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Role of human endogenous retrovirus ERV-3 envelope gene in human placental BeWo cell proliferation and differentiation
A.12
Placenta
Workshop THE CELL CYCLE AND CANCER. M. Knbfler, of Obstetrics and Gynecology, Faculty of University of Vienna, Vienna, Austria
Department Medicine,
Cancer is believed to result from unlimited cell proliferation due to loss of regulatory mechanisms controlling cellular growth. Therefore, it is suggestedthat the molecular machinery of the cell cycle, which governs the progression of cells from Gl- (resting) to M- (mitosis) phase, is involved in tumorgenesis. During the last decade factors controlling the
various stages of the cell cycle were discovered. SignaIling pathways that initiate cell cycle events seem to be primarily associated
with
the Gl-phase.
We will
review
the general
concept of the cell cycle and discussgenes which are involved in Gl checkpoint function. At the heart of the cell cycle’s regulatory apparatus is a family of enzymes, the cyclindependent kinases (Cdks), which regulate a number of target molecules by phosphorylation. Their downstream molecules carry out steps that lead ultimately to DNA replication (Sphase) and mitosis. The most studied Gl-cyclin/Cdk substrate is the product of the retinoblastoma tumor suppressor gene (pRb), which upon phosphorylation dissociatesfrom pRE3-E2F complexes, allowing free E2F to stimulate S-phase entry by gctivating transcription of S-phase-specific genes. Besides positively acting cyclins, Cdk-activities are modulated by specific Cdk inhibitors, which are required for cell cycle arrest and differentiation in response to growth factor deprivation. Finally, we will discuss the tumor suppressor p53-dependent Gl checkpoint which allows damaged cells to arrest in Gl and either repair their DNA before replication or initiate programmed cell death. Mutations in different Cdk inhibitors, cyclins and, most frequently in p53 and pRb, were found in numerous tumor cells suggesting that deregulation of the cell cycle is crucially involved in tumorgenesis.
Roles of differentiation
HOX .
genes in trophoblast Satoshi HAYAKAWA,
growth and Maki ISHII
and .Kazuo SATOH Department of Obstetrics and Gynecology . Nihon University School of Medicine, Tokyo JAPAN Evolutionary conserved homeobox (HOX) genes encode transcription factors in the genetic control of development and differentiation of body plans, as well as malignant transformation. We have revealed stage specific cxprcssion of HOX genes in human placentae and loss ol’ their expression in clinical samples of hydatidiform mole and choriocarcinoma. In this study, we demonstrated rctinoic acid(RA) induced HOX expression associated with phenotypic differentiation in cllorioc;trcii1011i;1 cell lines in vitro. Materials and cell lines methods Three human choriocarcinoma JEG3 . BeWo and JAR were treated with various concentrations of RA over 4 days. We examined molophological changes and growth suppression by RA. The pattern of expression of HOX genes were examined with RT-PCR . We also examined effects of transfection with HOX genes on growth and morphology. Resu I ts Growth suppression and morphological clx~ngcs of cboriocarcinoma cell lines were induced in a dose-dependent manner by RA treatment. De novo expression or augmentation of HOX gene expression was induced in choriocucinoma cell lines by RA.Transfection of C4/.5/6 genes resulted growth suppression and diffcrcntiation. Conclusion Our results suggest possible roles of HOX genes in growth, differentiation and malignant transformation of human trophoblasts.
ONCOGENES AND TUMOR SUPPRESSOR GENES INTHE PLACENTA. D.W.Morrish, J.Dakour, H.Li, Department of Medicine, University of Alberta, Edmonton, AB, Canada. Gene regulation of placental function is not well understood. There are few genes known that contribute to this process (Hxt and MASH-2 in mice). In humans, possible tumor suppressor-type genes include PL48 (Morrish, Li,Dakour, 1997) and one on chromosome 7 (Matsuda). PI48 inhibits cell differentiation and promotes differentiation. In the regulation of trophoblast function, a final common pathway are the oncogenes. Little is known about signal transduction pathways converging on these genes and will be reviewed Oncogene function has been studied in a variety of circumstances including in vitro culture. These studies including our own indicate that as the cytotrophoblast differentiates into syncytium, these is decreased expression of c-myc, cfos, and c-jun with a peak in expression of these early in culture. Later, as the syncytial phenotype predominates, there is increasing expression of junB but continued c-myc expression though at a lower Level. EGF activates these pathways. The involvement of other oncogenes and PKC transduction pathways has also been studied. Signal transduction trophoblast
studies function
of processes regulating deserve greater nltcntion.
