TGF beta1 induces multiple independent signals to regulate human trophoblastic differentiation: mechanistic insights

Krüppel-like factor 6 (KLF6) requires its amino terminal domain to promote villous trophoblast cell fusion

INTRODUCTION

Villous cytotrophoblast (vCTB) cells fuse to generate and maintain the syncytiotrophoblast layer required for placental development and function. Krüppel-like factor 6 (KLF6) is a ubiquitous transcription factor with an N-terminal acidic transactivation domain and a C-terminal zinc finger DNA-binding domain. KLF6 is highly expressed in placenta, and it is required for proper placental development. We have demonstrated that KLF6 is necessary for cell fusion in human primary vCTBs, and in the BeWo cell line.

MATERIALS AND METHODS

Full length KLF6 or a mutant lacking its N-terminal domain were expressed in BeWo cells or in primary vCTB cells isolated from human term placentas. Cell fusion, gene and protein expression, and cell proliferation were analyzed. Moreover, Raman spectroscopy and atomic force microscopy (AFM) were used to identify biochemical, topography, and elasticity cellular modifications.

RESULTS

The increase in KLF6, but not the expression of its deleted mutant, is sufficient to trigger cell fusion and to raise the expression of β-hCG, syncytin-1, the chaperone protein 78 regulated by glucose (GRP78), the ATP Binding Cassette Subfamily G Member 2 (ABCG2), and Galectin-1 (Gal-1), all molecules involved in vCTB differentiation. Raman and AFM analysis revealed that KLF6 reduces NADH level and increases cell Young's modulus. KLF6-induced differentiation correlates with p21 upregulation and decreased cell proliferation. Remarkable, p21 silencing reduces cell fusion triggered by KLF6 and the KLF6 mutant impairs syncytialization and decreases syncytin-1 and β-hCG expression.

DISCUSSION

KLF6 induces syncytialization through a mechanism that involves its regulatory transcriptional domain in a p21-dependent manner.

Role of ARID1A in the Regulation of Human Trophoblast Migration and Invasion

Migration and invasion of trophoblasts is critical for human placental development, trophoblastic differentiation, and pregnancy-associated diseases. AT-rich interactive domain-containing protein 1A (ARID1A), a subunit of the SWI-SNF complex, has been suggested to participate in the regulation of fertility via placental disruption in mice. However, whether ARID1A regulates human placental development and function remains unknown. Here, using human trophoblast-like JEG-3 cell line, we report that ARID1A controls trophoblast cell migration and invasion. Overexpression of ARID1A inhibits JEG-3 cell migration and invasion, whereas knockdown of ARID1A promotes migration and invasion in JEG-3 cells. Mechanistically, while ARID1A reduces JEG-3 cell migration by down-regulation of Snail transcription, it restrains JEG-3 cell invasion by binding to and destabilization of MMP-9 protein. Finally, ARID1A is apparently up-regulated in placental tissues of preeclampsia compared to that of normal pregnancies. Our results thereby imply that ARID1A acts as a critical gene in supporting the physiological function of human mature placenta.

Unveiling the role of microRNA-7 in linking TGF-β-Smad-mediated epithelial-mesenchymal transition with negative regulation of trophoblast invasion

Several pregnancy complications result from abnormal trophoblast invasion. The dichotomous effect of TGF-β on epithelial-mesenchymal transition (EMT) between trophoblast invasion and cancer progression remains unknown and a critical concern. We attenuated the expression of TGF-β type 1 receptor (coding by TGFBR1) with RNA interference in trophoblastic cells and significantly enhanced the trophoblastic invasion. Analysis of microRNA profiles in trophoblasts indicated microRNA-7 as a key molecule linking TGF-β with the negative regulation of trophoblast invasion. We then attenuated TGFBR1 and miR-7 transcription by transducing either short hairpin RNA targeting TGFBR1 or anti-miR-7-locked nucleonic acid, and we observed an up-regulation of EMT-related transcription factors (TFs) and their downstream effectors, causing a mesenchymal transition of trophoblasts. Conversely, overexpression of TGFBR1 or miR-7 led to the epithelial transition of trophoblasts. Our results showed that TGF-β-induced miR-7 expression negatively modulated the TGF-β-SMAD family member 2-mediated EMT pathway via targeting EMT-related TFs and down-regulating their mesenchymal markers. These findings possibly explain, at least in part, why TGF-β exerts an opposite effect on EMT during trophoblast invasion and cancer progression.-Shih, J.-C., Lin, H.-H., Hsiao, A.-C., Su, Y.-T., Tsai, S., Chien, C.-L., Kung, H.-N. Unveiling the role of microRNA-7 in linking TGF-β-Smad-mediated epithelial-mesenchymal transition with negative regulation of trophoblast invasion.

