Growth differentiation factor myostatin regulates epithelial-mesenchymal transition genes and enhances invasion by increasing serine protease inhibitors E1 and E2 in human trophoblast cells.

Placental insufficiency disorders, including preeclampsia and intrauterine growth restriction, are major obstetric complications that can have devastating effects on both the mother and the fetus. These syndromes have underlying poor placental trophoblast cell invasion into uterine tissues. Placental invasion is controlled by many hormones and growth factors. Myostatin (MSTN) is a transforming growth factor-ß superfamily member recognized for its important role in muscle growth control. MSTN has also been shown to be secreted and functioning in the placenta, and its serum and/or placental levels were found to be upregulated in preeclampsia and intrauterine growth restriction. Considering that the mechanistic role of MSTN in placentation remains poorly understood, we hypothesized that MSTN uses ALK4/5-SMAD2/3/4 signaling to increase human trophoblast invasion through a group of epithelial-mesenchymal transition genes including SERPINE2, PAI-1, and SOX4. mRNA sequencing of control and MSTN-treated primary human trophoblast cells (n = 5) yielded a total of 610 differentially expressed genes (false discovery rate <0.05) of which 380 genes were upregulated and 230 were downregulated. These differentially expressed genes were highly enriched in epithelial-mesenchymal transition genes, and a subset including SERPINE2, PAI-1, and SOX4 was investigated for its role in MSTN-induced trophoblast cell invasion. We found that MSTN induced upregulation of SERPINE2 via ALK4/5-SMAD2/3/4 signaling; however, SMAD2 was not involved in MSTN-induced PAI-1 upregulation. SOX4 was involved in MSTN-induced upregulation of SERPINE2, but not PAI-1. Collectively, this study discovers novel molecular mechanisms of MSTN-induced human trophoblast cell invasion and provides insight into the functional consequences of its dysregulation in placental insufficiency disorders.

Dysregulated BMP2 in the Placenta May Contribute to Early-Onset Preeclampsia by Regulating Human Trophoblast Expression of Extracellular Matrix and Adhesion Molecules.

Many pregnancy disorders, including early-onset preeclampsia (EOPE), are associated with defects in placental trophoblast cell invasion and differentiation during early placental development. Bone morphogenetic protein 2 (BMP2) belongs to the TGF-ß superfamily and controls various physiological and developmental processes. However, the expression of BMP2 in the placenta and underlying molecular mechanisms of how BMP2 regulates trophoblast function remain unclear. In this study, we analyzed several publicly available microarray and RNA-seq datasets and revealed differences in expression of TGF-ß superfamily members between gestational age-matched non-preeclamptic control and EOPE placentas. Importantly, BMP2 levels were significantly reduced in EOPE placentas compared with controls, and RNAscope in situ hybridization further demonstrated BMP2 expression was disrupted in EOPE placental villi. To explore the molecular mechanisms of BMP2-regulated early trophoblast differentiation, we examined BMP2 expression in first-trimester human placenta and found it to be localized to all subtypes of trophoblasts and the decidua. RNA-seq analysis on control and BMP2-treated primary human trophoblast cells identified 431 differentially expressed genes, including several canonical TGF-ß/BMP signaling targets (BAMBI, ID1, INHBA, IGFBP3). Gene ontology annotations revealed that differentially expressed genes were involved in cell adhesion and extracellular matrix organization. Furthermore, we identified adhesion molecule with IgG-like domain 2 (AMIGO2) as a novel target for BMP2 that contributed to BMP2-induced trophoblast invasion and endothelial-like tube formation. Overall, our findings provide insight into the molecular processes controlled by BMP2 during early placental development that may contribute to the pathogenesis of EOPE.

Bone morphogenetic protein 2 inhibits growth differentiation factor 8-induced cell signaling via upregulation of gremlin2 expression in human granulosa-lutein cells.

