Reduced expression of tissue inhibitor of metalloproteinase (TIMP)-2 in gestational trophoblastic diseases

To elucidate the involvement of type IV collagenases [matrix metalloproteinase (MMP)-2 and MMP-9] and their tissue inhibitors (TIMP-1 and TIMP-2) in the development of gestational trophoblastic disease (GTD), we quantified their levels in hydatidiform mole and choriocarcinoma tissues using specific enzyme-linked immunosorbent assays, and the results were compared with those from normal first trimester placenta. Levels of pro-MMP-2 were increased in hydatidiform mole, and they were further elevated in choriocarcinoma. Levels of pro-MMP-9 in choriocarcinoma and those of TIMP-1 in both hydatidiform mole and choriocarcinoma were also increased. In contrast, TIMP-2 levels were markedly decreased in both hydatidiform mole and choriocarcinoma. Similar results were obtained by the tissue culture of first trimester placenta and hydatidiform mole. Gelatin zymography indicated that the levels of both pro- and activated forms of MMP-2 and MMP-9 were higher in hydatidiform mole and choriocarcinoma. The decreased expression of TIMP-2 in hydatidiform mole and choriocarcinoma was confirmed by Western blot, Northern blot and immunohistochemistry, with the decrease being more pronounced in choriocarcinoma. Taken together, the present study shows that both TIMP-2 mRNA and protein levels are markedly decreased in GTD and the imbalance of MMP-TIMP production, shifted toward greater MMP activity, may be involved in the pathogenesis of GTD.     

DEVELOPMENTAL REGULATION OF TISSUE TRANSGLUTAMINASE DURING HUMAN PLACENTATION AND EXPRESSION IN NEOPLASTIC TROPHOBLAST

The expression of tissue transglutaminase (tTG) was studied during the formation of the normal human placenta and in molar pregnancies and choriocarcinoma, in order to correlate its expression with the functional characteristics of the recognized trophoblast cell types. tTG expression was found to be developmentally regulated. Before 6–7 weeks' gestation, only the chorionic villous cytotrophoblast expresses tTG. Thereafter the overlying syncytiotrophoblast becomes positive. tTG expression is gradually downregulated in the intermediate trophoblast cells emerging from the tips of the chorionic villi invading the uterine tissue. In the decidual wall, the intermediate trophoblast does not express tTG, whereas scattered syncytial cells, the placental bed giant cells, express tTG. Villi from complete hydatidiform mole (CHM) show tTG expression in both the cyto- and the syncytiotrophoblast. The intermediate trophoblast cells from CHM show heterogeneous tTG expression, with a majority of negative cells, whereas extravillous syncytia always express tTG. In choriocarcinoma, the tumour cells show heterogeneous tTG expression, with a majority of positive cells. Analysis of tTG protein and mRNA in placental extracts by Western and Northern blotting did not provide evidence for expression of the truncated form of tTG found in some cell types. The regulated expression of tTG in the normal placenta suggests that the enzyme is involved in important trophoblastic functions and may participate in the control of invasion. © 1997 by John Wiley & Sons, Ltd.     

Serum prolactin levels and immunohistochemical localization of prolactin in trophoblastic disease

The circulating levels of chorionic gonadotropin, pregnancy specific beta-I-glycoprotein, prolactin and oestradiol were estimated by radioimmunoassay in 219 serum samples from 18 patients with choriocarcinoma and 45 samples from 8 patients with hydatidiform mole. Prolactin and oestradiol concentrations were higher in samples which also contained trophoblastic markers. This difference was also seen in patients with choriocarcinoma and it was not due to chemotherapy, since the difference between hCG positive and hCG negative samples was maintained during chemotherapy. Prolactin was found by immunoperoxidase technique in the syncytiotrophoblast of normal placenta throughout gestation, and also in hydatidiform mole, invasive mole and choriocarcinoma. It is suggested that the malignant syncytiotrophoblast may contribute to circulating prolactin levels either by direct secretion of prolactin or by oestrogen stimulation of the pituitary.     