Megalin Is Predominantly Observed in Vesicular Structures in First and Third Trimester Cytotrophoblasts of the Human Placenta

The membrane receptor megalin is crucial for normal fetal development. Besides its expression in the developing fetus, megalin is also expressed in the human placenta. Similar to its established function in the kidney proximal tubules, placental megalin has been proposed to mediate uptake of vital nutrients. However, details of megalin expression, subcellular localization, and function in the human placenta remain to be established. By immunohistochemical analyses of first trimester and term human placenta, we showed that megalin is predominantly expressed in cytotrophoblasts, the highly proliferative cells in placenta. Only limited amounts of megalin could be detected in syncytiotrophoblasts and least in term placenta syncytiotrophoblasts. Immunocytochemical analyses furthermore showed that placental megalin associates with structures of the endolysosomal apparatus. Combined, our results clearly place placental megalin in the context of endocytosis and trafficking of ligands. However, due to the limited expression of megalin in syncytiotrophoblasts, especially in term placenta, it appears that the main role for placental megalin is not to mediate uptake of nutrients from the maternal bloodstream, as previously proposed. In contrast, our results point toward novel and complex functions for megalin in the cytotrophoblasts. Thus, we propose that the perception of placental megalin localization and function should be revised.

Id2 Mediates Differentiation of Labyrinthine Placental Progenitor Cell Line, SM10

The placenta is an organ that is formed transiently during pregnancy, and appropriate placental development is necessary for fetal survival and growth. Proper differentiation of the labyrinthine layer of the placenta is especially crucial, as it establishes the fetal-maternal interface that is involved in physiological exchange processes. Although previous studies have indicated the importance of inhibitor of differentiation/inhibitor of DNA binding-2 (Id2) helix-loop-helix transcriptional regulator in mediating cell differentiation, the ability of Id2 to regulate differentiation toward the labyrinthine (transport) lineage of the placenta has yet to be determined. In the current study, we have generated labyrinthine trophoblast progenitor cells with increased (SM10-Id2) or decreased (SM10-Id2-shRNA) Id2 expression and determined the effect on TGF-β-induced differentiation. Our Id2 overexpression and knockdown analyses indicate that Id2 mediates TGF-β-induced morphological differentiation of labyrinthine trophoblast cells, as Id2 overexpression prevents differentiation and Id2 knockdown results in differentiation. Thus, our data indicate that Id2 is an important molecular mediator of labyrinthine trophoblast differentiation. An understanding of the regulators of trophoblast progenitor differentiation toward the labyrinthine lineage may offer insights into events governing pregnancy-associated disorders, such as placental insufficiency, fetal growth restriction, and preeclampsia.

Maternal insulin-like growth factor 1 and 2 differentially affect the renin-angiotensin system during pregnancy in the guinea pig

OBJECTIVE

Insulin-like growth factors (IGFs) are known to interact with the renin-angiotensin system (RAS). We previously demonstrated that administration of IGF1 to guinea pigs in early to mid pregnancy promotes placental function and fetal growth in mid to late gestation. Early administration of IGF2 had sustained, but not acute, effects on these parameters and also on placental structural differentiation. Here, we aimed to determine whether the IGFs interact with the placental RAS in early to mid gestation to modulate placental development and increase fetal growth and survival, and if IGF2 binding the IGF2R is implicated in the sustained effects of IGF2 treatment.

DESIGN

At day 20 of pregnancy, guinea pigs were infused with 1m g/kg/day of IGF1, IGF2, (Leu27)IGF2 or vehicle for 18days and sacrificed on either day 62 (late pregnancy) or during the infusion period on day 35 (early-mid pregnancy). Placental structure at day 35 was analyzed using morphometric technique and expression of RAS genes in the placenta and placental and plasma renin activity were measured at both time points.

RESULTS

Compared with vehicle at day 35 of gestation, IGF1 infusion reduced the total midsagittal cross-sectional area of the placenta (-17%, p = 0.02) and the labyrinth area (-22%, p = 0.014) but did not alter the labyrinth volume nor labyrinth:interlobium ratios. IGF2 treatment did not affect placental structure. IGF1 did not alter placental mRNA for any of the RAS genes quantified at day 35 (AGTR1, ACE, AGT, TGFB1) but increased TGFB1 expression by more than 16-fold (p = 0.005) at day 62. IGF2 increased placental expression of AGTR1 (+88%, p = 0.03) and decreased AGT (-73%, p = 0.01) compared with the vehicle-treated group at day 35, and both IGF2 and (Leu27)IGF2 increased expression of TGFB1 at day 62 by 9-fold (p = 0.016) and 6-fold (p = 0.019) respectively. Both IGFs increased the ratio of active:total placental renin protein (+22% p = 0.026 p = 0.038) compared to vehicle compared to vehicle at day 35 but not 62. At day 62, IGF2-treated mothers showed a marked increase in total plasma renin (+495%) and active renin (+359%) compared to vehicle but decreased the ratio of active to total renin by 41% (p = 0.042). (Leu27)IGF2-treated animals had higher levels of placental active renin (+73%, p = 0.001) and total renin (+71%, p = 0.001) compared with the vehicle control.