BACKGROUND: Bone morphogenetic protein 2 (BMP2), growth differentiation factor 8 (GDF8) and their functional receptors are expressed in human ovarian follicles, and these two intrafollicular factors play essential roles in regulating follicle development and luteal function. As BMP antagonists, gremlin1 (GREM1) and gremlin2 (GREM2) suppress BMP signaling through blockage of ligand-receptor binding. However, whether BMP2 regulates the expression of GREM1 and GREM2 in follicular development remains to be determined. METHODS: In the present study, we investigated the effect of BMP2 on the expression of GREM1 and GREM2 and the underlying mechanisms in human granulosa-lutein (hGL) cells. An established immortalized human granulosa cell line (SVOG) and primary hGL cells were used as study models. The expression of GREM1 and GREM2 were examined following cell incubation with BMP2 at different concentrations and time courses. The TGF-ß type I inhibitors (dorsomorphin, DMH-1 and SB431542) and small interfering RNAs targeting ALK2, ALK3, SMAD2/3, SMAD1/5/8 and SMAD4 were used to investigate the involvement of the SMAD-dependent pathway. RESULTS: Our results showed that BMP2 significantly increased the expression of GREM2 (but not GREM1) in a dose- and time-dependent manner. Using a dual inhibition approach combining kinase inhibitors and siRNA-mediated knockdown, we found that the BMP2-induced upregulation of GREM2 expression was mediated by the ALK2/3-SMAD1/5-SMAD4 signaling pathway. Moreover, we demonstrated that BMP2 pretreatment significantly attenuated the GDF8-induced phosphorylation of SMAD2 and SMAD3, and this suppressive effect was reversed by knocking down GREM2 expression. CONCLUSIONS: Our findings provide new insight into the molecular mechanisms by which BMP2 modulates the cellular activity induced by GDF8 through the upregulated expression of their antagonist (GREM2).

Transcription factor SOX4 facilitates BMP2-regulated gene expression during invasive trophoblast differentiation.

The interplay between growth factors, signaling pathways and transcription factors during placental development is key to controlling trophoblast differentiation. Bone morphogenetic protein 2 (BMP2) has been implicated in trophoblast invasion and spiral artery remodeling during early placental development. However, the molecular mechanisms by which these are accomplished have not been fully elucidated, particularly for transcriptional regulation of key transcription factors. Here, we identified SOX4 as a direct target gene induced by BMP2 in first-trimester placental trophoblasts. Analysis of single-cell RNA-seq data from first-trimester placentas and decidua tissues revealed that SOX4 expression is mainly localized in extravillous trophoblast and decidual stromal cells. Moreover, gain- and loss-of-function approaches demonstrated that SOX4 exerts a pro-invasive role in human trophoblasts, and this effect contributes to BMP2-enhanced trophoblast invasion. Importantly, we found that SOX4 was required for BMP2-induced regulation of a subset of genes associated with cell migration and extracellular matrix organization. We also show that SOX4-dependent regulation of the BMP2 target SERPINE2 occurs via binding of SOX4 to regulatory elements such as enhancers, thereby promoting BMP2-induced trophoblast invasion. In conclusion, these findings uncover a novel mechanism involving SOX4 that shapes the BMP2-regulated transcriptional network during invasive trophoblast development.

Bone morphogenetic protein 2 upregulates SERPINE2 expression through noncanonical SMAD2/3 and p38 MAPK signaling pathways in human granulosa-lutein cells.