Expression pattern alterations of syndecans and glypican-1 in normal and pathological trophoblast

Syndecans (syn-1, -2, -3, -4) and glypican-1 are proteoglycans expressed during development in association with changes in tissue organization and differentiation. They participate in the modulation of growth factor actions and in cell-cell and cell-matrix adhesion. The expression of syn-1, -2, -3, -4, and glypican-1 has been studied in normal human placenta and in gestational trophoblastic disease such as hydatidiform mole, invasive mole, and choriocarcinoma, using immunohistochemistry and western blots. Syndecan-3 was not expressed in normal or pathological tissues. During normal gestation, the other proteoglycans showed a specific staining pattern, which for some was modified during pregnancy. For instance, syn-1 was only expressed in syncytiotrophoblast; syn-4 was mainly localized in the villous and extravillous cytotrophoblast in the first trimester, whereas at term it was expressed in the syncytiotrophoblast. The most striking results are the altered expression patterns of syndecans and glypican-1 in pathological tissues. These proteoglycans showed a progressive decrease of immunostaining related to the increase of severity of trophoblastic disease, in particular in invasive mole and choriocarcinoma. In addition, dysregulation in the localization of the expression patterns was observed for syn-2 and -4. Because changes in syndecan expression enable cells to become more or less responsive to their micro-environment, the down-regulation and/or dysregulation of syndecans in relation to the degree of severity of trophoblastic diseases provides new insights into the progression of these pathologies.     

Promyelocytic leukaemia (PML) protein expression in human placenta and choriocarcinoma

Promyelocytic leukaemia (PML) protein, the product of the pml gene, is heterogeneously expressed in various normal and neoplastic tissues, and the fusion of the pml gene with retinoic acid receptor-alpha is believed to be a central mechanism in acute PML tumourigenesis. As PML is important for controlling major cellular processes, such as growth and differentiation, it is believed that it plays an important role during human gestation. The human placenta is a critical organ for the maintenance of gestation, but the expression pattern and functional significance of PML in the placenta have not been documented. The present study has therefore investigated the expression of PML in the human placenta and in choriocarcinoma, and has observed the biological effects following the overexpression of PML in choriocarcinoma cell lines (BeWo and JEG-3). In the human placenta, PML expression was readily found in villous stromal fibroblasts, capillary endothelial cells, Hofbauer cells, and occasionally in amnion cells. Moreover, immunoblotting of placental lysates demonstrated increased PML expression with increasing gestation. Interestingly, PML expression was confined to intermediate trophoblasts and syncytiotrophoblastic giant cells at the placental site (placental site giant cells) in the trophoblastic cell population. Intermediate trophoblasts at non-placental sites, and villous cytotrophoblasts and syncytiotrophoblasts consistently did not express PML. Further screening of PML expression in hydatidiform moles (n = 4) and choriocarcinomas (n = 7) also revealed selective PML expression in intermediate trophoblastic cells and syncytiotrophoblastic cells, but not in the cytotrophoblastic populations, which corresponds well with observations in the placental bed. Adenoviral transduction of PML resulted in a marked reduction in cell growth in both choriocarcinoma cell lines, which was associated with increased apoptosis. The findings of the present study strongly suggest that PML plays an important role in human placental development and growth, and in the pathobiology of trophoblasts and trophoblastic neoplasia.     

P57kip2 immunohistochemical expression and ultrastructural findings of gestational trophoblastic disease and related disorders