CONCLUSIONS

The data obtained in the current study suggest the potential for alternate roles for the induction of the RAS after IGF treatment. IGF1 and 2 treatments increase the activation of prorenin to renin in the placenta, possibly due to increased protease activity. In addition, IGF2 treatment in early pregnancy may enhance the maternal adaptation to pregnancy through stimulation of renin in the kidney. The sustained effects on placental differentiation and function after IGF2 treatment suggest therapeutic potential for exogenous administration of IGFs in improving pregnancy outcomes.

The impact of TGF-β1 on the mRNA expression of TβR I, TβR II, Smad4 and the invasiveness of the JEG-3 placental choriocarcinoma cell line

Human choriocarcinoma is one of the most aggressive malignant tumors characterized by early hematogenous spread to lung and brain tissues, and may be a cause of death in patients. Choriocarcinoma may occur following pregnancy and during implantation; however, trophoblastic invasion in human pregnancy is tightly regulated. The transforming growth factor-beta 1 (TGF-β1) has been suggested to play a role in controlling this process. In this study, we investigated the impact of TGF-β1 on invasion, as well as its sites of action in the TGF-β1/Smad pathway using a JEG-3 choriocarcinoma cell line. Following the treatment of cells with different doses of TGF-β1, cell invasion was observed. We also detected the expression of TGF-β receptor type I (TβR I) and TGF-β receptor type II (TβR II), Smad4, matrix metalloprotease (MMP)-9 and tissue inhibitor of metalloproteinase (TIMP)-1 in JEG-3 cells. Our data demonstrated that TGF-β1 promoted the invasive capability of JEG-3 cells depending on the downregulation of TβR I, TβR II, Smad4 and the upregulation of MMP-9 and TIMP-1. These observations suggest that TGF-β1 may play a critical role in the initiation of the trophoblastic invasion process.

MAD1 and its life as a MYC antagonist: an update

The MYC/MAX/MAD network is of central importance for controlling cell physiology. The network is compiled of transcriptional regulators that form different heterodimers, which can either activate or repress the expression of target genes. Thus these proteins function as a molecular switch to control gene expression. MAD1, a member of this network, acts as a transcriptional repressor. It interacts with MAX to form the OFF position of the switch, antagonizing MYC/MAX complexes that define the ON position. MAD1 regulates cell proliferation and apoptosis through a number of target genes. In addition recent evidence indicates that the expression and activity of MAD1 are regulated at multiple levels. Here the recent developments are summarized, in comparison to MYC, of our understanding how the expression of the MAD1 gene and protein are controlled and what the functional consequences and downstream effectors of MAD1 are, which relay its activity as a transcriptional regulator.

Human telomerase expression regulation

Since telomerase has been recognized as a relevant factor distinguishing cancer cells from normal cells, it has become a very promising target for anti-cancer therapy. A correlation between short telomere length and increased mortality was revealed in many studies. The telomerase expression/activity appears to be one of the most crucial factors to study to improve cancer therapy and prevention. However, this multisubunit enzymatic complex can be regulated at various levels. Thus, several strategies have been proposed to control telomerase in cancer cells such as anti-sense technology against TR and TERT, ribozymes against TERT, anti-estrogens, progesterone, vitamin D, retinoic acid, quadruplex stabilizers, telomere and telomerase targeting agents, modulation of interaction with other proteins involved in the regulation of telomerase and telomeres, etc. However, the transcription control of key telomerase subunits seems to play the crucial role in whole complexes activity and cancer cells immortality. Thus, the research of telomerase regulation can bring significant insight into the knowledge concerning stem cells metabolism but also ageing. This review summarizes the current state of knowledge of numerous telomerase regulation mechanisms at the transcription level in human that might become attractive anti-cancer therapy targets.