Serine protease inhibitor-E2 (SERPINE2) is highly expressed in the granulosa cells of growing follicles and the dynamic changes in SERPINE2 expression are correlated with follicular development and ovulation in several mammals, including mice, cattle, sheep, and humans. Bone morphogenetic proteins (BMPs) and their functional receptors are extensively expressed in the ovary and play critical roles in the regulation of ovarian folliculogenesis and luteal function. To date, whether BMPs regulate the expression of SERPINE2 during human follicular development remains to be elucidated. The aim of this study was to investigate the effects of BMPs on the regulation of SERPINE2 expression (a major regulator of plasminogen activators [PA]) and the underlying mechanisms using primary and immortalized human granulosa-lutein (hGL) cells. Our results demonstrated that these BMPs (BMP2, BMP4, BMP6, BMP7, and BMP15) induced differential upregulation of SERPINE2 expression. In this regard, BMP2 is the major modulator that has the best cellular activity, which further decreased the production of urokinase PA and tissue PA in hGL cells. In addition to canonical SMAD1/5/8 signaling, BMP2 also activates noncanonical SMAD2/3 and p38 mitogen-activated protein kinase (MAPK) signaling. Using two inhibition approaches (kinase receptor inhibitors and siRNA-mediated knockdown), we found that SMAD2/3-SMAD4 and p38 MAPK, but not SMAD1/5/8 signaling, was involved in the BMP2-induced upregulation of SERPINE2 expression via activin receptor-like kinase 3. These findings deepen our understanding of the differential effect of BMPs in regulating follicular function and provide new insights of the molecular mechanisms by which BMP2 regulates the expression of SERPINE2 in human granulosa cells.

BMP6 increases CD68 expression by up-regulating CTGF expression in human granulosa-lutein cells.

Bone morphogenetic protein 6 (BMP6) and connective tissue growth factor (CTGF) are critical growth factors required for normal follicular development and luteal function. Cluster of Differentiation 68 (CD68) is an intraovarian marker of macrophages that plays an important role in modulating the physiological regression of the corpus luteum. The aim of this study was to investigate the effect of BMP6 on the expression of CTGF and the subsequent increase in CD68 expression as well as its underlying mechanisms. Primary and immortalized (SVOG) human granulosa cells obtained from infertile women undergoing in vitro fertilization treatment were used as cell models to conduct the in vitro experiments. Our results showed that BMP6 treatment significantly increased the expression levels of CTGF and CD68. Using BMP type I receptor inhibitors (dorsomorphin, DMH-1 and SB431542), we demonstrated that both activin receptor-like kinase (ALK)2 and ALK3 are involved in BMP6-induced stimulatory effects on the expression of CTGF and CD68. Additionally, SMAD4-knock down reversed the BMP6-induced up-regulation of CTGF and CD68, indicating that the canonical SMAD signaling pathway is required for these effects. Moreover, CTGF-knock down abolished the BMP6-induced up-regulation of CD68 expression. These findings indicate that intrafollicular CTGF mediates BMP6-induced increases in CD68 expression through the ALK2/ALK3-mediated SMAD-dependent signaling pathway.

The BMP2 Signaling Axis Promotes Invasive Differentiation of Human Trophoblasts.

Embryo implantation and trophoblast invasion are principal limiting factors of pregnancy establishment. Aberrant embryo development or improper trophoblast differentiation and invasion may lead to various unfavorable pregnancy-related outcomes, including early pregnancy loss (EPL). Our clinical data show that the serum BMP2 levels were significantly increased during the first trimester of pregnancy and that the serum and BMP2 expression levels were lower in women with EPL than in women with normal early pregnancies. Moreover, we observed that BMP2 was expressed in oocytes and trophoblast cells of cleaved embryos and blastocysts prior to implantation in both humans and mice. Exogenous BMP2 promoted embryonic development by enhancing blastocyst formation and hatching in mice. LncRNA NR026833.1 was upregulated by BMP2 and promoted SNAIL expression by competitively binding to miR-502-5p. SNAIL induced MMP2 expression and promoted cell invasion in primary extravillous trophoblast cells. BMP2 promotes the invasive differentiation of mouse trophoblast stem cells by downregulating the expression of TS cell marker and upregulating the expression of trophoblast giant cell marker and labyrinthine/spongiotrophoblast marker. Our findings provide significant insights into the regulatory roles of BMP2 in the development of the placenta, which may give us a framework to explore new therapeutic strategies to pregnancy-related complications.

