancer cell biological behaviors was examined through observing in vitro tumor cell proliferation, colony formation, cell migration and invasion. Moreover, the mammalian NDRG1 expression vector pcDNA3.1(+)/NDRG1 was constructed to determine the effects of NDRG1 overexpression on cell proliferation and migration. Additionally, gene expression microarray analysis was conducted to identify NDRG1 downstream target genes after NDRG1 knockdown.

Results

It was demonstrated that NDRG1 knockdown significantly enhanced Ishikawa cell proliferation and dramatically promoted cell migration and invasion. Furthermore, overexpression of NDRG1 in Ishikawa cells greatly inhibited cell proliferation and migration. Through microarray analysis and data mining, a large cohort of NDRG1-repressed target genes were identified. Additionally, through comparing the current microarray results with those obtained previously in studies of cervical and ovarian cancer cells conducted by us, 19 more specific common downstream target genes were identified.

Conclusions

It was demonstrated that NDRG1 might carry out a tumor suppressor function during endometrial carcinogenesis. The identification of downstream target genes should afford meaningful hints for prospective investigations. The tumor suppressor function of NDRG1 may open a new window for the target therapy of endometrial cancer.     

Comparative analysis of genes regulated by PML/RAR alpha and PLZF/RAR alpha in response to retinoic acid using oligonucleotide arrays

Acute promyelocytic leukemia (APL) is associated with chromosomal translocations involving retinoic acid receptor alpha (RAR alpha) and its fusion partners including promyelocytic leukemia (PML) and promyelocytic leukemia zinc finger (PLZF). Using oligonucleotide arrays, we examined changes in global gene expression mediated by the ectopic expression of either PML/RAR alpha (retinoid-sensitive) or PLZF/RAR alpha (retinoid-resistant) in U937 cells. Of more than 5000 genes analyzed, 16 genes were commonly up-regulated, and 57 genes were down-regulated by both fusion proteins suggesting their role in the APL phenotype. In our APL model, for example, TNFAIP2, TNFR2, ELF4, RAR gamma, and HoxA1 were down-regulated by both fusion proteins in the absence of retinoic acid (RA). RA strongly up-regulated these genes in PML/RAR alpha, but not in PLZF/RAR alpha expressing U937 cells. Expression studies in NB4, retinoid-resistant NB4-R2, normal human CD34+ cells, and APL patient samples strongly suggest their role in the regulation of granulocytic differentiation. Furthermore, combined treatment with tumor necrosis factor alpha (TNF alpha) and RA synergistically enhanced granulocytic differentiation in NB4 cells but not in NB4-R2 cells. Our data indicate that APL pathogenesis and retinoid-induced granulocytic differentiation of APL cells involve genes in the cell death pathway, and that cooperation between the RA and TNFalpha signaling pathways exists. Targeting both the retinoid-dependent differentiation and the cell death pathways may improve leukemic therapy, especially in retinoid-resistant acute myeloid leukemia.     

AM580, a stable benzoic derivative of retinoic acid, has powerful and selective cyto-differentiating effects on acute promyelocytic leukemia cells

All-trans retinoic acid (ATRA) is successfully used in the cyto- differentiating treatment of acute promyelocytic leukemia (APL). Paradoxically, APL cells express PML-RAR, an aberrant form of the retinoic acid receptor type alpha (RAR alpha) derived from the leukemia- specific t(15;17) chromosomal translocation. We show here that AM580, a stable retinobenzoic derivative originally synthesized as a RAR alpha agonist, is a powerful inducer of granulocytic maturation in NB4, an APL-derived cell line, and in freshly isolated APL blasts. After treatment of APL cells with AM580 either alone or in combination with granulocyte colony-stimulating factor (G-CSF), the compound induces granulocytic maturation, as assessed by determination of the levels of leukocyte alkaline phosphatase, CD11b, CD33, and G-CSF receptor mRNA, at concentrations that are 10- to 100-fold lower than those of ATRA necessary to produce similar effects. By contrast, AM580 is not effective as ATRA in modulating the expression of these differentiation markers in the HL-60 cell line and in freshly isolated granulocytes obtained from the peripheral blood of chronic myelogenous leukemia patients during the stable phase of the disease. In NB4 cells, two other synthetic nonselective RAR ligands are capable of inducing LAP as much as AM580, whereas RAR beta- or RAR gamma-specific ligands are totally ineffective. These results show that AM580 is more powerful than ATRA in modulating the expression of differentiation antigens only in cells in which PML-RAR is present. Binding experiments, using COS-7 cells transiently transfected with PML-RAR and the normal RAR alpha, show that AM580 has a lower affinity than ATRA for both receptors. However, in the presence of PML-RAR, the synthetic retinoid is a much better transactivator of retinoic acid-responsive element-containing promoters than the natural retinoid, whereas, in the presence of RAR alpha, AM580 and ATRA have similar activity. This may explain the strong cyto-differentiating potential of AM580 in PML-RAR-containing leukemic cells.     