Pre-eclampsia: fitting together the placental, immune and cardiovascular pieces

The success of pregnancy is a result of countless ongoing interactions between the placenta and the maternal immune and cardiovascular systems. Pre-eclampsia is a serious pregnancy complication that arises from multiple potential aberrations in these systems. The pathophysiology of pre-eclampsia is established in the first trimester of pregnancy, when a range of deficiencies in placentation affect the key process of spiral artery remodelling. As pregnancy progresses to the third trimester, inadequate spiral artery remodelling along with multiple haemodynamic, placental and maternal factors converge to activate the maternal immune and cardiovascular systems, events which may in part result from increased shedding of placental debris. As we understand more about the pathophysiology of pre-eclampsia, it is becoming clear that the development of early- and late-onset pre-eclampsia, as well as intrauterine growth restriction (IUGR), does not necessarily arise from the same underlying pathology.

Trophoblast invasion

Trophoblast invasion can be seen as a tightly regulated battle between the competing interests of the survival of the fetus and those of the mother. Successful pregnancy is dependent on the trophoblast invading the mother, attaching the pregnancy to the uterus and securing an adequate supply of oxygen and nutrient to the fetus. For successful invasion to occur, extravillous trophoblast has to perform a range of functions; transformation of the maternal spiral arteries, tolerate hypoxia, proliferate and die by apoptosis (programmed cell death), differentiate, adhere to and digest the extracellular matrix, move and interact with the maternal immune system. Each of these functions has multiple overlapping control systems so that trophoblast invasion is a finely controlled balance of competing mechanisms.

Effect of leptin on mouse trophoblast giant cells

Leptin plays a role in both energy homeostasis and reproduction, and it is required in early pregnancy. It stimulates metalloproteinase activity in cultured human trophoblasts and invasiveness of cultured mouse trophoblasts. Our goal has been to examine mechanisms that underpin the ability of leptin to promote trophoblast invasiveness in primary cultures of mouse trophoblasts. Leptin stimulated the phosphorylation of MEK (MAP2K1) but not signal transducer and activator of transcription 3 (STAT3) in the cultures, increased the concentration of the suppressor of cytokine signaling 3 (SOCS3) protein, and upregulated metalloproteinase activity. Microarray analysis revealed that leptin stimulated select genes with roles in cell motility, including Stmn, a gene linked to invasiveness in other cell types. There was also an increase in activity of several genes associated with MAPK and RhoGTPase signaling. In addition, leptin muted expression of genes correlated with terminal differentiation of trophoblast giant cells, including ones associated with the TGFbeta signaling pathway and endoreduplication of DNA, and upregulated selected prolactin-related family members. Feulgen staining of leptin-treated cells revealed a loss of cells with low ploidy. The data suggest that leptin accelerates disappearance of non-giant cells while inhibiting terminal differentiation of committed giant cells, possibly by maintaining cells in an intermediate stage of differentiation.

Opposite effects of transforming growth factor-beta activation and rho-associated kinase inhibition on human trophoblast migration in a reconstituted placental-endometrial coculture system

Placental implantation involves highly regulated trophoblast invasion of the endometrial stroma. TGFbeta is a known regulator of this process. This study examines the effect of TGFbeta on extravillous cytotrophoblastic cell (EVCT) migration in cocultures of first-trimester human chorionic villus explants and primary human endometrial fibroblasts. Migration of EVCTs was followed by phase-contrast time-lapse microscopy and was shown to highly depend on the endometrial fibroblast matrix. Interstitial EVCT invasion was also analyzed by confocal microscopy of fluorescently prelabeled trophoblasts and endometrial fibroblasts. As expected, addition of TGFbeta led to inhibition of EVCT invasion of the endometrial cell layer. This inhibition was characterized by formation of compact EVCT stacks at migration fronts and displacement of endometrial fibroblasts. We tested the role of the RhoA/Rho-associated kinase (ROCK) pathway, a TGFbeta-dependent pathway known to regulate cell migration. Interestingly, blocking ROCK with the chemical inhibitor Y27632 had an effect opposite to TGFbeta activation because it promoted superficial EVCT migration on the endometrial cell layer. These data suggest a role for ROCK in the TGFbeta-dependent control of trophoblast migration. Furthermore, they indicate that even though ROCK signaling plays a role in human trophoblast cell invasion, EVCT migration can still occur in the absence of ROCK activity.

Comparison of cell cycle regulatory gene mRNA in three different types of human trophoblasts and effect of transforming growth factor

AIM

Identifying the factors responsible for reducing the proliferation, syncytialization, and invasiveness of trophoblast tissues, as seen with preeclampsia, intrauterine growth restriction, and spontaneous miscarriage, is a current challenge in reproductive biology. These factors, transforming growth factor (TGF)-beta as an example, can work by altering trophoblast differentiation or proliferation. We therefore investigated and compared specific markers of trophoblast proliferation and differentiation in three commonly used trophoblast tissue cell models, and also investigated the influence of TGF-beta on these markers.