NPFF increases fusogenic proteins syncytin 1 and syncytin 2 via GCM1 in first trimester primary human cytotrophoblast cells.

Neuropeptide FF (NPFF) is well-known for its roles in the central nervous system. Despite studies demonstrating that NPFF receptor 2 (NPFFR2) mRNA is highest in placenta, nothing is known about NPFF-NPFFR2 functions in placental development. Here, we investigated the effects of NPFF-NPFFR2 on expression of syncytial [human chorionic gonadotropin (hCG) ß] and fusogenic [syncytin 1, syncytin 2, and glial cells missing 1 (GCM1)] genes in first trimester primary human cytotrophoblast cells. By analyzing two publicly available microarray data sets, we found that NPFF is consistently expressed throughout gestation whereas NPFFR2 increases in first trimester and is elevated in placenta samples from women with preeclampsia. Immunohistochemistry showed that NPFFR2, syncytin 1/2, and GCM1 each displayed unique patterns of expression among different trophoblast populations in first trimester placenta. Treatment of primary human cytotrophoblast cells with NPFF increased the mRNA and protein levels of hCG ß, syncytin 1, syncytin 2, and GCM1; and knockdown of NPFFR2 abolished these effects. Interestingly, GCM1 mediated NPFF-induced upregulation of syncytin 1 and syncytin 2, but not hCG ß, in primary human cytotrophoblasts. Our results demonstrate that NPFF acts via NPFFR2 to enhance production of hCG ß and promote GCM1-dependent expression of syncytin 1 and 2 in human cytotrophoblasts.

TGF-ß1 induces VEGF expression in human granulosa-lutein cells: a potential mechanism for the pathogenesis of ovarian hyperstimulation syndrome.

Ovarian hyperstimulation syndrome (OHSS) is one of the most serious and iatrogenic complications that can occur during in vitro fertilization treatment. Although the pathogenesis of OHSS is not fully understood, vascular endothelial growth factor (VEGF) has been recognized as an important mediator of the development of OHSS. Transforming growth factor-beta-1 (TGF-ß1) is known to regulate various ovarian functions. However, whether VEGF can be regulated by TGF-ß1 in human granulosa cells has not been determined. In addition, the role of TGF-ß1 in the pathogenesis of OHSS remains unknown. In the present study, we demonstrate that TGF-ß1 stimulates VEGF expression in and secretion from both immortalized human granulosa-lutein (hGL) cells and primary hGL cells. Our results demonstrate that the SMAD2/3, ERK1/2, and p38 MAPK signaling pathways are involved in TGF-ß1-induced VEGF expression and secretion. Using a mouse OHSS model, we show that the expression levels of TGF-ß1 and VEGF are increased in the ovaries of OHSS mice. Blocking TGF-ß1 signaling inhibits the development of OHSS by attenuating VEGF expression. Moreover, clinical results reveal that the protein levels of TGF-ß1 and VEGF are increased in the follicular fluid of patients with OHSS, and that the levels of these two proteins in the follicular fluid are positively correlated. The results of this study help to elucidate the mechanisms by which VEGF expression is regulated in hGL cells, which could lead to the development of alternative therapeutic approaches for treating OHSS.

TGF-ß1 promotes vitamin D-induced prostaglandin E2 synthesis by upregulating vitamin D receptor expression in human granulosa-lutein cells.