ROLE OF HUMAN ENDOGENOUS RETROVIRUS ERV-3 ENVELOPE GENE IN HUMAN PLACENTAL AND BeWo CELL PROLIFERATION L.Lin’, B.Xu’, N.S.Rote”, DIFFERENTIATION. Department of Microbiology and Immunology’, and Obstetrics and Gynecologf, Wright State University School of Medicine, Dayton, Ohio, 45435, USA. ERV-3 envelope (env) gene is expressed during trophoblast differentiation. The expression of ERV-3 mRNA is concurrent with forskolin-induced BeWo cell differentiation and intercellular fusion. Over expression of ERV-3 env in Bewo cells inhibits DNA synthesis and induces production of ~21, a negative regulator of the cell cycle, indicating that EVR-3 causes BeWo cell growth inhibition. Over expression of ERV-3 env in BeWo cells also increases fl -hCG production and causes cell morphologic changes characteristic of differentiation. The increased fi -hCG production in ERV-3 env overexpressed cells is inhibited by the addition of 10 uM H-89, a protein kinase A(PKA) inhibitor, suggesting that PK4 pathway is involved in ERV-3 env induced /? -hCG production. We have also tested the effect of anti-sense ERV-3 env on forskolininduced BeWo cell differentiation. Compared with cells transfected with vector alone, cell transfected with antisense ERV-3 show significantly reduction in forskolininduced fi -hCG production. Our findings provide the first evidence showing the biological role of ERV-3 env in placental development.
(lYY8),
Vol. 19
Placenta
Workshop THE CELL CYCLE AND CANCER. M. Knbfler, of Obstetrics and Gynecology, Faculty of University of Vienna, Vienna, Austria
Department Medicine,
Cancer is believed to result from unlimited cell proliferation due to loss of regulatory mechanisms controlling cellular growth. Therefore, it is suggestedthat the molecular machinery of the cell cycle, which governs the progression of cells from Gl- (resting) to M- (mitosis) phase, is involved in tumorgenesis. During the last decade factors controlling the
various stages of the cell cycle were discovered. SignaIling pathways that initiate cell cycle events seem to be primarily associated
with
the Gl-phase.
We will
review
the general
concept of the cell cycle and discussgenes which are involved in Gl checkpoint function. At the heart of the cell cycle’s regulatory apparatus is a family of enzymes, the cyclindependent kinases (Cdks), which regulate a number of target molecules by phosphorylation. Their downstream molecules carry out steps that lead ultimately to DNA replication (Sphase) and mitosis. The most studied Gl-cyclin/Cdk substrate is the product of the retinoblastoma tumor suppressor gene (pRb), which upon phosphorylation dissociatesfrom pRE3-E2F complexes, allowing free E2F to stimulate S-phase entry by gctivating transcription of S-phase-specific genes. Besides positively acting cyclins, Cdk-activities are modulated by specific Cdk inhibitors, which are required for cell cycle arrest and differentiation in response to growth factor deprivation. Finally, we will discuss the tumor suppressor p53-dependent Gl checkpoint which allows damaged cells to arrest in Gl and either repair their DNA before replication or initiate programmed cell death. Mutations in different Cdk inhibitors, cyclins and, most frequently in p53 and pRb, were found in numerous tumor cells suggesting that deregulation of the cell cycle is crucially involved in tumorgenesis.