METHODS

In this study, we isolated human trophoblasts from first trimester and term placentas, and additionally used human choriocarcinoma cells (JEG-3). Baseline values of human chorionic gonadotropin (hCG) secretion and relative mRNA levels of cell cycle regulators (cyclin E, p21, p27, and p57) were investigated for each cell type. We also investigated the influence of TGF-beta on these parameters.

RESULTS

Quantitative and longitudinal production of hCG differed between the three cell types. Significantly different amounts of cyclin E, p21, p27, and p57 mRNA were demonstrated within each cell type, as well as between all the cell types, throughout the culture time period. Each trophoblast type demonstrated a reduction of hCG secretion in response to TGF-beta. TGF-beta did not show a consistent effect on the cell cycle mRNA of any of the cell types.

CONCLUSION

We were able to characterize and compare the differential production of hCG, as well as the differential expression of cell cycle-associated mRNA of early trophoblasts, term trophoblasts, and choriocarcinoma cells. The production of hCG was altered by TGF-beta, although mRNA levels were not markedly altered by TGF-beta.

Gene expression profiling during Forskolin induced differentiation of BeWo cells by differential display RT-PCR

The differentiation of cytotrophoblasts into syncytiotrophoblasts in the placenta has been employed as a model to investigate stage specific expression as well as regulation of genes during this process. While the cytotrophoblasts are highly invasive and proliferative with relatively less capacity to synthesize pregnancy related proteins, the multinucleated syncytiotrophoblasts are non-proliferative and non-invasive. However, syncytiotrophoblasts are the site of synthesis of a variety of protein, peptide and steroid hormones as well as several growth factors. Both the freshly isolated cytotrophoblasts from human placenta as well as the BeWo cell, a choriocarcinoma cell line model which retain several characteristic of cytotrophoblasts has been employed by us to study regulation of differentiation. In the present study, we have employed the differential display RT-PCR analysis (DD-RT-PCR) to evaluate gene expression changes during Forskolin induced in vitro differentiation of BeWo cells. We have identified several genes which are differentially expressed during differentiation and the differential expression of 10 transcripts was confirmed by Northern blot analysis. Based on the identity of the transcripts an attempt has been made to relate the known function of the gene products, to changes observed during differentiation. Of the several transcripts, one of the transcripts, namely Secretory Leukocyte Protease Inhibitor (SLPI) which is known to have multiple functions was found to increase 15-fold in the syntiotrophoblast.

VEGF- and LPA-induced telomerase in human ovarian cancer cells is Sp1-dependent

OBJECTIVE

Both vascular endothelial growth factor (VEGF) and lysophosphatidic acid (LPA) are secreted by ovarian cancer cells and are known to promote cancer cell growth though the exact mechanism(s) are not completely understood. Since telomerase, a ribonucleprotein expressed in 95% of ovarian cancers, plays an important role in cellular immortalization, growth, and tumor progression, we examined whether telomerase is a molecular target of LPA and VEGF in ovarian cancer.

METHODS

Telomerase-positive ovarian carcinoma cell lines PA-1, SW 626, and one telomerase-negative, non-tumorigenic SV40 large-T antigen-transfected human ovarian surface epithelial (IOSE) cell line, FHIOSE 118, derived from normal ovarian surface epithelium were cultured with and without VEGF and LPA for 4 h and 24 h, respectively. Telomerase PCR-ELISA, RT-PCR, VEGF ELISA and luciferase assays were performed to determine the effect of VEGF and LPA on telomerase activity in ovarian cancer cells. Western blot analyses were used to examine the signaling pathway involved in telomerase regulation by VEGF and LPA.

RESULTS

We report that: (1) both VEGF and LPA upregulate telomerase activity; (2) LPA induction of telomerase activity is VEGF-dependent; (3) VEGF and LPA induction of telomerase activity is ERK 1/2-dependent; and (4) Sp1 binding sites within the proximal 976- to 378-bp regions of the hTERT promoter are essential for VEGF- and LPA-induced hTERT promoter activity.

CONCLUSION

Consequently, these data show the novel finding that VEGF can regulate telomerase activity in non-endothelial cells and that telomerase appears to be a novel molecular target of LPA.