There is increasing evidence showing the importance of vitamin D (Vit D) and its nuclear receptor, the Vit D receptor (VDR), in female reproductive health. Transforming growth factor-ß1 (TGF-ß1) and its functional receptors are expressed in human oocytes and granulosa cells that participate in follicular development and ovulation. Recently, Sma- and Mad-related protein 3 (SMAD3; a downstream effector of TGF-ß1) has been proposed to mediate crosstalk between the Vit D and TGF-ß1 signaling pathways, but this relationship has not been fully explored and has yet to be tested in human granulosa-lutein (hGL) cells. In this study, we showed that TGF-ß1 significantly promoted the expression of VDR, and this stimulatory effect occurred through the activin receptor-like kinase 5 type I receptor-mediated SMAD3 and ERK1/2 signaling pathways in hGL cells. Additionally, we showed that Vit D increased the expression of cyclooxygenase 2 (COX-2) and the synthesis of prostaglandin E2 (PGE2) in a time- and dose-dependent manner. Furthermore, we demonstrated a synergistic effect of TGF-ß1 and Vit D on the expression of COX-2 and synthesis of PGE2, and this effect could be attenuated by silencing the expression of VDR. Our findings indicate that TGF-ß1 upregulates the expression of VDR, which promotes Vit D-induced COX-2 expression and subsequent PGE2 production by activating the SMAD3 and ERK1/2 signaling pathways in hGL cells.

TGF-ß1 Increases GDNF Production by Upregulating the Expression of GDNF and Furin in Human Granulosa-Lutein Cells.

Glial cell line-derived neurotrophic factor (GDNF) is expressed at a high level in the human ovary and GDNF signaling is involved in the direct control of follicular activation and oocyte maturation. Transforming growth factor-ß1 (TGF-ß1) plays an important role in the regulation of various ovarian functions. Furin is an intracellular serine endopeptidase of the subtilisin family that is closely associated with the activation of multiple protein precursors. Despite the important roles of GDNF and TGF-ß1 in the regulation of follicular development, whether TGF-ß is able to regulate the expression and production of GDNF in human granulosa cells remains to be determined. The aim of this study was to investigate the effect of TGF-ß1 on the production of GDNF and its underlying mechanisms in human granulosa-lutein (hGL) cells. We used two types of hGL cells (primary hGL cells and an established immortalized hGL cell line, SVOG cells) as study models. Our results show that TGF-ß1 significantly induced the expression of GDNF and furin, which, in turn, increased the production of mature GDNF. Using a dual inhibition approach combining RNA interference and kinase inhibitors against cell signaling components, we showed that the TßRII type II receptor and ALK5 type I receptor are the principal receptors that mediated TGF-ß1-induced cellular activity in hGL cells. Additionally, Sma- and Mad-related protein (SMAD)3 and SMAD4 are the downstream signaling transducers that mediate the biological response induced by TGF-ß1. Furthermore, furin is the main proprotein convertase that induces the production of GDNF. These findings provide additional regulatory mechanisms by which an intrafollicular factor influences the production of another growth factor through a paracrine or autocrine interaction in hGL cells.

Betacellulin enhances ovarian cancer cell migration by up-regulating Connexin43 via MEK-ERK signaling.

Epithelial ovarian cancer is the fifth common cause of cancer death in women and the most lethal gynecological malignancies. Our previous studies have shown that up-regulation of Connexin43, a gap-junction subunit crucial for cell-cell communication, enhances ovarian cancer cell migration. Betacellulin is a member of the epidermal growth factor (EGF) family which can bind to multiple EGF family receptors. Overexpression of betacellulin is found in a variety of cancers and is associated with reduced survival. However, the specific roles and molecular mechanisms of betacellulin in ovarian cancer progression are poorly understood. In the current study, we tested the hypothesis that betacellulin induces ovarian cancer cell migration by up-regulating Connexin43. Our results showed that treatment with betacellulin significantly increased Connexin43 expression and cell migration in both OVCAR4 and SKOV3 ovarian cancer cell lines. Moreover, betacellulin induced the activation of MEK-ERK signaling, and its effects on Connexin43 were inhibited by pre-treatment with U0126. Pre-treatment with AG1478 totally blocked the activation of MEK-ERK signaling but only partially inhibited betacellulin-induced Connexin43 expression and cell migration. Most importantly, betacellulin-induced cell migration was attenuated by knockdown of Connexin43, and co-treatment with gap junction inhibitor carbenoxolone did not alter this effect. Our results suggest a bilateral role of Connexin43 in ovarian cancer migration, and also demonstrate a gap junction-independent mechanism of betacellulin.