Prokineticin 1 signaling and gene regulation in early human pregnancy

Prokineticin 1 (PROK1) is a recently described protein with a wide range of functions including tissue-specific angiogenesis, modulation of inflammatory responses, and regulation of hematopoiesis. The objective of this study was to investigate the role of PROK1 and prokineticin receptor 1 (PROKR1) in human endometrium during early pregnancy. PROK1 and PROKR1 expression is significantly elevated in first-trimester decidua, compared with nonpregnant endometrium. Expression of PROK1 and PROKR1 was localized in glandular epithelial and various cellular compartments within the stroma. To investigate the signaling pathways and target genes activated by PROK1, we generated an endometrial epithelial cell line stably expressing PROKR1 (Ishikawa PROKR1 cells). PROK1-PROKR1 interaction induced inositol phosphate mobilization and sequential phosphorylation of c-Src, epidermal growth factor receptor, and ERK 1/2. Gene microarray analysis on RNA extracted from Ishikawa PROKR1 cells treated with 40 nm PROK1 for 8 h revealed 49 genes to be differentially regulated. A number of these genes, including cyclooxygenase (COX)-2, leukemia inhibitory factor, IL-6, IL-8, and IL-11 are regulated in the endometrium during implantation and early pregnancy. We subsequently investigated the effect of PROK1 on expression of COX-2 in Ishikawa PROKR1 cells and first-trimester decidua. COX-2 mRNA and protein expression, and prostaglandin synthesis, were elevated in response to treatment with PROK1. Moreover, expression of COX-2 by PROK1 was dependent on activation of the Gq-phospholipase C-beta-cSrc-epidermal growth factor receptor-MAPK/ERK kinase pathway. These data demonstrate that PROK1 and PROKR1 expression is elevated in human decidua during early pregnancy and that PROK1-PROKR1 interaction regulates expression of a host of implantation-related genes.     

Expression, localization, and signaling of prostaglandin F2 alpha receptor in human endometrial adenocarcinoma: regulation of proliferation by activation of the epidermal growth factor receptor and mitogen-activated protein kinase signaling pathways

Prostaglandin F(2 alpha)(PGF(2 alpha)) is a bioactive lipid biosynthesized by cyclooxygenase (COX) enzymes and mediates its biological activity via the heptahelical G(q)-coupled PGF(2 alpha)receptor (FP receptor). This study investigated the expression and molecular signaling of the FP receptor in human endometrial adenocarcinomas. Real-time RT-PCR and Western blot analysis confirmed FP receptor expression in endometrial adenocarcinoma of all grades and differentiation. The expression of FP receptor was up-regulated in all endometrial adenocarcinomas compared with normal endometrium. The site of FP receptor expression was localized by in situ hybridization and immunohistochemistry to the neoplastic epithelial cells in all adenocarcinomas. Treatment of endometrial adenocarcinoma explants with PGF(2 alpha) resulted in mobilization of inositol phosphate signaling, indicating functional FP receptor expression. We investigated whether PGF(2 alpha) could trans-activate the epidermal growth factor receptor (EGFR) and trigger the MAPK signaling pathway. Treatment of adenocarcinoma explants and endometrial adenocarcinoma cells (Ishikawa) with PGF(2 alpha)-phosphorylated EGFR, triggered MAPK signaling and enhanced the proliferation of Ishikawa cells. Inactivation of phospholipase C, EGFR kinase, and MAPK kinase with specific inhibitors abolished PGF(2 alpha)-induced trans-activation of EGFR, MAPK signaling, and Ishikawa cell proliferation. These data suggest that PGF(2 alpha)-FP receptor promote endometrial tumorigenesis via a phospholipase C-mediated phosphorylation of the EGFR and MAPK signaling pathways.     