Gestational trophoblastic disease (GTD) is a unique spectrum of diseases ranging from complete hydatidiform mole (CHM), partial hydatidiform mole (PHM), and invasive mole (IM) to choriocarcinoma (CC). Placental site trophoblastic tumor (PSTT) and epithelioid trophoblastic tumor (ETT) have been classified as related disorders. Mesenchymal dysplasia (MD) may be misdiagnosed as PHM; however, it is said to have a quite different histogenesis from PHM. P57kip2 is the protein product of a paternally imprinted or maternal gene that inhibits cyclin-dependent kinases (CDK), thus serving to inhibit cell proliferation and to suppress tumor growth. Its lack of expression in trophoblastic disease plays a role in its abnormal proliferation and differentiation. In this study, P57kip2 immunostaining was absent in the trophoblastic layers of CHM and was positive in the trophoblast layer of nonmolar villi and MD. Ultrastructure of complete molar cystic villi showed tree-like branching of microvillous processes and intracytoplasmic lacunae without capillaries in the stroma, whereas MD contained many newly formed blood vessels and collagen. Also, large lacunae with microvilli and polymorphic nuclei of syncytiotrophoblast cells with well-developed organelles were observed in IM. Lung ETT following CHM and normal deliveries showed two types of large mononuclear cells and binuclear cells with abundant organelles and bundles of intermediate-type filaments in the stroma.     

Choriocarcinoma following a partial hydatidiform mole: a case report.

Hydatidiform moles are classified as partial or complete by histologic criteria (Am J Obstet Gynecol 131:665-671, 1978 and Am J Obstet Gynecol 132:20-27, 1978). While persistent gestational trophoblastic tumors follow both types, there remains controversy as to whether the malignant extreme of gestational trophoblastic tumors, choriocarcinoma, can follow a partial hydatidiform mole (Am J Obstet Gynecol 127:167-170, 1977 and Arch Gynecol 234:161-166, 1984). In this instance, a 37-year-old woman presented with a partial hydatidiform mole that persisted and was treated with one course of chemotherapy. She attained a remission for 10 months, when a routine follow-up examination revealed an asymptomatic rise in serum beta-human chorionic gonadotropin from baseline to 14,600 mIU/mL. Dilatation and curettage revealed abundant avillous cytotrophoblast and syncytiotrophoblast with marked atypia, diagnostic of choriocarcinoma. Flow cytometry of paraffin blocks of both specimens showed the partial hydatidiform mole to be triploid and the choriocarcinoma diploid. The patient had no evidence of metastatic disease and was successfully treated with multiple-agent chemotherapy.     

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.     

Serum protein distribution in hydatidiform mole. An immunohistochemical study

In normal placentas during the first trimester of pregnancy, the syncytiotrophoblast appeared to be immunoreactive to alpha-antitrypsin (alpha 1-AT), alpha 1-antichymotrypsin, albumin, IgG, and transferrin. The underlying cytotrophoblast was negative for these same serum proteins. In the hydatidiform mole, these findings were profoundly different. The syncytiotrophoblast lost its immunoreactivity to albumin, IgG, transferrin, and, less frequently, to alpha 1-AT. Furthermore, the underlying cytotrophoblast became immunoreactive to albumin, alpha 1-AT, IgG, transferrin, ferritin, orosomucoid, and, sometimes, to alpha 1-antichymotrypsin. This altered immunohistochemical pattern suggested a notable change in the pinocytotic activity of the trophoblast in the placenta during molar degeneration. The absence of pinocytosis in the syncytiotrophoblast for several proteins can be explained by the partial loss of specific membrane receptors. The contemporaneous appearance of numerous serum proteins in the cytotrophoblast could indicate an activation, not only proliferative, but also functional, in the germinative cytotrophoblast. Diagnostically, this histochemical finding in the hydatidiform mole, which was quite different from that seen in normal placentas during the first trimester of pregnancy, could provide additional evidence concerning trophoblastic abnormalities in the chorionic villi during molar degeneration.     

妊娠滋养细胞肿瘤HCG及HPL检测意义的探讨

Preliminary results of observation on the immunohistochemical localization of HCG and HPL are reported, involving totally 15 cases of hydatidiform moles, 17 cases of invasive moles and 15 cases of choriocarcinoma. An intermediate type of trophoblast (IT) was identified in the gestational trophoblastic tumors. The presence of HCG and HPL in both IT and syncytiotrophoblast (ST) varied with the type of trophoblastic tumors. Syncytiotrophoblast sometimes contained both of the hormones, whereas IT contained HPL predominantly. Cytotrophoblasts were devoid of HCG and HPL except in choriocarcinoma.     