Transforming growth factor-beta induces differentiation of the labyrinthine trophoblast stem cell line SM10

The mammalian placenta consists of different trophoblast cell types that assist in the variety of functions required for the maintenance of pregnancy. In rodents, labyrinthine trophoblasts of the placenta are especially important, because they are capable of differentiating into fused labyrinthine cells, which form the feto-maternal exchange surface. Even though the molecular signals triggering labyrinthine trophoblast differentiation are poorly understood, transforming growth factor-beta (TGF-beta) has been shown to be present in the placental environment and alter trophoblast development. In this study, we investigated the effects of TGF-beta on the differentiation of the labyrinthine trophoblast stem cell lines SM10 and HRP-1. RT-PCR analyses demonstrated that while the molecular expression of labyrinthine-specific lineage markers (Esx1, Tfeb, and Tec) was maintained in TGF-beta-treated SM10 and HRP-1 cells, TGF-beta induced the down-regulation of trophoblast stem cell markers Id2 and Cdx2. In contrast, TGF-beta induced the expression of a marker of differentiated labyrinthine trophoblasts, Gcm1, only in the SM10 cell line. Furthermore, we demonstrated an increased glucose uptake in the TGF-beta-treated SM10 cells, indicative of functional differentiation. Finally, cell fusion in TGF-beta-treated SM10 and HRP-1 cells was investigated by western blotting analysis of placental alkaline phosphatase and cadherin-11 and by microscopic analyses of cell morphology using green fluorescent protein (GFP) and rhodamine phalloidin staining. The western blotting and morphological analyses indicate TGF-beta-induced cell fusion and morphological differentiation in the SM10 cell line. The SM10 cell line will provide a new and unique model for detailed analysis of TGF-beta-induced molecular events associated with labyrinthine trophoblast differentiation and function.

8-chloroadenosine induced HL-60 cell growth inhibition, differentiation, and G(0)/G(1) arrest involves attenuated cyclin D1 and telomerase and up-regulated p21(WAF1/CIP1)

8-Chloroadenosine, an active dephosphorylated metabolite of the antineoplastic agent 8-chloroadenosine 3',5'-monophosphate (8-Cl-cAMP), induces growth inhibition in multiple carcinomas. Here we report that 8-chloroadenosine inhibits growth in human promyelocytic leukemia HL-60 cells by a G(0)/G(1) phase arrest and terminates cell differentiation along the granulocytic lineage. The mechanism of 8-chloroadenosine-induced G(0)/G(1) arrest is independent of apoptosis. The expressions of cyclin D1 and c-myc in HL-60 are suppressed by 8-chloroadenosine, whereas the cyclin-dependent kinases inhibitor p21(WAF1/CIP1) is up-regulated. 8-Chloroadenosine has less effect on the expressions of cyclin-dependent kinase (cdk)2 and cdk4, G(1) phase cyclin-dependent kinases, and only moderately induces the expression of transforming growth factor beta1 (TGFbeta1) and the mitotic inhibitor p27(KIP1). Telomerase activity is reduced in extracts of 8-chloroadenosine treated HL-60 cells, but 8-chloroadenosine does not directly inhibit the catalytic activity of telomerase in vitro. Therefore, anti-proliferation of HL-60 cells by 8-chloroadenosine involves coordination of cyclin D1 suppression, reduction of telomerase activity, and up-regulation of p21(WAF1/CIP1) that arrest cell-cycle progression at G(0)/G(1) phase and terminate cell differentiation.

Hypoxia regulates the expression of PHLDA2 in primary term human trophoblasts

Hypoxia influences gene expression in placental trophoblasts. We sought to examine the effect of hypoxia on trophoblast expression of human PHLDA2 (also termed IPL, TSSC3 or BWR-1C), a product of an imprinted gene on human chromosome 11p15.5 whose murine ortholog plays a pivotal role in placental development. We initially confirmed that PHLDA2 was expressed in term placental villi, primarily in the trophoblast layer. Using quantitative PCR we found that the expression of PHLDA2 gradually declined during differentiation of primary term human trophoblasts. A similar expression pattern was seen for p57(Kip2) and IGF-II, both products of imprinted genes on chromosome 11p15.5. Exposure of trophoblasts to hypoxia in vitro (O(2)<or=2%) markedly reduced the expression of PHLDA2 mRNA and protein. This effect was not consistent among other chromosome 11p15.5 genes products, as the expression of p57(Kip2) decreased, but that of IGF-II increased in hypoxic trophoblasts. PHLDA2 expression in trophoblasts exposed to TGFbeta1, -beta2 or -beta3 was unchanged. We conclude that hypoxia down-regulates the expression of PHLDA2 in human term placental trophoblasts. As murine PHLDA2 limits placental growth, our results suggest that down-regulation of PHLDA2 attenuates the impact of hypoxia on placental growth.