CCN2 Mediates S1P-Induced Upregulation of COX2 Expression in Human Granulosa-Lutein Cells.

CCN1 and CCN2 are members of the CCN family and play essential roles in the regulation of multiple female reproductive functions, including ovulation. Cyclooxygenase-2 (COX2) is a critical mediator of ovulation and can be induced by sphingosine-1-phosphate (S1P) through the S1P1/3-mediated Yes-associated protein (YAP) signaling. However, it is unclear whether CCN1 or CCN2 can mediate S1P-induced upregulation of COX2 expression and increase in prostaglandin E2 (PGE2) production in human granulosa-lutein (hGL) cells. In the present study, we investigated the effects of S1P on the expressions of CCN1 and CCN2 in hGL cells. Additionally, we used a dual inhibition approach (siRNA-mediated silencing and small molecular inhibitors) to investigate the molecular mechanisms of S1P effects. Our results showed that S1P treatment significantly upregulated the expression of CCN1 and CCN2 in a concentration-dependent manner in hGL cells. Additionally, inhibition or silencing of S1P1, but not S1P3, completely abolished the S1P-induced upregulation of CCN2 expression. Furthermore, we demonstrated that S1P-induced nuclear translocation of YAP and inhibition or silencing of YAP completely abolished the S1P-induced upregulation of CCN1 and CCN2 expression. Notably, silencing of CCN2, but not CCN1, completely reversed the S1P-induced upregulation of COX2 expression and the increase in PGE2 production. Thus, CCN2 mediates the S1P-induced upregulation of COX2 expression through the S1P1-mediated signaling pathway in hGL cells. Our findings expand our understanding of the molecular mechanism underlying the S1P-mediated cellular activities in the human ovary.

Bone morphogenetic protein 6 affects cell-cell communication by altering the expression of Connexin43 in human granulosa-lutein cells.

Connexin 43 (Cx43)-coupled gap junctions in granulosa cells play an important role in follicular development, oocyte maturation, and corpus luteum maintenance. Bone morphogenetic protein 6 (BMP6) is highly expressed in human oocytes and granulosa cells and is involved in the regulation of female reproduction. Currently, whether oocyte- and granulosa cell-derived BMP6 affects the expression of Cx43 and its related gap junction intercellular communication (GJIC) activity in human granulosa cells remains unknown. In this study, we demonstrate that BMP6 treatment significantly suppressed the expression of Cx43 in both primary and immortalized (SVOG) human granulosa-lutein cells. Using both pharmacological inhibitors and small interfering RNA-mediated knockdown approaches, we demonstrate that ALK2 and ALK3 BMP type I receptors are involved in BMP6-induced suppressive effects on Cx43 expression and GJIC activity in SVOG cells. Furthermore, these cellular activities are most likely mediated by the SMAD1/SMAD5-SMAD4-dependent signaling pathway. Notably, the ChIP analyses demonstrated that phosphorylated SMADs could bind to human Cx43 promoter. Our findings provide new insight into the molecular mechanisms by which an intrafollicular growth factor regulates cell-cell communication in human granulosa cells.

TGF-ß1 promotes hyaluronan synthesis by upregulating hyaluronan synthase 2 expression in human granulosa-lutein cells.