Roles of differentiation
HOX .
genes in trophoblast Satoshi HAYAKAWA,
growth and Maki ISHII
and .Kazuo SATOH Department of Obstetrics and Gynecology . Nihon University School of Medicine, Tokyo JAPAN Evolutionary conserved homeobox (HOX) genes encode transcription factors in the genetic control of development and differentiation of body plans, as well as malignant transformation. We have revealed stage specific cxprcssion of HOX genes in human placentae and loss ol’ their expression in clinical samples of hydatidiform mole and choriocarcinoma. In this study, we demonstrated rctinoic acid(RA) induced HOX expression associated with phenotypic differentiation in cllorioc;trcii1011i;1 cell lines in vitro. Materials and cell lines methods Three human choriocarcinoma JEG3 . BeWo and JAR were treated with various concentrations of RA over 4 days. We examined molophological changes and growth suppression by RA. The pattern of expression of HOX genes were examined with RT-PCR . We also examined effects of transfection with HOX genes on growth and morphology. Resu I ts Growth suppression and morphological clx~ngcs of cboriocarcinoma cell lines were induced in a dose-dependent manner by RA treatment. De novo expression or augmentation of HOX gene expression was induced in choriocucinoma cell lines by RA.Transfection of C4/.5/6 genes resulted growth suppression and diffcrcntiation. Conclusion Our results suggest possible roles of HOX genes in growth, differentiation and malignant transformation of human trophoblasts.
ONCOGENES AND TUMOR SUPPRESSOR GENES INTHE PLACENTA. D.W.Morrish, J.Dakour, H.Li, Department of Medicine, University of Alberta, Edmonton, AB, Canada. Gene regulation of placental function is not well understood. There are few genes known that contribute to this process (Hxt and MASH-2 in mice). In humans, possible tumor suppressor-type genes include PL48 (Morrish, Li,Dakour, 1997) and one on chromosome 7 (Matsuda). PI48 inhibits cell differentiation and promotes differentiation. In the regulation of trophoblast function, a final common pathway are the oncogenes. Little is known about signal transduction pathways converging on these genes and will be reviewed Oncogene function has been studied in a variety of circumstances including in vitro culture. These studies including our own indicate that as the cytotrophoblast differentiates into syncytium, these is decreased expression of c-myc, cfos, and c-jun with a peak in expression of these early in culture. Later, as the syncytial phenotype predominates, there is increasing expression of junB but continued c-myc expression though at a lower Level. EGF activates these pathways. The involvement of other oncogenes and PKC transduction pathways has also been studied. Signal transduction trophoblast
studies function
of processes regulating deserve greater nltcntion.
ROLE OF HUMAN ENDOGENOUS RETROVIRUS ERV-3 ENVELOPE GENE IN HUMAN PLACENTAL AND BeWo CELL PROLIFERATION L.Lin’, B.Xu’, N.S.Rote”, DIFFERENTIATION. Department of Microbiology and Immunology’, and Obstetrics and Gynecologf, Wright State University School of Medicine, Dayton, Ohio, 45435, USA. ERV-3 envelope (env) gene is expressed during trophoblast differentiation. The expression of ERV-3 mRNA is concurrent with forskolin-induced BeWo cell differentiation and intercellular fusion. Over expression of ERV-3 env in Bewo cells inhibits DNA synthesis and induces production of ~21, a negative regulator of the cell cycle, indicating that EVR-3 causes BeWo cell growth inhibition. Over expression of ERV-3 env in BeWo cells also increases fl -hCG production and causes cell morphologic changes characteristic of differentiation. The increased fi -hCG production in ERV-3 env overexpressed cells is inhibited by the addition of 10 uM H-89, a protein kinase A(PKA) inhibitor, suggesting that PK4 pathway is involved in ERV-3 env induced /? -hCG production. We have also tested the effect of anti-sense ERV-3 env on forskolininduced BeWo cell differentiation. Compared with cells transfected with vector alone, cell transfected with antisense ERV-3 show significantly reduction in forskolininduced fi -hCG production. Our findings provide the first evidence showing the biological role of ERV-3 env in placental development.
(lYY8),
Vol. 19