Role of estrogen in regulation of cellular differentiation: a study using human placental and rat Leydig cells

Estrogen classically is recognized as a growth-promoting hormone. Recent evidence suggests that estrogens are also involved in a wide variety of cellular and physiological functions involving the central nervous system, immune system, cardiovascular system and bone homeostasis. Our studies in cytotrophoblasts and BeWo cells, demonstrated that 17beta-estradiol induces terminal differentiation of placental trophoblasts directly and this differentiation is coupled with an increased production of TGFbeta1, which, in turn, affects telomerase activity and telomerase associated components at the level of hTERT. Furthermore, using rats treated in vivo with either EDS or estradiol and in vitro Leydig cell cultures, we proposed that 17beta-estradiol mediated down-regulation of collagen IV alpha4 expression could be one of the possible mechanisms for the inhibition of progenitor Leydig cell proliferation. In this review, we summarize the results from both the model systems, the human placental cytotrophoblast and rat Leydig cells to conclude that 17beta-estradiol has a unique stage-specific role in differentiation.

Differential effects of TGF-β1 on telomerase activity in thyroid carcinoma cell lines

The aim of the present study was to investigate the effect of transforming growth factor-beta1 (TGF-beta1) on telomerase activity in a panel of human anaplastic thyroid carcinoma (ATC) cell lines. Addition of TGF-beta1 decreased the telomerase activity in HTh 74 and KTC-1 cells, while in C 643 and HTh 7 an increased activity was observed. The decreased telomerase activity appeared to be due to transcriptional repression of the hTERT promoter. Addition of a PI-3 kinase inhibitor (LY294002) abrogated the stimulatory effect of TGF-beta1 on the telomerase activity, indicating the possible involvement of hTERT activation via phosphorylation. Furthermore, the MEK-inhibitor U0126 had similar effects suggesting dual regulatory mechanisms. Interestingly, the cell lines differed genetically in that ATC cell lines responding with increased telomerase activity harbored a p53 mutation. In conclusion, TGF-beta1 exerts opposing effects on telomerase activity in ATC cell lines, possibly reflecting deregulation of TGF-beta1 signaling in a more malignant genotype.

HtrA3, a serine protease possessing an IGF-binding domain, is selectively expressed at the maternal-fetal interface during placentation in the mouse

Hemochorial placentation involves highly regulated interactions between fetal- and maternal-derived cells. HtrA3, a novel serine protease containing an insulin-like growth factor (IGF) binding domain, was previously shown to increase during early pregnancy in the mouse uterus, being dramatically upregulated post-implantation. The present study examined the regulation of HtrA3 gene in the mouse uterus from post-implantation to late gestation. Both mRNA and protein of HtrA3 were localized specifically in the maternal decidua. In contrast, HtrA3 expression was below detection in trophoblasts, including the giant cells that are in direct contact with the decidua. This pattern persisted from the early stages of placentation to near term. The level of decidual HtrA3 mRNA and its protein gradually decreased as the placenta matured. In the decidua, only the maternal decidual cells, but not blood vessels or uterine NK cells that are present in large numbers, were positive for HtrA3. The specific localization of a protease possessing an IGF-binding domain at the maternal-fetal interface suggests that HtrA3 plays a critical role in mediating maternal decidual remodelling and maintenance, likely in association with the IGF system, in placental development and function.

Effects of ICI 182780 on estrogen receptor expression, fluid absorption and sperm motility in the epididymis of the bonnet monkey

Background

The importance of estrogen in regulation of fluid absorption and sperm maturation in the rodent epididymis has been established from studies on estrogen receptor-alpha knockout mice. However, functional studies on the role of estrogen in primate epididymis have been few. The main objective of this study was therefore to extend these observations and systematically analyze the presence and function of estrogen receptors in modulating the function of the primate epididymis, using the bonnet monkey (Macaca radiata) as a model system.

Methods

A steroidal estrogen receptor (ER) antagonist, ICI 182780 (ICI), was administered to adult male bonnet monkeys via mini-osmotic pumps for a duration of 30 to 180 days. The expression of key estrogen-regulated genes (ER-alpha, Na-K ATPase alpha-1 and Aquaporin-1) was examined at specific time points. Further, the effect of ICI in modulating fluid reabsorption in efferent ductules was monitored, and critical sperm-maturation parameters were also analyzed.

Results

Our studies in the bonnet monkey revealed that both ER-alpha and ER-beta were expressed in all the three regions of the epididymis. We observed an increase in ER-alpha mRNA and protein in the caput of ICI-treated monkeys. Steady state mRNA levels of the water-channel protein, Aquaporin-1, was significantly lower in the caput of ICI-treated monkeys compared to controls, whereas the mRNA levels of Na-K ATPase alpha-1 remained unchanged. In vitro incubation of efferent ductules with ICI resulted in two-fold increase in tubular diameter, indicating affected fluid reabsorption capacity. Furthermore, sperm from ICI-treated monkeys were immotile.

Conclusion

Taken together, our results point to an integral role for estrogen in modulating the functions of the bonnet monkey epididymis. This study also demonstrates possible differences in the epididymal physiology of rodents and non-human primates, and thus underscores the significance of reports such as these, that examine the physiology of non-human primates (as opposed to rodents), in an attempt to understand similar events in the human.

