The expression and localization of neutral endopeptidase 24.11/CD10 in human gestational trophoblastic diseases

Renin-angiotensin system (RAS) enzymes and placental trophoblast syncytialisation

Placental renin-angiotensin system (RAS) components; prorenin, angiotensinogen, and angiotensin (Ang) II type 1 receptor (AT₁R) are upregulated during syncytialisation. This study examined whether angiotensin-converting enzyme (ACE), ACE2 and neprilysin (NEP) are also altered during syncytialisation. Two in vitro models of syncytialisation were used: forskolin-treated BeWo cells and spontaneously syncytialising primary human trophoblast cells. Term placentae and primary trophoblasts had the highest levels of ACE, ACE2 and NEP mRNA. In primary trophoblasts, ACE mRNA levels significantly increased with syncytialisation, ACE2 and NEP mRNA levels decreased. ACE, ACE2 and NEP protein levels and ACE2 activity did not change. Syncytialisation of primary trophoblasts decreased soluble (s)ACE and sNEP but not sACE2 levels. In primary trophoblasts, the balance between the enzymes controlling the two opposing pathways of the RAS was maintained. These findings were unable to be reproduced in BeWo cells. Future studies exploring placental levels of these enzymes in pregnancies complicated by placental insufficiency are warranted.

CD10 Expression in Pure Stromal and Sex Cord-Stromal Tumors of the Ovary

CD10 has been recently advocated as a good immunohistochemical marker for endometrial stromal tumors. Metastatic endometrial stromal tumors to the ovary and primary endometrioid stromal sarcomas may show overlapping histological features with pure stromal and sex cord-stromal tumors (SCSTs). We investigated CD10 expression in a large series of pure stromal and SCSTs of the ovary to ascertain whether CD10 may aid in this differential diagnosis. Archival material from 11 fibromas, 10 thecomas, 10 sclerosing stromal tumors (SSTs), 10 adult granulosa cell tumors (AGCTs), 4 luteinized AGCTs, 9 juvenile granulosa cell tumors (JGCTs), 9 Sertoli cell tumors, 9 Sertoli-Leydig cell tumors, 11 sex cord tumors with annular tubules, 10 steroid cell tumors (StCTs), and 8 fibrosarcomas of the ovary were immunostained for CD10. The percentage of cells stained (<5%, 5%-39%, 40%-75%, and >75%) and intensity of staining (1+, 2+, 3+) were evaluated. CD10 was expressed in 7 of 10 thecomas (4 with 5%-75% and mostly 1+), 9 of 10 SSTs (7 with 5%-39% + cells, mostly 1+), 9 of 10 AGCTs (<5%-39%, four 1+, five 2+), 1 of 4 luteinized AGCTs (<5% and 1+), 8 of 9 JGCTs (mostly <5% to 39% and +1), 4 of 9 Sertoli cell tumors (either focal or >75% with variable intensity), 4 of 9 Sertoli-Leydig cell tumors (mostly <10% with variable staining), with the Leydig cells being positive in only 1 tumor (1+ and <5%), and 7 of 10 StCTs (4 tumors with more than 75% + cells, from 1+ to 3+). All fibromas, all but 1 fibrosarcoma (<5% and 1+), and all sex cord tumors with annular tubules were CD10 negative. CD10 expression was frequently seen in StCTs, SSTs, and thecomas of the ovary, although the latter 2 categories usually showed only faint immunoreactivity. In conclusion the frequency and intensity of CD10 immunoreactivity in pure stromal and sex cord-stromal ovarian tumors are low and contrast with the typical strong and diffuse immunostaining seen in endometrial stromal tumors; however, faint CD10 positivity is consistent with the diagnosis of ovarian SCST. Steroid cell tumors are often positive for CD10, but these tumors do not pose problems in differential diagnosis with endometrial stromal tumors. CD10 may play a useful role in aiding the differential between endometrial stromal tumors in the ovary and SCST and stromal tumors.