Hyaluronan serves as a structural component of ovarian follicles, and hyaluronan-mediated signaling cascades lead to follicular development, oocyte maturation, and ovulation. Transforming growth factor-ß (TGF-ß1) is highly expressed in human oocytes and granulosa cells and involved in the regulation of follicular development and ovulation. Previous studies have shown the imperative role for TGF-ß signaling in the regulation of hyaluronan-mediated cumulus expansion and ovulation in human granulosa-lutein (hGL) cells. However, the detailed underlying molecular mechanisms by which TGF-ß regulates the synthesis of hyaluronan in hGL cells are not fully elucidated. Using both primary and immortalized hGL cells as study models, we provide the first data showing that TGF-ß1 significantly promoted the synthesis of hyaluronan by upregulating the expression of hyaluronan synthase 2 in these cells. Additionally, using dual inhibition approaches, we show that the TGF-ß type II (TßRII) receptor and TGF-ß type I (ALK5) receptor are functional receptors that mediate stimulatory effects in response to TGF-ß1. Moreover, we found that the canonical SMAD2/SMAD3-SMAD4 signaling pathway is the principal intracellular signaling pathway that upregulates the expressionhyaluronan synthase and subsequent hyaluronan synthesis. Notably, we showed that SNAIL transcription factor is a critical molecule mediating the TGF-ß signaling, which contributes to the increase in hyaluronan synthesis. These results of our in vitro studies suggest that intraovarian TGF-ß1 plays a functional role in the local regulation of hyaluronan synthesis in hGL cells.

SMAD-dependent signaling mediates morphogenetic protein 6-induced stimulation of connective tissue growth factor in luteinized human granulosa cells†.

Connective tissue growth factor (also known as CTGF or CCN2) is a secreted matricellular protein that belongs to the CCN family. With wide-ranging biological activities and tissue expression patterns, CTGF plays a critical role in regulating various cellular functions. In the female reproductive system, CTGF is highly expressed in granulosa cells in growing ovarian follicles and is involved in the regulation of follicular development, ovulation, and luteal function. In the mammalian ovary, bone morphogenetic protein 6 (BMP6) is an important intraovarian modulator of follicular development. In this study, we demonstrated that BMP6 treatment significantly increased the expression of CTGF in both primary and immortalized human granulosa cells. Using both pharmacological inhibitors and Small interfering RNA-mediated knockdown approaches, we showed that ALK2 and ALK3 type I receptors are required for BMP6-induced cellular activities. Furthermore, this effect is most likely mediated by a Sma- and Mad-related protein (SMAD)-dependent pathway. Our studies provide novel insight into the molecular mechanisms by which an intraovarian growth factor affects the production of another factor via a paracrine effect in human granulosa cells.

Activin A promotes ovarian cancer cell migration by suppressing E-cadherin expression.

The highly invasive and metastatic properties of ovarian cancer make it the leading cause of death among gynecological cancers. Elevated levels of activin A and its receptors have been found in ovarian tumors and are associated with reduced survival in ovarian cancer patients. The role of activin A in promoting ovarian cancer cell migration and invasion has been previously reported, however, the underlying molecular mechanisms remain largely unknown. Here, we show that treatment of SKOV3 and OVISE cells with activin A decreases the expression of E-cadherin. These effects are completely diminished by inhibition or knockdown of the activin type I receptor. Treatment with activin A activates SMAD2/3 signaling but does not alter MEK-ERK1/2 or PI3K/AKT signaling pathway activity. Knockdown of SMAD2, SMAD3 or SMAD4 abolishes the downregulation of E-cadherin by activin A. Moreover, activin A treatment induces the expression of transcription factors SNAIL and SLUG, which mediate the suppressive effects of activin A on E-cadherin expression. Importantly, forced-expression of E-cadherin inhibits both basal and activin A-induced cell migration. Taken together, our results suggest that activin A downregulates E-cadherin expression by upregulating SLUG and SNAIL expression via SMAD2/3-SMAD4-dependent signaling. Loss of E-cadherin contributes to activin A-induced ovarian cancer cell migration.

ALK4-SMAD2/3-SMAD4 signaling mediates the activin A-induced suppression of PTX3 in human granulosa-lutein cells.