Retinoblastoma protein function and p16INK4a expression in actinic keratosis, squamous cell carcinoma in situ and invasive squamous cell carcinoma of the skin and links between p16INK4a expression and infiltrative behavior

p16INK4a is involved in many important regulatory events in the cell and the expression and function is closely associated with the retinoblastoma protein (Rb). Earlier, we have in colorectal cancer and in basal cell carcinoma showed that p16INK4a is upregulated at the invasive front causing cell cycle arrest in infiltrative tumor cells via a functional Rb. This role for p16INK4a as a regulator of proliferation when tumor cells infiltrate might besides a general cyclin-dependent kinase (cdk) inhibitory effect explain why p16INK4a is deregulated in many tumor forms. The expression pattern of p16INK4a in relation to Rb-function in squamous cancer and precancerous forms of the skin has not been fully detailed. We therefore characterized the expression of p16INK4a, Rb-phosphorylation and proliferation in actinic keratosis, squamous cell carcinoma in situ and invasive squamous cell carcinoma with special reference to infiltrative behavior. The expression of p16INK4a varied between the lesions, with weak and cytoplasmic p16INK4a expression and functional Rb in actinic keratosis. Strong nuclear and cytoplasmic p16INK4a expression was observed in all carcinomas in situ in parallel with lack of Rb-phosphorylation but high proliferation indicating a nonfunctional Rb. Invasive squamous carcinoma showed a mixed p16INK4a expression pattern where some tumors had strong cytoplasmic p16INK4a expression, large fraction of Rb-phosphorylated cells and high proliferation. Interestingly, despite this disability of p16INK4a to inhibit proliferation there was an upregulation of cytoplasmic p16INK4a in infiltrative cells compared to tumor cells towards the tumor center. A similar scenario but strong and combined nuclear and cytoplasmic p16INK4a expression in infiltrative cells, was observed in other invasive squamous cancers. This suggests that the p16INK4a upregulation in infiltrative cells is governed independently of the subcellular localization or of the potential to affect proliferation via Rb, and suggests a potentially proliferation independent function for p16INK4a in infiltrative behavior.

Hormonal regulation of human trophoblast differentiation: a possible role for 17beta-estradiol and GnRH

We have examined the role of 17beta-estradiol and gonadotropin releasing hormone (GnRH) in the regulation of functional differentiation in human trophoblasts. In contrast to its recognized functions as a proliferation-promoting hormone in a variety of cell types, we found that 17beta-estradiol induced terminal differentiation in human trophoblastic cells, and that this event was estrogen-receptor-mediated. This process involved a loss in expression of Cyclins A2 and E, and a coincident increase in p27(Kip1). The anti-proliferative effects of 17beta-estradiol were annulled by specific transforming growth factor-beta 1 (TGFbeta1)-neutralizing antibody, suggesting that 17beta-estradiol may mediate its growth-inhibitory actions, through TGFbeta1 activity. Following exposure to Buserelin, cultured human trophoblastic cells stopped proliferating and formed functionally mature syncytiotrophoblasts. This differentiation event, that involved a drastic loss in expression of proliferating-cell-nuclear-antigen, could be blocked by Cetrorelix, suggesting the involvement of functional GnRH receptors. Preliminary studies on the characterization of the human placental GnRH receptor, indicate the presence of multiple receptor isoforms across human gestation.

Trophoblast 'pseudo-tumorigenesis': significance and contributory factors

Trophoblast cells of the human placenta proliferate, migrate, and invade the pregnant uterus and its vasculature in order to nourish the developing fetus, in a way that is imitated by malignant tumors. Many similarities exist between embryo implantation and the growth of cancer cells. We begin this article by reviewing decades of studies that have helped unearth the mechanisms that contribute to the tumor-like phenotype of human trophoblast cells. Interestingly, these attributes are only transient in nature, with stringent spatial and temporal confines. The importance of intrinsic molecular controls that effectively circumscribe the extent and duration of trophoblast incursion, becomes increasingly evident in abnormal pregnancies that are characterized by aberrant trophoblast proliferation/invasion. We summarize and discuss the significance of abnormalities in these regulatory mechanisms, and finally, speculate about the use of human trophoblastic cells as model systems for the study of a variety of cellular processes. While on one hand, human placental cells are bestowed with a capacity to proliferate indefinitely and invade extensively, on the other, these cells are also replete with mechanisms to regulate these tumor-like attributes and eventually progress to a senescent apoptotic state. This is therefore, a 'well-behaved' tumor. The comparison in the present review is between the invasive cytotrophoblastic cell type and the tumor cell type.