Multiple androgen response elements cooperate in androgen regulated activity of the type 1 neutral endopeptidase promoter

The neutral endopeptidase (NEP) gene is transcriptionally regulated by androgen in prostate cancer cells. We previously identified in the NEP gene an androgen responsive element (NEP-ARE) and an androgen responsive region (NEP-ARR) that together conveyed only moderate androgen-inducibility [Mol. Cell. Endocrinol. 170 (2000) 131]. Therefore, we characterized the entire genomic structure of the NEP gene and identified ARE1 (ACTCAACAttgTGTCCTTT) and ARE2 (CAGGACAtttTGTCCC), which are located in the 3'-untranslated region and in intron 17, respectively. Steroid-dependent enhancement of transcription was assayed by transfecting the pGL-3-luciferase reporter plasmid containing three copies of ARE1 or ARE2 into PC-3 cells. Luciferase activities were increased 3.6-fold (ARE1) and 5-fold (ARE2) by androgen (AR), 4.2-fold (ARE1) and 8.2-fold (ARE2) by dexamethasone, and 3-fold (ARE1) and 4.1-fold (ARE2) by progesterone. Mutation of the ARE1 and ARE2 sequences completely abrogated androgen-inducibility. We next showed that both ARE1 and ARE2 are involved in the transcriptional regulation of the NEP gene, demonstrating in vitro and in vivo binding with AR as determined by electrophoretic mobility gel shift and chromatin immunoprecipitation (ChIP) assays, Furthermore, ARE1 and ARE2 mediate coordinated androgen-inducibility in both an SV40 promoter and the native NEP type 1 promoter. These data indicate the newly identified ARE1 and ARE2 together with the previously identified NEP-ARE function as androgen response elements, and that androgen regulation of the NEP gene is regulated by the coordinated action of multiple AREs in prostate cancer cells.

Neutral Endopeptidase 24.11/CD10 Suppresses Progressive Potential in Ovarian Carcinoma In vitro and In vivo

Recently, numerous studies have shown that endothelin-1 (ET-1) is expressed in ovarian carcinoma and that ET-1 selectively acts as an autocrine or paracrine growth factor through the endothelin A receptor (ET(A)R), and is involved in cell proliferation, invasiveness, neovascularization, and prevention of apoptosis. Neutral endopeptidase 24.11 (NEP) is a cell surface aminopeptidase with a ubiquitous expression and is capable of degrading a number of bioactive peptides including ET-1. Our previous report showed that stromal NEP expression in ovarian carcinoma was down-regulated as the histologic grade advanced. Here, we confirmed that NEP was expressed in tumor cells as well as stromal tissues in ovarian carcinoma, and investigated the functions of NEP in this carcinoma. We showed that there was a significant decrease in cell proliferation and invasiveness with a reduction in the concentration of ET-1 in the conditioned medium on the NEP overexpression of NEP in ovarian carcinoma cells. In addition, the overexpression of NEP enhanced susceptibility to paclitaxel, resulting in an increased occurrence of apoptotic morphologic change. Furthermore, tumorigenesis was reduced in vivo with the overexpression of NEP, down-regulation of both matrix metalloproteinase-2, and vascular endothelial growth factor expression. This evidence suggests that NEP functionally suppresses the progression of ovarian carcinoma and further study of this enzyme may reveal an effective way to target ET-1 for the treatment of this carcinoma.

Signal pathway involved in increased expression of neutral endopeptidase 24.11 by gonadotropin releasing hormone in choriocarcinoma cells