As one of the members of the transforming growth factor-ß (TGF-ß) superfamily, activin A plays an important role in regulating follicular development and oocyte maturation. Pentraxin 3 (PTX3) is the key component that promotes the process of cumulus expansion during mammalian ovulation. At present, the regulation of PTX3 expression in human granulosa cells remains largely unknown. This study aimed to examine the effects of activin A on the expression of PTX3 in human granulosa-lutein (hGL) cells and to investigate the underlying molecular mechanisms. Using an established immortalized hGL cell line (SVOG) and primary hGL cells as study models, we demonstrated that activin A significantly increased the phosphorylation of SMAD2 and SMAD3, which suppressed the expression of PTX3 at both the mRNA and protein levels. Additionally, these effects induced by activin A were completely reversed by pretreatment with the TGF-ß type I receptor inhibitor SB431542 and knockdown of ALK4. Furthermore, knockdown of SMAD2, SMAD3, or SMAD4 completely reversed the activin A-induced suppressive effects on PTX3 expression. Notably, the ChIP analyses demonstrated that phosphorylated SMADs could bind to human PTX3 promoter. Collectively, our results showed that the ALK4-SMAD2/3-SMAD4 signaling pathway most likely mediates the suppressive effect of activin A on PTX3 expression in hGL cells.

Lapatinib Inhibits Amphiregulin-induced BeWo Choriocarcinoma Cell Proliferation by Reducing ERK1/2 and AKT Signaling Pathways.

BACKGROUND: Human choriocarcinoma is the most aggressive type of gestational trophoblastic neoplasia. The expression of epidermal growth factor receptor (EGFR) in choriocarcinomas is significantly higher than those of trophoblastic cells in healthy placentas. Lapatinib is a potent EGFR and human epidermal growth factor receptor 2 (HER2) inhibitor that inhibits cell proliferation and induces apoptosis in various human cancer cells. Amphiregulin (AREG) is the most abundant EGFR ligand in amniotic fluid during human pregnancy. AIM: To explore the role of AREG in human choriocarcinoma cell proliferation. MATERIALS AND METHODS: The effect of lapatinib and AREG on cell proliferation was examined by the MTT assay. Western blots were used to investigate EGFR and HER2 expression, and the activation of caspase-3, extracellular signal-regulated kinases 1/2 (ERK1/2) and phosphatidylinositol 3-kinase /protein kinase B (PI3K/AKT) signaling pathways. RESULTS: Treatment with lapatinib reduced BeWo cell proliferation by inducing apoptosis. Moreover, AREG treatment stimulated BeWo cell proliferation by activating ERK1/2 and PI3K/AKT signaling pathways, which was blocked by lapatinib. CONCLUSION: Targeting EGFR/HER2 might be a useful therapeutic strategy for human choriocarcinoma.

YAP transcriptionally regulates ErbB2 to promote liver cell proliferation.

The Hippo signaling pathway is implicated in regulation of liver size and dysregulation of this pathway contributes to tumorigenesis. The transcriptional targets and downstream pathways of the Hippo pathway effector YAP that contribute to liver growth have yet to be well-characterized. We examined the liver transcriptome in response to YAP overexpression and identify the ErbB signaling pathway as a mediator of cell growth downstream of YAP. ErbB2 is transcriptionally regulated by YAP in both the mouse liver and in HepG2 human hepatoma cells. Knockdown of YAP or pharmacological inhibition with verteporfin reduced ERBB2 levels in HepG2 cells. Analysis of ChIP-seq data revealed enrichment of the transcription factor TEAD4 at the ERBB2 promoter. Using luciferase reporter and chromatin immunoprecipitation assays, we show that YAP and TEAD4 directly bind to and activate a regulatory element in the ErbB2 promoter in both the mouse liver and HepG2 cells. Functionally, knockdown of YAP reduced EGF-induced ERBB2-mediated HepG2 cell proliferation and PI3K/AKT activation. Our findings highlight a mechanism by which YAP exerts its effects on liver cell proliferation through the ErbB signaling pathway by directly regulating the transcription of ErbB2.