Differential regulation of cathepsin D by sex steroids in mammary cancer and uterine cells

The precursor of cathepsin D, a lysosomal acidic protease, is secreted by human breast cancer cells, where its synthesis is specifically induced by estrogens and growth factors. In this study, we investigated the hormonal regulation of cathepsin D and its mRNA in uterine cells. In the Ishikawa endometrial cancer cell line, epidermal growth factor (EGF) increased the level of cathepsin D and its mRNA 2- to 3-fold. Although expression of the transiently transfected estrogen-responsive recombinant (Vit. tk. CAT) and the endogenous progesterone receptor was markedly increased by estradiol in Ishikawa cells, estradiol did not alter the level of cathepsin D or its mRNA. The progestin R5020 induced the expression of the LTR sp65 CAT, which contains the progesterone-responsive element of the MMTV but it too was without effect on cathepsin D. By contrast, the expression of cathepsin D gene, in normal rat uterus, was increased by R5020 but not by estradiol. We conclude that cathepsin D gene expression is regulated differently by sex steroid hormones in endometrial and breast cancer cell lines, whereas it is similarly induced by EGF in these cells.     

Gene expression profiles in an hepatitis B virus transfected hepatoblastoma cell line and differentially regulated gene expression by interferon-α

AIM: To study interactions between hepatitis B virus (HBV)and interferon-α in liver- derived cells.METHODS: mRNAs were separately isolated from an HBVtransfected cell line (HepG22.2.15) and its parental cell line (HepG2) pre- and post-interferon-α (IFN-α) treatment at 6,24 and 48 h, followed by hybridization with a cDNA microarray filter dotted with 14 000 human genes. After hybridization and scanning of the arrays, the data were analyzed using ArrayGauge software. The microarray data were further verified by Northern blot analysis.RESULTS: Compared to HepG2 cells, 14 genes with known functions were down-regulated 3 to 12- magnitudes, while 7genes were up-regulated 3-13 magnitudes in HepG22.2.15cells prior to IFN-α treatment. After interferon-α treatment,the expression of four genes (vascular endothelial growth factor, tyrosine phosphate 1E, serine protein with IGF-binding motif and one gene of clathrin light chain) in HepG22.2.15were up-regulated, while one gene encoding a GTP-binding protein, two genes of interferon-induced kinases and two proto-oncogenes were further down- regulated. Interestingly,under IFN-α treatment, a number of differentially regulated genes were new ESTs or genes with unknown functions.CONCLUSION: The up-regulated genes in HepG22.2.15cell line suggested that under IFN-α treatment, these repressed cellular genes in HBV infected hepatocytes could be partially restored, while the down- regulated genes were most likely the cellular genes which could not be restored under interferon treatment. These down-regulated genes identified by microarray analysis could serve as new targets for anti-HBV drug development or for novel therapies.     

Expression analysis of estrogen-metabolizing enzymes in human endometrial cancer

Estrogen-dependent endometrial cancer is related to unopposed and prolonged estrogen stimulation. We examined the expression of estrogen-metabolizing enzymes in correlation with the ERalpha and ERbeta estrogen receptors in human endometrial Ishikawa adenocarcinoma cells and in endometrial cancer specimens and adjacent normal endometrium from the same patients. Real-time PCR analysis revealed that both estrogen receptors and selected estrogen-metabolizing enzymes were expressed in the Ishikawa cells and in endometrial tissue. We detected higher expression of ERalpha than ERbeta, higher expression of sulfatase than sulfotransferase and low expression of aromatase in the Ishikawa cells and the tissue, as well as higher levels of type 2 17beta-hydroxysteroid dehydrogenase (17beta-HSD) in normal and diseased tissue than in the Ishikawa cells. When we compared the expression in endometrial cancer samples and in the adjacent normal endometrium, ERalpha and ERbeta, sulfatase and sulfotransferase were seen to be downregulated in the majority of the cancerous tissue specimens.     

Prostacyclin receptor up-regulates the expression of angiogenic genes in human endometrium via cross talk with epidermal growth factor Receptor and the extracellular signaling receptor kinase 1/2 pathway

Prostacyclin (PGI) is a member of the prostanoid family of lipid mediators that mediates its effects through a seven-transmembrane G protein-coupled receptor (IP receptor). Recent studies have ascertained a role for prostanoid-receptor signaling in angiogenesis. In this study we examined the temporal-spatial expression of the IP receptor within normal human endometrium and additionally explored the signaling pathways mediating the role of IP receptor in activation of target angiogenic genes. Quantitative RT-PCR analysis demonstrated the highest endometrial expression of the IP receptor during the menstrual phase compared with all other stages of the menstrual cycle. Immunohistochemical analysis localized the site of IP receptor expression to the glandular epithelial compartment with stromal and perivascular cell immunoreactivity. Expression of the immunoreactive IP receptor protein was greatest during the proliferative and early secretory phases of the menstrual cycle. To explore the role of the IP receptor in glandular epithelial cells, we used the Ishikawa endometrial epithelial cell line. Stimulation of Ishikawa cells and human endometrial biopsy explants with 100 nm iloprost (a PGI analog) rapidly activated ERK1/2 signaling and induced the expression of proangiogenic genes, basic fibroblast growth factor, angiopoietin-1, and angiopoietin-2, in an epidermal growth factor receptor (EGFR)-dependent manner. Furthermore, EGFR colocalized with IP receptor in the glandular epithelial compartment. These data suggest that PGI-IP interaction within glandular epithelial cells can promote the expression of proangiogenic genes in human endometrium via cross talk with the EGFR.     