Neutral endopeptidase 24.11 (NEP) is known to regulate cellular functions by degrading several bioactive peptides, such as gonadotropin-releasing hormone (GnRH). The present study was performed to clarify the mechanisms of NEP expression by GnRH in human choriocarcinoma (BeWo) cells. GnRH increased NEP expression and enzyme activity in a dose- and time-dependent manner in BeWo cells. The phosphorylation levels of protein kinase C (PKC) delta, p38 mitogen-activated protein kinase (MAPK), and c-Jun N-terminal kinase (JNK1 and 2) were enhanced after 10 min exposure of 10(-6)m GnRH. The effect of GnRH on both NEP expression and enzyme activity was completely inhibited by inhibitors of PKC, PKC delta, and p38MAPK. Cell number was reduced by 54.4 per cent of the control by culture with 10(-6)m GnRH for 24 h. However, phosphoramidon, a NEP specific inhibitor, inhibited antiproliferative effect of GnRH and reverted to the control level. In conclusion, GnRH induces NEP expression by PKC delta and p38MAPK, and increased NEP expression may be involved in antiproliferative effect in BeWo cells.

Regulatory role of membrane-bound peptidases in the progression of gynecologic malignancies

Membrane-bound peptidases play a key role in the control of growth, differentiation, and signal transduction of many cellular systems by degrading bioactive peptides. Thus, abnormal changes in their expression pattern and catalytic function result in altered peptide activation, which contributes to neoplastic transformation or progression. In this review, we describe our recent findings along with work from other groups on the expression and biological functions of membrane-bound peptidases in cancer, focusing on the regulatory roles of three peptidases, aminopeptidase A (APA), neutral endopeptidase (NEP) and placental leucine aminopeptidase (P-LAP), in the progression of gynecologic malignancies. APA, NEP and P-LAP are differentially expressed and localized in various gynecologic malignancies including cervical cancer, endometrial cancer, ovarian cancer and choriocarcinoma in a tumor-type specific pattern. The expression levels are up- or down-regulated depending on histological grade or disease progression. These peptidases play regulatory roles in tumor cell proliferation, invasion or angiogenesis via degradation/inactivation of target peptides such as angiotensin II, endothelin-1 and oxytocin, which act on cancer cells as stimulatory or inhibitory factors. Thus, membrane-bound peptidases may become not only a new diagnostic/prognostic marker, but also a novel molecular target for the treatment of gynecologic malignancies.

Expression of placental leucine aminopeptidase and adipocyte-derived leucine aminopeptidase in human normal and malignant invasive trophoblastic cells

We recently identified two novel aminopeptidases, placental leucine aminopeptidase (P-LAP) and adipocyte-derived leucine aminopeptidase (A-LAP). Enzymatically, P-LAP degrades oxytocin, vasopressin, and angiotensin III, while A-LAP degrades angiotensin II and kallidin. In this study we investigated the expression and localization of P-LAP and A-LAP in human trophoblastic cells in the normal placenta (n = 26), gestational choriocarcinoma (n = 8), and placental site trophoblastic tumor (n = 3). On immunoblot analysis both P-LAP and A-LAP proteins were detected in normal placenta and five choriocarcinoma tissues, as well as in two choriocarcinoma cell lines. Immunohistochemical staining of normal placental tissues demonstrated that P-LAP was not only localized in villous syncytiotrophoblasts but also highly expressed in extravillous trophoblasts (EVTs) invading the decidua or maternal spiral arteries. The expression level of P-LAP on these invasive EVTs reached a maximum during the late first to second trimesters of pregnancy, and it decreased in the third trimester. Similarly, A-LAP was strongly expressed in EVTs invading the decidua or spiral arteries in the second trimester of pregnancy, while it was weakly or moderately expressed in villous cytotrophoblasts or EVTs located in the cell columns. These two aminopeptidases were more strongly expressed in all eight choriocarcinomas and three placental site trophoblastic tumors and mainly localized to the intermediate-type trophoblastic tumor cells invading the uterine myometrium or stromal vessels. In summary P-LAP and A-LAP were predominantly expressed in the invasive phenotype of EVTs during placentation, as well as in the invasive tumor cells of trophoblastic neoplasms. These results suggest the involvement of these aminopeptidases in invasiveness of both normal and malignant intermediate-type trophoblasts possibly through degradation of specific peptide substrates.

VEGF-, KIT protein- and neutral endopeptidase (NEP/CD10)-positive myofibroblasts-precursors of angiogenesis in chorioangiomas?