Caspase activity is downregulated in choriocarcinoma: a cDNA array differential expression study

BACKGROUND: Placental trophoblast can be considered to be pseudomalignant tissue and the pathogenesis of gestational trophoblastic diseases remains to be clarified.AIMS: To examine the role of caspases 8 and 10, identified by differential expression, on trophoblast tumorigenesis. METHODS: cDNA array hybridisation was used to compare gene expression profiles in choriocarcinoma cell lines (JAR, JEG, and BeWo) and normal first trimester human placentas, followed by confirmation with quantitative real time polymerase chain reaction and immunohistochemistry. Caspase 10 and its closely related family member caspase 8 were analysed. RESULTS: Downregulation of caspase 10 in choriocarcinoma was detected by both Atlastrade mark human cDNA expression array and Atlastrade mark human 1.2 array. Caspase 10 mRNA expression was significantly lower in hydatidiform mole (p = 0.035) and chorioarcinoma (p = 0.002) compared with normal placenta. The caspase 8 and 10 proteins were expressed predominantly in the cytotrophoblast and syncytiotrophoblast, respectively, with significantly lower expression in choriocarcinomas than other trophoblastic tissues (p < 0.05). Immunoreactivity for both caspase 8 and 10 correlated with the apoptotic index previously assessed by terminal deoxynucleotidyl transferase mediated dUTP nick end labelling (p = 0.02 and p = 0.04, respectively) and M30 (p < 0.001 and p = 0.003, respectively) approaches. CONCLUSIONS: These results suggest that the downregulation of capases 8 and 10 might contribute to the pathogenesis of choriocarcinoma.     

Telomerase activity in gestational trophoblastic disease

AIMS: To investigate the pattern of telomerase activity in hydatidiform mole as compared with normal placenta and choriocarcinoma, and to determine the prognostic significance of telomerase activity in hydatidiform mole. METHODS: Telomerase activity in 35 cases of hydatidiform mole, 35 normal placentas, one choriocarcinoma sample, and two choriocarcinoma cell lines (JAR, JEG3) was determined using the sensitive polymerase chain reaction based telomeric repeat amplification protocol (TRAP) assay. Two cases of breast carcinoma and two cases of ovarian carcinoma were also included as positive controls in the telomerase assay. RESULTS: Telomerase activity was detected in 11 of 30 early placentas (36.7%), one of five term placentas (20%), five of 27 hydatidiform moles which regressed spontaneously (18.5%), and six of eight hydatidiform moles which developed persistent trophoblastic disease (75%) (including three which developed metastases). Hydatidiform moles which subsequently developed persistent disease, especially those which metastasised, were more likely to express telomerase activity (p < 0.01). However, there was no significant difference in the frequency of telomerase activity between early placentas and hydatidiform mole. Strong telomerase activity was observed in choriocarcinoma tissue, choriocarcinoma cell lines, and ovarian and breast carcinomas. CONCLUSIONS: Telomerase activation occurs in hydatidiform mole with a similar incidence to early normal placentas. This supports the concept that hydatidiform mole is essentially an abnormal conceptus. There is an association between telomerase activation and the development of persistent trophoblastic disease. Further study is warrant to confirm the prognostic significance of telomerase activity in hydatidiform mole.     