Acidic preparations of lysed platelets upregulate proliferative pathways in osteoblast-like cells as demonstrated by genome-wide microarray analysis

Platelets contain numerous growth factors essential for wound and fracture healing. We investigated the gene expression in human osteoblast-like cells stimulated with lysed platelets prepared in acidic, neutral, or alkaline buffers. Lysed platelets prepared in buffers at pH 5.4, 7.4, and 7.9, were added after neutralization to hFOB 1.19?cells. Genome-wide microarray analysis was performed using the Affymetrix GeneChip 7G Scanner. Biometric, cluster, and pathway analyses were performed with GeneSpring GX. Biometric analyses demonstrated that 53 genes were differentially regulated (p?≤?0.005, ≥2-fold increase). Pathway analysis revealed 10 significant pathways of which eight are common ones regulating bone formation and cancer growth. Eleven genes were selected for quantitative real-time polymerase chain reaction (PCR) based on the microarray analysis of the lysed platelets prepared in the pH 5.4 experiments. In conclusion, acidic preparations of lysed platelet concentrates release factors essential for cell proliferation and particularly cell metabolism under hypoxic conditions. The genetic response from these factors was dominated by genes associated with the same pathways observed in bone formation and cancer growth. Activation of TGF-β in the acidic preparation could be a stimulatory key factor of cell proliferation. These results support the hypothesis that acidification of platelets modifies the stimulatory response of mesenchymal cells in?vitro, which is analogous with the observed milieu of a low pH present in wound and fracture sites, as well as in growing tumors.     

Reexpression of retinoic acid receptor (RAR) gamma or overexpression of RAR alpha or RAR beta in RAR gamma-null F9 cells reveals a partial functional redundancy between the three RAR types.

Disruption of retinoic acid receptor (RAR) gamma in F9 embryonal carcinoma cells leads to aberrent differentiation and reduced activation of expression of several all-trans-retinoic acid (RA)-induced genes. We have analyzed the expression of several additional RA-responsive genes in RAR alpha- and RAR gamma-null F9 cells. The RA-induced activation of Cdx1, Gap43, Stra4, and Stra6 was specifically impaired in RAR gamma-null cells, supporting the idea that each RAR may regulate distinct subsets of target genes. To further investigate the role of RAR gamma in F9 cell differentiation, "rescue" cell lines reexpressing RAR gamma 2 or overexpressing either RAR alpha 1 or RAR beta 2 were established in RAR gamma-null cells. Reexpression of RAR gamma or overexpression of RAR alpha restored both target-gene activation and the differentiation potential. In contrast, over-expression of RAR beta only poorly restored differentiation, although it could replace RAR gamma for the activation of target genes. Functional redundancy between the various RARs is discussed.     

Acidic preparations of lysed platelets upregulate proliferative pathways in osteoblast-like cells as demonstrated by genome-wide microarray analysis

Platelets contain numerous growth factors essential for wound and fracture healing. We investigated the gene expression in human osteoblast-like cells stimulated with lysed platelets prepared in acidic, neutral, or alkaline buffers. Lysed platelets prepared in buffers at pH 5.4, 7.4, and 7.9, were added after neutralization to hFOB 1.19?cells. Genome-wide microarray analysis was performed using the Affymetrix GeneChip 7G Scanner. Biometric, cluster, and pathway analyses were performed with GeneSpring GX. Biometric analyses demonstrated that 53 genes were differentially regulated (p?≤?0.005, ≥2-fold increase). Pathway analysis revealed 10 significant pathways of which eight are common ones regulating bone formation and cancer growth. Eleven genes were selected for quantitative real-time polymerase chain reaction (PCR) based on the microarray analysis of the lysed platelets prepared in the pH 5.4 experiments. In conclusion, acidic preparations of lysed platelet concentrates release factors essential for cell proliferation and particularly cell metabolism under hypoxic conditions. The genetic response from these factors was dominated by genes associated with the same pathways observed in bone formation and cancer growth. Activation of TGF-β in the acidic preparation could be a stimulatory key factor of cell proliferation. These results support the hypothesis that acidification of platelets modifies the stimulatory response of mesenchymal cells in vitro, which is analogous with the observed milieu of a low pH present in wound and fracture sites, as well as in growing tumors.