Chorioangiomas are benign angiomatous tumours of the placenta occurring with a frequency of approximately one per cent of all examined placentae. Hypoxia and genetic factors are discussed to be predisposing factors for chorioangiomas. However, not much is known about the tumorigenesis of these benign tumours. Screening with various antibodies in a rare case of chorangiomatosis, we found disseminated spindle cells coexpressing vascular epithelial growth factor (VEGF), neutral endopeptidase 24.11 (NEP/CD10), and KIT protein (CD117) within the tumour stroma. A possible involvement of such factors in angiogenesis and tumorigenesis of chorioangiomas/chorangiomatosis has not been studied so far.Seven placentae with chorioangiomas (n=6) or chorangiomatosis (n=1), six normal placentae, and four cutaneous haemangiomas were analysed immunohistochemically (ABC and APAAP methods) using antibodies against VEGF, NEP, KIT protein, as well as endothelial markers like PECAM-1 (CD31), CD34, v. Willebrand factor (factor VIII), and ulex europaeus. In addition, analysis of c-kit 'gain of function' mutation Asp 816 to Val by means of Hinfl digestion and direct sequencing of semi-nested polymerase chain reaction products was performed. All chorioangiomas and haemangiomas strongly expressed the endothelial markers CD34, CD31, and FVIII, while only weak expression of ulex lectin was noted. Disseminated groups of VEGF-, NEP-, and KIT protein-positive spindle cells, which coexpressed vimentin and smooth-muscle actin were identified as myofibroblasts in the stroma of four chorioangiomas. These spindle cells were quantified as numerous in two and as rare in two other cases. No VEGF-positive myofibroblasts, however, were detected in the villous stroma of normal control placentae and haemangiomas. Only scattered perivascular myofibroblasts expressing KIT protein and NEP were detected in early gestational placenta controls. In all chorioangiomas and chorangiomatosis PCR analysis failed to unveil c-kit 'gain of function' mutation Asp 816 to Val in KIT protein-positive spindle cells. Moreover, a significant increase in mast cells was observed only in the haemangiomas. As expected, endothelial origin of chorioangiomas/chorangiomatosis was verified by CD31, CD34, FVIII expression. Myofibroblastic spindle cells expressing VEGF and NEP may be precursor cells in these peculiar angiomatous tumours. Although activating c-kit mutation Asp 816 to Val was not detected by PCR, the presence of KIT protein (CD117)-positive intratumoral myofibroblastic spindle cells in chorioangiomas and chorangiomatosis might suggest involvement of the stem cell factor (SCF)-receptor in pathologically enhanced angiogenesis.

Neutral endopeptidase/CD10 expression in the stroma of epithelial ovarian carcinoma

This study investigated the immunohistochemical expression and localization of neutral endopeptidase (NEP) (CD10), which plays a functional role by degrading bioactive peptides, in ovarian tumors. In normal ovaries and benign cystadenomas, NEP was not detected in any epithelial or stromal cells. In borderline tumors, NEP was detected in the stromal cells in 6 of 7 serous tumors, but not in those from mucinous tumors. In ovarian carcinomas, NEP in the stromal cells was observed in 13 of 20 serous, 8 of 10 endometrioid, and 7 of 10 clear-cell adenocarcinomas. NEP was weakly detected in only 1 of 9 mucinous adenocarcinomas. The staining intensity of stromal NEP was decreased in grades 2 and 3 serous carcinomas compared with that in grade 1 serous carcinomas. In conclusion, NEP was specifically expressed in the stroma of borderline and malignant ovarian tumors, but not in adenomas. Furthermore, stromal NEP was downregulated as the histological grade advanced. These results suggest that NEP may play a role in the regulation of neoplastic transformation and tumor differentiation in epithelial ovarian carcinomas.