Intraplacental choriocarcinoma with fetomaternal transfusion

Intraplacental choriocarcinoma is very rare, and is usually found only after maternal and fetal metastatic disease is identified. The purpose of this case report is to review the incidence and findings of intraplacental choriocarcinoma. A term placenta was investigated because the newborn was born with severe anemia (Hb 3.0 g/dL). A 2 cm nodule was noted on the surface of the amniotic membrane and grossly resembled an infarction. The tumor was examined microscopically with immunohistochemical staining for the alpha- and beta-human chorionic gonadotropin (alpha-hCG, beta-hCG) subunits, human placental lactogen (hPL) and Ki-67. Microscopically, the tumor consisted of necrotic areas with proliferation of atypical trophoblastic cells and destruction of the villi and capillaries. The cells were positive for the alpha-hCG, beta-hCG subunits, hPL and Ki-67, consistent with intraplacental choriocarcinoma. The mother and newborn were investigated for the presence of metastatic disease. Computed tomography scans and magnetic resonance imaging of the mother and infant were negative for metastatic disease. Choriocarcinoma, limited only to the placenta with no evidence of metastatic disease is very rare. Primary intraplacental choriocarcinoma may frequently be overlooked or missed, and choriocarcinoma may possibly arise in the placenta more often than in retained or persistent trophoblast following pregnancy.     

妊娠滋养细胞病变中FHIT和PTEN蛋白的表达

目的　探讨抑癌基因FHIT、PTEN蛋白表达在妊娠滋养细胞疾病发生、发展中的作用及临床病理意义。方法　采用免疫组化S P法分别检测了 30例完全性葡萄胎、15例侵袭性葡萄胎、15例绒毛膜细胞癌中FHIT、PTEN的蛋白表达。结果　完全性葡萄胎中FHIT蛋白表达低于正常早孕绒毛 (P <0 0 1) ,FHIT蛋白表达与葡萄胎滋养细胞增生呈负相关关系。侵袭性葡萄胎和绒毛膜细胞癌中FHIT蛋白表达均低于完全性葡萄胎 (P <0 0 5 ,P <0 0 1)。侵袭性葡萄胎和绒毛膜细胞癌中核PTEN蛋白表达均低于完全性葡萄胎 (P <0 0 1,P <0 0 1)。绒毛膜细胞癌中核PTEN蛋白表达与临床分期呈负相关关系。结论　FHIT和PTEN蛋白表达下降或缺失可能参与了妊娠滋养细胞疾病的发生、发展过程。     

Expression of merosin, a tissue-specific basement membrane protein, in the intermediate trophoblast cells of choriocarcinoma and placenta

Merosin is a novel tissue-specific basement membrane-associated protein found in basement membranes of trophoblast, striated muscle and Schwann cells. In placental extracts, the immuno-reactivity for merosin was detected in a protein band of 80 kilodaltons, and a 65 kilodalton polypeptide fragment of merosin could be isolated from proteolytic digests of placenta. In the present study, we describe the expression of merosin in human choriocarcinomas and normal placentas using immunoperoxidase staining of paraffin-embedded tissues. All five choriocarcinomas studied show immunoreactivity for merosin. Tumor cells, exhibiting the morphology typical of the intermediate trophoblast, stained distinctly for merosin. The cytotrophoblast and syncytiotrophoblast cells in these tumors showed negligible or no staining. In second and third trimester human placentas, merosin immunoreactivity was found in large extravillar mononuclear trophoblast cells of the basal plate as well as in the trophoblast basement membranes of the chorionic villi. The results indicate that merosin is mainly expressed in the intermediate trophoblast cells of both neoplastic and normal origin, whereas almost no expression is seen in cytotrophoblast and syncytiotrophoblast. Consequently, it is suggested that the intermediate trophoblast may represent a third, independently differentiated trophoblastic cell type.     

Intermediate trophoblast: further immunocytochemical characterization.

Intermediate trophoblast has been recently described as a distinctive subpopulation of trophoblast. Previous immunocytochemical studies demonstrated that these cells react with antibodies against human placental lactogen (hPL) but fail to react with antibodies against beta-human chorionic gonadotropin (beta-hCG). To further characterize the immunocytochemical features of intermediate trophoblast and to possibly identify a more sensitive marker, we studied 88 placentas and implantation sites ranging from 4 to 40 wk gestation with a panel of antibodies that included keratin, epithelial membrane antigen (EMA), placental alkaline phosphatase (PLAP), alpha-hCG, and prolactin. Keratin was found in all intermediate trophoblast cells throughout gestation, and EMA was present in intermediate trophoblast in the second and third trimesters but was less consistently expressed than keratin. Comparison with the distribution of hPL revealed that keratin and EMA were present in intermediate trophoblast cells that were hPL-positive as well as many that were hPL-negative. alpha-hCG showed reactivity in intermediate trophoblast in the first and second trimester. PLAP and prolactin showed little or no reactivity in intermediate trophoblast. Decidual cells, which may be difficult to distinguish from intermediate trophoblast at the implantation site, failed to react with any of the antibodies tested. Cytotrophoblast and syncytiotrophoblast were positive for keratin throughout gestation, but EMA was negative in cytotrophoblast and inconsistently expressed in syncytiotrophoblast. Thus, antibodies against keratin and EMA are more sensitive than those directed against hPL in identifying intermediate trophoblast and are therefore useful in distinguishing intermediate trophoblast from decidua.     