Neutral endopeptidase/CD10 expression during phorbol ester-induced differentiation of choriocarcinoma cells through the protein kinase C- and extracellular signal-regulated kinase-dependent signalling pathway

Neutral endopeptidase 24.11 (NEP) is identical to CD10, which is a differentiation antigen for early B-lymphoid progenitors in the B-cell differentiation pathway. This ectoenzyme is known to have a key role in the control of growth, differentiation, and signal transduction of many cellular systems by regulating bioactive peptides and cytokines. Recently, we demonstrated that NEP/CD10 is upregulated during forskolin-induced choriocarcinoma cell differentiation, suggesting that NEP/CD10 is a trophoblast differentiation marker. The purpose of this study was to clarify the enhancement of NEP/CD10 expression and its signal transduction pathway during phorbol ester (PMA)-induced differentiation of BeWo choriocarcinoma cells. PMA-induced differentiation of BeWo cells was confirmed by morphological change and human chorionic gonadotropin (hCG) secretion, which was completely blocked by a protein kinase C (PKC) inhibitor, Bisindolylmaleimide I (Bis I). On immunoblot analysis, PMA enhanced NEP/CD10 expression in a dose- and time-dependent manner, which was completely abolished by Bis I and a mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor, PD98059. PMA also induced phosphorylation of p44/p42 extracellular signal-regulated kinases (ERK) 1 and 2. These observations indicated that activation of PKC by PMA induced differentiation of BeWo cells, and that PMA activated MAPK/ERK, which resulted in the enhancement of NEP/CD10 expression. Furthermore, immunocytochemical analysis showed that NEP/CD10 expression was detected on the membranes of PMA-treated differentiated BeWo cells. In summary, we demonstrated that NEP/CD10 was enhanced during PMA-induced differentiation of BeWo choriocarcinoma cells through a PKC-dependent MEK/ERK signalling pathway. Our findings also suggest that NEP/CD10 may play a functional role in the process of trophoblast differentiation.

Endogenous opiates: 2000

This paper is the twenty-third installment of the annual review of research concerning the opiate system. It summarizes papers published during 2000 that studied the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress; tolerance and dependence; learning, memory, and reward; eating and drinking; alcohol and other drugs of abuse; sexual activity, pregnancy, and development; mental illness and mood; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; gastrointestinal, renal, and hepatic function; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Upregulation of neutral endopeptidase expression and enzymatic activity during the differentiation of human choriocarcinoma cells

Neutral endopeptidase (NEP)/CD10, a cell-surface peptidase degrading various bioactive peptides, is mainly present in syncytiotrophoblasts in the human placenta. However, the change in NEP expression upon trophoblast differentiation remains to be clarified. In the present study, we examined the expression of NEP in the differentiating trophoblast using the BeWo choriocarcinoma cell line as a model system. Under the normal culture conditions, NEP was very weakly expressed on most proliferating cytotrophoblastic BeWo cells, while a minority of the cell population (less than 5 per cent ), consisting of giant, multinucleated cells, clearly expressed NEP at the cell membrane. Treatment of BeWo cells with forskolin (FSK) for 48-72 h resulted in an 11- to 44-fold increase in the level of hCG secretion and induced cell fusion leading to the formation of multinucleated syncytiotrophoblasts, indicating functional and morphological differentiation. Fluorescence-activated cell sorting (FACS) analysis revealed that treatment with FSK significantly increased the cell-surface protein expression of NEP on differentiating BeWo cells. Consistently, there was a significant increase in the NEP enzymatic activity after FSK treatment. The level of hCG secretion from the FSK-treated cells was further enhanced when the cells were treated in the presence of the NEP inhibitor phosphoramidon. Immunohistochemical analysis of normal chorionic villi and choriocarcinoma tissues revealed the localization of NEP in syncytiotrophoblastic cells, as opposed to weak or negative staining in cytotrophoblastic cells. These data demonstrate that induction of choriocarcinoma cell differentiation is associated with an increase of NEP/CD10 expression at the cell surface, suggesting a role of this enzyme in regulating differentiated trophoblast functions such as hCG secretion. NEP/CD10 may also be a new cellular differentiation marker of both the normal and neoplastic trophoblast.