胎盘部位过度反应及胎盘部位结节的临床病理分析

目的探讨胎盘部位过度反应及胎盘部位结节的临床病理学特征以及免疫组织化学染色在鉴别诊断中的意义。方法对15例胎盘部位过度反应及4例胎盘部位结节的临床及病理表现进行回顾性研究,并应用人绒毛膜促性腺激素(hCG)、人胎盘催乳素(hPL)、细胞角蛋白(CK)18、胎盘碱性磷酸酶(PLAP)、α-抑制素(inhibin),进行免疫组织化学染色。结果15例胎盘部位过度反应患者的年龄为25～40岁(平均31．5岁),4例胎盘部位结节患者年龄为26～39岁(平均34．3岁)。15例胎盘部位过度反应的组织学特征为：在子宫内膜、子宫肌层及螺旋动脉中有索条状及片状种植部位中间滋养细胞浸润,子宫内膜及肌层的结构没有破坏。4例胎盘部位结节在子宫内膜组织及变性坏死的绒毛间有多个以致密的嗜酸性玻璃样物质为背景的结节性病变,结节内为绒毛膜型中间滋养细胞。15例胎盘部位过度反应对hPL及CK18均呈阳性反应;4例胎盘部位结节均对CK18、α-抑制素及PLAP均呈阳性反应。所有15例胎盘部位过度反应Ki-67增生指数均≤5％。4例胎盘部位结节Ki-67增生指数均为0。结论胎盘部位过度反应及胎盘部位结节的临床及病理形态学特征不同于滋养细胞肿瘤。免疫组织化学染色对鉴别诊断有帮助。     

IGF-II regulates metastatic properties of choriocarcinoma cells through the activation of the insulin receptor

Choriocarcinoma is a highly malignant tumor that can arise from trophoblasts of any type of gestational event but most often from complete hydatidiform mole. IGF-II plays a fundamental role in placental development and may play a role in gestational trophoblastic diseases. Several studies have shown that IGF-II is expressed at high levels in hydatidiform moles and choriocarcinoma tissues; however, conflicting data exist on how IGF-II regulates the behaviour of choriocarcinoma cells. The purpose of this study was to determine the contribution of the receptors for IGF-I and insulin to the actions of IGF-II on the regulation of choriocarcinoma cells metastasis. An Immuno Radio Metric Assay was used to analyse the circulating and tissue levels of IGF-I and IGF-II in 24 cases of hydatidiform mole, two cases of choriocarcinoma and eight cases of spontaneous abortion at the same gestational age. The JEG-3 choriocarcinoma cell line was used to investigate the role of IGF-II in the regulation of cell invasion. We found that mole and choriocarcinoma tissue express high levels of IGF-II compared to first trimester placenta. Both IGF-I and IGF-II regulate choriocarcinoma cell invasion in a dose dependent manner but through a different mechanism. IGF-II effects involve the activation of the InsR while IGF-I uses the IGF-IR. The positive effects of IGF-II on invasion are the result of enhanced cell adhesion and chemotaxis (specifically towards collagen IV). The actions of IGF-II but not those of IGF-I were sensitive to inhibition by the insulin receptor inhibitor HNMPA(AM)3. Our results demonstrate that the insulin receptor regulates choriocarcinoma cell invasion.